Dataset Information

Detection of toxigenicity by a probe for the microcystin synthetase A gene (mcyA) of the cyanobacterial genus Microcystis: comparison of toxicities with 16S rRNA and phycocyanin operon (Phycocyanin Intergenic Spacer) phylogenies.

ABSTRACT: The relationship between toxigenicity and phylogeny within the cyanobacterial genus Microcystis is unclear. To investigate this issue, we have designed PCR primers for the N-methyltransferase (NMT) domain of the microcystin synthetase gene mcyA and have probed 37 Microcystis sp. cultures as well as several field samples. The NMT region was present in all 18 laboratory strains that gave positive reactions in the protein phosphatase inhibition assay for microcystin but was absent in 17 nontoxic strains. Two other nontoxic strains, one of which had previously been reported to produce microcystin, possessed the NMT region. Detection of NMT-specific DNA in field samples corresponded to periods of toxicity as assessed by protein phosphatase inhibition. The Microcystis strains formed a monophyletic cluster based on 16S rRNA gene sequences but comprised two groups with respect to phycocyanin intergenic spacer (PC-IGS) sequences. Toxic and nontoxic strains appeared to be erratically distributed within the PC-IGS and 16S rRNA trees. Sequence analysis of the NMT domain revealed two coherent groups. The genomic region immediately downstream of the mcyABC cluster in all 20 NMT-positive strains contained an open reading frame of unknown function (uma1) at a conserved distance from mcyC. All nontoxic strains also contained uma1, which is not cotranscribed with mcyABC. The consistent linkage of mcyC to uma1 suggests that mcyC has not been frequently transferred into nontoxic strains via any mechanism involving insertion at random chromosomal locations. These results are discussed with respect to various mechanisms that could explain the patchy distribution of toxigenicity among the various Microcystis clades.

SUBMITTER: Tillett D

PROVIDER: S-EPMC92942 | biostudies-literature | 2001 Jun

REPOSITORIES: biostudies-literature

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Publications

Detection of toxigenicity by a probe for the microcystin synthetase A gene (mcyA) of the cyanobacterial genus Microcystis: comparison of toxicities with 16S rRNA and phycocyanin operon (Phycocyanin Intergenic Spacer) phylogenies.

Tillett D D Parker D L DL Neilan B A BA

Applied and environmental microbiology 20010601 6

The relationship between toxigenicity and phylogeny within the cyanobacterial genus Microcystis is unclear. To investigate this issue, we have designed PCR primers for the N-methyltransferase (NMT) domain of the microcystin synthetase gene mcyA and have probed 37 Microcystis sp. cultures as well as several field samples. The NMT region was present in all 18 laboratory strains that gave positive reactions in the protein phosphatase inhibition assay for microcystin but was absent in 17 nontoxic st ...[more]

PMID: 11375198

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Project description:Clostridium difficile is a major spore-forming environmental pathogen that causes serious health problems in patients undergoing antibiotic therapy. Consequently, reliable and sensitive methods for typing individual strains are required for epidemiological and environmental studies. Ribotyping is generally considered the best method, but it fails to account for sequence diversity which might exist in intergenic 16S-23S rRNA spacer regions (ISRs) within and among strains of this organism. Therefore, this study was undertaken to compare the sequence of each individual ISR in five strains of C. difficile to explore the extent of this diversity and see whether such information might provide the basis for more sensitive and discriminatory strain typing methods. After targeted PCR amplification, cloning, and sequencing, the diversity of the ISRs was used as a measure of rRNA operon copy number. In C. difficile strains 630, ATCC 43593, A, and B, 11, 11, 7, and 8 ISR length variants, respectively, were found (containing different combinations of sequence groups [i to xiii]), suggesting 11, 11, 7, and 8 rrn copies in the respective strains. Many ISRs of the same length differed markedly in their sequences, and some of these were restricted in occurrence to a single strain. Most of these ISRs did not contain any tRNA genes, and only single copies of the tRNA(Ala) gene were found in those that did. The presence of ISR sequence groups (i to xiii) varied between strains, with some found in one, two, three, four, or all five strains. We conclude that the intergenic 16S-23S rRNA spacer regions showed a high degree of diversity, not only among the rrn operons in different strains and different rrn copies in a single strain but also among ISRs of the same length. It appears that C. difficile ISRs vary more at the inter- and intragenic levels than those of other species as determined by empirical comparison of sequences. The precise characterization of these sequences has demonstrated a high level of mosaic sequence block rearrangements that are present or absent in multiple strain-variable rrn copies within and between five different strains of C. difficile.

Dataset Information

Detection of toxigenicity by a probe for the microcystin synthetase A gene (mcyA) of the cyanobacterial genus Microcystis: comparison of toxicities with 16S rRNA and phycocyanin operon (Phycocyanin Intergenic Spacer) phylogenies.

Publications

Detection of toxigenicity by a probe for the microcystin synthetase A gene (mcyA) of the cyanobacterial genus Microcystis: comparison of toxicities with 16S rRNA and phycocyanin operon (Phycocyanin Intergenic Spacer) phylogenies.

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