Bacterial Composition and Diversity in Deep-Sea Sediments from the Southern Colombian Caribbean Sea

Abstract

Deep-sea sediments are considered an extreme environment due to high atmospheric pressure and low temperatures, harboring novel microorganisms. To explore marine bacterial diversity in the southern Colombian Caribbean Sea, this study used 16S ribosomal RNA (rRNA) gene sequencing to estimate bacterial composition and diversity of six samples collected at different depths (1681 to 2409 m) in two localities (CCS_A and CCS_B). We found 1842 operational taxonomic units (OTUs) assigned to bacteria. The most abundant phylum was Proteobacteria (54.74%), followed by Bacteroidetes (24.36%) and Firmicutes (9.48%). Actinobacteria and Chloroflexi were also identified, but their dominance varied between samples. At the class-level, Alphaproteobacteria was most abundant (28.4%), followed by Gammaproteobacteria (24.44%) and Flavobacteria (16.97%). The results demonstrated that some bacteria were common to all sample sites, whereas other bacteria were unique to specific samples. The dominant species was Erythrobacter citreus, followed by Gramella sp. Overall, we found that, in deeper marine sediments (e.g., locality CCS_B), the bacterial alpha diversity decreased while the dominance of several genera increased; moreover, for locality CCS_A, our results suggest that the bacterial diversity could be associated with total organic carbon content. We conclude that physicochemical properties (e.g., organic matter content) create a unique environment and play an important role in shaping bacterial communities and their diversity.

Diversidade e Estrutura de Comunidades Microbianas em Áreas de Pockmarks e Diápiros de Sal na Margem Continental Brasileira (Sudoeste do Oceano Atlântico)

“…In inactive pockmarks and the adjacent sediment, the sedimentation of carbon compounds, for example, sea snow, terrestrial runoff, and fecal pellets of zooplankton, through the water column is the main factor responsible for microbial diversity (ORCUTT et al, 2011;HAVERKAMP;HAMMER;JAKOBSEN, 2014;HONG et al, 2016). However, some studies report that the sedimentation rate is different in inactive pockmarks and surrounding sediments (BARTLETT et al, 2010;PAU;.…”

“…In addition to sedimentation, another difference found between inactive pockmarks and the surrounding sediment is sediment granulometry. Inside the pockmarks, finer granulometry sediments are described, which may be related to the action of bottom currents that act differently when going through a depression, becoming slower due to the depth of the cavity (Figure 3) (PAU; HAVERKAMP;HAMMER;JAKOBSEN, 2014).…”

“…Idiomarinaceae was the dominant family in all enriched ones except for the Cult_Control_255 sample, in which the dominant family was Bacillaceae with 41.8% followed by Idiomarinaceae with 40% relative abundance. The Idiomarinacea family is composed of halophilic organisms and all its members have been isolated from saline environments, mainly marine habitats (IVANOVA et al, 2000;IVANOVA;FLAVIER;CHRISTEN, 2004;FRANCO et al, 2021).…”

“…They were primarily isolated from marine and/or saline environments and, like Idiomarinaceae, can grow across a broad salinity gradient (VENTOSA et al, 1989;GARCÍA;MELLADO, 2005;. The high abundance of this family is very interesting, since they are organisms of great biotechnological interest, especially for their ability to synthesise osmoprotectants, biopolymers, biosurfactants, and mediate the degradation of aromatic compounds (GARCÍA; VENTOSA; MELLADO, 2005;CORTI MONZÓN et al, 2018;FLORES-FERNÁNDEZ et al, 2019). When comparing the presence of this family in the environmental sediment samples, we observed that the maximum abundance found was 0.12%.…”

“…Although the genus Chromohalobacter has already been found in different studies in marine environments (FRANCO et al, 2021;, the work carried out on microbiology in pockmark fields did not report the presence of the Halomonadaceae family and, consequently, there is no record of the Chromohalobacter genus in similar regions, even in inactive pockmark fields OMOREGIE et al, 2009;HAVERKAMP;HAMMER;JAKOBSEN, 2014;GIOVANNELLI et al, 2016;IDCZAK et al, 2020;. According to the Silva database v.138, all sequences of our isolates belonging to the genus Chromohalobacter correspond to 100% similarity with the sequences of Chromohalobacter salexigens (formerly H. elongata DSM 3043), a highly remarkable species for its tolerance to salt (ARAHAL et al, 2001) (Figure 5).…”