Streptococcus rattusstrain BHT produces both a class I two-component lantibiotic and a class II bacteriocin

Abstract

Streptococcus rattus strain BHT is a species representative and strong bacteriocin producer. Here we report that S. rattus BHT produces two quite different types of bacteriocin activity, named BHT-A and BHT-B. The two bacteriocins were purified and analysed for activity and by MALDI-TOF mass spectrophotometry. BHT-A was found to be a variant of the two-component lantibiotic, Smb. BHT-B is a non-modified 5195Da peptide with some similarity to the tryptophan-rich Staphylococcus aureus bacteriocin, aureocin A53. Six S. rattus and two S. mutans strains were found to contain both the BHT-A and BHT-B genetic loci.

Discovery and in vitro biosynthesis of haloduracin, a two-component lantibiotic

“…The three remaining cysteines are believed to form one Lan and two MeLan rings with the same connectivity as confirmed (21) or proposed for all other known two-component lantibiotics ( Fig. 1) (17,18,29,30). Importantly, the six-aminoacid-containing MeLan B-ring in Hal␣, which is believed to be important for lipid II binding in mersacidin's C-ring (32), is conserved including the invariant and essential Glu within this ring (33).…”

“…We show conclusively that these peptides are part of a two-component system. Including haloduracin, seven two-component lantibiotics have now been documented (10,11,17,18,29,30). Interestingly, by searching the nonredundant database for homologs to the haloduracin peptides we discovered another gene cluster in Bacillus lichenformis that encodes two prepeptides, two modification enzymes, and several additional transport, immunity, and regulation proteins involved in lantibiotic biosynthesis.…”

“…The biological activity displayed by these mature products depended on the presence of both modified peptides in the bioassay. Ltn␣ of lacticin 3147 and BHT␣ exhibit low level antibacterial activity by themselves, presumably by weak binding to lipid II (12,30). It is possible that Hal␣ may also demonstrate biological activity at higher concentrations, but so far we have been limited in the accessible concentrations of in vitro product because of its poor solubility.…”

Investigating the importance of charged residues in lantibiotics

“…8 The majority of these share a significant degree of homology (with the Enterococcusassociated cytolysin being a notable exception) and thus much of the information gleaned from the detailed investigation of a number of these two peptide lantibiotics, and lacticin 3147 and haloduracin in particular, is likely to also be relevant to the two peptide group as a whole (which also includes staphylococcin C55, plantaricin W, Smb, BHT-A, lichenicidin and a predicted pneumococcin). [9][10][11][12][13][14][15][16] Two peptide It was previously noted that a number of lantibiotics resemble cationic antimicrobial peptides (cAMPS) by virtue of having long linear structures and a cationic charge as well as being able to form pores. 21 cAMPS typically have a positive charge of between +2 to +9 and have broad spectrum of activity against bacteria through disruption of anionic bacterial membrane.…”

Salivaricin E and abundant dextranase activity may contribute to the anti-cariogenic potential of the probiotic candidate Streptococcus salivarius JH

“…It appears that this assay system may be a useful method for identifying strains that produce more than one anti-MS BLIS. For example, S. rattus strain BHT, which is known to produce multiple bacteriocins (Hyink et al, 2005), retained full activity against some indicator strains while failing to inhibit others, indicating that the different bacteriocins are not affected by the presence of EPS to the same extent. The fact that 8 of the 13 strains tested had narrower spectra of activity against MS in the presence of EPS-conducive growth conditions indicates that the presence of EPS does reduce the sensitivity of bacteria to certain antibacterial agents, and therefore is likely to be ecologically significant for the survival and proliferation of MS in the oral cavity.…”