13. Characterize sliding bacteria. What features of their morphology and structure of cells. The habitat and representatives.

Sliding (Moving) bacteria - representatives of different taxonomic groups - the lack of flagella and when moving over the surface of the solid medium leaves a slimy trail. The speed of movement of cells may be from 2 to 60 um / min and younger age cells more flexible. Actively moving cells have advantages over fixed: they can move on the surface of a solid substrate, thus are able to use such complex insoluble compounds such as chitin and cellulose, and the ability to help move the sliding movement of the solid substrate (soil, rainfall, and small channels in rotting wood) to select the optimum position on gradients oxygen, light, hydrogen sulfide, temperature and other factors. Sliding movement varies in speed and gear. Beggiatoa, cyanobacteria and some other bacteria in the sliding motion of rotating around the long axis of the cell. Many cells are bent or twitch when sliding. Such differences in the movement may reflect the existence of different mechanisms of sliding. Although the sliding cell secretes mucus, are not she pushes cells. Mucus is rather necessary to wet the surface to improve slip. They are observed in large numbers on the surface of the sludge, where they are in the way of movement of interstitial water between the particles is most comfortable. Despite their abundance and diversity, only a few members of this important group of bacteria known. Moving bacteria forming fruiting bodies - are strict aerobes hemoorganotrophs and without flagella which can slide on a hard surface. When exhaustion of nutrients cells aggregate and form fruiting bodies consisting of modified and mucus cells are often brightly colored and having macroscopic dimensions. Fruiting bodies vary in size and complexity of the structure. Inside the fruiting bodies are formed miksospores or microcysts. Gram-negative bacteria (gracilicutes, bacteria of aquatic origin) were adapted to life in biotopes with constant osmotic pressure such as sea-water, freshwater, or animal fluids. Division Gracilicutes. Gram-negative cell wall. Non-endospore-forming. Includes photosynthetic and nonphotosynthetic types; can exhibit swimming or gliding motility; includes rods, cocci, and curved forms. Class Scotobacteria Nonphotosynthetic gram-negative bacteria. Order Spirochaetales. Spiral cells that swim by flexion; found in water and in the bodies of vertebrates; genera include Borrelia, Treponema, and Leptospira, all parasites of humans and other animals. Order Pseudomonadales. Rigid-walled cells of variable shape, in some species forming chains; photosynthetic pigment present in certain species; cells usually motile by means of a single flagellum. Species in soil and in fresh water and salt water. Examples of genera: Vibrio ( cholera bacteria), Pseudomonas, Nitrosomonas, Thiobacillus.