Dong, Ke

A strictly aerobic, Gram-stain-negative, ovoid-shaped and non-motile bacterium, designated as strain MJ-SS7T, was isolated from tidal mudflat sediment collected at a macro-tidal clam farm in Gochang, Republic of Korea. Strain MJ-SS7T exhibited oxidase- and catalase-positive activities. Growth occurred at 20–37 °C (optimum: 30 °C), pH 6–8 (optimum: pH 7) and in the presence of 0–9% (w/v) NaCl (optimum: 3%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that MJ-SS7T belonged to the family Roseobacteraceae. Its closest relatives, based on sequence similarity, were Rhodophyticola porphyridii KACC 18805T (95.9%), Kangsaoukella pontilimi KCTC 72224T (95.8%) and Actibacterium pelagium JN33T (95.5%). The major fatty acids included summed feature 8 (C18:1  ω7c/C18:1  ω6c), C16:0, C16:0 2OH and C18:0. The major polar lipids consisted of phosphatidylglycerol, five unidentified phospholipids, four unidentified aminolipids, two unidentified aminophospholipids and four unidentified lipids. The major respiratory quinone was ubiquinone-10. The genome size was 5.20 Mb, with a DNA G+C content of 63.4 mol%, encoding 5,031 protein-coding genes, 3 rRNA genes and 46 tRNA genes. Comparative genomic analyses confirmed its novelty, with average nucleotide identity (<73%) and average amino acid identity (<70%) values below the species delineation thresholds. Based on polyphasic taxonomic data, strain MJ-SS7T represents a novel species of a new genus within the family Roseobacteraceae, for which the name Ovoidimarina sediminis gen. nov., sp. nov. is proposed. The type strain is MJ-SS7T (=KEMB 21436T=KCTC 8329T=JCM 36750T).

The Xiphinema americanum-group is a large species complex containing more than 50 nematode species. They are economically important because they are vectors of nepoviruses. The species differentiation of X. americanum-group is problematic because the species share similar morphological characters. In the present study we collected nematode samples from different locations in the USA, Italy and Russia. Six valid species, X. americanum s. str., X. brevicolle, X. californicum, X. pachtaicum, X. rivesi and X. simile, and four unidentified putative Xiphinema species were characterised by morphology and sequencing of D2-D3 of 28S rRNA, ITS1 rRNA and mitochondrial COI genes. New nematode sequences generated totalled 147. Phylogenetic relationships of the X. americanum-group species reconstructed by Bayesian inference for D2-D3 of 28S rRNA gene sequences did not provide clear species delimitation of the samples studied, although the mtDNA presented interspecific variations useful for demarcation among species. Xiphinema americanum s. str., X. californicum, X. pachtaicum, X. rivesi, and two unidentified Xiphinema species were found in 72 soil samples from California. We also reconstructed the phylogenetic relationships using partial 16S rRNA gene sequences within endosymbiotic bacteria of the genus Candidatus Xiphinematobacter and provided solid evidence for distinguishing 17 species of this genus based on the analysis of new and previously published sequences. Fifty-five new bacterial sequences were obtained in the present study and comparison of the bacterial 16S rRNA and nematode COI phylogenies revealed a high level of co-speciation events between host and symbiont.