Review
25.1 Some groups of bacteria can be distinguished based on the Gram stain.
25.3 Prokaryotes differ with respect to oxygen metabolism.
25.3 Prokaryotes play important roles in nitrogen cycling.
Bacteria are increasingly used for a variety of purposes that range from treating medical conditions to mitigating toxic waste spills. Determining which bacterial species would be appropriate for a particular purpose requires the application of knowledge of the diverse phenotypic characteristics of these bacteria.
The table below lists the characteristics of four bacteria, Clostridium novyi, Thermus aquaticus, Paracoccus denitrificans, and Trichodesmium thiebautii. Use this information to address the questions that follow.
| C. novyi | T. aquaticus | P. denitrificans | T. thiebautii | |
|---|---|---|---|---|
| Metabolism | Obligate anaerobic |
Obligate aerobic |
Facultative anaerobic |
Facultative anaerobic |
| Gram status | Positive | Negative | Negative | Negative |
| Optimal temperature (°C) |
10°–40° | 50°–80° | 5°–30° | 10°–30° |
| Typical habitat | Terrestrial | Aquatic | Aquatic | Aquatic |
| Miscellaneous | Chemotroph | Denitrifier | Nitrogen fixer |
Questions
The concentration of nitrates in a sample of municipal sewage water is well above acceptable levels. Which of these bacteria would be expected to be most appropriate for reducing nitrate concentrations? Explain your answer.
As a denitrifier, Paracoccus denitrificans would be most appropriate to reduce nitrate concentrations. Its thermal range would also be appropriate under most environmental conditions.
Because tumors often grow much faster than they can acquire blood supply, cancerous tumors can have large regions where oxygen concentrations are very low. These hypoxic conditions are generally not found elsewhere in the body. Biomedical researchers can take advantage of this unusual property to inject bacteria that would specifically target the tumor cells and have as little effect on the rest of the body as possible. Based on the information in the table, which bacterium would be expected to be most appropriate for this application? Explain your answer.
As an obligate anaerobe, Clostridium novyi would be appropriate to use in hypoxic conditions. Its thermal range is also suitable for mammalian body temperatures.
Adding small amounts of ammonium increased the productivity of an aquatic ecosystem, but the effect was short-
Trichodesmium thiebautii. Because the addition of ammonium temporarily increased the productivity of the ecosystem, one can infer that the ecosystem is nitrogen-
The antibiotic vancomycin inhibits peptidoglycan synthesis in bacteria that have a thick cell wall with much peptidoglycan. Which bacterium would most likely be sensitive to this antibiotic? Explain your answer.
Clostridium novyi. Vancomycin targets bacteria with thick peptidoglycan-