Micrococcus ureæ produces urinal fermentation (transformation of urinal matter into ammonium carbonate); aerobic; round cells generally united to form bent chains or a zooglœa.—Several other kinds of Bacteria have the same action as this one: in damp soil containing ammonia-compounds, saltpetre-formations are produced by M. nitrificans and several different kinds of Bacteria.
Micrococcus prodigiosus is found on articles of food containing starch; “bleeding bread” is caused by this Bacterium, which has the power of forming a red pigment; it also occurs in milk, and produces lactic acid.
Leuconostoc mesenterioides is the frog-spawn Bacterium (Fig. [27]) which is found in sugar manufactories, and has the power of producing a viscous fermentation in saccharine solutions which have been derived from plants, e.g. in beetroot-sugar manufactories, where large accumulations of mucilage are formed at the expense of the sugar, with an evolution of carbonic acid. The cell-rows, resembling somewhat a pearl necklace, have thick mucilaginous cell-walls, and form white “Nostoc”-lumps. The mucilage eventually deliquesces and the cells separate from each other; arthrospores?—Similar viscous deteriorations occur in beer and wine, which may then be drawn out into long, string like filaments—“ropiness.”
Bacterium aceti, the Vinegar-bacterium, oxidizes alcohol into acetic acid (acetous-fermentation) and forms a greyish covering of Bacteria (“Vinegar-mother”) on the surface of the liquid; the acetic acid formed, becomes by continued oxidization by B. aceti, again transformed into carbonic acid and water. Aerobic; short cylindrical cells, often united into chains, or to form a zooglœa; sometimes also rod-and spindle-shaped. The Vinegar-bacteria and other kinds with ball- or rod-forms sometimes become swollen, spindle-shaped, or oval links; they are supposed to be diseased forms[8] (“Involution-forms”).
Bacillus lacticus (Bacterium acidi lactici, Zopf) is always found in milk which has stood for some time, and in sour foods (cabbage, cucumbers, etc.); it turns the milk sour by producing lactic acid fermentation in the sugar contained in the milk; the lactic acid formed, eventually causes the coagulation of the casein. It resembles the Vinegar-bacteria, occurring as small cylindrical cells, rarely in short rows; not self-motile.—Several other Bacteria appear to act in the same way, some occurring in the mouth of human beings; some of these Bacteria give to butter its taste and flavour.
The kefir-grains which are added to milk for the preparation of kefir, contain in large numbers a Bacterium (Dispora caucasica) in the zooglœa-form, a Yeast-fungus, and Bacillus lacticus. Kefir is a somewhat alcoholic sour milk, rich in carbonic acid; it is a beverage manufactured by the inhabitants of the Caucasus, from the milk of cows, goats, or sheep, and is sometimes used as a medicine. In the production of kefir, lactic acid fermentation takes place in one part of the sugar contained in the milk, and alcoholic fermentation in another part, and the casein which had become curdled is partially liquefied (peptonised) by an enzyme of a Zooglœa-bacterium.
Bacillus amylobacter (Bacillus butyricus), the Butyric-acid-bacterium (Fig. [29]), is a very common anaerobic which produces fermentation in sugar and lactic-acid salts, and whose principal product is butyric acid. It destroys articles of food and (together with other species) plays a part in the butyric acid fermentation which is necessary in the making of cheese; it is very active wherever portions of plants are decaying, in destroying the cellulose in the cell-walls of herbaceous plants, and is thus useful in the preparation of flax and hemp. The cells are self-motile, generally cylindrical, sometimes united into short rows; endosporous; the spore-forming cells swell, assume very different forms, and show granulose reaction. The germ-tube grows out in the direction of the long axis of the spore.
Bacillus subtilis, the Hay-bacillus, is developed in all decoctions of hay; a slender, aerobic, self-motile Bacillus; endosporous (aplanospores); the spore-wall ruptures transversely on germination.
Crenothrix kuehniana occurs in the springs of many baths, in wells, in water or drain-pipes.
