How do Microbes Grow?

The development of microbial growth is influenced by various natural conditions (both physical and synthetic) like pH, temperature, saltiness, gas focus (O2, CO2, and H2), nutrients, water action, and assimilation. Knowing the distinctive physical and chemical factors that influence the development and endurance of microbial growth in the climate will assist with reinforcing endeavors outfitted towards their control. These lines lessen or diminish their harmful impacts on humankind, creatures, and the climate.

Bacterial Division

Microbial growth like those seen in bacteria and archaea follows asexual replication, whereas eukaryotic organisms can participate in either sexual or agamic generation. Microorganisms, like the bacterium, most ordinarily take part in an interaction known as fission, where a single cell parts into two similar cells. Other uncommon ways of division are the formation of spores.

The interaction starts with cell elongation, which requires a cautious extension of the cell membrane. The cell begins to duplicate its DNA, one for each daughter cell. The protein FtsZ is fundamental for developing a septum, which at first shows as a ring in the elongated cell. After the nucleoids are isolated at the ends of the stretched cell, the septum arrangement gets completed, partitioning the extended cell into two similarly measured bacterium cells. The whole interaction or bacterium cell cycle can take 20 minutes for functioning E. coli microbes.


Water is a fundamental part of the development of microbes. 80% of the bacterium microbial growth is comprised of water. In this way, the presence of a free water atom is significant for the ideal development. For instance, Treponema pallidum, N. gonorrhea, can utilize the dust effectively because of parching. While microbes like M. tuberculosis, S. aureus can endure parching for half a month.


Based on the prerequisite of oxygen, microbial are arranged under three gatherings

  • Aerobes: Oxygen is rigorously needed for the development of these bacteria. These are likewise called committed aerobes because of the necessity of oxygen for development. Example: Pseudomonas aeruginosa.
  • Facultative Anaerobes: These can develop both in the presence and absence of oxygen. A large portion of the pathogenic microbes is facultative anaerobes. Example: E. coli.
  • Anaerobes: These are called anaerobes as they can survive in the absence of oxygen in the climate. Example: Clostridium tetani.

Apart from these, another group called microaerophilic bacteria needs a certain measure of oxygen. Example: Helicobacter pylori. 

Carbon Dioxide 

The vast majority of microbial growth requires a modest quantity of carbon dioxide for development. The climate normally gives this carbon dioxide, or microscopic organisms may create it because of cell digestion. Living beings, for example, Brucella abortus, require a significant degree of Carbon dioxide (5-10%) for development. Microbes that require a significant degree of Carbon dioxide for development are known as capnophilic microorganisms.


It is a fundamental natural factor that can impact the development of living beings. A large portion of the microbes develops at 37 0 C (internal heat level). Microscopic organisms are sorted under three gatherings based on the ideal temperature range.

Mesophile: The ideal temperature range for mesophiles is 250C to 400. Most of the pathogenic microbes go under this gathering.

Psychrophile: The ideal temperature for psychrophiles is under 200

Thermophile: The ideal temperature range for thermophiles is 550C to 800 Eg: Bacillus stearothermophilus.


pH is a fundamental factor in the development of organisms. Many microbes can release a few natural acids that lower the medium's pH and confine the development of different microorganisms. Apart from that, some media constituents can be influenced by low pH. Accordingly, maintaining the ideal pH is exceptionally imperative to acquire sufficient development of the life forms. Microbes are generally requiring nonpartisan pH (7.2). For example, mechanically significant microorganisms, Lactobacillus lactis, require a lower pH for ideal development. Enzymes can be produced when fermented media is provided. Enzymes are used in the industrial production of enzymes, a bacterial enzyme in cosmetics.


Phototrophic microscopic organisms require light for development. Be that as it may, the majority of the microscopic organisms can fill well in obscurity. The presence of bright beams and radiation can diminish bacterial development. Photo chromogenic mycobacterium is an interesting animal variety that produces shades just in the presence of light.

Osmotic Effect

Bacterial cell divider assumes a significant part in withstanding the osmotic pressing factor. Plasmolysis (osmotic withdrawal of water prompting shrinkage of cellular material) can happen if the microorganisms are out of nowhere moved into a hypertonic arrangement. Then again, plasmoptysis (exorbitant osmotic imbibitions of water prompting expanding and break of the cell) can happen if the microorganisms are moved into a concentrated arrangement.

Mechanical and Sonic Stress

The bacterial cell divider gives security from stress-related issues. Nonetheless, the cell divider can be cracked by vigorous shaking with glass globules and openness to ultrasonic vibrations.

These nutrients provided to the bacterium can be seen as a marker as nutrients play an important role in the growth medium of the microbiology of cells. These nutrients can differ in all microbiology mediums. 

"Microbial Cell Division"

Growth Curve

A growth curve is an empirical representation of a quantity's evolution through time. In biology, growth curves are commonly used to calculate population size or biomass, individual body height, or biomass. Values for the measured property can be plotted as a function of time on a graph. The bacterial growth curve represents the number of living cells in a bacterial population over time.

"Cell phases of growth"

Lag phase

This initial stage is distinguished by cellular activity but not by growth. A limited number of cells are placed in nutrient-rich media, allowing them to manufacture proteins and other molecules required for replication. During the phase, these cells grow in size but do not divide.

Log phase

Bacterial cells reach the exponential or log phase after the lag phase. This is the stage when the cells divide via binary fission and double in size after each generation. Metabolic activity is strong as DNA, RNA, cell wall components, and other growth-related compounds are produced for division. Antibiotics and disinfectants are most effective during this growth phase because these drugs often target bacteria cell walls or the protein synthesis processes of DNA transcription and RNA translation.

  • Bacterial Growth Rates- The exponential growth of a bacterial culture is expressed as generation time, which is also the time required for the bacterial population to double. The time (t) per generation (n = number of generations) is specified as generation time (G). As a result, G=t/n is the equation used to calculate generation time.

Stationary Phase

As available nutrients diminish and waste items build, the population expansion witnessed during the log phase begins to slow. Bacterial cell growth eventually reaches a halt, or stationary phase, in which the number of dividing cells equals the number of dying cells. As a result, there is no overall population growth. Under less favorable conditions, healthy competition intensifies, and cells become less metabolically active. In this phase, spore-forming bacteria make endospores, and pathogenic bacteria begin to manufacture chemicals (virulence factors) that enable them to withstand harsh environments and, as a result, cause disease.

Death Phase

The number of dying cells continues to rise as nutrients become scarce and waste products accumulate. The number of alive cells drops exponentially during the death phase, and population growth slows dramatically. When dead cells lyse or split open, their contents flow into the environment, making nutrients available to other bacteria. This allows spore-producing bacteria to survive long enough to produce spores. Spores can survive the harsh conditions of the death phase and develop into bacteria when placed in a life-supporting environment. 

"Microbial Growth"

Estimations of Microbial Growth

  • There are different approaches to measures microbial development for the assurance of development rates and age times.
  • Development can be estimated by one of the accompanying kinds of estimations:
  • Estimation of growth either by microscopy or by utilizing an electronic molecule counter or by implication by a manual counter.
  • Cell growth in this development can be estimated straightforwardly by gauging or estimating nitrogen concentration in cells or in a roundabout way by the assurance of turbidity utilizing a spectrophotometer.
  • Cell functioning in the growth can be estimated in a roundabout way by investigating the level of biochemical transfer to the size of the populace.

Direct Growth Check

  1.  Electronic cell counters
  2.  Plate Assay
  3.  Turbidity assay
  4.  Determination of nitrogen content
  5.  Determination of dry weight
  6.  Filtration
  7.  Most Probable Number (MPN) Method.


  • Enzymes - produced in the cell growth phase
  • Growth rate - how fast the microbes grow or double their population in a given time phase

 Common Mistakes

  • Growth rate cell cycle- learn by the image given
  • Microbiology of cells- learn differentiating features 

Context and Application

  • Industrial enzyme production
  • Food processing
  • Bachelor and Master of Science microbiology
  • Medical Entrance Exams
  1. Bacterial cell cycle
  2. Enzyme production

Want more help with your biology homework?

We've got you covered with step-by-step solutions to millions of textbook problems, subject matter experts on standby 24/7 when you're stumped, and more.
Check out a sample biology Q&A solution here!

*Response times may vary by subject and question complexity. Median response time is 34 minutes for paid subscribers and may be longer for promotional offers.

Search. Solve. Succeed!

Study smarter access to millions of step-by step textbook solutions, our Q&A library, and AI powered Math Solver. Plus, you get 30 questions to ask an expert each month.

Tagged in


Microbial growth

Microbial culture

Microbial Growth Homework Questions from Fellow Students

Browse our recently answered Microbial Growth homework questions.

Search. Solve. Succeed!

Study smarter access to millions of step-by step textbook solutions, our Q&A library, and AI powered Math Solver. Plus, you get 30 questions to ask an expert each month.

Tagged in


Microbial growth

Microbial culture