Salivaricin G32, a Homolog of the Prototype Streptococcus pyogenes

Salivaricin G32, a 2667 Da novel member of the SA-FF22 cluster of lantibiotics, has been purified and characterized from Streptococcus salivarius strain G32. The inhibitory peptide differs from the Streptococcus pyogenes—produced SA-FF22 in the absence of lysine in position 2. The salivaricin G32 locus was widely distributed in BLIS-producing S. salivarius, with 6 (23%) of 26 strains PCR-positive for the structural gene, slnA. As for most other lantibiotics produced by S. salivarius, the salivaricin G32 locus can be megaplasmid encoded. Another member of the SA-FF22 family was detected in two Streptococcus dysgalactiae of bovine origin, an observation supportive of widespread distribution of this lantibiotic within the genus Streptococcus. Since the inhibitory spectrum of salivaricin G32 includes Streptococcus pyogenes, its production by S. salivarius, either as a member of the normal oral microflora or as a commercial probiotic, could serve to enhance protection of the human host against S. pyogenes infection

WEIBULL BASED METHODOLOGY FOR CONDITION ASSESSMENT OF CAST IRON WATER MAINS AND ITS APPLICATION

Abstract A qualitative and quantitative understanding of how cast iron water distribution pipes fail in service would facilitate a targeted approach to the management of rehabilitation in the water industry. This paper proposes a technique for assessing the condition of pipes, based on strength characteristics obtained from small samples; this offers an alternative way of estimating the likelihood of failure to current methodologies based on pit-depth measurements. Examination of recovered pipe samples indicates that the strength of the cast iron pipe reduces over time as a result of corrosion, although other time-dependent processes, such as fatigue, may also contribute to this degradation. Taken with previous work, this paper suggests that the variation in strength of small samples removed from cast iron water distribution pipes can be characterised using Weibull methods. It is argued that the Weibull modulus provides a useful indicator of the condition of the pipe. Using scaling arguments, inherent in the Weibull methodology, it is then possible to use data from small samples to predict the likely strength characteristics of water distribution pipes in the ground, which is reasoned to be a good measure of the potential performance of the pipe in service. The Weibull approach is applied to a number of different data sets obtained from testing samples extracted from a range of pipes, which have seen service at various locations in the Thames Water region. One of these data sets was from locations where failure had occurred in service. It is shown that the use of Weibull analysis can identify pipes in the network that have degraded the most significantly. A methodology is suggested whereby this information taken with other performance indicators can be used to identify the local regions where rehabilitation is required most urgently. Alternatively it can be used to identify those regions of the network which are in good condition and unlikely to need repair or replacement work

Contribution of Exogenous Genetic Elements to the Group A Streptococcus Metagenome

Variation in gene content among strains of a bacterial species contributes to biomedically relevant differences in phenotypes such as virulence and antimicrobial resistance. Group A Streptococcus (GAS) causes a diverse array of human infections and sequelae, and exhibits a complex pathogenic behavior. To enhance our understanding of genotype-phenotype relationships in this important pathogen, we determined the complete genome sequences of four GAS strains expressing M protein serotypes (M2, M4, and 2 M12) that commonly cause noninvasive and invasive infections. These sequences were compared with eight previously determined GAS genomes and regions of variably present gene content were assessed. Consistent with the previously determined genomes, each of the new genomes is ∼1.9 Mb in size, with ∼10% of the gene content of each encoded on variably present exogenous genetic elements. Like the other GAS genomes, these four genomes are polylysogenic and prophage encode the majority of the variably present gene content of each. In contrast to most of the previously determined genomes, multiple exogenous integrated conjugative elements (ICEs) with characteristics of conjugative transposons and plasmids are present in these new genomes. Cumulatively, 242 new GAS metagenome genes were identified that were not present in the previously sequenced genomes. Importantly, ICEs accounted for 41% of the new GAS metagenome gene content identified in these four genomes. Two large ICEs, designated 2096-RD.2 (63 kb) and 10750-RD.2 (49 kb), have multiple genes encoding resistance to antimicrobial agents, including tetracycline and erythromycin, respectively. Also resident on these ICEs are three genes encoding inferred extracellular proteins of unknown function, including a predicted cell surface protein that is only present in the genome of the serotype M12 strain cultured from a patient with acute poststreptococcal glomerulonephritis. The data provide new information about the GAS metagenome and will assist studies of pathogenesis, antimicrobial resistance, and population genomics

Prospects for the development of probiotics and prebiotics for oral applications

There has been a paradigm shift towards an ecological and microbial community-based approach to understanding oral diseases. This has significant implications for approaches to therapy and has raised the possibility of developing novel strategies through manipulation of the resident oral microbiota and modulation of host immune responses. The increased popularity of using probiotic bacteria and/or prebiotic supplements to improve gastrointestinal health has prompted interest in the utility of this approach for oral applications. Evidence now suggests that probiotics may function not only by direct inhibition of, or enhanced competition with, pathogenic micro-organisms, but also by more subtle mechanisms including modulation of the mucosal immune system. Similarly, prebiotics could promote the growth of beneficial micro-organisms that comprise part of the resident microbiota. The evidence for the use of pro or prebiotics for the prevention of caries or periodontal diseases is reviewed, and issues that could arise from their use, as well as questions that still need to be answered, are raised. A complete understanding of the broad ecological changes induced in the mouth by probiotics or prebiotics will be essential to assess their long-term consequences for oral health and disease

Altering the probiotic epigneome, its potential application in fermentation

Epigenetics is the study of changes in gene expression and function that occur without a change in the underlying DNA sequence. These changes in humans, can be caused by a variety of factors, including dietary intake, environmental exposures, and lifestyle factors. Epigenetic modifications, such as DNA methylation and histone modifications, can turn genes on or off and affect the expression of certain proteins. However, epigenetics also has great potential for interdisciplinary applications, including in the fields of microbiology and fermentation science. This study aimed to investigate the impact of certain human dietary compounds on probiotic strains which also present in the gut, specifically focusing on Lactobacillus acidophilus, and to apply the acquired knowledge to enhance the effectiveness of probiotic strains used in fermentation processes. The study explored epigenetic effects of six dietary compounds on the target probiotic strains. These compounds were compared to a known DNA methyltransferase inhibitor, 5-aza-2’-deoxycytidine, as a positive control. The microbial epigenetic effects were evaluated using whole genome bisulphite sequencing, RNA sequencing, and metabolomic profiling. The results show that each dietary compound has a unique epigenetic-based impact on regulation of gene expression in L. acidophilus. The study also investigates the application of epigenetically-modified probiotics in milk fermentation to develop a novel probiotic yogurt that could provide additional functional benefits in the gut and overall health benefits to the body

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

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

Salivaricin 9, a new lantibiotic produced by Streptococcus salivarius

Salivaricin 9 (Sal9) is a 2560 Da lantibiotic having just 46% amino acid identity with its closest known homologue, the Streptococcus pyogenes lantibiotic SA-FF22. The Sal9 locus (designated siv) in Streptococcus salivarius strain 9 was partially sequenced and localized to an approximately 170 kb megaplasmid, which also harbours the locus for the lantibiotic salivaricin A4. The entire locus was fully characterized in the draft genome sequence of S. salivarius strain JIM8780 and shown to consist of eight genes, having the following putative functions: sivK, sensor kinase; sivR, response regulator; sivA, Sal9 precursor peptide; sivM, lantibiotic modification enzyme; sivT, ABC transporter involved in the export of Sal9 and concomitant cleavage of its leader peptide; and sivFEG, encoding lantibiotic self-immunity. Intriguingly, in contrast to strain 9, the siv locus was chromosomally located in strain JIM8780 the first lantibiotic locus shown not to be exclusively plasmid-associated in S. salivarius. Sal9-containing extracts specifically induced lantibiotic production in both strain 9 and strain JIM8780, indicating that Sal9 functions as a signal peptide for upregulation of its own biosynthesis. Screening representative strains of three streptococcal species (S. salivarius, S. pyogenes and S. mitis) for sivA indicated that it was present only in S. salivarius, with 12 of 28 tested S. salivarius positive. Since Sal9 was inhibitory to all tested S. pyogenes strains it appears to have potential as an important component of the bacteriocin armoury of S. salivarius probiotics intended to control S. pyogenes infections of the human oral cavity

Novel viscoelastic gelling agent with unique physico-chemical properties

A novel innovative viscoelastic gelling agent (novel gel, NG) has been developed by combining citric acid (CA) and disodium 5-guanylate (DG). NG has the potential to replace other gelling agents such as gelatine, which has been commonly used in foods, dietary supplements, pharmaceutical and cosmetic products including ointments and sprays. NG has unique physico-chemical properties, including a wide range of concentration-dependent, temperature-sensitive gel strengths. Based on the rheological measurement results, NG depicted similar shear thinning behaviour to gelatine, within shear rates ranging from 25.8 to 129 (s¯¹ ). NG also significantly increased the shelf-life (by 21 days) of minced beef, as well as inhibited the growth of major spoilage pathogens, such as E. coli, S. aureus, Salmonella sp., Listeria sp., yeast and moulds, making it an ideal candidate for gelatine replacement