Plesiocystis pacifica gen. nov., sp. nov., a marine myxobacterium that contains dihydrogenated menaquinone, isolated from the Pacific coasts of Japan

Abstract

Plesiocystis pacifica gen. nov., sp. nov., a marine myxobacterium that contains dihydrogenated menaquinone, isolated from the Pacific coasts of Japan Two strains of a novel myxobacterium (designated SIR-1 T and SHI-1) were isolated from Japanese coasts located in the Pacific subtropical zone. Cells of both strains were Gram-negative, rodshaped and motile by gliding. The strains were chemoheterotrophic and strictly aerobic. They had the common characteristics associated with myxobacteria, such as bacteriolytic action and fruitingbody formation. The characteristic feature of the strains was a NaCl growth requirement with an optimum concentration of 2?0-3?0 % (w/v), comparable to that of sea water. In addition, other cationic components of sea water, such as Mg 2+ , Ca 2+ and K + , were needed for growth. The major respiratory quinone was MK-8(H 2 ). The cellular fatty acid profile was characterized by the predominance of iso-C 15 : 0 . Characteristic fatty acids anteiso-C 16 : 0 and anteiso-C 17 : 0 , and a long-chain polyunsaturated fatty acid (C 20 : 4 ), were also detected. The G+C content of the genomic DNA of strains SIR-1 T and SHI-1 was between 69?3 and 70?0 mol% (as determined by HPLC). Strains SIR-1 T and SHI-1 shared almost identical 16S rDNA sequences, and clustered with the genus Nannocystis as their closest relative upon phylogenetic analysis. However, the phylogenetic distance between the novel strains and the genus Nannocystis was large enough to warrant their different generic allocation. This finding was supported by significant phenotypic differences between the novel strains and Nannocystis. Thus, strains SIR-1 T and SHI-1 represent a novel genus and species, for which the names Plesiocystis and Plesiocystis pacifica, respectively, are proposed. The type strain of the species is SIR-1 T (=JCM 11591 T =DSM 14875 T =AJ 13960 T ). INTRODUCTIONThe myxobacteria are Gram-negative, rod-shaped, gliding bacteria with a high G+C content. One unique characteristic of myxobacteria is a process of intercellular development that leads to fruiting-body formation. Morphological features of fruiting bodies have been regarded as a key criterion for the classification of this group of bacteria (McCurdy, 1989;Reichenbach, 1993). 16S rDNA sequence studies have revealed that they form a relatively homogeneous cluster within the d-Proteobacteria (Shimkets & Woese, 1992; Spröer et al., 1999).Abbreviation: PUFA, polyunsaturated fatty acid.

Different strategies of osmoadaptation in the closely related marine myxobacteria Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1

“…salina SWB007; 1-4 % NaCl for Ple. pacifica SIR-1) determined with this method are in accordance with previous results (Iizuka et al, 2003a;Schäberle et al, 2010). Such a relatively high degree of flexibility to environmental salt concentrations indicates an adaptation strategy involving organic osmolyte accumulation, rather than the salt-in strategy (Sleator & Hill, 2002).…”

“…Ple. pacifica SIR-1 (DSM 14875, type strain) was isolated from a Japanese coastal sea grass (Zostera) (Iizuka et al, 2003a). Escherichia coli BKA13 is a derivative of E. coli MKH13 (Haardt et al 1995) and cannot synthesize the compatible solute trehalose (DotsB, otsA').…”

Biogeography and phylogenetic diversity of a cluster of exclusively marine myxobacteria

“…Some myxobacteria were isolated from marine environments but exhibited a growth optimum at rather low salinities and, therefore, were thought to be salt tolerant and brought in from the terrestrial surroundings, comparable to those in freshwater habitats (Rü ckert, 1984). During the recent past, several myxobacteria have been isolated from marine habitats and shown to be able to grow at sodium chloride concentrations around that of sea water, for example, Haliangium ochraceum and H. tepidum (Foudou et al, 2002), Plesiocystis pacifica (Iizuka et al, 2003a) and Enhygromyxa salina (Iizuka et al, 2003b). All these species originate from coastal regions of Japan and affiliate to the suborder Nannocystineae.…”

Minicystis rosea gen. nov., sp. nov., a polyunsaturated fatty acid-rich and steroid-producing soil myxobacterium

“…The past three decades have seen success in the isolation of myxobacteria from diverse terrestrial sources, yielding thousands of isolates that have been classified into different taxonomic groups (Reichenbach, 2005;Dawid, 2000). The search for myxobacteria in marine, estuarine and anoxic conditions has led to the discovery of obligately halophilic, halotolerant and facultatively anaerobic isolates (Iizuka et al, 1998(Iizuka et al, , 2003a(Iizuka et al, , b, 2013Fudou et al, 2002;Sanford et al, 2002). These strains have contributed to the increasing diversity and number of myxobacteria isolated to date.…”