Microbial diversity of sediments from an inactive hydrothermal vent field, Southwest Indian Ridge

Abstract

The Southwest Indian Ridge, which is the slowest-spreading of the main ridges, separates the African and Antarctic plates. The slow expanding rate is associated with less density of hydrothermal vent fields, shorter longevity of hydrothermal activity, cold mantle temperatures and thick lithosphere. However, the microbial communities adapting to such specific characteristics of this area have remained largely unexplored. To study the microbial diversity at the Southwest Indian Ridge, we sampled three sediment cores in a newly found inactive vent field, the Tianzuo field, and used high-throughput sequencing of 16S rRNA genes to reveal the microbial composition. Microbial communities of three sampling sites were very similar at the surface, and underwent a gradient change along depth. Gammaproteobacteria, namely Alteromonadaceae, Nitrosococcus and the JTB255 marine benthic group, were the most dominant bacterial taxa. Marine Group I was the dominant archaeal taxon in our samples. In addition, microbial populations capable of ammonia oxidation, nitrite oxidation, sulfur oxidation and manganese oxidation were detected to be the main chemolithoautotrophs. The enrichment of sulfur-oxidizing and manganese-oxidizing bacteria was observed in deep layers. When compared with other vent fields along different ocean ridges, the Tianzuo field showed distinct composition in both archaeal and bacterial communities. These results provide the first view of microbial communities of the Tianzuo field at the Southwest Indian Ridge, and give a better understanding of metabolic potential possessed by the microbial populations.

Gramella bathymodioli sp. nov., isolated from a mussel inhabiting a hydrothermal field in the Okinawa Trough

“…Following the in-depth study of hydrothermal areas, it has been reported that abundant and diverse microbial communities can be found living near hydrothermal vents [8, 9], and have close relationships with the hydrothermal animal communities, including tubeworms, shrimp, crabs and mussels. Mussel samples ( Bathymodiolus azoricus ) were collected from Tangyin hydrothermal field (station R11, 25° 0′ N, 122° 34′ E) at a depth of 1165 m in the Okinawa Trough during the cruise HOBAB4 conducted by the R/V Kexue in June 2016.…”

Vertical diversity and association pattern of total, abundant and rare microbial communities in deep‐sea sediments

“…Previous studies have discussed vertical benthic microbial diversity in varied depth ranges (Inagaki et al, 2003, 2015; Nunoura et al, 2016, 2018; Schauer et al, 2010; Starnawski et al, 2017; Vuillemin, Vargas, et al, 2020; Vuillemin et al, 2019; Walsh et al, 2016), and highly resolved vertical profiles of microbial communities in sediments will help to better depict the stratified community structure and continuous variations in microbial diversity. However, so far, the majority of these studies have often focused on specific types of sedimentary environment (Nunoura et al, 2018; Yang et al, 2020) or comparison of microbial community over large spatial or temporal scales (Böer et al, 2009; Hoshino et al, 2020; Hoshino & Inagaki, 2019). Parallel comparison of site‐to‐site microbial diversity at different depths in a less varied sediment region is scarce.…”

Muricauda alvinocaridis sp. nov., isolated from shrimp gill from the Okinawa Trough

“…Diverse microbial communities are found in deep sea hydrothermal vent fields globally, including free-living and symbiotic bacteria [9]. Shrimp samples ( Alvinocaris longirostris ) were collected from the Tangyin hydrothermal field (station R11, 25° 0′ N, 122° 34′ E) at the sea water depth of 1165 m in the Okinawa Trough during the cruise ‘HOBAB4’ conducted by the R/V Kexue in June 2016 [10].…”