Microbial physiology microbial stress response slideshare ppt 29/03/2020 latest ppt

1. MICROBIALSTRESS
RESPONSE
PRAGYA TYAGI
MICROBIOLOGY

2.  Just like human beings, microbes have to deal with continuous stress. However, stress
 for microbes is different from the stress humans are used to-it causes damage to
 macromolecules, membranes, proteins and nucleic acids.
 It can be chemical stress, caused by toxic and harmful compounds, or physical stress.
 For example heat.

3. • A limited supply of nutrients can also be regarded as stress. Microbes have developed stress responses,
to temporarily increase tolerance limits.
• Some stress responses facilitate bacterial transition from a free living organism to a host-invading
pathogen.
• When supplied with sufficient nutrients and optimal growth temperature, pH ,Oxygen levels and solute
concentrations, will grow at a maximum growth rate characteristics for the organisms.
• Variations in these parameters can affect the maximum growth rate and thus, can represent an
environmental stress for the microbe.
• As a result, bacteria live in a constant state of stress.

4. • Cells respond to hypoosmotic environment by sudden rapid cell swelling, but within
minutes, they start to return to their original volume

5. • Osmotic stress-----
• Bacteria experience osmotic stress when the osmotic pressure of their
environment is variable, extremely low, or extremely high.
• Osmotic stress tolerance mechanisms determine whether bacteria survive or
grow because osmotic stress profoundly affects the structure, physics, and
chemistry of bacterial cells.
• Water flows out of cell as their medium become more concentrated and into
cells as their medium becomes more dilute.
• Bacteria attenuates such water fluxes by accumulating and releasing electrolytes
and small organic solutes.

6. Basically Osmotic stress is a sudden change in the solute
concentration around a cell, causing change in the movement of
water across its cell Membrane.
OSMOTIC STRESS
HYPEROSMOTIC HYPOOSMOTIC

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