bio 207 lecture 4: environmental influences and control of microbial growth

extremophile

any organism that lives outside of our “normal” human range of reference

• temperature

• ph

• osmolarity

• oxygen

• pressure

what determines the ability for and rate of growth?

• nutrients available

• physical parameters

• chemical and biological control agents

stress response

response to unfavorable conditions

adaptation

changes that arose through evolution and allowed organism to thrive under “extreme” conditions

what are the “normal” growth conditions?

• sea level pressure

• temperature of 20 - 40 degrees C

• ph- near neutral

• salt concentration: 0.9%

• ample nutrients

the earliest microbes likely grew in

extreme conditions

thermophile

survives in extremely high temperatures (hyperthermophile lives in even more extreme temperatures)

alkaliphile

lives in high pH above 9

neutralophile

lives between pH 5 and 8

acidophile

lives in pH below 3

halophile

lives in high salt environments

barophile

live in high pressure

facultative microbe

can survive in both presence and absence of oxygen

relative to external environment, what are the factors microbes can and cannot control?

can:

• pH, osmolarity, oxygen inside cell

cannot:

• temperature (matches the environment)

• pressure

• cell membrane composition (fluidity)

• protein sequences (more vs. less flexible)

classifications for microbial optimal growth temperature

• psychrophiles (below 15)

• mesophiles (15-45)

• thermophiles (50-80)

• hyperthermophiles (80+)

when the environment’s temperature is too high,

• cellular function quickly degrades, proteins denature, membrane fails, DNA/RNA not stable

• cells may die

• membrane will want to become more rigid with more saturated fatty acids, rigid proteins, monolayer

when the environment’s temperature is too low,

• may affect membrane fluidity, nutrient transport, DNA/RNA stability, enzyme structure and function

• cells want to include more unsaturated fatty acids

• more flexible proteins for growth and insertion of transport/functioning proteins

• inclusion of more glycine residues, addition of antifreeze proteins

microbes that grow at higher temperatures typically achieve

higher rates of growth

barophilic vs barotolerant

• barophilic: need high pressures to survive

• barotolerant: can withstand high pressure

increased pressure and cold temperatures, like at the bottom of the ocean,

reduce membrane fluidity

water activity

measure of how much water is available for use; becomes lower when solutes increases

osmolarity

measure of the number of solute molecules in a solution, inversely related to water activity; increasing solutes could help preserve food