. Biology. Biology. 36 PROTOPLASM AND THE CELL fluences as well as internal influences produced by the bacteria themselves. The environment is soon changed because of their own physiological activities and multiplication is soon checked. Reproduction is quickly stopped by natural factors like dessi- cation, unsuitable temperature, acid- ity or alkalinity of the medium, but many bacteria have the power to p H resist such adverse conditions by forming internal spores or Dauers- poren (enduring spores). These are FIG. 17.— Spore formation usually spherical, ellipsoidal or oval and germination of
. Biology. Biology. 36 PROTOPLASM AND THE CELL fluences as well as internal influences produced by the bacteria themselves. The environment is soon changed because of their own physiological activities and multiplication is soon checked. Reproduction is quickly stopped by natural factors like dessi- cation, unsuitable temperature, acid- ity or alkalinity of the medium, but many bacteria have the power to p H resist such adverse conditions by forming internal spores or Dauers- poren (enduring spores). These are FIG. 17.— Spore formation usually spherical, ellipsoidal or oval and germination of spores in . bacteria. A, A pair of rods in form and possess a dense envelope. B the hour later; C, one hour later of the chromatin granules and some still; D, a five-celled rod with , /T^. ,—,, three ripe spores which were Cytoplasm (Fig. 17, D). These Spores placed in a nutrient medium possess a much higher resistance to after drying for several days; . ' E, F, the same spores from one external influences than do the cells to three hours later; G, a pair <• v • i ,v r j / of rods in active growth and from whlch they are formed (man7 movement. ^ (From de Bary for example, can withstand a tern- after Sedgwick and Wilson.) 0 N perature of from 70 to 100 C.). One spore per cell is the rule, but in rare instances, two similar spores may be formed. Spore formation in bacteria, therefore, is not always a method of reproduction but maybe an adaptation for the preservation of the organism corresponding to what is known as the " encysted state" of many unicellular animals. Physiology of Bacteria --The food of bacteria is most diverse. The majority are known as saprophytes, that is, they obtain their nourishment from dead organic matter. Many are para- sites, getting their food from other living organisms in the form of complex chemical compounds of protein substance or protein derivatives. Some live in the soil, and get their food supply and their energy from
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