Bacillus safensis APC 4099 has broad-spectrum antimicrobial activity against both bacteria and fungi and produces several antimicrobial peptides, including the novel circular bacteriocin safencin E.

Bacillus safensis APC 4099, isolated from bees' gut, has been identified as a promising candidate for food biopreservation. Antimicrobial activity screening revealed a broad-spectrum inhibition potential, ranging from gram-positive pathogenic bacteria to fungi responsible for food spoilage. Genomic analysis identified biosynthetic gene clusters coding for several antimicrobial peptides and secondary metabolites. Specifically, a novel, anionic, 6 kDa circular bacteriocin, named safencin E, was detected, showing 52.5% similarity to butyrivibriocin AR10. Additionally, gene clusters coding for the biosynthesis of bacteriocins such as pumilarin and plantazolicin and biosynthetic pathways for secondary metabolites, including pumilacidin A, bacilysin, and bacillibactin, were identified. Matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis detected molecular masses correlating to safencin E, plantazolicin, pumilarin, and pumilacidin A from the cell-free supernatant, cell extracts, or both. Overall, the broad-spectrum antimicrobial activity of B. safensis APC 4099 indicates that this strain is a promising candidate for the biological control of food ecosystems and thus has the potential to enhance food safety.

Importance: The present article highlights the importance of the strain Bacillus safensis APC 4099 as a potential biocontrol agent. The strain possesses biosynthetic gene clusters coding for various antimicrobial peptides and secondary metabolites, including a novel circular bacteriocin, safencin E, and the bacteriocins pumilarin and plantazolicin. This diversity in the production of antimicrobial peptides renders the producer with broad-spectrum antimicrobial activity, ranging from gram-positive pathogenic and spoilage bacteria to spoilage molds. Considering that 1.3 billion tons of food appropriate for human consumption is lost or wasted annually, identifying strains or novel antimicrobial peptides capable of biopreservation is highly relevant. This strain and its bioactive compounds offer a solution to this global problem as biocontrol agents for food ecosystems against spoilage and pathogenic microbes.