Alkalicaulis satelles gen. nov., sp. nov., a novel haloalkaliphile isolated from a laboratory culture cyanobacterium Geitlerinema species and proposals of Maricaulaceae fam. nov., Robiginitomaculaceae fam. nov., Maricaulales ord. nov. and Hyphomonadales ord. nov.

Abstract

A prosthecate bacterial strain, designated G-192T, was isolated from decaying biomass of a haloalkaliphilic cyanobacterium Geitlerinema sp. Z-T0701. The cells were aerobic, Gram-negative, non-endospore-forming and dimorphic, occurring either as sessile bacteria with a characteristic stalk or as motile flagellated cells. The strain utilized a limited range of substrates, mostly peptonaceous, but was able to degrade whole proteins. Growth occurred at 5–46 °C (optimum, 35–40 °C), pH 7.3–10.3 (optimum, pH 8.0–9.0), 0–14 % NaCl (v/w; optimum, 2.0–6.0 %, v/w). The G+C content of the genomic DNA of strain G-192T was 66.8%. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain G-192T formed a distinct evolutionary lineage within the family Hyphomonadaceae . Strain G-192T showed the highest 16S rRNA sequence similarity to Glycocaulis profundi ZYF765T (95.2%), Oceanicaulis stylophorae GISW-4T (94.2%) and Marinicauda salina WD6-1T (95.5%). The major cellular fatty acids (>5% of the total) were C18:1 ω9c, C18:0 and 11-methyl-C18:1 ω7c. The major polar lipids were glycolipids and phospholipids. The only respiratory quinone was ubiquinone-10 (Q-10). Based on polyphasic results including phylogenomic data, the novel strain could be distinguished from other genera, which suggests that strain G-192T represents a novel species of a new genus, for which the name Alkalicaulis satelles gen. nov., sp. nov. is proposed. The type strain is G-192T (=VKM B-3306T=KCTC 72746T). The strain is the first representative of the stalked bacteria associated with a haloalkaliphilic cyanobacterium. Based on phylogenomic indices and phenotypic data, it is proposed to evolve two novel families Maricaulaceae fam. nov. and Robiginitomaculaceae fam. nov. out of the current family Hyphomonadaceae . In addition, it is proposed to place the first two families in the novel order Maricaulales ord. nov. and novel order Hyphomonadales ord. nov. is proposed to accommodate the family Hyphomonadaceae .