What Causes A Bacterial Culture To Enter The Stationary Phase

Rohde – Bio

Rather than referring to a rise in the size of an individual cell, the phrase “microbial growth” refers to the expansion of a population (or an increase in the number of cells). Cell division results in an increase in the number of cells in a population. Microbes are capable of two types of asexual reproduction: Fission is a basic kind of cell division that does not need the use of a spindle fiber system, and it is the mode of reproduction through which bacteria reproduce. [Most eukaryotic cells include a spindle fiber system consisting of protein filaments that is responsible for moving the chromosomes around during cell division (mitosismeiosis).

The bacterial cell grows in size by a factor of two and repeats its chromosomes.

A few bacteria and certain eukaryotes (including yeasts) have the ability to replicate via budding, which results in a bubble-like growth that grows in size and eventually splits from the parent cell.

Development Stages – A microbial lab culture normally progresses through four distinct, sequential growth phases that combine to produce the classic bacterial growth curve.

1.Lag Phase – During the lag phase, there is no rise in the number of cells.

When the cells used to inoculate a fresh culture are in the log phase, this phase may not occur (as long as the inoculating parameters are the same).

The number of microorganisms in an exponentially rising population starts slowly at initially, but subsequently climbs tremendously quickly as the population grows exponentially.

While the number of cells does not increase, changes in the cells do occur: cells become smaller and synthesize components that allow them to survive longer periods without growing (some may even produce endospores); the signal to enter this phase may be caused by overcrowding; the signal to enter this phase may be caused by overcrowding (accumulation of metabolic byproducts, depletion of nutrients, etc.).

Death Phase – Cells begin to die during this phase of the cell’s life. Death happens at an exponentially increasing pace, although at a low rate. When a cell dies, it is because its internal ATP supplies have been depleted. Not all cells will certainly perish during this period, though.

B.Continuous Culture of Microbes

In the laboratory, cultures often go through all of the development phases; however, this is not the case in nature. Nutrients enter the cell’s surroundings at low quantities on a constant basis in nature, and populations expand at a slow but steady rate throughout the course of the year. The concentration of the scarcest or limiting ingredient determines the pace of development, not the accumulation of metabolic byproducts, because in nature there is always another microorganism that may utilise these metabolic byproducts for its own metabolism, hence restricting the rate of growth.

II.Measuring Numbers of Microbes

A.Measurements taken in an indirect manner (measure a property of the mass of cells and thenESTIMATEthe number of microbes) When testing for turbidity, you may bring the tube up to the light and examine for cloudiness, which indicates that there has been growth (difficult to detect slight growth). An instrument called a spectrophotometer may be used to measure how much light is transmitted by an aqueous solution of microorganisms. The more mass of cells in the culture, the greater its turbidity (cloudiness), and the less light that will be transmitted.

  1. 2.Metabolic Activity can be measured in three ways: a.The rate at which a culture generates metabolic products, such as gases or acids, as measured in microliters per minute.
  2. c.The pace at which particular dyes are degraded or reduced.
  3. B.Direct Measures – Provide more accurate counts of microorganisms than indirect measurements.
  4. Bacterial colonies are examined under a magnifying lens and counted against the grid of a Quebec colony counter, which is used to keep track of how many bacteria are present (we have this in the lab).
  5. Microbial cells are unable to pass through the filter because the holes are too tiny.
  6. There are a certain number of viable microbial cells in the volume of liquid that was filtered, which is represented by the number of colonies that form.
  7. In addition to being tiny and readily disseminated, bacteria require only little amounts of nutrients and have a wide range of nutritional requirements.

Aspects of the physical environment bacteria can be categorised according to their pH level, which is: a.

neutrophiles – these cells live in pH ranges ranging from 5.4 to 8.5; they are responsible for the majority of bacteria that cause human illness.

alkaliphiles (base-loving) — bacteria that thrive in pH ranges from 7.0 to 11.5; for example, Vibrio cholerae (causes cholera) 2.Temperature – bacteria may be classed as follows:a.

b.mesophiles – grow best at temperatures ranging from 25 to 40 degrees Celsius; the average human body temperature is 37 degrees Celsius.

thermophiles (heat-loving); found in compost heaps and boiling hot springs.

4.Hydrostatic pressure – the pressure exerted by standing water (for example, lakes, oceans, and so on); some bacteria can only survive in high hydrostatic pressure environments (for example, ocean valleys exceeding 7000 meters in depth); the high pressure is required to keep their enzymes in the proper 3-D shape; if the pressure is not present, the enzymes lose their shape and denature, and the cell dies.

Tonality (hypotonic, hypertonic, isotonic) – The fact that hypertonic environments may kill or prevent microbial development explains why salt is used as a preservative in curing meats and sugar is used in manufacturing jams and jellies.

6.Radiation–Ultraviolet and gamma rays have the potential to induce DNA alterations and potentially kill microorganisms.

B.Requirements for Oxygen 1.strict or obligatory anaerobes – bacteria that cannot survive in the presence of oxygen; for example, Clostridium tetani 2.strict or obligatory aerobes – bacteria are killed by a lack of oxygen; for example, Pserdomonas aeruginosa 3.facultative anaerobes – bacteria that may alter their metabolism (from anaerobic to aerobic when oxygen is lacking to anaerobic when oxygen is available); for example, E.

  • coli and Staphylococcus aureus.
  • 5.microaerophiles – organisms that thrive in environments with low oxygen concentrations and high carbon dioxide concentrations, such as Campylobacter.
  • Nitrogen is required for the synthesis of amino acids and nucleotides; some bacteria can manufacture all 20 amino acids, but others require nitrogen to be given in their medium.
  • Phosphorus is required for the production of ATP, phospholipids, and nucleotides.
  • Copper, iron, zinc, sodium, chloride, potassium, calcium, and so on The methods used to get pure cultures are listed in Section A.
  • It is necessary to burn the loop in order to pick up a few bacteria from the zone where they have previously been deposited and streak them onto a newly formed region.
  • Individual organisms (individual cells) are deposited in the region that has been streaked the most recently.

The loop is used to pick up a piece of a colony that has been isolated and transfer it to another media for further investigation. It is ensured by the use of aseptic technology that the new medium will only include organisms belonging to a single species. This will be done in the lab.

A. Types of Media

1.Synthetic medium – a medium created in the laboratory from components with a precise or relatively well-defined chemical makeup. 2.Complex media – a medium that contains certain components that are relatively well-known, but whose chemical composition changes significantly from batch to batch (for example, beef extracts, yeast extracts, and blood extracts); for example, nutrient agar and nutrient broth.

B. SelectiveDifferential Media(we will learn about these in detail in lab!)

A selective growth promoter is one that promotes the development of specific bacteria while suppressing the growth of others. 2.Differential – contains an ingredient that, when a specific biochemical reaction occurs, causes an observable change in the medium to be observed (ex. a color or pH change).

C. Controlling Oxygen Content of Media

2.Candelabras – the inoculated tube or plate is placed in a jar; a candle is lit before the jar is sealed; the burning candle consumes all of the oxygen in the jar and adds carbon dioxide to it; when the carbon dioxide extinguishes the flame, the conditions are optimal for the growth of microorganisms that require only small amounts of carbon dioxide (ex.Neisseria gonorrhoeae) 2.Thioglycollate medium – a medium that contains an oxygen-binding agent that prevents oxygen from having deleterious effects on anaerobes; the medium is often distributed in screw-cap tubes to avoid contamination.

  • 3.Anaerobic Chamber (Brewer Jar) – A catalyst is put to a reservoir in the lid of the jar, which serves as a reservoir for the catalyst.
  • Hydrogen gas and carbon dioxide are produced by the breakdown of water.
  • A methylene blue test strip is provided in the jar to check that anaerobic conditions have been attained before proceeding.
  • Return to the index of H 2 O-CO 2+ H 2H 2 +O 2-H 2 OReturn to the index of Chp.

Bacterial growth – Wikipedia

2.Candelabras – the inoculated tube or plate is placed in a jar; a candle is lit before the jar is sealed; the burning candle consumes oxygen in the jar and adds carbon dioxide to it; when the carbon dioxide extinguishes the flame, the conditions are optimal for the growth of microorganisms that require small amounts of carbon dioxide (ex.Neisseria gonorrhoeae) The use of thioglycollate medium, which contains an oxygen-binding agent, prevents anaerobes from becoming hazardous due to oxygen.

Thioglycollate medium is often distributed in screw-cap tubes to prevent contamination.

The gas-pak is being refilled with water.

As a result, the hydrogen gas may connect with any oxygen present in the jar and combine to make water.

To guarantee that anaerobic conditions are achieved, a methylene blue test strip is provided in the jar. It is blue when the strip is oxidized (oxygen present); it is transparent if the strip is reduced (no oxygen). To return to the Chp. index, multiply H 2 O by CO 2.


In autecological investigations, the development of bacteria (or other microorganisms, such as protozoa, microalgae, or yeasts) in batch culture may be described using four separate phases: the lag phase (A), the log phase or exponential phase (B), the stationary phase (C), and the death phase (D) (D).

  1. During the lag phase, bacteria adjust their growth circumstances to their surroundings. It is the time period during which the individual bacteria are developing and are unable to reproduce. During the lag phase of the bacterial development cycle, RNA, enzymes, and other compounds are synthesized, among other things. Due to the fact that cells do not instantly replicate in a fresh medium, cells undergo relatively little change during the lag phase. During this time of little or no cell division, which can last anywhere from an hour to many days, the term “lag phase” is used. Cells are not inactive during this phase
  2. The log phase (also known as the logarithmic phase or the exponential phase) is a period defined by cell doubling. The log phase is a period characterized by cell doubling. The number of new bacteria that arise in a unit of time is directly proportional to the current population of bacteria. If growth is not restricted, doubling will continue at a constant pace, resulting in a situation in which both the number of cells and the rate of population expansion double with each successive time period in which the process occurs. Calculating the naturallogarithmof cell number versus time for this form of exponential development provides a line that is straight in this case. When this line is plotted against time, the slope represents the organism’s specific growth rate, which is a measure of the number of divisions per cell per unit time. The exact pace of this growth (i.e., the slope of the line in the image) is determined by the growth circumstances, which influence the frequency of cell division events and the likelihood of both daughter cells surviving. Figure 1: Cell division events and survival probability Cyanobacteria can quadruple their population four times a day under regulated conditions, and then they can treble their number. Exponential growth, on the other hand, cannot be sustained indefinitely because the medium quickly becomes depleted of nutrients and enriched with wastes
  3. The stationary phase is frequently caused by a growth-limiting factor such as the depletion of an essential nutrient and/or the formation of an inhibitory product such as an organic acid
  4. A circumstance in which the growth rate and death rate are equal leads in the occurrence of a stationary phase. The growth factor has a limit on the number of new cells that may be generated, and as a result, the rate of cell growth is equal to the rate of cell death. A “smooth” horizontal linear component of the curve appears during the stationary period as a result of this technique. During the stationary phase, mutations might arise. According to research published by Bridges et al. (2001), DNA damage is responsible for a large number of mutations occurring in the genomes of stationary phase or hungry bacterias. It appears that endogenously produced reactive oxygen species are a significant cause of such damage
  5. Bacteria die during the death phase (decline phase). This might be caused by a shortage of nutrients, an ambient temperature that is above or below the species’ tolerance zone, or other harmful factors.
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This fundamental batch culture growth model identifies and underlines elements of bacterial development that may be distinct from the growth of macrofauna, such as the presence of a cell wall. Asexual binary division, short development time compared to replication itself, an apparently low mortality rate, the necessity of transitioning from a dormant to a reproductive state or conditioning the media, and lastly the tendency of lab-adapted strains to deplete their resources are all highlighted.

Unless explicitly and continuously prompted (as in experiments with stalked bacteria), the cells do not reproduce in synchrony, and their exponential phase growth is frequently not at all a constant rate, but rather a slowly decaying rate, a constant stochastic response to pressures to both reproduce and go dormant in the face of declining nutrient concentrations and increasing waste concentrations.

  • The decline in the number of bacteria may even become logarithmic as a result of this process.
  • The ability to undergo natural genetic transformation can be induced at the end of the logarithmic phase of a batch culture, as has been shown in Bacillus subtilis and other bacteria.
  • Despite the fact that batch culture is the most popular laboratory growth method used to study bacterial growth, it is simply one of several options available.
  • With only a single batch of media, the bacterial culture is incubated in a closed vessel for 24 hours.
  • In the most severe situation, this results in a continuous replenishment of the nutrients.
  • It is in a steady state characterized by the rates of nutrition delivery and bacterial growth, and is idealized to be both geographically and temporally unstructured.
  • Turbidostats and auxostats are two devices that are related to each other.
  • Bacteriostats can be used to inhibit the development of bacteria without necessarily killing the germs themselves.
  • When it comes to antibiotics (also known as antibacterial pharmaceuticals), they are medications that kill germs.
  • The proliferation of microorganisms is more dynamic and continuous in an asynecological, true-to-nature setting in which more than one bacterial species is present.

Liquid is not the only environment in which bacteria may thrive in the laboratory. Biofilms and agar surfaces, for example, are spatially organized environments that provide extra complicated growth models.

Environmental conditions

This sectionneeds expansion. You can help byadding to it.(October 2016)

Factors such as acidity (pH), temperature, water activity, macro and micronutrients, oxygen levels, and toxins all impact the pace of bacterial growth. pH is a measure of how acidic or alkaline a solution is. With the exception of extremophiles, bacteria’s environmental conditions are generally constant among themselves. Bacterium have ideal growth parameters in which they flourish, but when they are forced to develop outside of those conditions, the stress they experience might result in decreased or stopped growth, dormancy (such as the creation of formationspores), or death.


Low temperatures have a tendency to slow development rates, which has resulted in refrigeration being increasingly important in food preservation. Bacteria can be categorized into the following groups based on their temperature: A psychrophile is an extremophilic cold-loving bacterium or archaea that thrives at temperatures as low as 15 degrees Celsius or below (maximum temperature for growth is 20 degrees Celsius, minimum temperature for growth is 0 degrees Celsius or lower). Psychrophiles are often found in Earth’s extremely cold environments, including as the polar ice caps, permafrost, the polar surface, and the deep waters.

Microorganisms known as mesophiles are those that survive at moderate temperatures, with the optimum growth occurring between 20° and 45°C.

Survive at temperatures ranging from 45 to 60 degrees Celsius.


pH 6.5 to 7.0 is generally considered optimal for bacteria, except in the case of acidophiles, who prefer higher acidity. Some bacteria can alter the pH of the environment, for example, by excreting acid, resulting in less-than-optimal circumstances.

Water activity

Bacteria can be classified as either anaerobes or aerobes. In accordance with the amount of oxygen required, bacteria can be classified into the following categories.

  1. Facultative anaerobes, that is, organisms that can grow in the absence of or with only a small amount of oxygen
  2. Obligate-anaerobes are organisms that can only survive in full lack of oxygen. Facultative aerobes are those that can grow in the presence or absence of oxygen. Aerobes that require oxygen to grow are known as obligatory aerobes.


There are plenty of nutrients.

Toxic compounds

Toxic substances, such as ethanol, can either inhibit or kill the development of microorganisms. This is used to clean and preserve food, which is a favorable combination.

See also

  • Cell proliferation
  • Michaelis–Menten kinetics
  • Monod equation


  1. A study of the cell cycle characteristics of a slowly developing Escherichia coli B/r strain using flow cytometry was published in 1983 by AbSkarstad, Steen, and Boye. In a study published in J. Bacteriol., 154(2): 656–62.PMC217513.PMID6341358
  2. Zwietering MH, Jongenburger I, Rombouts FM, van ‘T Riet K (1990). “Modeling of the Bacterial Growth Curve.” J. Bacteriol. 154(2): 656–62.PMC217513.PMID6341358
  3. Applied and Environmental Microbiology.56(6): 1875–1881.PMC184525.PMID16348228
  4. Fankhauser, David B. Applied and Environmental Microbiology.56(6): 1875–1881.PMC184525.PMID16348228
  5. (July 17, 2004). The “Bacterial Growth Curve” is an abbreviation. Clermont College is part of the University of Cincinnati. The original version of this article was published on February 13, 2016. On December 29, 2015, I was able to get a hold of In the tenth edition of Microbiology An Introduction, Case, Christine
  6. Funke, Berdell
  7. Tortora, Gerard
  8. And ab”24, 2007, at the Wayback Machine “. abBridges BA, Foster PL, Timms AR (2001). “Effect of endogenous carotenoids on “adaptive” mutation in Escherichia coli FC40.” Retrieved on May 7, 2008
  9. Ab”Marshall T. Savage – An Exponentialist View.” Mutat. Res.473(1): 109–19.doi: 10.1016/s0027-5107(00)00144-5.PMC2929247.PMID11166030
  10. Novick A (1955). “Growth of Bacteria.” Mutat. Res.473(1): 109–19.PMC2929247.PMID11166030
  11. Novick A (1955). “Growth of Bacteria.” PMID13259461
  12. Anagnostopoulos C, Spizizen J (1961). “REQUIREMENTS FOR TRANSFORMATION IN BACILLUS SUBTILIS.” Annual Review of Microbiology.9: 97–110.doi: 10.1146/annurev.mi.09.100155.000525.PMID13259461
  13. Anagnostopoulos C, Spizizen J (1961). 81(5): 741–6.doi: 10.1128/JB.81.5.741-746.1961.PMC279084.PMID16561900
  14. “Psychrophiles and Psychrotrophs.” J. Bacteriol. 81(5): 741–6.doi: 10.1128/JB.81.5.741-746.1961.PMC279084.PMID16561900
  15. “Psychrophiles and Psychrotrophs.” On February 6, 2018, I found the term “Mesophile” in the Biology-Online Dictionary. Obtainable on February 6, 2018
  16. Blamire, John, “Effect of pH on Growth Rate,” Journal of Experimental Botany, vol. Brooklyn College is a private liberal arts college in Brooklyn, New York. Obtainable on October 8, 2016

External links

  • In this study, the exponential expansion of bacterial populations is investigated. Bacterial Growth is a useful science tool. Microbial Growth, BioMineWiki is a useful resource for high school students (GCSE and Alevel). From the Wolfram Demonstrations Project—requires the use of the free CDF player:
  • In this study, the exponential expansion of bacterial populations is investigated
  • Bacterial Growth is a useful science resource. Microbial Growth, BioMineWiki
  • High School (GCSE, Alevel) Resources
  • Wolfram Demonstrations Project — needs the use of the CDF player (which is available for free).

Contains content from an article published on Nupedia on April 26, 2003; prepared by Nagina Parmar; reviewed and approved by the Biology group; edited by Gaytha Langlois; lead reviewer, Gaytha Langlois; lead copyeditors, Ruth Ifcher and Jan Hogle; and published with permission of the author.

9: Microbial Growth

Microbes may develop quite fast if they are provided with the proper circumstances (food, appropriate temperature, etc.). Depending on the scenario, this might be beneficial to people (yeast growing in wort to produce beer) or detrimental (yeast growing in wort to cause disease) (bacteria growing in your throat causing strep throat). It is critical to understand their growth in order to be able to forecast or regulate their growth under certain situations.

While multicellular animals’ development is normally assessed in terms of the rise in size of a single organism, microbial growth is measured in terms of the increase in population, which may be quantified either by counting the increase in cell number or by counting the increase in total mass.

Bacterial Division

Bacteria and archaea can only reproduce asexually, but eukartyotic microorganisms can reproduce both sexually and asexually, depending on the species. Bacteria and archaea are the most frequent organisms to participate in binary fission, which is a process in which a single cell divides into two cells of equal size. Other, less common processes include multiple fission, budding, and the formation of spores, to name a few examples. Cell elongation is the first step in the process, and it necessitates the meticulous expansion of the cell membrane and cell wall, as well as an increase in cell volume, to get started.

When an elongated cell divides into two halves, the protein FtsZ is required for the creation of a septum, which appears initially as a ring in the centre of the elongated cell.

For an active culture of E.

Growth Curve

Bacterial growth has been extensively investigated in the laboratory due to the ease with which they may be grown. It has been determined that bacteria will grow in a predictable pattern in a closed system or batch culture (with no food added and no wastes removed), resulting in a growth curve composed of four distinct phases of growth: the lag phase, the exponential or log phase, the stationary phase, and the death or decline phase. This growth curve may also be used to calculate the generation time for a given organism, which is defined as the length of time it takes for the population to double in size.

Written by Micha Komorniczak.

For further information, please contact me at the following e-mail address: [email protected], or through Wikimedia Commons.

The pattern of four different periods of growth, on the other hand, is likely to persist.

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Lag phase

The lag phase is a time of adaptation during which the bacteria are becoming used to their new surroundings. The length of the lag phase can vary significantly depending on how different the current conditions are from the conditions in which the bacteria originated, as well as the condition of the bacterial cells in their native environment. Transferring actively developing cells from one kind of medium to another, while maintaining the same environmental conditions, will result in the smallest lag period, according to the literature.

For the most part, cells in this stage of development are synthesizing RNA and enzymes, as well as essential metabolites that may be lacking in their new environment (such as growth factors or macromolecules), as well as adjusting to environmental shifts such as temperature changes, pH shifts, or oxygen availability.

They may also be engaged in any essential cell repair that is required in the case of injury.

Exponential or Log phase

Cell division occurs when cells have acquired all of the materials they require for growth and have begun to divide. The exponential or log phase of growth is characterized by predictable doublings of the population, where 1 cell becomes 2 cells, which then becomes 4, which then becomes 8, which then becomes 16. Optimal growth circumstances for the cells will result in very rapid growth (and a steeper slope on the growth curve), but less than perfect growth conditions result in slower growth.

  • Calculating Bacterial Growth Rates.
  • Microbiologists employ this information in both basic and applied research, as well as in industry.
  • The line has a slope of 0.301 g, which is equal to 0.301 g.
  • The generation time (g) can be expressed as the ratio t/n, where t is the given period of time in minutes, hours, days, or months and n is the number of generations.
  • Then, using the amount of time that was allowed for growth to continue (t), one can calculate the rate of growth.

Stationary Phase

It is necessary for all wonderful things to come to an end (otherwise, bacteria would have equaled the mass of the entire planet in 7 days!). A point is reached when the bacterial population has exhausted all of its available essential nutrients and/or chemicals, or when its growth is slowed by its own waste products (remember, it is in a closed container), or when there is insufficient physical space, causing the cells to enter the stationary phase. It is at this stage when the number of new cells generated equals the number of cells dying off, or that growth has completely stopped, which results in a flattening out of the growth curve.

  • The few new cells that are created are smaller in size, with bacilli taking on an almost spherical appearance as they grow in number.
  • This condensing of the nucleoid results in DNA binding proteins from starving cells (DPS) attaching to the DNA, which helps to preserve the DNA from harm.
  • Cells in oligotrophic or low-nutrient environments employ the same methods as those in nutrient-rich settings.
  • Cells are also more prone to creating secondary metabolites, which are metabolites that are formed after vigorous growth, such as antibiotics, when in the stationary phase.

It is at this stage that cells that are capable of forming an endospore will activate the genes that will allow the sporulation process to begin.

Death or Decline phase

The last phase of the growth curve, also known as the death or decline phase, is characterized by a predictable (or exponential) drop in the number of viable cells. The steepness of the slope corresponds to the rate at which cells are losing their viability, and vice versa. Due to the failure of cells collected during this phase to develop when transferred to new media, it is believed that the culture conditions have worsened to the point where the cells are irrevocably injured. It is crucial to note that if the turbidity of a culture is being tested in order to assess cell density, readings may not decrease during this phase due to the possibility that cells are still alive.

This state may be important for pathogens because it allows them to enter a state of extremely low metabolism and cellular division before resuming development at a later period, when the conditions are more favorable.

There is frequently a tailing effect observed, in which a tiny population of cells is unable to be killed out completely.

Key Words

The number of viable cells falls in a predictable (or exponential) manner during the final phase of the growth curve, known as the death or decline phase. Viability is measured by how quickly cells lose their viability, and the steepness of the slope reflects this. Given the failure of cells collected during this phase to grow when placed in fresh medium, it is believed that the culture conditions have deteriorated to the point where the cells are irreparably damaged. It is crucial to note that if the turbidity of a culture is being measured in order to assess cell density, readings may not decrease during this phase due to the possibility that cells are still present.

Especially for pathogens, this state may be of importance because it allows them to enter a state of very low metabolism and cell division, only to reactivate their growth at a later time when conditions improve.

When a tiny population of cells cannot be killed out, this is referred to as a tailing effect, and it occurs frequently.

In addition, these cells may profit from the death of their fellow cells, which release nutrients into the environment when they lyse and release the contents of their cellular contents, allowing these cells to survive.

Essential Questions/Objectives

  1. • How is the expansion of microbial communities determined? What is the difference between the reproductive mechanisms of eukaryotes and bacteria/archaea
  2. In binary fission, what are the stages that must be taken? At each stage, describe what is taking place. Understand the shape of the growth curve of an organism that has been grown in a closed system. Be familiar with the different stages and what is happening biologically at each level. What factors can have an impact on the lag phase? When it comes to cell loss during the death or senescence phase, what are the two different theories
  3. Understand the concept of generation time and how it may be calculated using a log number of cells versus time graph. Learn about the advantages of charting the log number of cells vs. time rather than the number of cells vs. time when analyzing data. What variables influence the time it takes for an organism to reproduce
  4. Example of a practice problem: A pastry chef inoculates six Staphylococcus aureus into a cream pie with the use of his or her hands. At room temperature, the production time of S. aureusin cream pie is 30 minutes. a) How many S. aureus are still in the pie after four hours at room temperature? b) After 24 hours have passed

Exploratory Questions (OPTIONAL)

  1. In what circumstances might the appearance of the VBNC be advantageous to cells? What kind of hazard may this represent to public health?

The Bacterial Growth Curve and the Factors Affecting Microbial Growth

Bacteria are prokaryotic creatures that most typically reproduce by the asexual process known as binary fission (also known as binary fission). Under favorable conditions, these microorganisms proliferate at an exponential pace, resulting in a large number of offspring. When bacteria are cultivated in culture, they develop a predictable pattern of development that can be seen. This trend may be depicted visually as the number of live cells in a population increasing over time, and it is referred to as the abacterial growth curve.

Key Takeaways: Bacterial Growth Curve

  • During the course of a certain time period, the bacterial growth curve indicates the number of living cells in a given bacterial population. It is possible to divide the growth curve into four separate phases: lag, exponential (log), stationary (stationary), and death. This is the lag phase, during which bacteria are metabolically active but not dividing
  • This is the first phase. The exponential phase, also known as the log phase, is a period of exponential development. The stationary phase is defined as the point at which the number of dying cells equals the number of dividing cells
  • Growth then comes to a halt. The death phase is characterized by an exponential decline in the number of live cells
  • This is the final phase of the life cycle.

In order for bacteria to develop, they require certain environmental conditions, which are not the same for all bacteria. Microbial development is influenced by a variety of factors, including oxygen, pH, temperature, and light. Osmotic pressure, atmospheric pressure, and the availability of moisture are all additional considerations. The generation time of a bacterial population, or the amount of time it takes for a population to double, varies from species to species and is dependent on how effectively growth needs are satisfied.

Phases of the Bacterial Growth Cycle

The bacterial growth curve depicts the change in the number of live cells in a population over time in a bacterial population. Wikimedia Commons/Michal Komorniczak/CC BY-SA 3.0 license Bacteria do not develop in ideal settings in nature because they do not have access to ideal environmental conditions. As a result, the species that live in a given ecosystem vary throughout the course of time. It is possible to achieve ideal conditions in the laboratory by cultivating bacteria in a closed culture environment, albeit this is not recommended in practice.

This curve indicates the amount of living cells that have developed in a bacterial population over an extended period of time (see Figure 1).

  • In the lag phase, cells are active but not growing, and this is the first phase of the cell cycle. One or a few cells are cultured in an environment rich in nutrients that allows them to manufacture proteins and other substances that are required for cell reproduction. During this phase, the size of the cells increases, but there is no cell division. Exponential (Log) Phase: After passing through the lag phase, bacterial cells start the exponential (or log) phase of their growth. This is the period of time during which the cells are dividing by binary fission and doubling in number after each generation time interval. Because DNA, RNA, cell wall components, and other chemicals required for growth are produced during cell division, metabolic activity is significant at this time. Because these compounds primarily target bacterium cell walls or the protein synthesis processes of DNA transcription and RNA translation during this growth phase, antibiotics and disinfectants are most effective at this stage of the organism’s life cycle. Stationary Phase: As the available nutrients get exhausted and waste products begin to build, the population increase witnessed during the log phase eventually begins to slow. A plateau, or stationary phase, is reached in the development of bacteria when the number of proliferating cells equals the number of dying cells, which is known as the stationary phase. As a result, there is no overall increase in population. Increased competition for resources results in cells being less metabolically active when environmental conditions are less favorable, as seen in Figure 1. Pathogenic bacteria begin to produce substances (virulence factors) that aid them in surviving harsh environments and, as a result of this, cause disease during this phase. Sporeforming bacteria produce endospores during this phase, and pathogenic bacteria begin to produce substances (virulence factors) that aid them in surviving harsh environments and, as a result, cause disease. In the death phase, the number of dying cells continues to climb as nutrients become less accessible and waste products become more abundant. During the death phase, the number of live cells drops rapidly, and the rate of population expansion slows dramatically. In the process of dying cells lysing or breaking apart, their contents are released into the surrounding environment, making these nutrients available to other bacteria. This allows spore-producing bacteria to live for a longer period of time, allowing them to produce more spores. When put in an environment that supports life, spores are able to survive the severe circumstances of the death phase and develop into bacteria that are capable of reproducing.
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Bacterial Growth and Oxygen

It is necessary to have low quantities of oxygen in order for Campylobacter jejuni to survive, which is illustrated below. The bacteria C. jejuni is responsible for the development of gastroenteritis. Photograph courtesy of Henrik Sorensen/The Image Bank/Getty Images Bacteria, like all living creatures, require an environment conducive to their growth in order to thrive. This habitat must have a number of distinct variables that encourage bacterial growth to be effective. Oxygen, pH, temperature, and light needs are examples of such considerations.

  • Bacteria can be divided into groups depending on their oxygen requirements and tolerability thresholds.
  • During cellular respiration, these microorganisms are reliant on oxygen for energy production because they turn oxygen into energy.
  • These microorganisms are referred to as obligate anaerobes, and their metabolic activities for energy generation are interrupted when they come into contact with air.
  • The creation of energy in the absence of oxygen is accomplished by either fermentation or anaerobic respiration.
  • Microaerophilic bacteria require oxygen to survive, yet they can only thrive in environments with low oxygen concentrations.

Microaerophilic bacteria such as Campylobacter jejuni, which dwells in the digestive tracts of animals and is a significant source of foodborne disease in humans, are examples of this type of bacteria.

Bacterial Growth and pH

Helicobacter pylori is a kind of microaerophilic bacterium that may be found in the gastrointestinal tract. This group of cells is composed of neutrophils, which release an enzyme that neutralizes stomach acid. Science Picture Co./Getty Images Science Picture Co. The pH of the environment is another essential component in bacterial development. In acidic situations, the pH value is less than 7, in neutral environments, the value is at or near 7, and in basic environments, the pH value is larger than 7.

These microorganisms may be found in a variety of environments, including hot springs, as well as in the human body, particularly in acidic places such as the vaginal area.

The bacteria Helicobacter pylori is an example of a neutrophile that thrives in the acidic environment of the digestive tract.

It is best for alkaliphiles to flourish in pH ranges between 8 and 10.

Bacterial Growth and Temperature

It is believed that Champagne Pool in New Zealand comprises a population of thermophilic and acidophilic bacteria whose distribution is influenced by the temperature and chemical environment of the water source. Photograph by Simon Hardenne/Biosphoto/Getty Images Another key component in bacterial proliferation is the temperature of the environment. Psycrophiles are bacteria that thrive in colder settings and are found in soil, water, and air. These microorganisms like temperatures ranging between 4°C and 25°C (39°F and 77°F), which is the range in which they thrive.

Mesophiles are bacteria that live at temperatures ranging from 20 to 45 degrees Celsius (68 to 113 degrees Fahrenheit).

Thermophiles are plants that thrive at hot temperatures (50-80°C/122-176°F), and they can be found in hot springs and geothermal soils, among other places.

Bacterial Growth and Light

Photograph of cyanobacteria (blue), which are photosynthesizing microorganisms that may be found in almost every environment where there is water. There are also a few pink spores to be found. Getty Images/Science Photo Library/Steve Gschmeissner/Getty Images Some bacteria require light in order to reproduce. These bacteria are equipped with light-capturing pigments, which enable them to collect light energy at certain wavelengths and convert it to chemical energy for use. Photoautotrophs, such as cyanobacteria, are organisms that require light for photosynthesis to occur.

Cyanobacteria may be found on land and in water, and they can also be found as phytoplankton, where they form symbiotic interactions with fungus (lichen), protists, and plants.

Other bacteria, such as purple and green bacteria, do not create oxygen and instead rely on sulfide or sulfur to carry out their photosynthetic functions.

Bacteriochlorophyll is found in these bacteria, and it is a pigment that has a shorter wavelength of light absorption than chlorophyll does. Purple and green bacteria can be found in deep aquatic environments.


  • “Bacterial Metabolism,” by Peter Jurtshuk, is available online. The National Center for Biotechnology Information at the National Library of Medicine in the United States was established on January 1, 1996. Parker, Nina, and colleagues Microbiology. “Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis,” according to Preiss et al., published in OpenStax by Rice University in 2017. Frontiers in Bioengineering and Biotechnology, published online by Frontiers on May 10, 2015.

What are the Stages of the Bacterial Growth Curve?

The ability to distinguish between the lag, log, stationary, and death phases of a cell growth curve may appear to be elementary biology information, but using that knowledge in active cell culture is an indication of a more fundamental grasp of microbiological processes and processes in general. The tiny details of cell culture that the uninformed may overlook can assist those of us who pay close attention in optimizing growth conditions or effectively scaling up output with less stress and anguish than those who do not.

  • The Lag Phase The metabolic activity of the cells during this first cell development phase is often greater than the rate of cell expansion.
  • This is the stage at which the cells begin to grow in size, but not necessarily in number, as they mature.
  • Understanding the physiological and regulatory processes that are responsible for reproduction is an essential factor that can be learnt from the cellular activity that occurs during the lag phase of the cell cycle.
  • It’s all about the numbers after cells enter the exponential growth or log phase, which occurs when they reach a certain size in terms of number of cells.
  • During this stage, metabolic activity is strong, but it is primarily focused on the processes essential for reproduction and not on anything else.
  • This type of cell culture is referred to as an exponentialfed-batch cell culture, and it necessitates regular monitoring of cell growth conditions, as well as sophisticated understanding of when and how much to feed the cells.
  • These considerations are especially important in industrial microbiology, where cost and time have a direct impact on the bottom line and might represent the difference between profits and losses.

Cells are theoretically still replicating at this point, but the rate is lower than it was previously and almost equivalent to the rate of cell death.

Depending on the kind of cell being produced, this might be the stage at which protein production and excretion begin, or it could be the stage at which spore-forming bacteria begin to generate endospores, which enable them to survive in hostile environments.

The addition of additional nutrients may be necessary to maintain the cells alive yet stressed enough so that they continue to produce rather than reproduce.

In cases where cell culture can last days, weeks, or months, such as the production of monoclonal antibodies by hybridoma cells or the production of ethanol and CO2 by yeast fermentation (to name a few examples), the stationary phase is critical.

As cells lyse and release the contents of their insides into the culture, the environment changes for the final time, and exponential deterioration begins to take hold.

When cells lyse and release amino acids, proteins, polysaccharides, and free fatty acids, which may be the anticipated products, this is true of the situation.

All those involved in bioprocessing and cell culture understand that the smallest details may make a significant impact, and in a subject that is rife with questions, understanding even a few of the answers can be the difference between success and failure.

Knowing what is happening to your cells at each step of their life cycle may just provide you with the competitive advantage you require in today’s world.


Bacteria divide and reproduce asexually, which is the basis of microbiological growth. Because of binary fission, all of the material is distributed evenly between the two daughter cells. The amount of time it takes for a single cell to divide from one division to the next is referred to as the generation time or doubling time. As a side note, this is also how long it takes for a population to double. Under “perfect” conditions, the doubling period for many “normal” bacteria can be as little as 20 minutes.

That is, (x)(2) n, where x is the number of bacterial cells at the start of the experiment and n is the number of generations.

Inoculation of an organism into a nutritional solution results in the observation of four different growth stages in the organism’s development: First, the organisms are “becoming acclimated to the medium and physical circumstances” – that is, they are inducing the enzymes required for development – during this phase.

More optimal conditions result in quicker growth – up to and including the maximum growth rate for the species in question.

As nutrients are reduced, the pH changes, hazardous wastes accumulate, and oxygen levels are diminished, the environment is becoming increasingly poisonous.

Death has the potential to accelerate and become exponential.

Source of Carbon: Water Natural organic molecules (heterotrophs) – sugars and other sugar-like substances, amino acids, and even complex preformed organic compounds (ie.

Carbon dioxide (from autotrophs) with inorganic carbon Nitrogen is found in the form of nitrates and nitrites, as well as elemental nitrogen in the case of a nitrogen fixer.

Sulfur Phosphorus Oxygen: Many organisms require it for the process of breathing.

2O 2-+ 2H +-superoxide dismutase-H 2 O 2+ O 22 H 2 O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2O 2+ O 2-catalase-H 2 O + O 2 is a kind of enzyme that breaks down H 2 O + O 2.

: Aerobes who are required to exist Microaerobic means “without oxygen” (formally called microaerophils).

Anaerobes with a purely fictitious origin Anaerobes who are required to exist Minerals: Magnesium, potassium, iron, calcium, zinc, molybdenum, cobalt, manganese, sodium, chlorine It should be noted that the human host is engaged in a war for iron with a variety of pathogenic pathogens.

Many bacteria produceiderophores, which are capable of capturing and retaining iron.

We routinely use the terms optimal, maximum, and minimal to describe several of them.

Helicobacter pylori, on the other hand, is a bacteria that lives in the stomach and has a pH close to 1.

pHor = 5 is preferred by many fungus since it is low in pH.

When it comes to temperature, psychophiles prefer a low temperature optimum (Listeria monocytogenes thrives best at low temperatures, and cultures can be supplemented by incubating at refrigerator temperature).

Thermophiles are characterized by having a high optimal growth temperature.

Microbes are not killed by freezing temperatures; rather, they are preserved in a state of “suspended animation.” Lyophilization, often known as freeze-drying, is a method of preserving microbial cultures.

Some organisms, known as thehalophiles, are capable of tolerating and even growing in high concentrations of sodium chloride or glucose.

The Staphylococci are a significant group of medicinal bacteria that fit into this category, and they are classified as such. What is meant by the phrases isotonic, hypertonic, and hypotonic in relation to one another?

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