Publications

4366

The genus Pseudovibrio is commonly associated with marine invertebrates, which are essential for ocean health and marine nutrient cycling. Traditionally, the phylogeny of the genus has been based on 16S rRNA gene analysis. The use of the 16S rRNA gene or any other single marker gene for robust phylogenetic placement has recently been questioned. We used a large set of marker genes from all available Pseudovibrio genomes for in-depth phylogenomic analyses. We identified divergent monophyletic basal lineages within the Pseudovibrio genus, including two strains isolated from polyclad flatworms. These strains showed reduced sulfur metabolism and biosynthesis capacities. The phylogenomic analyses revealed distinct evolutionary trajectories and ecological adaptations that differentiate the divergent strains from the other Pseudovibrio members and suggest that they fall into a novel genus. Our data show the importance of widening the use of phylogenomics for better understanding bacterial physiology, phylogeny, and evolution.

A novel Gram-stain-positive, rod shaped and anaerobic bacterium, designated as W6T, was isolated from Shengli oilfield in China. Strain W6T was observed to grow from 20 to 45 °C with pH 6.5–9.0 (optimally at 40 °C and pH of 7.5) and without addition of NaCl. The major cellular fatty acids were iso-C15 : 0 (29.1%), C14 : 0 (27.0%) and C16 : 0 (12.2%), and the main polar lipids were lipids (L) and aminolipids (AL). The DNA G+C content is 42.9 mol%. Based on 16S rRNA gene sequence analysis, strain W6T showed highest similarities to Tissierella creatinini DSM 9508T (94.9%) and Soehngenia saccharolytica DSM 12858T (94.1%). The morphological, physiological, biochemical, phylogenetic and phylogenomic analyses demonstrated strain W6T (CCAM 534T=DSM 28124T=CGMCC 1.5291T) represents a novel species in a new genus, for which the name Gudongella oleilytica gen. nov. sp. nov. is proposed. The family Tissierellaceae is proposed as a new family containing the genera Anaerosalibacter , Gudongella, Keratinibaculum , Soehngenia , Sporanaerobacter , Tepidimicrobium , Tissierella , Urmitella and species Clostridium ultunense based on the phylogenetic and phylogenomic analyses.

Abstract“Candidatus Liberibacter solanacearum” (Lso) are phloem‐restricted and unculturable Gram‐negative bacteria. Presently five haplotypes have been identified worldwide; but only haplotypes A and B are associated with the vector Bactericera cockerelli (Šulc.) in the Americas. Previous studies showed that Lso‐infection reduces B. cockerelli reproductive output and that Lso haplotype B is more pathogenic than Lso haplotype A. To understand the interaction of Lso haplotype B and B. cockerelli, the fitness of Lso‐free and Lso B‐infected insects, and the expression of vitellogenin (BcVg1‐like), a gene involved directly in the insect reproduction were analyzed. Statistical differences in the number of eggs oviposited, and the total number of progeny nymphs and adults were found among crosses of insects with or without Lso. Significant differences in sex proportions were found between Lso B‐infected and Lso‐free crosses: a higher proportion of F1 adult females were obtained from Lso B‐infected mothers. A significant reduction of BcVg1‐like was observed in crosses performed with Lso B‐infected females compared to the Lso‐free insects. In female cohorts of different age, a significant reduction of BcVg1‐like expression was measured in 7‐d‐old Lso B‐infected females (virgin and mated) compared with 7‐d‐old Lso‐free females (virgin and mated), respectively. The reduction of BcVg1‐like transcript was associated with a lower number of developing oocytes observed in female's reproductive systems. Overall, this study represents the first step to understand the interaction of Lso B with B. cockerelli, highlighting the effect of Lso B infection on egg production, BcVg1‐like expression, and oocyte development.