bacte'rium, pi. bacteria

[G. bakterion, dim. of bakiron, a staff.] Any unicellular vegetable microorganism, microphyte, especially one of the schizomycetes or fi ion fungi, endoter'ic b., one which forms an endotoxin, exoter'ic b., a b. which secretes an exotoxin, ni'trifying b., a microorganism which oxidizes ammonia to nitrous or nitric acid, or draws the nitrogen from the air and fixes it in the soil where it can be appropriated by growing plants, pole b., a rod-shaped form which stains deeply at each extremity, found in certain cases of whooping-cough called also Czaplewski's bacillus, rod b., bacillus, one of the Bacteriacece. round b., coccus, one of the CoccacecB. spi'ral b., spirillum, one of the Spirit lace a. sul'phur b., a microorganism found in sulphur water, usually one of the Beggiatoa; these bacteria are frequently colored, owing to the presence of bacteriopurpurin. difficulties, owing to their minute size, their simple structure, and the present impo ibility of differentiating some of their forms, especially the Spirillacem, from protozoan organisms. The following cla ification, the one most generally accepted, is that of Migula, proposed in 1897. The families are denoted by black type, the genera by italics. Coccaceae. Spherical forms, with division in one to BacteriaceEB. Elongated straight cells, dividing in Spirillacefe. Cells forming spirals or parts of spirals,