liveonearth (liveonearth) wrote,

Microbiology: Food Poisoning and Anthrax Bacilli

One kind of food poisoning and anthrax are caused by bacterium in the genus Bacillus. They are gram positive rods that make spores and have exotoxins. In lecture there was mention of its marshmallowy capsule containing d-glutamate and that being unusual. The capsule and the exotoxin are plasmid encoded, and this organism is also unique in that it has two plamids.

Bacilli are facultative aerobes--meaning they use oxygen as the final electron acceptor in their electron transport chain, and have catalase and superoxide dismutase. But they can grow in the absence of oxygen by fermenting for energy. The two medically important species of Baccilus are cereus and anthrasis.

B. cereus is ubiquitous in the soil and commonly found in low levels in raw, dried and processed foods. It takes four or more hours in food held at the wrong temperature (warm) to grow enough to make you sick. Beware of steam trays! The food poisoning it causes is similar to that caused by Staphylococcus aureus---watery nonbloody diarrhea 6-18 hours after ingesting the poison, or a faster boot out the top end, or both. Bacillus cereus likes growing in cooked white rice.

Bacterial DNA do not contain introns.

B. anthrasis causes three forms of anthrax: cutaneous (95%), inhaled, and gastrointestinal. Cutaneous anthrax begins with a single itchy bump and progresses to black areas of necrotic tissue, swelling lymph nodes. It has a 20% mortality rate if not treated, and treatment is cipro. The inhalation form is known as "wool sorter's disease" because the microbes are most common in grazing animals. This form is the deadly, perhaps because it is so hard to diagnose. The big clue it seems is the xray shows a difference from pneumonia. The problem is not the bacteria but the exotoxin on them. The GI form is very rare, begins with eating undercooked meat, getting D/V and progresses to a systemic infection that kills.

Anthrax toxin is tripartite, meaning his has three proteins. They are known as the protective antigen (PA), edema factor (EF) and lethal factor (LF). EF and LF together make the A part of the A-B subunit configuration. The B part is PA. The protective antigen PA binds the virus to the host cell, and is the part for which the vaccine is made. LF is a protease, it kills a kinase causing cell apoptosis. The EF part contributes to getting inside the cell so that LF can disrupt signalling and kill the cell. I think.

The difference between gram positive and gram negative: gram + stains blue, has a thick peptidoglycan layer, not outer membrane, yes capsule. Gram - stains red, has a think petidoglycan layer, has an outer membrane and more layers.
Tags: anthrax, food poisoning, genetics, microbes, protein, public health, terrorism

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