Bacillus megaterium

Bacillus megaterium is a rod-like, Gram-positive, mainly aerobic spore forming bacterium found in widely diverse habitats. With a cell length of up to 4 µm and a diameter of 1.5 µm, B. megaterium is amongst the biggest known bacteria. The cells often occur in pairs and chains, where the cells are joined together by polysaccharides on the cell walls. In the 1960s, prior to the development of Bacillus subtilis, B. megaterium was the main model organism among Gram-positive bacteria for intensive studies on biochemistry, sporulation and bacteriophages. Recently, its popularity has started increasing in the field of biotechnology for its recombinant protein production capacity. B. megaterium grows at temperatures from 3 °C to 45 °C, with the optimum around 30 °C. Some isolates from an Antarctic geothermal lake were found to grow at temperatures up to 63 °C. B. megaterium has been recognized as an endophyte and is a potential agent for the biocontrol of plant diseases. Nitrogen fixation has been demonstrated in some strains of B. megaterium. B. megaterium has been an important industrial organism for decades. It produces penicillin amidase used to make synthetic penicillin, various amylases used in the baking industry and glucose dehydrogenase used in glucose blood tests. Further, it is used for the production of pyruvate, vitamin B12, drugs with fungicidal and antiviral properties, etc. It produces enzymes for modifying corticosteroids, as well as several amino acid dehydrogenases. B. megaterium is known to produce poly-γ-glutamic acid. The accumulation of the polymer is greatly increased in a saline (2–10% NaCl) environment, in which the polymer comprises largely of L-glutamate (L-isomer content up to 95%). At least one strain of B. megaterium can be considered a halophile, as growth on up to 15% NaCl has been observed. Phylogenetically, based on 16S rRNA, B. megaterium is strongly linked with B. flexus, the latter distinguished from B. megaterium a century ago, but only recently confirmed as a different species. B. megaterium has some phenotypic and phylogenetic similarities with pathogens B. anthracis and B. cereus, although itself being relatively harmless. B. megaterium is ubiquitous in the environment around us. In addition to being a common soil bacterium and an endophyte, it can be found in various foods (including honey, in which most microorganisms do not grow) and on a variety of surfaces, including clinical specimens, leather, paper, stone etc. It has also been isolated from cow feces, emperor moth caterpillars and greater wax moth frass.