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A single gene (tts) located outside the cap locus directs the formation of Streptococcus pneumoniae type 37 capsular polysaccharide. Type 37 pneumococci are natural, genetically binary strains.

ABSTRACT: The molecular aspects of the type 37 pneumococcal capsular biosynthesis, a homopolysaccharide composed of sophorosyl units (beta-d-Glc-(1-->2)-beta-d-Glc) linked by beta-1,3 bonds, have been studied. Remarkably, the biosynthesis of the type 37 capsule is driven by a single gene (tts) located far apart from the cap locus responsible for capsular formation in all of the types characterized to date in Streptococcus pneumoniae. However, a cap37 locus virtually identical to the cap33f cluster has been found in type 37 strains, although some of its genes are inactivated by mutations. The tts gene has been sequenced and its transcription start point determined. Tts shows sequence motifs characteristic of cellulose synthases and other beta-glycosyltransferases. Insertion of the tts gene into the pneumococcal DNA causes a noticeable genome reorganization in such a way that genes normally separated by more than 350 kb in the chromosome are located together in clinical isolates of type 37. Encapsulated pneumococcal strains belonging to 10 different serotypes (or serogroups) transformed with tts synthesized type 37 polysaccharide, leading to the formation of strains that display the binary type of capsule. Type 37 pneumococcus constitutes the first case of a natural, genetically binary strain and represents a novel alternative to the mechanisms of intertype transformation.

SUBMITTER: Llull D

PROVIDER: S-EPMC2195575 | biostudies-literature | 1999 Jul

REPOSITORIES: biostudies-literature

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A single gene (tts) located outside the cap locus directs the formation of Streptococcus pneumoniae type 37 capsular polysaccharide. Type 37 pneumococci are natural, genetically binary strains.

Llull D D Muñoz R R López R R García E E

The Journal of experimental medicine 19990701 2

The molecular aspects of the type 37 pneumococcal capsular biosynthesis, a homopolysaccharide composed of sophorosyl units (beta-d-Glc-(1-->2)-beta-d-Glc) linked by beta-1,3 bonds, have been studied. Remarkably, the biosynthesis of the type 37 capsule is driven by a single gene (tts) located far apart from the cap locus responsible for capsular formation in all of the types characterized to date in Streptococcus pneumoniae. However, a cap37 locus virtually identical to the cap33f cluster has bee ...[more]

PMID: 10432287

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Project description:The major virulence factor of the pneumococcus, and target for conjugate vaccines, is the polysaccharide capsule, which is usually encoded by the highly variable cps locus. Serotype 37 is an unusual pneumococcal type in which the single β-glucosyltransferase gene responsible for serotype capsule production (tts) is located outside of the capsular operon region. Using a previously described automated whole genome sequence (WGS)-based serotyping bioinformatics tool, PneumoCaT, we identified and investigated seven clinical isolates (three from blood cultures) of non-pneumococcal streptococci containing a highly homologous tts and included them in a study panel of 20 isolates which included a 11 further clinical isolates of S. pneumoniae serotype 37, a reference strain of serotype 37 and the S. pseudopneumoniae type strain BAA 960T. The seven non-pneumococcal isolates generated novel alleles at all pneumococcal MLST loci and gave low percentage similarity (<45%) to S. pneumoniae or S. pseudopneumoniae species by comparison of short sequence patterns in genomic data (k-mer analysis). The S. pseudopneumoniae BAA-960T isolate generated two novel alleles in the MLST and gave a high similarity (>99%) to the reference sequence for BAA-960T. Twelve isolates gave high similarity (>77%) to the Streptococcus pneumoniae 5652-06 serotype 19A reference genome sequence and had previously reported MLST alleles. Each of the seven clinical non-pneumococcal strains and all of the 12 S. pneumoniae possessed a β-glycosyltransferase gene (tts) with >95% similarity to the pneumococcal tts reference DNA sequence with 20-22 non-synonymous SNPs. All but two strains in which the tts gene was detected gave positive reactions for serotype 37 in slide agglutination tests with serotype 37 typing sera. Phylogenetic analysis using both SNP and MLST data showed distinct clades corresponding to strains identified as pneumococcus or non-pneumococcus by kmer WGS analysis. Extended k-mer database analysis and ribosomal MLST placed the non-pneumococcal isolates within the S. mitis group. Biochemical and bile solubility assays showed differences between the unusual isolates and S. pneumoniae. All isolates had detectable pneumolysin (ply) genes, but only those that identified as pneumococcus contained the genes for autolysin (lytA) or the ABC transporter lipoprotein A (piaA) with >80% coverage and >95% similarity. Here we report the existence of a novel group of strains distinct from S. pneumoniae, but which can express a pneumococcal serotype 37 capsular polysaccharide which can be associated with clinical disease.

Project description:Context:This review summarizes key findings of the Tehran thyroid study (TTS), a large scale community-based study with approximately a two decade follow-up, about the incidence, prevalence, and natural course of thyroid disorders as well as associations between thyroid diseases and metabolic syndrome (MetS), dysglycemia, and cardiovascular disease (CVD). Evidence Acquisition:PubMed, Scopus, and Web of Science databases, and the library of Research Institute for Endocrine Sciences were used to search for TTS articles. Articles were subdivided based on the fields of prevalence, incidence and natural course, and associations of thyroid function with the incident hypertension (HTN), MetS and CVDs. Results:The 2.5th and 97.5th percentiles of serum thyrotropin (TSH) were 0.32 and 5.06 mU/L, respectively. Estimated reference intervals (2.5th and 97.5th percentiles) for thyroid peroxidase antibody (TPOAb) levels were 1.5 - 32.8 and 2.1 - 35?IU/mL in men and women, respectively. Euthyroid persistency was 93.24% during 6 years. There was a negative association between free thyroxine (FT4) levels and insulin resistance. Decreasing FT4 values over time would predict MetS in euthyroid and subclinical hypothyroid subjects (TSH < 10 mU/L). The incidence of thyroid disorders in patients with diabetes, pre-diabetes and healthy controls was 14, 18, and 21 per 1000 person-years, respectively, indicating significantly lower incidence in individuals with diabetes compared to healthy controls. Serum FT4 within the reference range was positively associated with all blood pressure (BP) measures in the total population and in men; however, serum TSH was positively associated with only systolic BP (SBP), diastolic BP (DBP) and mean arterial pressure of men. No associations were found between various states of thyroid function and prevalence and incidence of CVD. Conclusions:A well designed cohort study aimed to investigate the gap in knowledge regarding thyroid disorders can generate many hypotheses to be examined in randomized controlled trials.

Dataset Information

A single gene (tts) located outside the cap locus directs the formation of Streptococcus pneumoniae type 37 capsular polysaccharide. Type 37 pneumococci are natural, genetically binary strains.

Publications

A single gene (tts) located outside the cap locus directs the formation of Streptococcus pneumoniae type 37 capsular polysaccharide. Type 37 pneumococci are natural, genetically binary strains.

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