Morphology of fusobacteria and features of their metabolism
The structure of fusobacteria is unicellular, in the form of a rod similar to spindle (in Latin fusus) - because of the sharp points on both sides. The rods can be thick and thin, straight and curved, and a threadlike shape can also occur. The length of these bacteria varies from 0.0005 to 0.008 mm, there are no organs of movement, although in some sources it is claimed that they have peritricchial (located on the entire surface) flagella.
Bacteriologists note that these microorganisms do not form a dispute, that is, in the case of deteriorating conditions of life, they can not turn into cells with a dense shell. Reproduction of fusobacteria occurs by mitotic cleavage of one cell into two with horizontal transfer of genes concentrated in the nucleoid.
The morphology of fusobacteria partly determines the habitats of their colonies: the mucous membranes of the mouth, respiratory tract, urogenital area and the lower part of the digestive tract - the large intestine. In the blood, their presence is not established, yes it is fusobacteria and to no avail, because the nutrients they receive by the oil fermentation of glucose, sucrose, maltose and some amino acids.
So in the basis of the metabolism of these microorganisms is the biochemical process of anaerobic (without oxygen) dissimilation of carbohydrates under the influence of enzymes. Metabolites are low molecular weight butane acid, carbon dioxide and hydrogen. To get the energy of the bacteria, hydrogen is needed, and its ions take the surface protein fuzobaktery Adhesin A (FadA), and then moves them inside the cell.
By the way, butyric acid is very important for maintaining intestinal homeostasis (absorption of water and electrolytes) and for the regeneration of cells of the mucosal epithelium; physicians have established a relationship between the lack of this acid in the intestine and the development of local inflammatory pathologies (for example, ulcerative colitis). In addition to fusobacteria, oleic acid is produced by bacteria of the genus Clostridium.
On the conditional pathogenicity of fusobacteria
Fusobacteria, like most gram-negative anaerobes, are considered bacteriologically opportunistic, but there are strains in which scientists no longer doubt the increased pathogenicity. In particular, it is found in the oral cavity and intestines of Fusobacterium necrophorum, as well as Fusobacterium nucleatum, which has chosen dental plaque for habitation.
How does their pathogenic mechanism work? The outer surface of the cytoplasmic membrane of fusobacteria consists of polymerized fats, proteins and carbohydrates in the form of lipopolysaccharides, which are bacterial toxic substances (endotoxins) and, simultaneously, antigens. That is, these compounds cause an immune response of the body and an inflammatory response without an obvious exogenous (external) effect on individual systems and organs.
There is an opinion that the pathogenicity of some bacteria of the family Fusobacteriaceae is manifested only in case of weakening of immunity, however, it should be taken into account that they have been shown to have the ability to increase aggressiveness, since fusobacteria produce phospholipase A, an enzyme that breaks down the lipids of cell membranes and opens up access of bacteria to the cells of all tissues. But "single-handedly" this enzyme microorganisms, as a rule, do not use, but in the presence of pathogenic microorganisms activity is significantly increased. In case of damage to the mucous streptococcus or Staphylococcus fusobacterium, taking advantage of the case, penetrate deeper and cause necrotic inflammation of the tissues. The most illustrative example of such synergistic action is gangrenous pharyngitis (or Simanovsky-Plaut-Vincent's angina), which arises from infection of the mucous membrane with gram-negative bacteria Spirochaetales Borrelia vincentii, Prevotella intermedia and Fusobacterium nucleatum.