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Morphological and phylogenetic characterizations of freshwater Thioploca species from Lake Biwa, Japan, and Lake Constance, Germany.

ABSTRACT: Filamentous, gliding, sulfide-oxidizing bacteria of the genus Thioploca were found on sediments in profundal areas of Lake Biwa, a Japanese freshwater mesotrophic lake, and were characterized morphologically and phylogenetically. The Lake Biwa Thioploca resembled morphologically Thioploca ingrica, a brackish water species from a Danish fjord. The diameters of individual trichomes were 3 to 5.6 microm; the diameters of complete Thioploca filaments ranged from 18 to 75 micro m. The cell lengths ranged from 1.2 to 3.8 micro m. In transmission electron microscope specimens stained with uranyl acetate, dense intracellular particles were found, which did not show any positive signals for phosphorus and sulfur in an X-ray analysis. The 16S rRNA gene of the Thioploca from Lake Biwa was amplified by using newly designed Thioploca-specific primers (706-Thioploca, Biwa160F, and Biwa829R) in combination with general bacterial primers in order to avoid nonspecific amplification of contaminating bacterial DNA. Denaturing gradient gel electrophoresis (DGGE) analysis of the three overlapping PCR products resulted in single DGGE bands, indicating that a single 16S rRNA gene had been amplified. With the same method, the Thioploca from Lake Constance was examined. The 16S rRNA sequence was verified by performing fluorescence in situ hybridization targeted at specific motifs of the Lake Biwa THIOPLOCA: Positive signals were obtained with the bacterial probe EUB-338, the gamma-proteobacterial probe GAM42a, and probe Biwa829 targeting the Lake Biwa THIOPLOCA: Based on the nearly complete 16S rRNA sequence and on morphological similarities, the Thioploca from Lake Biwa and the Thioploca from Lake Constance are closely related to T. ingrica and to each other.

SUBMITTER: Kojima H

PROVIDER: S-EPMC152410 | biostudies-literature | 2003 Jan

REPOSITORIES: biostudies-literature

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Morphological and phylogenetic characterizations of freshwater Thioploca species from Lake Biwa, Japan, and Lake Constance, Germany.

Kojima Hisaya H Teske Andreas A Fukui Manabu M

Applied and environmental microbiology 20030101 1

Filamentous, gliding, sulfide-oxidizing bacteria of the genus Thioploca were found on sediments in profundal areas of Lake Biwa, a Japanese freshwater mesotrophic lake, and were characterized morphologically and phylogenetically. The Lake Biwa Thioploca resembled morphologically Thioploca ingrica, a brackish water species from a Danish fjord. The diameters of individual trichomes were 3 to 5.6 microm; the diameters of complete Thioploca filaments ranged from 18 to 75 micro m. The cell lengths ra ...[more]

PMID: 12514020

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Project description:Background and aimsLake Biwa is one of the world's few ancient lakes. Formed ∼4 million years ago, the lake harbours many coastal species that commonly inhabit seashores. The beach pea Lathyrus japonicus is a typical coastal species of this freshwater lake, but its inland populations are faced with the threat of extinction. Here, we investigated the phylogeographical and population structures of both inland and coastal populations of L. japonicus. We also elucidated the historical isolation of the Lake Biwa population.MethodologyIn total, 520 individuals from 50 L. japonicus populations were sampled throughout the species distribution in Japan. Chloroplast haplotyping using intergenic spacers psbA-trnH and atpI-atpH was performed to investigate the phylogeographical structure as well as the genetic diversity of L. japonicus. Six nuclear microsatellite markers were also used to analyse the population structure.Principal resultsPopulation structure analyses of chloroplast DNA (cpDNA) and nuclear DNA (nDNA) identified inland and coastal groups. Based on the genetic differentiation, inland populations exhibited a single cpDNA haplotype and significantly lower values of H(S), AR and F(IS) than coastal populations. In addition to the presence of a bottleneck, the lack of gene flow among inland populations was supported by estimates of recent migration rates between subpopulations.ConclusionsOur data revealed that inland populations have been isolated in Lake Biwa as 'landlocked' populations since the predecessor lake was isolated from sea. This was also seen in a previous study of Calystegia soldanella. However, the high genetic differentiation, accompanied by a lack of gene flow among the Lake Biwa populations (according to the BAYESASS(+) analysis), contradicts the results with C. soldanella. We conclude that because of the presence of a bottleneck and low genetic diversity of the inland populations, self-sustaining population persistence may be difficult in the future. Conservation strategies must consider the genetic properties of such isolated populations.

Dataset Information

Morphological and phylogenetic characterizations of freshwater Thioploca species from Lake Biwa, Japan, and Lake Constance, Germany.

Publications

Morphological and phylogenetic characterizations of freshwater Thioploca species from Lake Biwa, Japan, and Lake Constance, Germany.

Similar Datasets

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