7 research outputs found
Population Turnover in a Microcystis Bloom Results in Predominantly Nontoxigenic Variants Late in the Seasonâ–ż â€
Surface samples of the 2007 Microcystis bloom occurring in Copco Reservoir on the Klamath River in Northern California were analyzed genetically by sequencing clone libraries made with amplicons at three loci: the internal transcribed spacer of the rRNA operon (ITS), cpcBA, and mcyA. Samples were taken between June and October, during which time two cell count peaks occurred, in mid-July and early September. The ITS and cpcBA loci could be classified into four or five allele groups, which provided a convenient means for describing the Microcystis population and its changes over time. Each group was numerically dominated by a single, highly represented sequence. Other members of each group varied by changes at 1 to 3 nucleotide positions, while groups were separated by up to 30 nucleotide differences. As deduced by a partial sampling of the clone libraries, there were marked population turnovers during the season, indicated by changes in allele composition at both the ITS and cpcBA loci. Different ITS and cpcBA genotypes appeared to be dominant at the two population peaks. Toxicity (amount of microcystin per cell) and toxigenic potential (mcyB copy number) were lower during the second peak, and the mcyB copy number fell further as the bloom declined
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A freshwater cyanophage whose genome indicates close relationships to photosynthetic marine cyanomyophages
Bacteriophage S-CRM01 has been isolated from a freshwater strain of Synechococcus and shown to
be present in the upper Klamath River valley in northern California and Oregon. The genome of this
lytic T4-like phage has a 178,563 bp circular genetic map with 297 predicted protein-coding genes
and 33 tRNA genes that represent all 20 amino acid specificities. Analyses based on gene sequence
and gene content indicate a close phylogenetic relationship to the “photosynthetic” marine
cyanomyophages infecting Synechococcus and Prochlorococcus. Such relatedness suggests that
freshwater and marine phages can draw on a common gene pool. The genome can be considered as
being comprised of three regions. Region 1 is populated predominantly with structural genes,
recognized as such by homology to other T4-like phages and by identification in a proteomic
analysis of purified virions. Region 2 contains most of the genes with roles in replication,
recombination, nucleotide metabolism and regulation of gene expression, as well as 5 of the 6
signature genes of the photosynthetic cyanomyophages (hli03, hsp20, mazG, phoH and psbA; cobS
is present in Region 3). Much of Regions 1 and 2 are syntenous with marine cyanomyophage
genomes, except that a segment encompassing Region 2 is inverted. Region 3 contains a high
proportion (85%) of genes that are unique to S-CRM01, as well as most of the tRNA genes. Regions
1 and 2 contain many predicted late promoters, with a combination of CTAAATA and ATAAATA
core sequences. Two predicted genes that are unusual in phage genomes are homologs of cellular
spoT and nusG.Keywords: Myoviridae, Phage tRNA, T4-like phage, Cyanomyophage, Freshwater phage, spoT, Klamath River, nus
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DreherTheoMicrobiologyFreshwaterCyanophageGenome_SupplementaryMaterial.zip
Bacteriophage S-CRM01 has been isolated from a freshwater strain of Synechococcus and shown to
be present in the upper Klamath River valley in northern California and Oregon. The genome of this
lytic T4-like phage has a 178,563 bp circular genetic map with 297 predicted protein-coding genes
and 33 tRNA genes that represent all 20 amino acid specificities. Analyses based on gene sequence
and gene content indicate a close phylogenetic relationship to the “photosynthetic” marine
cyanomyophages infecting Synechococcus and Prochlorococcus. Such relatedness suggests that
freshwater and marine phages can draw on a common gene pool. The genome can be considered as
being comprised of three regions. Region 1 is populated predominantly with structural genes,
recognized as such by homology to other T4-like phages and by identification in a proteomic
analysis of purified virions. Region 2 contains most of the genes with roles in replication,
recombination, nucleotide metabolism and regulation of gene expression, as well as 5 of the 6
signature genes of the photosynthetic cyanomyophages (hli03, hsp20, mazG, phoH and psbA; cobS
is present in Region 3). Much of Regions 1 and 2 are syntenous with marine cyanomyophage
genomes, except that a segment encompassing Region 2 is inverted. Region 3 contains a high
proportion (85%) of genes that are unique to S-CRM01, as well as most of the tRNA genes. Regions
1 and 2 contain many predicted late promoters, with a combination of CTAAATA and ATAAATA
core sequences. Two predicted genes that are unusual in phage genomes are homologs of cellular
spoT and nusG