[A-OS17] Marine microbial ecology

[AOS17-11] Microbial community analysis of marine sediments in the inner Tokyo Bay

*Takeshi Terahara¹ (1.Tokyo University of Marine Science and Technology)

Keywords:Microbial community, Marine sediment, Tokyo Bay

Procaryotes are ubiquitous in marine and terrestrial environments. Marine sediment covers approximately 70% of the Earth's surface. The inner Tokyo Bay, where some rivers such as the Arakawa and Tamagawa Rivers flow into, is one of the areas of interest in terms of biodiversity. The 16S rRNA gene has been widely utilized for microbial community analysis as a molecular marker. In this study, microbial communities of marine sediments in the inner Tokyo Bay were analyzed by amplicon sequencing using a NextSeq 1000 system (Illumina). The sediment samples were collected at several sites such as the Arakawa River mouth and the Tamagawa River mouth in the inner Tokyo Bay using the training ship Hiyodori in May, August and November 2024 and January 2025. DNA was extracted from the samples using the ISOIL for Beads Beating (Nippon Gene). Amplicon sequencing was performed targeting the V4 region of bacterial and archaeal 16S rRNA genes. After merging the paired-end reads and removing the chimeras, 37,102–38,812 reads (the average reads per sample: 37,987) were obtained. A total of 21,684 amplicon sequence variants (ASVs) were detected. The number of ASVs ranged from 2,001 to 2,524 (the average ASVs per sample: 2,265). The classes Deltaproteobacteria or Gammaproteobacteria were most predominant in all of the samples, followed by the classes Anaerolineae, Epsilonproteobacteria, Thermoplasmata or Parvarchaea (the proposed lineage), which were different among the samples. Members of the class Deltaproteobacteria, which are ecologically and metabolically diverse, were recently reclassified into four phyla, the Desulfobacterota, Myxococcota, Bdellovibrionota and a phylum comprising the uncultured SAR324 cluster (Waite et al., Int. J. Syst. Evol. Microbiol. 2020). Gammaproteobacteria are abundant and globally distributed, and would play an important role of marine carbon and sulfur cycles (Dyksma et al., ISME J. 2016). In addition, the families Desulfobacteraceae, Desulfobulbaceae or Helicobacteraceae were most predominant in all of the samples. The microbial communities of the sediments in the inner Tokyo Bay could be affected by geological and environmental factors such as water depth and river mouth.