13. Characterize anaerobic spiral Gram- bacterium. What features of their morphology and structure of cells. The habitat and representatives.

The genus Anaerobiospirillum , containing the single species Anaerobiospirillum succiniciproducens, was described by Davis et al. in 1976 as a genus of anaerobic spiral bacteria with bipolar tufts of flagella. Later, A. succiniciproducens was implicated as a cause of human bacteremia. In 1983 Anaero- biospirillum-like organisms were isolated from two patients with diarrhea. This led to further studies which demon- strated that both A. succiniciproducens and Anaerobiospirillum- like organisms are part of the normal fecal flora of cats and dogs and that Anaerobiospirillum-like organisms may cause diarrhea in humans. Cell morphology. Spiral cells of both A. succiniciproducens and A. thomasii were usually 0.6 to 0.8 pm in diameter and 3 to 15 pm long, although cells up to 32 pm long were sometimes seen. All strains were negative for catalase activity, oxidase activity, nitrate reduction, and hydrolysis of esculin, hippurate, and urea. Acid was produced fronl galactose, glucose, and maltose but not from cellobiose, mannitol, salicin, sorbitol, and trehalose. Anaerobic bacteria - Bacteria that do not require oxygen for survival. Anaerobic bacteria cannot bear oxygen and may die if kept in an oxygenated environment. Such types of bacteria are usually found in places like, under the surface of the Earth, deep oceans, and bacteria which live in some medium. Most of these microorganisms are oxygen-intolerant fusiform-shaped bacteria. At least one type of these tapered, rod-shaped bacteria can be seen in layers in the epithelial mucin in frozen-section histological preparations of the large bowels of mice. These fusiform-shaped bacteria predominate in the mucin layers. Also, such organisms can be seen in negatively-stained preparations of washings of the colonic mucosal epithelia examined in an electron microscope. At least three types of spiral-shaped organisms, including both spiral-shaped bacteria and spirochetes, can be found in preparations from mice from three of the four colonies. One anaerobic spiral bacterium was isolated in pure culture. This particular organism was found by immunofluorescence to be intermingled with the fusiform-shaped bacteria in the mucin on the mucosal epithelium in the mouse large bowel. Anaerobic bacteria are organisms that cannot grow on a solid surface in the presence of oxygen. They can be divided into those that are strict anaerobes, such as Treponema spp., and the moderate anaerobes such as Bacteroides fragilis . They include both Gram-positive (e.g. Propionibacterium spp.) and Gram-negative (e.g. Bacteroides spp.) organisms and certain spiral bacteria. The family Bacteroidaceae consists of Gram-negative, rod-shaped bacilli with rounded or pointed ends. Some are fusiform. They are non-motile, do not form spores and are strict anaerobes. Within the family are four genera: Bacteroides, Prevotella, Porphyromonas and Fusobacterium. These include the Bacteroides fragilis group, many of which are gastrointestinal tract commensals. The different genera can be classified according to nutritional requirements, pigmentation and morphology. Anaerobic bacteria are microorganisms that thrive in the absence of oxygen; in fact numerous anaerobes cannot survive in the presence of oxygen. Araerobic metabolism typically involves inorganic/organic redox reactions, including anaerobic respiration and fermentation reactions, producing volatile fatty acids and gaseous molecules, such as methane. Anaerobic bacteria are also involved in the digestion process of grazing animals. The change in the morphology of bacterial cells over time gives a representation of their life cycle. Thus many aerobic and anaerobic bacteria form oval and round shining spores. Such types of bacteria are called spore-forming bacteria (or bacilli). The spores are very small in most spore-forming bacteria, and therefore the formation of spores does not alter the rodlike shape of the bacteria. Later on the remains of the vegetative cell disintegrate and the spore is released. The cycle of bacterial development can vary.