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.

Mesonia aestuariivivens sp. nov., isolated from a tidal flat

A Gram-negative, aerobic, non-flagellated and ovoid or rod-shaped bacterial strain (JHPTF-M18^T), which was isolated from a tidal flat sediment in Republic of Korea, was taxonomically characterized. Strain JHPTF-M18^T grew optimally at 25 °C, at pH 7.0-7.5 and in the presence of 2.0-3.0% (w/v) NaCl. 16S rRNA gene sequence analysis showed that strain JHPTF-M18^T forms a phylogenetic lineage within the radiation comprising type strains of Mesonia species. The 16S rRNA gene of strain JHPTF-M18^T shared sequence similarities of 97.7% with that of type strain of M. mobilis and 92.5-96.8% with those of type strains of the other nine Mesonia species. The DNA G+C content was 33.1% based on its genomic sequence. AAI, ANI and dDDH values between strain JHPTF-M18^T and the type strains of M. mobilis, M. hitae, M. oceanica, M. phycicola and M. algae were 72.1-83.7%, 73.1-79.7% and 18.5-22.8%, respectively. Strain JHPTF-M18^T contained MK-6 as the predominant menaquinone and iso-C_15:0, iso-C_17:0 3-OH and summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c) as its major fatty acids. Major polar lipids of strain JHPTF-M18^T were phosphatidylethanolamine and two unidentified lipids. Strain JHPTF-M18^T was separated from recognized Mesonia species by its phenotypic properties together with the phylogenetic and genetic distinctiveness. Based on data presented in this study, strain JHPTF-M18^T is considered to represent a novel species of the genus Mesonia. The name Mesonia aestuariivivens sp. nov. is proposed for JHPTF-M18^T (=KACC 22185^T = NBRC 115119^T).

Description of Abyssalbus ytuae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from the sediment of the Mariana Trench

In this study, we describe a Gram-stain-negative, rod-shaped, non-motile and aerobic bacterium, named strain MT3330T, which was isolated from the deep-sea sediment of the Mariana Trench. Growth of MT3330T occurred at 15–40 °C (optimum, 25–30 °C), pH 5.0–10.0 (optimum, 7.0–8.0) and with 0–8.0 % (w/v) NaCl (optimum, 0–2.0 %). The results of phylogenetic analysis based on 16S rRNA gene sequence indicated that MT3330T represented a member of the family Flavobacteriaceae and was most closely related to Zhouia spongiae HN-Y44T (92.3 % sequence similarity). The results of genomic analysis indicated that MT3330T contains a circular chromosome of 4 365 036 bp with a DNA G+C content of 35.2 %. The predominant respiratory quinone of MT3330T was MK-6. The polar lipids of MT3330T included phosphatidylethanolamine, three unidentified amino lipids and four unidentified lipids. The major fatty acids of MT3330T included C15 : 0, iso-C15 : 1G, iso-C15 : 0 3-OH, and iso-C17 : 0 3-OH. On the basis of the results of the phylogenetic, physiological, biochemical and morphological analyses, it is suggested that strain MT3330T represents a novel genus and a novel species of the family Flavobacteriaceae , and the name Abyssalbus ytuae gen. nov., sp. nov. is proposed. The type strain is MT3330T (=MCCC 1K06012T=KCTC 82823T).

Pseudobizionia ponticola gen. nov., sp. nov., isolated from seawater

A Gram-stain-negative, aerobic, non-motile and ovoid or rod-shaped bacterial strain, designated MM-14^T, was isolated from seawater sampled from the Yellow Sea in the Republic of Korea and its taxonomic position was investigated using a polyphasic approach. Strain MM-14^T grew optimally at 30 °C and in the presence of approximately 2.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain MM-14^T clustered with the type strain of Hanstruepera neustonica. The novel strain exhibited a 16S rRNA gene sequence similarity value of 96.06 % to the type strain of H. neustonica, but higher 16S rRNA gene sequence similarity values (96.13-96.69 %) to the type strains of Bizionia echini, Bizionia hallyeonensis and Bizionia psychrotolerans. Strain MM-14^T contained MK-6 as the predominant menaquinone and iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH as the major fatty acids. The major polar lipids were phosphatidylethanolamine, one unidentified lipid and one unidentified aminolipid. The DNA G+C content of strain MM-14^T was 34.6 mol%. The phylogenetic and chemotaxonomic data and other phenotypic properties revealed that strain MM-14^T constitutes a new genus and species within the family Flavobacteriaceae of the phylum Bacteroidetes, for which the name Pseudobizionia ponticola gen. nov., sp. nov. is proposed. The type strain of Pseudobizionia ponticola is MM-14^T (=KACC 19434^T=KCTC 62139^T=NBRC 113019^T).