Devosia sediminis sp. nov., isolated from subterranean sediment

Linking bacterial life strategies with the distribution pattern of antibiotic resistance genes in soil aggregates after straw addition

Straw addition markedly affects the soil aggregates and microbial community structure. However, its influence on the profile of antibiotic resistance genes (ARGs), which are likely associated with changes in bacterial life strategies, remains unclear. To clarify this issue, a soil microcosm experiment was incubated under aerobic (WS) or anaerobic (AnWS) conditions after straw addition, and metagenomic sequencing was used to characterise ARGs and bacterial communities in soil aggregates. The results showed that straw addition shifted the bacterial life strategies from K- to r-strategists in all aggregates, and the aerobic and anaerobic conditions stimulated the growth of aerobic and anaerobic r-strategist bacteria, respectively. The WS decreased the relative abundances of dominant ARGs such as QnrS5, whereas the AnWS increased their abundance. After straw addition, the macroaggregates consistently exhibited a higher number of significantly altered bacteria and ARGs than the silt+clay fractions. Network analysis revealed that the WS increased the number of aerobic r-strategist bacterial nodes and fostered more interactions between r-and K-strategist bacteria, thus promoting ARGs prevalence, whereas AnWS exhibited an opposite trend. These findings provide a new perspective for understanding the fate of ARGs and their controlling factors in soil ecosystems after straw addition. ENVIRONMENTAL IMPLICATIONS: Straw soil amendment has been recommended to mitigate soil fertility degradation, improve soil structure, and ultimately increase crop yields. However, our findings highlight the importance of the elevated prevalence of ARGs associated with r-strategist bacteria in macroaggregates following the addition of organic matter, particularly fresh substrates. In addition, when assessing the environmental risk posed by ARGs in soil that receives crop straw, it is essential to account for the soil moisture content. This is because the species of r-strategist bacteria that thrive under aerobic and anaerobic conditions play a dominant role in the dissemination and accumulation of ARG.

Microvirga puerhi sp. nov., isolated from Puerh tea garden soil

Strain WGZ8^T was isolated from a soil sample of Puerh tea garden in Pu'er city, Southwest China. The isolate was rod-shaped, Gram-stain negative, facultative anaerobic, non-motile. Growth occurred within 0-3.0% (w/v) NaCl (optimal concentration, 0-1.0%), pH 5.0-11.0 (optimal pH, 7.0) and 10-40 °C (optimal temperature, 28 °C). 16S rRNA gene sequence-based phylogenetic and phylogenomic analysis revealed that WGZ8^T belonged to the genus Microvirga. Its major cellular fatty acids were C_19:0 cyclo ω8c, C_16:0, C_18:1ω7c and/or C_18:1ω6c. The profile of polar lipids included phosphatidyldimethylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol and phosphatidylglycerol. The only respiratory quinone was detected as ubiquinone 10 (Q-10). The genome size of strain WGZ8^T was 5.17 MB, and the content of DNA G + C was 61 mol%. Based on the results of digital DNA-DNA hybridization and phenotypic results, strain WGZ8^T could be concluded as a novel species of the genus Microvirga, for which the name Microvirga puerhi sp. nov. is proposed. The type strain is WGZ8^T (= CGMCC 1.19171 ^T = JCM 35317 ^T).

Devosia salina sp. nov., isolated from South China Sea sediment

An aerobic, Gram-stain-negative, rod-shaped and motile strain, designated SCS-3T, was isolated from deep-sea sediment of the South China Sea. Phylogenetic analysis based on the 16S rRNA gene sequence similarities revealed that strain SCS-3T represented a novel species of the genus Devosia , with closely related strains ' Devosia sediminis ' MSA67T (98.61 %), Devosia riboflavina IFO13584T (98.22 %) and Devosia indica IO390501T (97.72 %). The G+C content of the genomic DNA is 63.44 mol%. The digital DNA–DNA hybridization values with ' D. sediminis ' MSA67T, D. riboflavina IFO13584T and D. indica IO390501T were 24.50, 21.8 and 24.80 %, respectively. The major polar lipids of strain SCS-3T were diphosphatidylglycerol, phosphatidylglycerol and three unidentified glycolipids. Ubiquinone-10 was the sole isoprenoid quinone, and C16 : 0, C18 : 1 ω7c 11-methyl and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) were the major fatty acids. Based on polyphasic taxonomic data, strain SCS-3T represents a novel species of the genus Devosia , for which the name Devosia salina sp. nov. is proposed. The type strain is SCS-3T (=JCM 34403T=GDMCC 1.2221T).