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Use of Persica mouthwash resulted in improved gingival health and lower carriage rate of cariogenic bacteria when compared with the pre-treatment values. The placebo (vehicle control) also improved gingival health significantly. Neither the Persica nor the placebo reduced the accumulation of dental plaque.

The production of streptocins STH 1 and STH 2 by Streptococcus gordonii DL1 (Challis) is directly controlled by the competence regulon, which requires intact comR and comAB loci. The streptocin (sth) locus comprises two functional genes, sthA and sthB. Whereas STH 1 activity requires sthA alone, STH 2 activity depends on both genes.In the 1970s, reported the production of streptocin STH 1 , a proteinaceous antimicrobial agent (bacteriocin), by the naturally transformable Streptococcus gordonii (formerly Streptococcus sanguis) strain Challis (also known as DL1 and NCTC 7868). Streptocin STH 1 biosynthesis coincided with the development of competence for genetic transformation (20, 21), a relationship supported by later studies (8,23). The inhibitory spectrum of streptocin STH 1 was initially reported to include other S. gordonii strains (e.g., strains Wicky and C219) and select strains of Streptococcus mitis and Streptococcus oralis (8,23). However, we have observed that the bacteriocin activity targeting S. mitis and S. oralis appears to be linked to the beta-hemolytic phenotype of strain Challis because S. gordonii OB164 (originally designated DL1-Challis), a non-beta-hemolytic strain indistinguishable from DL1 biochemically (API 20 Strep; bioMérieux, France) and genotypically (18), exhibited inhibitory activity only against S. gordonii isolates. This suggested that strain DL1 produces two bacteriocins: the previously described STH 1 (20) and the newly designated STH 2 , a bacteriocin that targets certain non-S. gordonii strains and is associated with the beta-hemolytic phenotype. Based on our speculation that genetic competence and bacteriocin production may be functionally related in strain DL1 (23), the aims of the present study were to determine whether bacteriocin biosynthesis is genetically associated with competence development and to define the locus encoding the inhibitory/hemolytic agents.(Parts of this work were presented at the 7th ASM Conference on Streptococcal Genetics, Saint Malo, France [7a].)Association of competence and bacteriocin/␤-hemolysin production. Competence development in S. gordonii is analogous to competence development in Streptococcus pneumoniae, occurring in two distinct stages, early and late (10, 13). The early stage involves a quorum-sensing signal transduction circuit comprising a secreted competence-stimulating peptide (CSP), its cell surface receptor ComD (a histidine kinase), and ComE, the primary transcriptional regulator of competence (10, 13). ComE, when activated by ComD, upregulates the comCDE (signal transduction), comAB (CSP secretion), and comX operons (13). ComX, an alternative sigma factor, connects the early and late stages by activating expression of the late competence operons that are responsible for DNA uptake and processing (17). Several key components of the S. gordonii competence regulon have been identified, including comCDE, comAB, comYA (DNA uptake), and duplicate comR (comX homologue) loci (6,7,15,16).In this study, early (comC, comE, comA, comB, an...

The influence of dietary ferric iron on the intestinal microbiota of mice was investigated with a view to promoting benign lactic acid bacteria (which have minimal iron requirements) in order to enhance colonization-resistance potential. Three groups of eight mice received a diet differing only in iron content, for a period of 12 weeks. Dietary iron deprivation resulted in overall increased small intestinal bacterial populations, including lactic acid bacteria, but these differences were generally not significant (p > 0.05). With the exception of coliforms, all examined bacterial groups (anaerobes, micro-aerophiles, lactobacilli, and enterococci) were significantly (p < 0.05) elevated in the colons of iron-deprived mice. The relatively low numbers of total anaerobes in the colons of iron-replete and iron-overloaded mice suggested that, as well as promotion of bacteria under iron-deprived condition, provision of ferric iron suppressed bacteria, probably by oxidation of normally reduced environments.

A radioligand assay was designed to detect and compare specific hemin binding by the periodontal anaerobic black-pigmenting bacteria (BPB) Porphyromonas gingivalis and Prevotella intermedia. The assay included physiological concentrations of the hemin-binding protein rabbit serum albumin (RSA) to prevent self-aggregation and nonspecific interaction of hemin with cellular components. Under these conditions, heme-starved P. intermedia cells (two strains) expressed a single binding site species (4,100 to 4,600 sites/cell) with a dissociation constant (K d ) of 1.0 ؋ 10 ؊9 M. Heme-starved P. gingivalis cells (two strains) expressed two binding site species; the higher-affinity site (1,000 to 1,500 sites/cell) displayed a K d of between 3.6 ؋ 10 ؊11 and 9.6 ؋ 10 ؊11 M, whereas the estimated K d of the lower-affinity site (1.9 ؋ 10 5 to 6.3 ؋ 10 5 sites/cell) ranged between 2.6 ؋ 10 ؊7 and 6.5 ؋ 10 ؊8 M. Specific binding was greatly diminished in heme-replete cells of either BPB species and was not displayed by iron-replete Escherichia coli cells, which bound as much hemin in the absence of RSA as did P. intermedia. Hemin binding by BPB was reduced following treatment with protein-modifying agents (heat, pronase, and N-bromosuccinimide) and was blocked by protoporphyrin IX and hemoglobin but not by Congo red. Hemopexin also inhibited bacterial hemin binding. These findings indicate that both P. gingivalis and P. intermedia express heme-repressible proteinaceous hemin-binding sites with affinities intermediate between those of serum albumin and hemopexin. P. gingivalis exhibited a 10-fold-greater specific binding affinity and greater heme storage capacity than did P. intermedia, suggesting that the former would be ecologically advantaged with respect to heme acquisition.