EVERYDAY SCIENCE

Detailed explanation-1: -Facultative anaerobes are bacteria that can grow in both the presence or absence of oxygen. In addition to oxygen concentration, the oxygen reduction potential of the growth medium influences bacterial growth.

Detailed explanation-2: -The most common examples of the facultative anaerobes are bacteria (e.g., Escherichia coli, Pseudomonas aeruginosa, Staphylococcus spp., Listeria spp., Salmonella, Shewanella oneidensis, and Yersinia pestis), Archaea, certain eukaryotes (e.g., Saccharomyces cerevisiae) and invertebrates, like nereid and polychaetes.

Detailed explanation-3: -Facultative anaerobes gather mostly at the top because aerobic respiration generates more ATP. Aerotolerant organisms can be found evenly spread throughout the test tube. Microaerophiles gather in the upper part of the test tube, but not the very top. Obligate aerobes survive and grow with oxygen.

Detailed explanation-4: -These are bacteria that, under normal circumstances, breathe anaerobically but can breathe aerobically when oxygen is available.

Detailed explanation-5: -Example of anaerobic bacteria: Escherichia coli: The rod-shaped, gram-negative bacteria, are found in the intestines of humans and the gut of some animals. It is a facultative anaerobe (that can grow in the presence and absence of oxygen).