Pseudenhygromyxa salsuginis gen. nov., sp. nov., a myxobacterium isolated from an estuarine marsh

Abstract

A myxobacterial strain, designated SYR-2(T), was obtained from a mud sample from an estuarine marsh alongside the Yoshino River, Shikoku, Japan. It had rod-shaped vegetative cells and formed bacteriolytic enlarging colonies or so-called 'swarms' in the agar media. Fruiting-body-like globular to polyhedral cell aggregates and myxospore-like spherical to ellipsoidal cells within them were observed. Those features coincided with the general characteristics of myxobacteria. The strain was mesophilic and strictly aerobic. Growth of SYR-2(T) was observed at 18-40 °C (optimum, 30-35 °C), pH 5.5-8.3 (optimum, pH 7.0-7.5) and with 0.0-2.5 % (w/v) NaCl (optimum, 0.2-1.0 %). Both Mg(2+) and Ca(2+) were essential cations for the growth. The predominant fatty acids were iso-C15 : 0 (43.8 %), iso-C17 : 0 (22.4 %) and iso-C16 : 0 (9.6 %). A C20 : 4 fatty acid [arachidonic acid (4.3 %)], iso-C19 : 0 (1.5 %) and anteiso-acids [ai-C15 : 0 (0.5 %), ai-C17 : 0 (0.3 %)] were also detected. The G+C content of the DNA was 69.7 mol%. The strain contained menaquinone-7 (MK-7) as the major respiratory quinone. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain SYR-2(T) belonged to the suborder Nannocystineae, order Myxococcales in the class Deltaproteobacteria, and the strain was most closely related to two type strains of marine myxobacteria, Enhygromyxa salina SHK-1(T) and Plesiocystis pacifica SIR-1(T), with 96.5 % and 96.0 % similarities, respectively. These characteristics determined in this polyphasic study suggested that strain SYR-2(T) represents a novel species in a new genus of myxobacteria. The name Pseudenhygromyxa salsuginis gen. nov., sp. nov. is proposed to accommodate this isolate, and the type strain of Pseudenhygromyxa salsuginis is SYR-2(T) ( = NBRC 104351(T) = DSM 21377(T)).