Bacteriocin production and sensitivity among coaggregating and noncoaggregating oral streptococci

Abstract

Twenty-one oral Streptococcus isolates of known interbacterial coaggregation groups were tested against one another (as both producers and indicators) to detect bacteriocin-like inhibitory activity. In agar-based antagonism tests, seven strains produced small inhibitory zones (< or = 3 mm diameter) but in liquid medium, only strain Streptococcus gordonii DL1 (Challis) produced a detectable antibacterial action (bacteriocin STH1). Five strains were sensitive to bacteriocin STH1, but neither the production of nor the sensitivity to any of the antagonistic agents correlated with coaggregation groupings. Four strains (C219, 903, 118 and Wicky) developed stable resistance in response to the bacteriocin, whereas one isolate (strain 34) remained sensitive following repeated bacteriocin exposure. With one exception (strain 903), bacteriocin STH1-sensitive strains were competent for genetic transformation, but not all competent strains were bacteriocin-sensitive. Bacteriocin-resistant derivatives of transformable strains exhibited decreased competence (80-90% reduction) compared with their parent strains.

Mutation of the Thiol-Disulfide Oxidoreductase SdbA Activates the CiaRH Two-Component System, Leading to Bacteriocin Expression Shutdown in Streptococcus gordonii

“…Bacteriocin production by the active site mutant was tested in an activity assay using the target strains S. mitis and S. oralis (10,12). Consistent with our previous results, supernatants obtained from early-exponential-phase cultures of the S. gordonii parent strain contained active bacteriocins that inhibited the growth of the target strains (Fig.…”

“…Because bacteriocin production is a transient, growth phasedependent phenomenon (12,42), it was possible that the window of growth in which bacteriocin production occurred was altered in the ⌬sdbA mutant and bacteriocins were being produced but at a different time point than in the parent strain. Bacteriocin expression peaks 15 min after exposure to CSP (13), and bacteriocin activity can be detected in culture supernatants during early exponential growth (2 h) but not in the mid-exponential to late exponential phase (6 h) (12).…”

“…Bacteriocin expression peaks 15 min after exposure to CSP (13), and bacteriocin activity can be detected in culture supernatants during early exponential growth (2 h) but not in the mid-exponential to late exponential phase (6 h) (12). To determine whether the ⌬sdbA mutant produced bacteriocins at a later growth stage than the parent strain, we assayed bacteriocin activity against S. mitis using S. gordonii supernatants harvested at different time points.…”

“…gordonii DL-1 Challis produces two nonlantibiotic bacteriocins, namely, Sth 1 and Sth 2 , encoded by sthA and sthB, respectively. Sth 1 is active against other S. gordonii strains, including C219 and Wicky (12), while Sth 1 and Sth 2 work in conjunction to target other streptococci, such as Streptococcus mitis and Streptococcus oralis (10). Sth 1 and Sth 2 are the only known bacteriocins produced by S. gordonii, and they are both regulated by the Com two-component regulatory system, which also controls natural genetic competence (10,13).…”

Communication among Oral Bacteria

“…These peptides are thought to influence the ecology of these bacteria, but their mechanism of communicating this influence is unknown. One investigation was conducted with several oral streptococci known to coaggregate with each other (147). One strain, S. gordonii DL1 (Challis), produced a bacteriocin, and five strains were sensitive to the bacteriocin, but neither the production of nor sensitivity to the bacteriocin could be correlated to the ability to coaggregate, suggesting that cell-cell attachment and bacteriocin production are not related.…”