Bacteria are microorganisms that play important roles in nature and have a ubiquitous distribution. Some bacteria may be pathogenic, but others are beneficial, for example they produce or secrete proteins, peptides and small organic metabolites which contribute to human or animal health; or protect crops from insects and phytopathogenic microorganisms. In particular Gram-positive bacteria are of special interest because they do not possess an outer membrane, and secreted proteins or other metabolites are released into culture media for easy harvesting and applied use.

Many secreted molecules allow for communication among bacteria through quorum sensing as they compete with other microorganisms to secure their ecological niches. Indeed, many of those compounds are secondary metabolites.

Examples of gram-positive bacteria of interest include: (i) Lactococci group, e.g. Lactococcus lactis, Lactobacillus fermentum, and Lactobacillus plantarum which produce therapeutic proteins and are also used as biological factories for heterologous expression; in particular, L. lactis not only provide special sensorial properties of yogurt, but also secrete antimicrobial peptides, or bacteriocins (i.e., nisin), that protect consumers from pathogenic bacteria; (ii) Bifidobacterium and Clostridium which produce therapeutic proteins; (iii) Streptomyces spp, which play an important role in the C and N cycle and synthesize chitinases, proteases, cellulases, amylases, and antibiotics of industrial and pharmaceutical interest; (iv) Bacillus species, including B. subtilis, B. thuringiensis, B. cereus, B. megaterium, B. stearothermophilus, B. amyloliquefaciens, B. clausii, B. halodurans, B. pseudomycoides, B. pumilis, and B. mojavensis which are isolated from a variety of environment niches. These bacilli secrete metabolites or produce proteins that are of applied values. For example, B. thuringiensis synthesizes antimicrobial peptides (bacteriocins) that could be used as food preservatives and antibiotics, and chitinases that have been demonstrated to synergize the insecticidal activity of Cry proteins produced by many strains of this bacterium; B. amyloliquefaciens synthesizes biosurfactants; B. subtilis produces a variety of metabolites and enzymes, including plant growth promoters, amylase, proteases, hydrolases, inosine, ribosides, and amino acids; B. mojavensis produces proteolytic and amylolytic enzymes that can be used as laundry detergent additives, and B. pumilis has antifungal activities. Other Bacillus species produce metabolites that confer antiviral, antioxidant, immunosuppressive and antitumor activities.

This Research Topic focuses on current insights of novel metabolites secreted by Gram-positive bacteria. Studies on cellular physiology and homologous and heterologous gene expression as they relate to production of secondary metabolites, and proteins with known or potential applied value are welcome. Particular emphasis on new research on metabolites currently reported, improvements in production through genetic engineering and synthetic biology, and industrial production, including fermentation, are also welcome.

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in the mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.

Keywords: hydrolytic enzymes, Gram-positive bacteria, secondary metabolites, secretion proteins, antimicrobial peptides

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.