[Morphology, ultrastructure and populational features of bacteria francisella]

The morphology, ultrastructure of cells and the structure of microbial populations of various bacteria of the Francisella genus were estimated by electron microscopy. The strain 503 has been found to produce a bacterial population that is most homogeneous in shape and size. It contains microbes of only round and avoid forms, 0.5-0.6 micron in size. In addition of oval and round microbes there are ellipsoid and rod-shaped ones in the strains 15/3M, A. Cole 120, 117, etc. The largest tularemia microbes are typical of the strain Schu. The bacteria of all strains are covered by a capsule-like coat with well-defined borders. A thick capsule (0.12-0.35 micron) is specific for virulent strains whereas a thin capsular coat (0.06-0.12 micron) is encountered in vaccinal and avirulent microbes. The cells of the strain 503 were also shown to have the thickest envelope. All tularemia microbes have an asymmetric structure in the outer and cytoplasmic membranes due to the location of the bulk of intramembrane particles on their inner hydrophobic surfaces. Some F. tularensis microbes are able to produce keel-like protrusions on the outer membrane. The microbial nucleotide occupies 55-65% of the cytoplasmic volume and forms about 20-30 DNA-membrane contacts. Under unfavourable conditions, the microbes are capable of producing cell envelop protrusions and involutional cells, 0.1-0.3 micron in size.