In: Biology
5. The bacterium Salmonella typhimurium is a facultative aerobe. a. Explain what this means in terms of its growth requirements. b. If you could mutate just one gene in the genome to convert it to a strict anaerobe, which protein would you eliminate? There is more than one correct answer, so please explain why.
a. A facultative aerobe organism can grow without oxygen but will grow in a rapid rate in resence of oxygen. When oxygen is present , the facultative aerobe produce energy through aerobic respiration whereas in absence of oxygen they depend on fermentation for energy production.
b. When oxygen is taken up, it will form a small amount of hydrogen peroxide (H2O2) and superoxide radicals. These two compunds are very toxic to cells But, aerobic bacteria have the enzymes like superoxide dismutase (SODM) or catalase to metabolize these compounds. Superoxide dismutase will convert superoxide to hydrogen peroxide and oxygen. Whereas, catalase further will convert hydrogen peroxide to oxygen and water. So they are not toxic anymore. But an stric anaerobic bacteria lacks these enzymes and as a result oxygen is toxic to them and they can not grow if oxygen is present. Thus to convert a facultative aerobe to strict anaerobe I will mutate the gene which is responsible for the protein superoxide dismutase. The gene is SOD1 and if its mutated in the genome of Salmonella typhimurium, it will be unable to catalyze superoxide radicle and can not grow anymore with the presence of oxygen.