. The chemical activities of bacteria. Bacteria. 200 pathogenicity; chemotherapy Formula of Streptomycin OH H MH — CZ /^\ HOCH HCOH I u HOCH C NH HO A O H L/CH^OH \|. (Streptidine) N- methyl-L-glucosamine 3. Toxic peptides secreted by bacteria: B. brevis is a spore-bearing soil organism which secretes an antibacterial substance, called tyrothricin. This is a mixture of peptides, the most important being Tyrocidin and Gramicidin. Tyro- cidin is a surface-active substance which kills both Gram- negative and Gram-positive bacteria by dissolving lipoid materials in their cell-walls. Gramicidin is
. The chemical activities of bacteria. Bacteria. 200 pathogenicity; chemotherapy Formula of Streptomycin OH H MH — CZ /^\ HOCH HCOH I u HOCH C NH HO A O H L/CH^OH \|. (Streptidine) N- methyl-L-glucosamine 3. Toxic peptides secreted by bacteria: B. brevis is a spore-bearing soil organism which secretes an antibacterial substance, called tyrothricin. This is a mixture of peptides, the most important being Tyrocidin and Gramicidin. Tyro- cidin is a surface-active substance which kills both Gram- negative and Gram-positive bacteria by dissolving lipoid materials in their cell-walls. Gramicidin is much less toxic and is bacteriostatic towards Gram-positive bacteria; it is thought to act by interfering with the assimilation and meta- boHsm of phosphate. Both tyrocidin and gramicidin are too toxic for general clinical application, although purified grami- cidin can be used locally in wounds. These two peptides proved to be the forerunners of a series of similar substances produced by bacteria, especially those of the genus Bacillus. Of recent years, antibiotics called Polymyxin, Aerosporin, Bacitracin, Subtilin, Bacillin, etc. have been described. They all seem to be polypeptide in nature and contain some un- natural D-amino-acid residues. Some are known to be cyclic polypeptides. They are stable substances and vary consider- ably in their antibacterial properties: bacitracin has a range of activities very similar to that of penicillin, while polymyxin is effective against organisms of the Gram-negative group which are comparatively resistant to penicillin. The clinical. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gale, E. F. (Ernest Frederick). New York, Academic Press
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