Bacterial growth

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Growth is shown as L = log(numbers) where numbers is the number of colony forming units per ml, versus T (time.)

Bacterial growth is process in which two clone daughter cells are produced by the cell division of one bacterium. Hence, local doubling of the bacterial population occurs. Both daughter cells from the division do not necessarily survive. However, if the number surviving exceeds unity on average, the bacterial population undergoes exponential growth. The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry), direct and bulk (biomass), indirect and individual (colony counting), or indirect and bulk (most probable number, turbidity, nutrient uptake) methods. Models reconcile theory with the measurements [1].

In autecological studies, bacterial growth in batch culture can be modeled with four different phases: lag phase (A), exponential or log phase (B), stationary phase (C), and death phase (D).

  1. During lag phase, bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide.
  2. During the exponential phase, the number of new bacteria appearing per unit time is proportional to the present population. This gives rise to the classic exponential growth curve, in which the logarithm of the population density rises linearly with time (see figure). The actual rate of this growth (i.e. the slope of the line in the figure) depends upon the growth conditions, which affect the frequency of cell division events and the probability of both daughter cells surviving. Exponential growth cannot continue indefinitely, however, because the medium is soon depleted of nutrients and enriched with wastes.
  3. During stationary phase, the growth rate slows as a result of nutrient depletion and accumulation of toxic products. This phase is reached as the bacteria begin to exhaust the resources that are available to them.
  4. At death phase bacteria run out of nutrients and die.

This basic batch culture growth model draws out and emphasizes aspects of bacterial growth which may differ from the growth of macrofauna. It emphasizes clonality, asexual binary division, the short development time relative to replication itself, the seemingly low death rate, the need to move from a dormant state to a reproductive state or to condition the media, and finally, the tendency of lab adapted strains to exhaust their nutrients.

Batch culture is the most common laboratory growth environment in which bacterial growth is studied, but it is only one of many. It is ideally spatially unstructured and temporally structured. Bacteria are presented with a single burst of nutrients and left to their own devices. In some experimental regimes, they are periodically removed to a new batch of nutrients. In the extreme case, this leads to the continual renewal of the nutrients. This is a chemostat aka continuous culture. It is ideally spatially unstructured and temporally unstructured, in an equilibrium state defined by the nutrient supply rate and the reaction of the bacteria. Related devices include turbidostats and auxostats.

Liquid is not the only laboratory environment for bacterial growth. Spatially structured environments such as biofilms or agar surfaces present additional complex growth models.


In reality, even in batch culture, the four phases are not well defined. The cells do not reproduce in synchrony without explicit and continual prompting (as in experiments with stalked bacteria ) and their logarithmic phase growth is often not ever a constant rate, but instead a slowly decaying rate, a constant stochastic response to pressures both to reproduce and to go dormant in the face of declining nutrient concentrations and increasing waste concentrations.

Bacterial growth can be suppressed with bacteriostats, without necessarily killing the bacteria. In a synecological, a true-to-nature situation, where more than one bacterial species is present, the growth of microbes is more dynamic and continual.

References

  1. Zwietering M H, Jongenburger I, Rombouts F M, van 'T Riet K (1990). "Modeling of the Bacterial Growth Curve". Applied and Environmental Microbiology. 56 (6): 1875–1881.

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==This article includes material from an article posted on 26 April 2003 on Nupedia; written by Nagina Parmar; reviewed and approved by the Biology group; editor, Gaytha Langlois; lead reviewer, Gaytha Langlois ; lead copyeditors, Ruth Ifcher. and Jan Hogle.

Cost Effectiveness of Bacterial growth

| group5 = Clinical Trials Involving Bacterial growth | list5 = Ongoing Trials on Bacterial growth at Clinical Trials.govTrial results on Bacterial growthClinical Trials on Bacterial growth at Google


| group6 = Guidelines / Policies / Government Resources (FDA/CDC) Regarding Bacterial growth | list6 = US National Guidelines Clearinghouse on Bacterial growthNICE Guidance on Bacterial growthNHS PRODIGY GuidanceFDA on Bacterial growthCDC on Bacterial growth


| group7 = Textbook Information on Bacterial growth | list7 = Books and Textbook Information on Bacterial growth


| group8 = Pharmacology Resources on Bacterial growth | list8 = AND (Dose)}} Dosing of Bacterial growthAND (drug interactions)}} Drug interactions with Bacterial growthAND (side effects)}} Side effects of Bacterial growthAND (Allergy)}} Allergic reactions to Bacterial growthAND (overdose)}} Overdose information on Bacterial growthAND (carcinogenicity)}} Carcinogenicity information on Bacterial growthAND (pregnancy)}} Bacterial growth in pregnancyAND (pharmacokinetics)}} Pharmacokinetics of Bacterial growth


| group9 = Genetics, Pharmacogenomics, and Proteinomics of Bacterial growth | list9 = AND (pharmacogenomics)}} Genetics of Bacterial growthAND (pharmacogenomics)}} Pharmacogenomics of Bacterial growthAND (proteomics)}} Proteomics of Bacterial growth


| group10 = Newstories on Bacterial growth | list10 = Bacterial growth in the newsBe alerted to news on Bacterial growthNews trends on Bacterial growth


| group11 = Commentary on Bacterial growth | list11 = Blogs on Bacterial growth

| group12 = Patient Resources on Bacterial growth | list12 = Patient resources on Bacterial growthDiscussion groups on Bacterial growthPatient Handouts on Bacterial growthDirections to Hospitals Treating Bacterial growthRisk calculators and risk factors for Bacterial growth


| group13 = Healthcare Provider Resources on Bacterial growth | list13 = Symptoms of Bacterial growthCauses & Risk Factors for Bacterial growthDiagnostic studies for Bacterial growthTreatment of Bacterial growth

| group14 = Continuing Medical Education (CME) Programs on Bacterial growth | list14 = CME Programs on Bacterial growth

| group15 = International Resources on Bacterial growth | list15 = Bacterial growth en EspanolBacterial growth en Francais

| group16 = Business Resources on Bacterial growth | list16 = Bacterial growth in the MarketplacePatents on Bacterial growth

| group17 = Informatics Resources on Bacterial growth | list17 = List of terms related to Bacterial growth


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