Microbiology Homework: Bacterial Growth and Oxygen Preferences

This microbiology assignment analyzes the growth patterns of bacteria in five different tubes, each representing a different oxygen environment and bacterial type. The solution explores the behavior of obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, and aerotolerant organisms. It details the metabolic processes occurring in each tube, including glycolysis, aerobic respiration, anaerobic respiration, and fermentation, and explains how these processes are influenced by the presence or absence of oxygen. The assignment also addresses antioxidant activity and the enzymes involved in bacterial survival in various oxygen conditions. The solution references key concepts in microbial metabolism and the specific oxygen requirements of different bacterial groups, providing a comprehensive analysis of bacterial growth in diverse environments.

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For tube 1
The first tube will require an obligate aerobe which requires oxygen since they cannot respire
ferment anaerobically (Pinchuk, 2011). Therefore the bacteria will gather at the top of the tube
because the concentration of oxygen is very high at the top of the tube.
a. Glycolysis
Glycolysis occurs in tube 1 occurs since in tube 1 there is maximum oxygen. And for glycolysis,
the process occurs with or without oxygen to produce 2 Pyruvate molecules, 2 molecules of
ATP, 2 molecules of water and 2 molecules of NADH.
b. Aerobic respiration
The process in the 1st tube is aerobic since aerobic respiration requires only oxygen to
produce cellular energy and as seen above the process in the first tube requires maximum use
of oxygen.
c. Anaerobic respiration
As seen from the description of the process in the first tube, the process requires maximum use
of oxygen while the aerobic process occurs without oxygen. Thus anaerobic respiration cannot
occur
d. Fermentation
Fermentation occurs in this process as the bacteria require oxygen to ferment.
e. Antioxidant Activity
Fermentation will not occur. This is because the anaerobes will lack some enzymes which are
very vital for the bacteria to survive in the oxygen presence.

Tube 2
This tube represents an obligate anaerobe which is poisoned by oxygen, therefore they collect at
the bottom of the tube where the concentration of oxygen is lowest.
a. Glycolysis
Glycolysis can occur in this tube since glycolysis occurs with or without oxygen and in tube 2
there is no oxygen (or very limited oxygen).
b. Aerobic respiration
Aerobic respiration cannot occur in this tube since there is a very limited supply of oxygen.
c. Anaerobic respiration
In this tube, anaerobic respiration occurs since this respiration occurs when there is no or limited
supply of oxygen. And also that is what is witnessed in this tube 2 where the amount of oxygen
is highly limited.
d. Fermentation.
Fermentation does not occur in this tube since fermentation needs oxygen and in this tube, there
is very limited or no supply of oxygen thus fermentation cannot occur.
e. Antioxidant Activity
In this tube there is a very limited supply of oxygen, thus there is no effect of toxic of oxygen.
Tube 3

In this tube, there are Facultative anaerobe grows with or without oxygen since they have the
ability to metabolize energy anaerobically or aerobically. These bacteria gather mostly at the top
of the tube since aerobic produces more ATPs than either anaerobic respiration or fermentation.
a. Glycolysis.
Glycolysis occurs in this tube since glycolysis can occur with or without oxygen which is an
atypical scenario in this tube (Huberts, 2012).
b. Aerobic respiration
Aerobic respiration will occur in this tube since aerobic respiration requires oxygen and also the
process in this tube occurs with or without oxygen.
c. Anaerobic respiration
Anaerobic respiration occurs in this tube since the process in the tube occurs with or without
oxygen and in this respiration there is limited or no oxygen required.
d. Fermentation
Since there are both aerobic and anaerobic fermentation we can say that fermentation will occur
in this tube (anaerobic respiration).
e. Antioxidant Activity
Fermentation will not occur. This is because the anaerobes will lack some enzymes which are
very vital for the bacteria to survive in the oxygen presence.
Tube 4.

In this tube, microaerophiles require oxygen since they cannot respire or ferment anaerobically.
Nevertheless, these bacteria are poisoned by higher oxygen concentrations. They collect mostly
at the top of the tube but not at the topmost part (Hansen, 2012).
a. Glycolysis
In this tube, Glycolysis will occur since in this test tube microaerophiles need oxygen as the
bacteria cannot ferment or respire anaerobically.
b. Aerobic respiration
Anaerobic respiration will occur in this tube since there are oxygen presence in the tube
c. Anaerobic respiration
Anaerobic respiration cannot occur since there is a higher amount of oxygen.
d. Fermentation
Fermentation will occur (aerobic fermentation) since there is oxygen in the tube.
e. Fermentation will not occur. This is because the anaerobes will lack some enzymes which
are very vital for the bacteria to survive in the oxygen presence.
Tube 5
In tube five there are aerotolerant organisms that are able to metabolize energy anaerobically (do
not need oxygen).
a. Glycolysis
Glycolysis will occur since in this tube there is no oxygen and the process of glycolysis can
occur with or without oxygen (Famiani, 2014).

b. Aerobic respiration
This cannot occur since in this tube there is no or limited supply of oxygen
c. Anaerobic respiration
Anaerobic respiration will occur since in this tube there is no oxygen thus suitable for anaerobic
respiration.
d. Fermentation
There will be anaerobic fermentation since there is less or no supply of oxygen in this tube.
e. In this tube there is a very limited supply of oxygen, thus there is no effect of toxic
oxygen.

References
Famiani, F. and Walker, R.P., 2014. Is stored malate the quantitatively most important substrate
utilised by respiration and ethanolic fermentation in grape berry pericarp during ripening?. Plant
physiology and biochemistry, 76, pp.52-57.
Hansen, S. and Büchs, J., 2012. Development of a modified Respiration Activity Monitoring
System for accurate and highly resolved measurement of respiration activity in shake flask
fermentations. Journal of biological engineering, 6(1), p.11.
Huberts, D.H. and Heinemann, M., 2012. A flux-sensing mechanism could regulate the switch
between respiration and fermentation. FEMS yeast research, 12(2), pp.118-128.
Pinchuk, G.E. and Fredrickson, J.K., 2011. Pyruvate and lactate metabolism by Shewanella
oneidensis MR-1 under fermentation, oxygen limitation, and fumarate respiration conditions.
Appl. Environ. Microbiol., 77(23), pp.8234-8240.