Priestia megaterium

Priestia megaterium (Bacillus megaterium prior to 2020) is a rod-like, Gram-positive, mainly aerobic, spore forming bacterium found in widely diverse habitats. It has cells of roughly 1.5 μm by 4 μm (up to about 2.5 μm by 10 μm in some reports), which is quite large for bacteria and 100 times larger than Escherichia coli. The cells often occur in pairs and chains, where the cells are joined by polysaccharides on the cell walls.

Before the rise of Bacillus subtilis as the dominant Gram-positive model organism, P. megaterium was widely used for studies on biochemistry, sporulation, and bacteriophages. Recently, its popularity has started increasing in the field of biotechnology for its recombinant protein-production capacity.

Characteristics

P. megaterium grows at temperatures from 3 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. 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 P. megaterium. It is used as a plant-growth-promoting rhizobacterium (PGPR) and biocontrol agent, which can reduce reliance on synthetic fertilizers and pesticides, and it contributes to phosphate solubilization and to microbially induced calcium carbonate precipitation (MICP), the latter being explored for applications such as self-healing concrete.

P. megaterium has been an important industrial organism for decades. It has been used to produce enzymes such as amylases used in the baking industry, glucose dehydrogenase used in glucose blood tests, enzymes for modifying corticosteroids, and several amino acid dehydrogenases.