Aureibaculum marinum gen. nov., sp. nov., a Novel Bacterium of the Family Flavobacteriaceae Isolated from the Bohai Gulf

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.

Metagenomic analysis of carbohydrate-active enzymes and their contribution to marine sediment biodiversity

Marine sediments constitute the world's most substantial long-term carbon repository. The microorganisms dwelling in these sediments mediate the transformation of fixed oceanic carbon, but their contribution to the carbon cycle is not fully understood. Previous culture-independent investigations into sedimentary microorganisms have underscored the significance of carbohydrates in the carbon cycle. In this study, we employ a metagenomic methodology to investigate the distribution and abundance of carbohydrate-active enzymes (CAZymes) in 37 marine sediments sites. These sediments exhibit varying oxygen availability and were isolated in diverse regions worldwide. Our comparative analysis is based on the metabolic potential for oxygen utilisation, derived from genes present in both oxic and anoxic environments. We found that extracellular CAZyme modules targeting the degradation of plant and algal detritus, necromass, and host glycans were abundant across all metagenomic samples. The analysis of these results indicates that the oxic/anoxic conditions not only influence the taxonomic composition of the microbial communities, but also affect the occurrence of CAZyme modules involved in the transformation of necromass, algae and plant detritus. To gain insight into the sediment microbial taxa, we reconstructed metagenome assembled genomes (MAG) and examined the presence of primary extracellular carbohydrate active enzyme (CAZyme) modules. Our findings reveal that the primary CAZyme modules and the CAZyme gene clusters discovered in our metagenomes were prevalent in the Bacteroidia, Gammaproteobacteria, and Alphaproteobacteria classes. We compared those MAGs to organisms from the same taxonomic classes found in soil, and we found that they were similar in its CAZyme repertoire, but the soil MAG contained a more abundant and diverse CAZyme content. Furthermore, the data indicate that abundant classes in our metagenomic samples, namely Alphaproteobacteria, Bacteroidia and Gammaproteobacteria, play a pivotal role in carbohydrate transformation within the initial few metres of the sediments.

Aureibaculum algae sp. nov. isolated from the Pacific red alga Ahnfeltia tobuchiensis

A Gram stain-negative, aerobic, rod-shaped, motile by gliding and yellow-orange-pigmented bacterium, designated strain 10Alg 115^T, was isolated from the red alga Ahnfeltia tobuchiensis. The phylogenetic analysis based on 16S rRNA gene sequences placed the novel strain within the family Flavobacteriaceae, phylum Bacteroidetes. The nearest neighbor of the new isolate was Aureibaculum marinum KCTC 62204^T with sequence similarity of 98.1%. The average nucleotide similarity and digital DNA-DNA hybridization values between the novel strain and Aureibaculum marinum KCTC 62204^T were 80% and 22.3%, respectively. The prevalent fatty acids of strain 10Alg 115^T were iso-C_15:0, iso-C_15:1 G_, iso-C_17:0 3-OH, iso-C_16:0 3-OH and C_15:0. The polar lipid profile consisted of phosphatidylethanolamine, two unidentified aminolipids and two unidentified lipids. The DNA G + C content of the type strain calculated from the whole-genome sequence was 32.2 mol%. A combination of the genotypic and phenotypic data showed that the algal isolate represents a novel species of the of genus Aureibaculum, for which the name Aureibaculum algae sp. nov. is proposed. The type strain is 10Alg 115^T (= KCTC 62086^T = KMM 6764^T).

Description of Aureibaculum luteum sp. nov. and Aureibaculum flavum sp. nov. isolated from Antarctic intertidal sediments

Two Gram-stain-negative, aerobic, non-motile, and rod-shaped bacterial strains, designated SM1352^T and A20^T, were isolated from intertidal sediments collected from King George Island, Antarctic. They shared 99.8% 16S rRNA gene sequence similarity with each other and had the highest sequence similarity of 98.1% to type strain of Aureibaculum marinum but < 93.4% sequence similarity to those of other known bacterial species. The genomes of strains SM1352^T and A20^T consisted of 5,108,092 bp and 4,772,071 bp, respectively, with the G + C contents both being 32.0%. They respectively encoded 4360 (including 37 tRNAs and 6 rRNAs) and 4032 (including 36 tRNAs and 5 rRNAs) genes. In the phylogenetic trees based on 16S rRNA gene and single-copy orthologous clusters (OCs), both strains clustered with Aureibaculum marinum and together formed a separate branch within the family Flavobacteriaceae. The ANI and DDH values between the two strains and Aureibaculum marinum BH-SD17^T were all below the thresholds for species delineation. The major cellular fatty acids (> 10%) of the two strains included iso-C_15:0, iso-C_15:1 G, iso-C_17:0 3-OH. Their polar lipids predominantly included phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified aminolipid, and two unidentified lipids. Genomic comparison revealed that both strains possessed much more glycoside hydrolases and sulfatase-rich polysaccharide utilization loci (PULs) than Aureibaculum marinum BH-SD17^T. Based on the above polyphasic evidences, strains SM1352^T and A20^T represent two novel species within the genus Aureibaculum, for which the names Aureibaculum luteum sp. nov. and Aureibaculum flavum sp. nov. are proposed. The type strains are SM1352^T (= CCTCC AB 2014243 ^T = JCM 30335 ^T) and A20^T (= CCTCC AB 2020370 ^T = KCTC 82503 ^T), respectively.

Mannheimia bovis sp. nov., Isolated from a Dead Cow with Hemorrhagic Pneumonia

Strain ZY190616^T was isolated from lung of a dead cow with hemorrhagic pneumonia in Yunnan Province, China. The strain was Gram-stain-negative, facultatively anaerobic bacterium. Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain was closely related to species of the genus Mannheimia and formed an independent clade with M.varigena CCUG 38462 ^T (97.0% similarity). Phylogenetic analysis based on recN gene indicated that the strain formed a clade with M.caviae CCUG 59995 ^T (87.8% similarity). Phylogenetic analysis based on rpoB gene indicated that the strain formed a clade with M.varigena CCUG 38462 ^T (94.7% similarity). The genomic OrthoANI values between strain ZY190616^T and M. ovis, M.haemolytica and M.granulomatis were 84.5%, 82.7% and 81.9%, respectively. The genomic G + C content was 39.8 mol%. The predominant fatty acids (> 5%) of the strain were C_16:0, C_14:0, C_18:1ω7c, summed feature 3 (C_16:1 ω7c and/ or C_16:1ω6c) and summed feature 2 (C14:0 3OH/ C16:1 Iso). The major polar lipids were phosphatidylglycerol (PG), phosphatidylethanolamine (PE), monophosphatidylglycerol (MGDG), triacylglycerol (TAG) and diphosphatidylglycerol (DLCL). The sole respiratory quinone was CoQ-7. Based on evidence from the taxonomic study, strain ZY190616^T represents a novel species of the genus Mannheimia, for which the name Mannheimia bovis sp. nov. is proposed. The type strain is ZY190616^T (= CCTCC AB 2020168 ^T = KCTC 25018 ^T).

Mannheimia ovis sp. nov., Isolated from Dead Sheep with Hemorrhagic Pneumonia

Two Gram-stain-negative, facultatively anaerobic bacteria, designated ZY170218^T and ZY180512, were isolated from lungs of dead sheep with hemorrhagic pneumonia in Yunnan Province, China and their taxonomic positions were studied by a polyphasic approach. The two isolates grew optimally at 37 °C, pH 9.0 and 1.0% NaCl (w/v), and showed identical 16S rRNA, recN and rpoB gene sequences. Phylogenetic analysis based on 16S rRNA gene sequence showed that the two strains fell within the cluster of species in the genus Mannheimia and formed a separated lineage with comparatively low similarity to the closest related species M. granulomatis (96.5%). Phylogenetic analysis based on rpoB gene indicated that the strains formed a monophyletic evolutionary lineage, with low sequence similarity ≤ 89.0% to the species of the genus Mannheimia. The genomic OrthoANI values between strain ZY170218^T and M. granulomatis and M. haemolytica were 80.4% and 83.1%, respectively. The genomic G + C content of strain ZY170218^T was 39.1 mol%. The predominant fatty acids (> 5%) of the two strains were C_16:0, C_14:0, C_18:1ω7c, summed feature 3 (C_16:1 ω7c and/ or C_16:1ω6c) and summed feature 2 (C_14:0 3OH/ C_16:1 Iso). The major polar lipids of strain ZY170218^T were phosphatidylglycerol, phosphatidylcholine, monogalactosyldiacylglycerol, bis(monoacylglycero)phosphate and diacylglycerols. The sole respiratory quinone of the two strains was CoQ-7. On the basis of phylogenetic, phenotypic and chemotaxonomic features, strain ZY170218^T and ZY180512 clearly represents a novel species of the genus Mannheimia, for which the name Mannheimia ovis sp. nov. is proposed. The type strain is ZY170218^T (= CGMCC 1.13620 ^T = KCTC 15731 ^T).