Ph

Question 1

Define pH.

Answer 1

○pH is a measure of how acidic a solution is, determined by the concentration of hydrogen ions in solution (Willey, et al., 2011, pp.163-181).
○pH is negative logarithm of hydrogen ion concentration (Willey, et al., 2011, pp.163-181).

References: Willey, J.M., Sherwood, L.M., Woolverton, C.J. (2011) Prescott’s Microbiology. 8th edn. New York: McGraw-Hill.

Question 2

Describe the mechanisms microbes use to maintain an internal neutral pH.

Answer 2

○Antiport transport system - exchanges external potassium for internal hydrogen ions (Willey, et al., 2011, pp.163-181).
○Proton-translocating ATPase enzyme - pump hydrogen ions out of cell, used in acidic conditions. (Willey, et al., 2011, pp.163-181)
○Acid shock proteins and heat shock proteins - used when external pH becomes too acidic, below 4.5, proteins prevent proteins from denaturing and refold denatured proteins (Willey, et al., 2011, pp.163-181).

References: Willey, J.M., Sherwood, L.M., Woolverton, C.J. (2011) Prescott’s Microbiology. 8th edn. New York: McGraw-Hill.

Question 3

Define acidophile.

Answer 3

○Acidophiles are microorganisms that have a growth optimum between 0 to 5.5 (Willey, et al., 2011, pp.163-181).

References: Willey, J.M., Sherwood, L.M., Woolverton, C.J. (2011) Prescott’s Microbiology. 8th edn. New York: McGraw-Hill.

Question 4

Define alkaphile.

Answer 4

○Alkaliphiles are microorganisms that have a growth optimum of pH 8.0 to 11.5 (Willey, et al., 2011, pp.163-181).

References: Willey, J.M., Sherwood, L.M., Woolverton, C.J. (2011) Prescott’s Microbiology. 8th edn. New York: McGraw-Hill.

Question 5

Explain how extreme pH values might harm microbes.

Answer 5

○Extreme pH can change cytoplasmic pH of microbes (Willey, et al., 2011, pp.163-181).
○Can cause harmful effects, such as:
could inhibit enzyme and protein activity,
disrupt plasma membrane,
could change the ionisation of nutrient molecules, reducing their availability to organism (Willey, et al., 2011, pp.163-181).
○If cytoplasmic pH decreases below 5.5, microbes could die (Willey, et al., 2011, pp.163-181).

References: Willey, J.M., Sherwood, L.M., Woolverton, C.J. (2011) Prescott’s Microbiology. 8th edn. New York: McGraw-Hill.