Paenibacillus

Paenibacillus is a genus of Gram-positive, rod-shaped, endospore-forming bacteria in the family Paenibacillaceae, order Bacillales. The genus was established in the early 1990s to accommodate Bacillus-like species that are distinct in phylogeny and physiology from the core Bacillus lineage. Members are typically facultatively aerobic or aerotolerant and are widely distributed in soil, water, decaying plant material, and the rhizosphere. Many species are associated with plants and can influence growth and health through nitrogen fixation, phosphate solubilization, production of phytohormones, or antagonism of plant pathogens; several strains are used as biofertilizers or biocontrol agents.

Notable species include Paenibacillus polymyxa, a soil bacterium known for nitrogen fixation and plant growth–promoting traits, and Paenibacillus larvae, a bee pathogen that causes American foulbrood in honeybees. Other members have been isolated from insects, soil, and food, reflecting ecological diversity.

Pathogenic potential in humans is generally low, but Paenibacillus species can act as opportunistic pathogens in immunocompromised individuals and have occasionally been reported in wound infections, bacteremia, and other clinical contexts. Clinical relevance is typically limited compared with major pathogens, but proper biosafety evaluation is advised in medical settings.

Applications and research focus on Paenibacillus include biocontrol of plant diseases, production of enzymes such as proteases and cellulases, and the discovery of antibiotic compounds. Genomic studies reveal diverse metabolic capabilities, including nitrogen fixation in some strains and the synthesis of extracellular enzymes and secondary metabolites relevant to agriculture and industry.