Question

Influence of environmental factors on growth of microbes: osmotic pressure, pH, temperature, oxygen, pressure, radiation—what are the key evolutionary adaptations that microbes have made to thrive in these extreme environments (give specific, complete examples)

Answer 1

Osmotic pressure: Microbes have internal mechanisms for maintaining osmotic pressure. If cells are kept in hypotonic solution swelling of cells occur. Due to increased pressure plasma membrane is stretched and mechanosensitive channel, located on plasma membrane,opens and allow solutes to leave from cell and lower osmotic pressure.

If cells kept in hypertonic solution water relesed from cell & dehydration occurs. So they used to take high concentration of potassium and chloride ions to maintain balance. E.g. Halophytes survive in high NaCl concentration.

P^H: Mostly microbes are neutrophils (p^H5.5-8),e.g E.Coli . Some are acidophyle (<5.5):e.g-Heliobacter pylori. Others are alkilophyle( 8- 11.5) e.g. Bacillus alcalophilus

Oxygen: Microbes use oxygen as final acceptor for aerobic respirayion.

Obligate aerobic: need at least 20% atmospheic oxygen to survive. E.g. Myobacterium tuberculosis.

Fecultative anaerobic: Preferably aerobic but can survive at anaerobic condition by switching their metabolism. They are versetile. E.g. E.coli

Microaerophilic - Need oxygen at very low amount (2%-10%) e.g. Nitrosomonous , Campylobacter : soil bacteria

Aerotolerant anaerobic : Survive either oxygen present or not. E.g Streptococcus pyrogenes.

Obligate anaerobic : can't survive if oxygen present. E.g -Methanobacter.

Pressure : most of microbes live in land or water surface. Some barophile bacteria also present,lives in bottom of ocean with 6000-10000 atm hydrostatic pressure. E.g Halomonas salaria

Radiation: UV rays causes DNA damage introducing thymidine dimer. Microbes have photolyase enzyme which absorb blue light and break the dimer so T =A occurs. E.g. After high dosing of radiation Deinococcus radiodurans is capable of reassembling their DNA.

Temparature: