Biology 1407 Exam questions and
answers graded A+
1. Why might a biofilm be a good habitat for bacterial cells living in a flowing system? -
ANS✅✅Nutrients are constantly flowing, becoming trapped. The cells do not detach easily.
2. Why form a biofilm - ANS✅✅Aids in cell communication, nutrient trapping, and surface
adherence - all of which act to improve survival, growth, and defense. A biofilm allows cells to
remain in a favorable niche and to live in close association with each other.
3. Know how a biofilm forms (info from paper helps here) - ANS✅✅Expression of biofilm-specific
genes initiate cell attachment to a surface. These genes encode proteins that synthesize intercellular
signaling molecules, initiating matrix formation. The matrix is first initiated by colonization of cells,
leading to growth and polysaccharide formation. It then develops as more growth occurs and more
polysaccharides form. Some bacteria then disperse, to repeat the process again and form another
biofilm elsewhere. 1) Adhesion 2) Slime Excretion 3) Increased Growth 4) Detachment
4. What is quorum sensing - ANS✅✅Intercellular communication crucial to developing and
maintaining the biofilm.
a. Know the Cpx system - ANS✅✅E. Coli uses the cpx system to promote stable cell-surface
interactions. There are 2 components to the cpx system: 1) CpxA, the sensor kinase/phosphatase
(increases biomass). 2) CpxR, the response regulator. (increases stability). When E. Coli interacts with
a hydrophobic surface, the cpx system is turned on. Pili formation is positively regulated via the cpx
system.
b. What happens with change in osmolarity? - ANS✅✅An increase in osmolarity can lead to
biofilm formation, because OmpR gets phosphorylated.
6. Understand soil as a habitat - ANS✅✅Soil is a complex habitat with numerous
microenvironments and niches. Microorganisms in the soil primary attach to soil particles. Surface
soil = H2O limits m/o's. Deep soil = nutrients limit.
7. Which phylum of Bacteria dominates bacterial diversity in vegetated soil? -
ANS✅✅Proteobacteria
, 8. What factors govern the extent and type of microbial activity in soils? - ANS✅✅Water
availability, nutrient sources, oxygen presence, soil type, geographical location
9. What region of soil is the most microbially active? - ANS✅✅Subsurface, because nutrients are
available from the ground water.
10. What is BOD? How do we measure it, what does it tell us? - ANS✅✅Biochemical Oxygen
Demand: a measure of the oxygen-consuming properties of a water sample. Steps: 1) Collect Water
2) Aerate 3) Bottle 4) Incubate 5) Measure O2
11. Will addition of organic matter to water samples increase or decrease its BOD? -
ANS✅✅Increase, because more bacteria use more O2 to consumer organic matter.
12. What factors might account for the prokaryotic diversity of freshwater lakes? -
ANS✅✅Increase in organic matter concentrations, salinity, average temperature, depth, oxygen
conc
13. What are the characteristics of marine bacteria (general)? - ANS✅✅Aerobic anoxygenic
phototroph. No CO2 fixation, light to ATP synthase.
14. What is proteorhodopsin? Why might proteorhodopsin make a bacterium such as Pelagibacter
more competitive in its habitat? - ANS✅✅It is a bacterial rhodopsin that provides some energy to
Pelagibacter, because carbon is limited. It increased the competitiveness in lower nutrient conc's.
15. How does pressure change with depth in a water column? - ANS✅✅Pressure increases the
further down you go. Increase 1 ATM per 10m. (Increased archaea ~ decreased bacteria)
16. What does it mean to be a barophile, barotolerant or extreme barophile. - ANS✅✅Barophile:
Grow best under pressure. Barotolerant: Can grow under elevated pressure, but grow best @ atm
pressures. Extreme barophile: obtained from greatest depths, requires high pressure for growth
17. What molecular adaptations are found in bacteria that allow them to grow optimally under high
pressure? - ANS✅✅Folding is different, decreasing the binding capacity of enzymes. Transport is
also affected because membranes have unsaturated fatty acids. OmpH (porin) is synthesized under
pressure.
answers graded A+
1. Why might a biofilm be a good habitat for bacterial cells living in a flowing system? -
ANS✅✅Nutrients are constantly flowing, becoming trapped. The cells do not detach easily.
2. Why form a biofilm - ANS✅✅Aids in cell communication, nutrient trapping, and surface
adherence - all of which act to improve survival, growth, and defense. A biofilm allows cells to
remain in a favorable niche and to live in close association with each other.
3. Know how a biofilm forms (info from paper helps here) - ANS✅✅Expression of biofilm-specific
genes initiate cell attachment to a surface. These genes encode proteins that synthesize intercellular
signaling molecules, initiating matrix formation. The matrix is first initiated by colonization of cells,
leading to growth and polysaccharide formation. It then develops as more growth occurs and more
polysaccharides form. Some bacteria then disperse, to repeat the process again and form another
biofilm elsewhere. 1) Adhesion 2) Slime Excretion 3) Increased Growth 4) Detachment
4. What is quorum sensing - ANS✅✅Intercellular communication crucial to developing and
maintaining the biofilm.
a. Know the Cpx system - ANS✅✅E. Coli uses the cpx system to promote stable cell-surface
interactions. There are 2 components to the cpx system: 1) CpxA, the sensor kinase/phosphatase
(increases biomass). 2) CpxR, the response regulator. (increases stability). When E. Coli interacts with
a hydrophobic surface, the cpx system is turned on. Pili formation is positively regulated via the cpx
system.
b. What happens with change in osmolarity? - ANS✅✅An increase in osmolarity can lead to
biofilm formation, because OmpR gets phosphorylated.
6. Understand soil as a habitat - ANS✅✅Soil is a complex habitat with numerous
microenvironments and niches. Microorganisms in the soil primary attach to soil particles. Surface
soil = H2O limits m/o's. Deep soil = nutrients limit.
7. Which phylum of Bacteria dominates bacterial diversity in vegetated soil? -
ANS✅✅Proteobacteria
, 8. What factors govern the extent and type of microbial activity in soils? - ANS✅✅Water
availability, nutrient sources, oxygen presence, soil type, geographical location
9. What region of soil is the most microbially active? - ANS✅✅Subsurface, because nutrients are
available from the ground water.
10. What is BOD? How do we measure it, what does it tell us? - ANS✅✅Biochemical Oxygen
Demand: a measure of the oxygen-consuming properties of a water sample. Steps: 1) Collect Water
2) Aerate 3) Bottle 4) Incubate 5) Measure O2
11. Will addition of organic matter to water samples increase or decrease its BOD? -
ANS✅✅Increase, because more bacteria use more O2 to consumer organic matter.
12. What factors might account for the prokaryotic diversity of freshwater lakes? -
ANS✅✅Increase in organic matter concentrations, salinity, average temperature, depth, oxygen
conc
13. What are the characteristics of marine bacteria (general)? - ANS✅✅Aerobic anoxygenic
phototroph. No CO2 fixation, light to ATP synthase.
14. What is proteorhodopsin? Why might proteorhodopsin make a bacterium such as Pelagibacter
more competitive in its habitat? - ANS✅✅It is a bacterial rhodopsin that provides some energy to
Pelagibacter, because carbon is limited. It increased the competitiveness in lower nutrient conc's.
15. How does pressure change with depth in a water column? - ANS✅✅Pressure increases the
further down you go. Increase 1 ATM per 10m. (Increased archaea ~ decreased bacteria)
16. What does it mean to be a barophile, barotolerant or extreme barophile. - ANS✅✅Barophile:
Grow best under pressure. Barotolerant: Can grow under elevated pressure, but grow best @ atm
pressures. Extreme barophile: obtained from greatest depths, requires high pressure for growth
17. What molecular adaptations are found in bacteria that allow them to grow optimally under high
pressure? - ANS✅✅Folding is different, decreasing the binding capacity of enzymes. Transport is
also affected because membranes have unsaturated fatty acids. OmpH (porin) is synthesized under
pressure.
