Microbes and the environment

Question 1

how do foods/products control the amount of microbial growth to preserve them

Answer 1

1. addition of acid - pickling
2. in situ fermentation by microbes

Question 2

what are the names of organisms with extreme pH

Answer 2

1. acidophiles
2. alkaliphiles

Question 3

how do acidophiles (require a low pH externally) maintain pH homeostasis inside the cell (neutral pH), the mechanism

Answer 3

1. active proton H+ pumping (out)
2. increase cation conc. inside cell creating + membrane potential (repelling protons)
3. make membrane less permeable to protons
4. reduce size/number of membrane channels (porins)

Question 4

how do alkaliphiles (require a high pH externally) maintain pH homeostasis inside the cell (neutral pH), the mechanism

Answer 4

1. activation of symporter system (uptake of Na+)
2. activation of antiporter system (uptake of H+)