growth, nutrition and reproduction of bacteria

7/28/2019 Growth, Nutrition and Reproduction of Bacteria

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Medical microbiology

1.Bacterial growth

2.Bacterial nutrition

3.Bacterial reproduction


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Bacteria Divide and Multiply

Bacteria are all around us. Given good growing conditions,a bacterium grows slightly in size or length, a new cellwall grows through the center forming two daughtercells, each with the same genetic material as the parent

cell. If the environment is optimum, the two daughtercells may divide into four in 20 minutes. Oh my! 1, 2, 4, 8,16, 32, 64... Then why isn't the earth covered withbacteria

The primary reason may be that conditions are rarelyoptimum. Scientists who study bacteria try to create theoptimum environment in the lab: culture medium with thenecessary energy source, nutrients, pH, and temperature,in which bacteria grow predictably.


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LAG PHASE :Growth is slow at first, while the "bugs" acclimate to the food

and nutrients in their new habitat.

LOG PHASE :Once the metabolic machinery is running, they startmultiplying exponentially, doubling in number every few minutes.

STATIONARY PHASE :As more and more bugs are competing for dwindling

food and nutrients, booming growth stops and the number of bacteria

stabilizes.

DEATH PHASE :Toxic waste products build up, food is depleted and thebugs begin to die.


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Bacterial growth

In bacteriology, Bacterial growth has four

different phases: lag phase (A), exponential orlog phase (B), stationary phase (C), and death

phase (D).

Growth is shown as L(log numbers) = colony forming units per

ml, over T(time)


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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.At exponential phase, bacteria are reproducing at their

maximum rate; therefore, their number increases during this

phase. It is a period ofexponential growth.

3.During stationary phase, the growth rate slows due to

depletion of nutrients. 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.

Bacterial growth can be suppressed with bacteriostats, without

necessarily killing the bacteria


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OXYGEN REQUIREMENTS & CULTURING ANAEROBIC BACTERIA

anaerobe ,aerobe, facultative anaerobe, microaerophilic


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Bacteria ReproductionBacteria Reproduction

nn Binary FissionBinary Fission

nn

ConjugationConjugationnn Spore FormationSpore Formation


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Cellular organism copies its genetic information then splits into

two identical daughter cells


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nn A type of Bacteria SexA type of Bacteria Sex

nn Two organism swapTwo organism swap

genetic information,genetic information,that contains thethat contains theinformation such as ainformation such as aresistance to penicillinresistance to penicillin

ConjugationConjugation


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Spore Formation: EndosporeSpore Formation: Endosporenn A type of dormant cellA type of dormant cellnn Exhibit no signs of lifeExhibit no signs of lifenn Highly resistant toHighly resistant to

environmental stresses such as:environmental stresses such as:--High temperaturesHigh temperatures--IrradiationIrradiation--Strong acidsStrong acids--DisinfectantsDisinfectants

nn Endospores are formed byEndospores are formed byvegetative cells in response tovegetative cells in response toenvironmental signals thatenvironmental signals that

indicate a limiting factor forindicate a limiting factor forvegetative growth, such asvegetative growth, such asexhaustion of an essentialexhaustion of an essentialnutrient.nutrient.

growth, nutrition and reproduction of bacteria

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