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    Salmonella is a gram-negative rod-shaped bacterium. They are motile and non-spore forming. They are facultative anaerobes that can survive in the absence of oxygen. These bacteria grow best at 37ᴼC but the temperature range is 5-45ᴼC. These bacteria grow at 5.5 – 9 pH ranges and grow best at neutral pH.


    Facultative aerobes can survive in the presence of oxygen but can’t grow in the presence of oxygen. They stop their growth if oxygen is present in their surroundings. They have catalase enzyme that catalase the oxygen radicle. They don’t have superoxide dismutase enzymes that break the superoxide radicle and allow bacteria to grow. Their metabolism stops when oxygen is present in the environment.

    These bacteria don’t have catalase, peroxidase and superoxide dismutase enzyme. So, when bacteria grow in the presence of oxygen, many superoxide and peroxide radicals are produced. These radicals are lethal for the bacteria.  These radicals denature the nucleic acid and protein of bacteria. These radicals are toxic to the growth of bacteria. Anaerobic bacteria don’t have catalase and superoxide dismutase enzymes. They used the other electron source than oxygen. They used nitrogen and sulfur as electron acceptor. The oxygen radicals are not present when nitrogen and sulfur are used. Thus, the bacteria survive in the environment.

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