Manual of bacteriology / by Robert Muir and James Ritchie.

  • Robert Muir
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Manual of bacteriology / by Robert Muir and James Ritchie. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    32/592 (page 8)
    spore formation only occurs at temperatures specially favourable for growth and multiplication. There is often a temperature below which, while vegetative growth still takes places, speculation will not occur, and in the case of B. anthracis, if it be kept at a temperature above the limit at which it grows best, not only are no spores formed, but the species may lose the power of sporulation. Furthermore, in the case of bacteria preferring the presence of oxygen for their growth, an abundant supply of this gas may favour sporulation. It is probable that even among bacteria pre- ferring the absence of oxygen for vegetative growth, the presence of this gas favours sporulation. Most bacterio- logists are, however, of opinion that when a bacterium forms a spore, it only does so when its surroundings, especially its food supply, become unfavourable for vegetative growth; it then remains in this condition until it is placed in more suitable surroundings. Such an occurrence would be analogous to what takes place under similar conditions in many of the protozoa. Often sporulation can be prevented from taking place for an indefinite time if a bacterium is constantly supplied with fresh food (the other conditions of life being equal). The presence of substances excreted by the bacteria themselves plays, however, a more important part in making the surroundings unfavourable than the mere exhaustion of the food supply. A living spore will always develop into a vegetative form if placed in a fresh food supply. With regard to the rapid formation of spores when the conditions are favourable for vegetative growth, it must be borne in mind that in such circumstances the conditions may really very quickly become unfavourable for a continu- ance of growth, for not only will the food supply around the growing bacteria be rapidly exhausted, but the excre- tion of effete and inimical matters will be all the more rapid. We must note that the usually applied tests of a body developed within a bacterium being a spore are (i) its staining reaction, namely, resistance to ordinary staining fluids, but capacity of being stained by the special methods