Bacillus megaterium
Bacillus megaterium is a rod-like, Gram-positive, mainly aerobic spore forming bacterium found in widely diverse habitats.[1][2] With a cell length of up to 4 µm and a diameter of 1.5 µm, B. megaterium is amongst the biggest known bacteria.[3] The cells often occur in pairs and chains,[1] where the cells are joined together by polysaccharides on the cell walls[citation needed].
In the 1960s, prior to the utilization of Bacillus subtilis for this purpose, 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.[3]
This species has been recently transferred into the genus Priestia.[4] The correct nomenclature is Priestia megaterium.
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.[1] It 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.[1]
Bacillus megaterium has been an important industrial organism for decades. It produces penicillin amidase used to make synthetic penicillin and several enzymes, like amylases used in the baking industry and glucose dehydrogenase used in glucose blood tests. It also produces enzymes for modifying corticosteroids, as well as several amino acid dehydrogenases. Further, it is used for the production of pyruvate, vitamin B12 and molecules with fungicidal and antiviral properties.[2] Several of these bioactive compounds are cyclic lipopeptides, belonging to the surfactin, iturin and fengycin lipopeptide families, which are also produced by several other Bacillus species.[5]
Bacillus 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%).[6] At least one strain of B. megaterium can be considered a halophile, as growth on up to 15% NaCl has been observed.[7]
