Biomedical subjects

John R Tagg

Publications and source records attributed to John R Tagg.

18 recordsLinked to original sources

PubMed2006

Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

The commercial probiotic Streptococcus salivarius strain K12 is the prototype of those S. salivarius strains that are the most strongly inhibitory in a standardized test of streptococcal bacteriocin production and has been shown to produce the 2,368-Da salivaricin A2 (SalA2) and the 2,740-Da salivaricin B (SboB) lantibiotics. The previously uncharacterized SboB belongs to the type AII class of lantibiotic bacteriocins and is encoded by an eight-gene cluster. The genetic loci encoding SalA2 and SboB in strain K12 have been fully characterized and are localized to nearly adjacent sites on pSsal-K12, a 190-kb megaplasmid. Of 61 strongly inhibitory strains of S. salivarius, 19 (31%) were positive for the sboB structural gene. All but one (strain NR) of these 19 strains were also positive for salA2, and in each of these cases of double positivity, the two loci were separated by fewer than 10 kb. This is the first report of a single streptococcus strain producing two distinct lantibiotics.

Bacterial Proteins↗

PubMed2006

The effect of ingestion of milk supplemented with salivaricin A-producing Streptococcus salivarius on the bacteriocin-like inhibitory activity of streptococcal populations on the tongue.

The colonization efficacies of salivaricin A (SalA)-producing Streptococcus salivarius strains 20P3 and 5 were compared when given in milk to 219 children, using either 2-day or 9-day dosing regimens. Colonization levels overall were superior for strain 5, and the 9-day dosing schedule resulted in higher levels of both initial colonization and strain persistence. The indigenous streptococcal tongue populations of 20 (10.9%) of the 189 children in the 2-day trial showed markedly increased SalA-like inhibitory activity following use of the S. salivarius-supplemented milk. All 20 of these children were found to have had relatively small (<5% of total S. salivarius) indigenous tongue populations of SalA-producing S. salivarius, and the relative proportions and/or inhibitory activity of these SalA producers on the childrens' tongues increased following ingestion of the S. salivarius-supplemented milk. Because SalA is known to be strongly inhibitory to Streptococcus pyogenes, an important implication of this study is that the consumption of SalA-producing probiotic S. salivarius could potentially help to effect a sustained increase in SalA-mediated protection against S. pyogenes infection.

Animals↗

PubMed2006

Competence-dependent bacteriocin production by Streptococcus gordonii DL1 (Challis).

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.

Bacterial Proteins↗

PubMed2006

Megaplasmids encode differing combinations of lantibiotics in Streptococcus salivarius.

Streptococcus salivarius strains commonly produce bacteriocins as putative anti-competitor or signalling molecules. Here we report that bacteriocin production by the oral probiotic strain S. salivarius K12 is encoded by a large (ca. 190 kb) plasmid. Oral cavity transmission of the plasmid from strain K12 to a plasmid-negative variant of this bacterium was demonstrated in two subjects. Tests of additional S. salivarius strains showed large (up to ca. 220 kb) plasmids present in bacteriocin-producing isolates. Various combinations (up to 3 per plasmid) of loci encoding the known streptococcal lantibiotics salivaricin A, salivaricin B, streptin and SA-FF22 were localised to these plasmids. Since all bacteriocin-producing strains of S. salivarius tested to date appear to harbour plasmids, it appears that they may function as mobile repositories for bacteriocin loci, especially those of the lantibiotic class.

Bacterial Proteins↗

PubMed2006

Dysgalacticin: a novel, plasmid-encoded antimicrobial protein (bacteriocin) produced by Streptococcus dysgalactiae subsp. equisimilis.

Dysgalacticin is a novel bacteriocin produced by Streptococcus dysgalactiae subsp. equisimilis strain W2580 that has a narrow spectrum of antimicrobial activity directed primarily against the principal human streptococcal pathogen Streptococcus pyogenes. Unlike many previously described bacteriocins of Gram-positive bacteria, dysgalacticin is a heat-labile 21.5 kDa anionic protein that kills its target without inducing lysis. The N-terminal amino acid sequence of dysgalacticin [Asn-Glu-Thr-Asn-Asn-Phe-Ala-Glu-Thr-Gln-Lys-Glu-Ile-Thr-Thr-Asn-(Asn)-Glu-Ala] has no known homologue in publicly available sequence databases. The dysgalacticin structural gene, dysA, is located on the indigenous plasmid pW2580 of strain W2580 and encodes a 220 aa preprotein which is probably exported via a Sec-dependent transport system. Natural dysA variants containing conservative amino acid substitutions were also detected by sequence analyses of dysA elements from S. dysgalactiae strains displaying W2580-like inhibitory profiles. Production of recombinant dysgalacticin by Escherichia coli confirmed that this protein is solely responsible for the inhibitory activity exhibited by strain W2580. A combination of in silico secondary structure prediction and reductive alkylation was employed to demonstrate that dysgalacticin has a novel structure containing a disulphide bond essential for its biological activity. Moreover, dysgalacticin displays similarity in predicted secondary structure (but not primary amino acid sequence or inhibitory spectrum) with another plasmid-encoded streptococcal bacteriocin, streptococcin A-M57 from S. pyogenes, indicating that dysgalacticin represents a prototype of a new class of antimicrobial proteins.

Amino Acid Sequence↗

PubMed2006

Identification and characterization of the loci encoding the competence-associated alternative sigma factor of Streptococcus gordonii.

In naturally-competent streptococci such as Streptococcus pneumoniae, expression of the late competence operons is regulated by ComX (sigma(X)), the competence-specific alternative sigma factor. In this study, duplicate genes (comR1 and comR2) encoding the putative ComX homologue of the oral bacterium Streptococcus gordonii were identified. Like the identical twin comX loci of S. pneumoniae, both comR determinants are independently functional as well as responsive to the ComDE signal transduction system activated by competence-stimulating peptide. However, in contrast to the comX system, nucleotide sequence analyses in combination with in trans complementation studies with a comR null mutant demonstrate that the identical 83 bp tracts (Region I) located immediately upstream of the comR structural genes are insufficient to confer wild-type competence levels. Wild-type transformation levels required additional distal nonhomologous DNA segments (Region II). Our findings suggest that alternative regulatory elements, under overall control of the ComDE pathway, may influence expression of the comR loci.

Bacterial Proteins↗

PubMed2006

Molecular and genetic characterization of a novel nisin variant produced by Streptococcus uberis.

Streptococcus uberis is one of the principal causative agents of bovine mastitis. In this study, we report that S. uberis strain 42 produces a lantibiotic, nisin U, which is 78% identical (82% similar) to nisin A from Lactococcus lactis. The 15.6-kb nisin U locus comprises 11 open reading frames, similar in putative functionality but differing in arrangement from that of the nisin A biosynthetic cluster. The nisin U producer strain exhibits specific resistance (immunity) to nisin U and cross-resistance to nisin A, a finding consistent with the 55% sequence similarity of their respective immunity peptides. Homologues of the nisin U structural gene were identified in several additional S. uberis strains, and in each case cross-protective immunity was expressed to nisin A and to the other producers of nisin U and its variants. To our knowledge, this is the first report both of characterization of a bacteriocin by S. uberis, as well as of a member of the nisin family of peptides in a species other than L. lactis.

Amino Acid Sequence↗

PubMed2006

Production of the lantibiotic salivaricin A and its variants by oral streptococci and use of a specific induction assay to detect their presence in human saliva.

Salivaricin A (SalA), the first Streptococcus salivarius lantibiotic to be characterized, appears to be inhibitory to most Streptococcus pyogenes strains. A variant of the SalA structural gene (salA1) is present in more than 90% of S. pyogenes strains, but only strains of M serotype 4 and T pattern 4 produce the biologically active peptide. The present study identifies four additional variants (salA2 to salA5) of the SalA structural gene and demonstrates that each of the corresponding inhibitory peptides (SalA2 to SalA5) is produced in vitro. These variants appear to be similar to SalA and SalA1 in their inhibitory activity against Micrococcus luteus and in their ability to act as inducers of SalA production. It had previously been shown that S. pyogenes strain SF370 had a deletion (of approximately 2.5 kb) in the salM and salT genes of the salA1 locus. In the present study, several additional characteristic deletions within the salA1 loci were identified. S. pyogenes strains of the same M serotype all share the same salA1 locus structure. Since S. salivarius is a predominant member of the normal oral flora of healthy humans, strains producing anti-S. pyogenes lantibiotics, such as SalA, may have excellent potential for use as oral probiotics. In the present study, we have used a highly specific SalA induction system to directly detect the presence of SalA in the saliva of humans who either naturally harbor populations of SalA-producing S. salivarius or who have been colonized with the SalA2-producing probiotic S. salivarius K12.

Amino Acid Sequence↗

PubMed2006

Safety assessment of the oral cavity probiotic Streptococcus salivarius K12.

Streptococcus salivarius is a prominent member of the oral microbiota and has excellent potential for use as a probiotic targeting the oral cavity. In this report we document safety data relating to S. salivarius K12, including assessment of its antibiogram, metabolic profiles, and virulence determinants, and we examine the microbial composition of saliva following the dosing of subjects with K12.

Anti-Bacterial Agents↗

PubMed2005

Streptococcus rattus strain BHT produces both a class I two-component lantibiotic and a class II bacteriocin.

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.

Amino Acid Sequence↗

PubMed2005

A preliminary survey of Atopobium vaginae in women attending the Dunedin gynaecology out-patients clinic: is the contribution of the hard-to-culture microbiota overlooked in gynaecological disorders?

Preliminary studies have indicated that the recently described bacterium Atopobium vaginae may have an association with bacterial vaginosis (BV). Fifty-five women attending the gynaecology out-patient's clinic were tested for the presence of this micro-organism, Gardnerella vaginalis, Mobiluncus and Bacteroides species by polymerase chain reaction (PCR)-based assays. The frequency of detection was 40%. PCR detection of Gardnerella vaginalis with A. vaginae, occurred in 50% of A. vaginae-positive cases. Due to the high detection rate of A. vaginae we believe that it is important to determine whether this and other hard-to-culture microorganisms have a role in gynaecological disorders.

Actinobacteria↗

PubMed2005

Bacteriocin (mutacin) production by Streptococcus mutans genome sequence reference strain UA159: elucidation of the antimicrobial repertoire by genetic dissection.

Streptococcus mutans UA159, the genome sequence reference strain, exhibits nonlantibiotic mutacin activity. In this study, bioinformatic and mutational analyses were employed to demonstrate that the antimicrobial repertoire of strain UA159 includes mutacin IV (specified by the nlm locus) and a newly identified bacteriocin, mutacin V (encoded by SMU.1914c).

Bacterial Proteins↗

PubMed2005

Identification of nlmTE, the locus encoding the ABC transport system required for export of nonlantibiotic mutacins in Streptococcus mutans.

Streptococcus mutans UA159, the genome sequence reference strain, exhibits nonlantibiotic bacteriocin (mutacin) activity. In this study, we have combined bioinformatic and mutational analyses to identify the ABC transporter designated NlmTE, which is required for mutacin biogenesis in strain UA159 as well as in another mutacin producer, S. mutans N.

ATP-Binding Cassette Transporters↗

PubMed2005

Non-culture-based analysis of bacterial populations from patients with chronic rhinosinusitis.

Middle meatus aspirates from patients with chronic rhinosinusitis were analyzed by bacterial culture, denaturing gradient gel electrophoresis (DGGE), and antibiotic sensitivity techniques. DGGE detected a greater bacterial diversity than culture methods. Although resistance to antibiotics was low, there was evidence of changes in the composition of the bacterial microbiota over time, and the presence of noncultured bacteria was demonstrated.

Bacteria↗

PubMed2004

Sequence analysis of pDN571, a plasmid encoding novel bacteriocin production in M-type 57 Streptococcus pyogenes.

Production of the novel bacteriocin streptococcin A-M57 (SA-M57) by Streptococcus pyogenes strains of M-protein type 57 is plasmid-associated. Plasmid pDN571 (3351bp) harbored by S. pyogenes 71-724, the prototype M-type 57 strain, has been completely sequenced and contains three putative open reading frames (repA, scnM57 and ORF3). In addition, the double-strand and single-strand (SSO) origins of replication were identified. Analysis of the replication-associated genetic elements places pDN571 in the ubiquitous pC194/pUB110 family of rolling-circle plasmids. The SSO of pDN571 is of the ssoA type. SA-M57 (encoded by scnM57) is synthesized as a secreted 179-amino acid polypeptide with a 27-residue secretion signal peptide and has no homology to proteins of known function.

Amino Acid Sequence↗

PubMed2003

Bacterial replacement therapy: adapting 'germ warfare' to infection prevention.

The individual bacterial members of our indigeneous microbiota are actively engaged in an on-going battle to prevent colonisation and overgrowth of their terrain by competing microbes, some of which might have pathogenic potential for the host. Humans have long attempted to intervene in these bacterial interactions. Ingestion of probiotic bacteria, particularly lactobacilli, is commonly practiced to promote well-balanced intestinal microflora. As bacterial resistance to antimicrobials has increased, so too has research into colonisation of human tissues with specific effector strains capable of out-competing known bacterial pathogens. Recent progress is particularly evident in the application of avirulent Streptococcus mutans to the control of dental caries, alpha hemolytic streptococci to reduction of otitis media recurrences and Streptococcus salivarius to streptococcal pharyngitis prevention.

Bacteria↗

PubMed2003

Purification and characterization of streptin, a type A1 lantibiotic produced by Streptococcus pyogenes.

Approximately 10% of Streptococcus pyogenes strains inhibit the growth of all nine indicators in a standardized streptococcal bacteriocin typing scheme. The present study has shown that this inhibitory profile, referred to as bacteriocin producer (P)-type 777 activity, is due to the type A1 lantibiotic streptin. Two major forms of streptin were purified to homogeneity from 95% acidified (pH 2) methanol extracts of S. pyogenes M25 cells by using a series of reversed-phase chromatographic separations. The fully processed form of streptin (streptin 1) is a 23-amino-acid peptide with a mass of 2,424 Da. The 2,821-M(r) form of the peptide (streptin 2) has three additional amino acids (TPY) at the N terminus. Strain M25 extracts also contained small quantities of the streptin 1 and streptin 2 peptides in various stages of dehydration. Streptin 1 and streptin 2 were each capable of specifically inducing streptin production when added to strain M25 cultures. The streptin gene cluster resembled that of other type A1 lantibiotics but appeared to lack a streptin-specific proteinase gene. Although the streptin structural gene (srtA) was widespread within S. pyogenes, being detected in 40 of 58 strains, each representing a different M serotype, only 10 of these srtA-positive strains produced active streptin. The failure of some strains to express streptin was attributed to an approximately 4.5-kb deletion in their streptin loci, encompassing genes putatively encoding proteins involved in streptin processing (srtB and srtC) and transport (srtT). In other strains, srtA transcription appeared to be defective. No direct association could be detected between the production of streptin and the production of the lantibiotic-like hemolysin streptolysin S in strain M25.

Amino Acid Sequence↗

PubMed2000

Haemolysin-deficient variants of Streptococcus pyogenes and S. dysgalactiae subsp. equisimilis may be overlooked as aetiological agents of pharyngitis.

Variants of large colony beta-haemolytic Lancefield group A, C and G streptococci that are non-haemolytic or alpha-haemolytic on sheep blood agar have been detected in clinical specimens due to their enhanced haemolytic activity when grown on a new selective and differential blood agar medium containing colistin, nalidixic acid and pH 7.5-adjusted PIPES buffer (CNA-P). The large colony Lancefield group C and G isolates were identified as Streptococcus dysgalactiae subsp. equisimilis by API 20 Strep classification and 16S rDNA profiling. The haemolytic activity of these variants on various blood agar media, including CNA-P, was closely similar to that of known streptolysin S-defective mutants of S. pyogenes and was blocked by addition of cholesterol, a specific inhibitor of the streptolysin O family of haemolysins. As haemolysin variants could be detected in large numbers in cultures from patients with clinical symptoms of pharyngitis it is suggested that they may function as primary pathogens in such infections. The high frequency with which haemolysin variants were isolated from clinical specimens during a 3-month trial (3%, 13% and 10%, respectively, of group A, C and G streptococcal isolates) indicated that a substantial proportion of streptococcal infections may go undetected if only conventional sheep blood agar media are used in clinical laboratories for the detection of beta-haemolytic streptococci. As haemolysin variants have been implicated in the development of serious streptococcal sequelae, further investigation of the full extent of their contribution to streptococcal disease is indicated.

Antigens, Bacterial↗