Roseovarius ponticola sp. nov., a novel lipolytic bacterium of the family Rhodobacteraceae isolated from seawater

Beach sand plastispheres are hotspots for antibiotic resistance genes and potentially pathogenic bacteria even in beaches with good water quality

Massive amounts of microplastics are transported daily from the oceans and rivers onto beaches. The ocean plastisphere is a hotspot and a vector for antibiotic resistance genes (ARGs) and potentially pathogenic bacteria. However, very little is known about the plastisphere in beach sand. Thus, to describe whether the microplastics from beach sand represent a risk to human health, we evaluated the bacteriome and abundance of ARGs on microplastic and sand sampled at the drift line and supralittoral zones of four beaches of poor and good water quality. The bacteriome was evaluated by sequencing of 16S rRNA gene, and the ARGs and bacterial abundances were evaluated by high-throughput real-time PCR. The results revealed that the microplastic harbored a bacterial community that is more abundant and distinct from that of beach sand, as well as a greater abundance of potential human and marine pathogens, especially the microplastics deposited closer to seawater. Microplastics also harbored a greater number and abundance of ARGs. All antibiotic classes evaluated were found in the microplastic samples, but not in the beach sand ones. Additionally, 16 ARGs were found on the microplastic alone, including genes related to multidrug resistance (blaKPC, blaCTX-M, tetM, mdtE and acrB_1), genes that have the potential to rapidly and horizontally spread (blaKPC, blaCTX-M, and tetM), and the gene that confers resistance to antibiotics that are typically regarded as the ultimate line of defense against severe multi-resistant bacterial infections (blaKPC). Lastly, microplastic harbored a similar bacterial community and ARGs regardless of beach water quality. Our findings suggest that the accumulation of microplastics in beach sand worldwide may constitute a potential threat to human health, even in beaches where the water quality is deemed satisfactory. This phenomenon may facilitate the emergence and dissemination of bacteria that are resistant to multiple drugs.

Roseovarius gahaiensis sp. nov., isolated from Gahai Saline Lake, PR China

A Gram-stain-negative, aerobic, non-motile and ovoid- to rod-shaped bacterial strain, designated GH877^T, was isolated from a water sample of Gahai saline lake in Qaidam Basin,PR China. The isolate grew at 5-45 °C, pH 6.0-9.0 (optima, 37 °C and pH 7.5) and with 0.5-20 % (w/v) NaCl (optimum, 2.0 %). The neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain GH877^T belonged to the genus Roseovarius, and had highest 16S rRNA gene sequence similarity of 97.7 % to Roseovarius pacificus 81-2^T, followed by Roseovarius halotolerans HJ50^T (97.5 %) and Roseovarius litoreus GSW-M15^T (96.8 %). Genome sequencing revealed a genome size of 3 378 519 bp and a G+C content of 59.8 mol %. Up-to-date bacterial core gene set analysis indicated that strain GH877^T represents one independent lineage with R. pacificus DSM29589^T. The average nucleotide identity values of GH877^T with R. pacificus 81-2^T and R. halotolerans HJ50^T are 80.7 and 77.3 %, respectively. In silico DNA-DNA hybridization values between strain GH877^T and R. pacificus 81-2^T and R. halotolerans HJ50^T are 23.2 and 20.0 %, respectively. Q-10 was the predominant respiratory quinone and summed feature 8 (C_{18  :  1} ω7c and/or C_{18  :  1} ω6c) and C_{16  :  0} were the major cellular fatty acids. The polar lipids of strain GH877^T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and two unidentified phosphoglycolipids. Based on polyphasic taxonomic analysis, strain GH877^T is proposed to represent a novel species of the genus Roseovarius, for which the name Roseovarius gahaiensis sp. nov. is proposed. (type strain GH877^T=CGMCC 1.13971^T=KCTC 72576^T).

Roseovarius spongiae sp. nov., a bacterium isolated from marine sponge

A taxonomic study was carried out on strain HN-E21^T, which was isolated from sponge collected from Yangpu Bay, Hainan, PR China. Cells of strain HN-E21^T were Gram-stain-negative, non-spore-forming, tumbling-motile, ovoid- to rod-shaped and pale-yellow-pigmented that could grow at 15-42 °C (optimum, 37 °C), at pH 6-11 (pH 7) and in 0-14 % (w/v) NaCl (2-3 %). This isolate was positive for oxidase and catalase, but negative for hydrolysis of aesculin and gelatin. The phylogenetic tree based on 16S rRNA gene sequences showed that strain HN-E21^T formed a clade with Pelagivirga sediminicola BH-SD19^T, Pontibaca methylaminivorans GRP21^T, Roseovarius antarcticus M-S13-148^T, Roseovarius aquimarinus CAU1059^T and Roseovarius nanhaiticus NH52J^T within the family Rhodobacteraceae. Strain HN-E21^T shared the highest similarity to Pelagivirga sediminicola BH-SD19^T (95.5 %), followed by Roseovarius lutimaris 112^T (95.3 %), Pelagicola litorisediminis D1-W8^T (95.2 %), Roseovarius gaetbuli YM-20^T (95.0 %) and Roseovarius marisflavi H50^T (95.0 %). The dominant fatty acids were summed feature 8 (C_18 : 1ω7c and/or C_18 : 1ω6c) and C_16:0. The major polar lipids comprised phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, three unidentified lipids and one unidentified phospholipid. The respiratory quinone was identified as Q-10. The G+C content of the genomic DNA was 66.4 mol%. Based on the phenotypic and phylogenetic data, strain HN-E21^T represents a novel species of the genus Roseovarius, for which the name Roseovarius spongiae sp. nov. is proposed, with the type strain HN-E21^T (=MCCC 1K03333^T=LMG 30456^T).