Streptococcus mutans, a human indigenous oral bacterial species,

is known to produce bacteriocins named mutacins [6]. It is believed that production of such mutacins may confer to S. mutans an advantage against competitive species living in the same niche [6]. To date, mutacins from class I and class II have been purified and characterised: the mono-peptide lantibiotic (mutacin B-Ny266), the di-peptide lantibiotic (mutacin GS-5), the mono-peptide non-lantibiotic (mutacin N) and the di-peptide non-lantibiotic (mutacin IV) selleck screening library [for review see reference 6 and references therein]. Production of more than one mutacin by a given strain has been experimentally demonstrated for several strains and is also predicted by bioinformatic analysis of sequenced strain genomes [6]. Mutacin-producing strains and some of their purified peptides have shown activity against Gram positive and some Gram negative bacteria in vitro and in vivo [7–9]. Because of their Dactolisib concentration biochemical diversity and activity spectra, many applications can be expected for mutacins as antibiotics or food preservatives [3, 10]. The main objective of our research is to further characterise mutacins to uncover new useful antibacterial substances active against bacterial pathogens. We previously classified

86 mutacin-producing selleck products strains into 24 groups (designated A to X) and subsequently seven clusters of activity were defined from the 24 type strains. This grouping was based only on their activity spectra towards other mutacinogenic strains and against various bacterial species including pathogens [8, 11]. S. mutans 59.1 and 123.1 were clearly distinct in their activity spectra and the mutacins Rho produced by these strains were not genetically related to the well known lantibiotics (nisin, gallidermin, epidermin, subtilin) nor

to previously well characterised mutacins (B-Ny266, B-JH1140 (mutacin III), J-T8 (mutacin II), H-29B) by using specific molecular probes [8, 12]. We present here results on the production, purification and characterisation of mutacins F-59.1 and D-123.1. Results Mutacin F-59.1 was produced in SWP and the activity was measured as 400 AU/mL while production of mutacin D-123.1 was achieved in semi-solid medium by using tryptic soy with yeast extract containing agarose. Activity of the crude mutacin D-123.1 preparation was measured to be 200 AU/mL. Mutacins D-123.1 and F-59.1 were purified by successive steps of hydrophobic chromatography. Active fractions of mutacin F-59.1 purification were recovered with an elution gradient of 50%-60% methanol in 10 mM HCl (Figure 1) and those of mutacin D-123.1 with a 60%-70% gradient (Figure 2). The final specific activities were 3.2 × 105 AU/mg for the purified mutacin F-59.1 and of 1.6 × 105 AU/mg for the purified mutacin D-123.1 (Table 1). Figure 1 Elution profile of mutacin F-59.1 on RP-HPLC. Active peak is boxed.