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The genome of the thermophilic bacterium, Aeribacillus pallidus 8, encodes the novel antibacterial peptide pallidocin. This bacteriocin belongs to the small class of glycocins and is post-translationally modified with a S-linked glucose on a specific Cys residue. The pallidocin biosynthetic machinery was successfully cloned and expressed in Escherichia coli to achieve its full biosynthesis and modification. The characterized biosynthetic machinery was employed to produce two other novel glycocins. All three novel post-translationally modified peptides exhibit antibacterial activity against thermophilic (Para)Geobacillus, Caldibacillus spp. and some Bacillus spp. strains. Moreover, pallidocin has demonstrated a very low MIC value. In addition, it was shown that the leader sequence removal of glycocin is not absolutely necessary for antibacterial activity, but that glycosylation is. Moreover, this is the first report of heterologous in vivo synthesis of glycocins, using pallidocin biosynthetic gene cluster and S-glycosyltransferase. This approach facilitates production of hypothetical glycocins, which can be found in many genomes of bacteria, and allows rapid in vivo screening. The Geobacillus stearothermophilus 15 is producing two proteinaceous nature antibacterial compounds which we named geobacillin 18 and geobacillin 26. Their molecular weights were determined 18 kDa and 26 kDa, respectively. Geo18 has high stability in 121°C temperature; meanwhile Geo26 is heat-labile and was completely inactivated by treatment in 90˚C temperature. Amino acid sequence of Geo26 was revealed and it has no sequence similarity to any known enzymes or characterized bacteriocins. |
