Taxonomic and Phylogenetic Studies on a New Taxon of Budding, Hyphal Proteobacteria, Hirschia baltica gen. nov., sp. nov.

Abstract

Four strains of budding, hyphal bacteria, which had very similar chemotaxonomic properties, were isolated from the Baltic Sea. The results of DNA-DNA hybridization experiments, indicated that three of the new isolates were closely related, while the fourth was only moderately related to the other three. Sequence signature and higher-order structural detail analyses of the 16s rRNA of strain IFAM 141gT (T = type strain) indicated that this isolate is related to the alpha subclass of the class Proteobacteriu. Although our isolates resemble members of the genera Hyphomicrobium and Hyphomonas in morphology, assignment to either of these genera was excluded on the basis of their markedly lower DNA guanine-plus-cytosine contents. We propose that these organisms should be placed in a new genus, Hirschiu baltica is the type species of this genus, and the type strain of H. bdtica is strain IFAM 1418 (= DSM 5838).Since the first description of a hyphal, budding bacterium, Hyphomicrobium vulgare (53), only the following additional genera having this morphological type have been formally described: Rhodomicrobium (9), Hyphomonas (40), Pedomicrobium (1, 14), Filomicrobium (49, and Dichotomicrobium (23). The taxonomy of these bacteria has been evaluated by using chemotaxonomic characteristics (56), DNA-DNA hybridization (15, 37), genome size determination (28), analysis of nucleotide distribution and DNA base ratio (16), and analysis of RNA cistron similarities (42). Phylogenetically , all of the above-mentioned genera are members of the alpha subclass of the class Proteobacteria, and they are not closely related to each other (51).In this paper we characterize genomically and phenetically four new isolates of budding, hyphal bacteria which have DNA base ratios of 45 to 47 mol%, values which are at least 10 mol% lower than the DNA base ratios of other hyphal, budding members of the Proteobacteria. MATERIALS AND METHODS Enrichment and isolation.At various times surface water samples (upper 5 cm) of the Kiel Fjord were taken from a boat landing. Different methods were used to enrich for budding, hyphal bacteria immediately after the samples arrived in our laboratory (Table 1). When a microscopic survey indicated the presence of such organisms, streaks were made on solidified M13 medium (44). Colonies were examined microscopically by using the toothpick procedure (23). Pure cultures were obtained within 6 months after sampling.Physiological tests. The isolates were grown in complex M13 medium, which contained 0.025% glucose, 0.025% peptone, and 0.025% yeast extract as carbon and nitrogen sources. Tests for utilization of carbon sources were performed in 100-ml Erlenmeyer flasks containing liquid M9 medium to which a filter-sterilized carbon source was added to a final concentration of 0.1% (wt/vol). Defined M9 medium contained 0.005% Na,HPO, and 0.1% KNO,. Metha-* Corresponding author. no1 and formamide were tested at concentrations of 0.02 and 0.1% (vol/vol). Utilization of nitrogen sources was tested in M9 medium containing gl...

Hirschia maritima sp. nov., isolated from seawater

“…1a), similar to species of the genera Hirschia (Schlesner et al, 1990) and Hyphomonas (Pongratz, 1957;Moore et al, 1984;Weiner et al, 2000). Vegetative cells produced prostheca 0.06-0.1 mm in diameter and a bud formed at the hyphal tip.…”

“…Catalase and oxidase activities were tested with 3 % (v/v) Schlesner et al, 1990 and the present study). +, Positive; 2, negative.…”

“…The genus Hirschia was proposed by Schlesner et al (1990) to accommodate a budding bacterium isolated from the Baltic Sea, Hirschia baltica. This genus, together with members of the genus Hyphomonas (Pongratz, 1957), comprises prosthecate, budding bacteria; the two genera are phylogenetically related to the genera Maricaulis (Abraham et al, 1999), Oceanicaulis (Strömpl et al, 2003) and Robiginitomaculum within the family Hyphomonadaceae, class Alphaproteobacteria.…”

Hirschia litorea sp. nov., isolated from seashore sediment, and emended description of the genus Hirschia

“…The genus Hirschia was first proposed by Schlesner et al (1990) to accommodate a single novel species, Hirschia baltica, which includes budding and hyphal strains of the class Proteobacteria, and a second species of the genus, Hirschia maritima, has been described (Kang & Lee, 2009). Phylogenetic analysis based on 16S rRNA gene sequences showed that the genus Hirschia belongs to the family Hyphomonadaceae of the Alphaproteobacteria (Lee et al, 2005;Lee et al, 2007;Kang & Lee, 2009).…”

“…Phylogenetic analysis based on 16S rRNA gene sequences showed that the genus Hirschia belongs to the family Hyphomonadaceae of the Alphaproteobacteria (Lee et al, 2005;Lee et al, 2007;Kang & Lee, 2009). Members of the genus Hirschia have been isolated from seawater of the Baltic Sea and the Pacific Ocean (Schlesner et al, 1990;Kang & Lee, 2009). In this study, we describe a bacterial strain, designated M-M23 T , which was isolated from seashore sediment collected at Geoje island of the South Sea, South Korea.…”