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weapons of brutal little beasties

© Narayan Dattatray Wadadekar

Some bacteria are deadly. They cause human diseases like- anthrax, bacterial dysentery, botulism, cholera, diphtheria, enteritis, gas gangrene, leprosy, leptospirosis, meningitis, the black death or plague, pneumonia, tetanus, tuberculosis, typhoid, trachoma, and a host of sexually transmitted diseases - like chlamydia, gonorrhoea, and syphilis. This list of alphabetically arranged names of the bacterial diseases is not complete. It just gives some idea of what a wide spectrum of diseases the bacteria cause. Most of us know if nothing else, at least the names, of many of these diseases and can imagine, how much people all over the world have suffered or are suffering in terms of pain, misery, energy, money, emotional strain etc.

I must mention here that one single bacterial disease, the tuberculosis, even now - with all our progress in medical sciences, is killing nearly two million people every year all over the world. Another bacterial disease, plague, infamous as the black death, killed nearly 30% of the entire human population of Europe in a brief period of just about 5 years in the 14th century.

Think about the massive scale of destruction and think of the minute size of the disease-producing bacteria.

How such little beasties can bring about such a great havoc? Bacteria act as infectious agents. Their ability to cause diseases is generally the result of toxins they secrete or release. The bacterial toxins can be killing. These poisonous substances are endotoxins and exotoxins. Endotoxins are fatty substances complexed with some carbohydrates, which are at their core. The endotoxins are a part of outer cell wall of the kind of bacteria called, Gram-negative bacteria. All Gram-negative bacteria in their cell walls have endotoxins. Examples of Gram-negative bacteria are - the Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria, Klebsiella, Serratia, Legionella, and Haemophilus. Endotoxins come out of bacterial cells when the bacteria disintegrate. Endotoxins are generally much less pathogenic, than exotoxins, cause fevers but rarely cause death.

The bacteria may disintegrate on their own or because of hostile enzymes or cells of the host or antibiotic's action. Bacterial cells broken open release endotoxins. On the other hand exotoxins are proteins in nature. They are soluble in water and diffuse out of bacterial cells. The exotoxins are not components intimately associated with any bacterial membrane. The exotoxins never produce a fever and are of three different types - (a) cytotoxins that destroy host cells e.g. alpha-toxin of Clostridium perfringens, (b) neurotoxins like the toxins of Clostridium tetani / botulinum and (c) enterotoxins (Exotoxin secreted in intestines) which affect cells lining the gut, example - enterotoxins of some Staphylococci.

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