Bacillus licheniformis produce several classes of antimicrobial substances which are mainly either peptides or proteins. Among of them bacteriocins - peptides or proteins of different structural composition including synthesized by bacteria ribosomally; non-ribosomally synthesized peptides and cyclic lipopeptides; exopolysaccharides. Different representatives of these classes act against Gram-positive, Gram-negative bacteria, fungal pathogens and amoebae cells. In this review, a detailed classification of antimicrobial substances produced by B. licheniformis based on their chemical structure and mode of the synthesis and activity is presented. For some (rather limited number) of secreted antimicrobials mechanism of their harmful effect on the target cells is established, however, for many of them it remains unknown. The antimicrobial activity for most substances was studied in vitro only, however some substances were characterized in vivo and are found practical applications in medicine and veterinary. The cyclic lipopeptides with surfactant properties are applied in industry.
In this review, a special attention on antimycobacterials produced by B. licheniformis is made as a possible approach to combat multidrug resistant and latent tuberculosis. Indeed, a number of peptides and proteins revealed strong antimycobacterial activity. However, medical application of some bacteriocins with promising in vitro antimycobacterial activity is limited by their toxicity for animals and humans. In this connection, similarly with the enhancement of the antimycobacterial activity of natural bacteriocins using genetic engineering, reduction of the toxicity by the same approach looks feasible.
A unique capability of B. licheniformis to synthesize and produce a bouquet of different antibacterial compounds allow to consider this organism as a universal natural vehicle for antibiotic substances in form of probiotic cultures strains to combat various types of pathogens including mycobacteria.