Sargasso Sea bacterioplankton community structure and drivers of variance as revealed by DNA metabarcoding analysis

Abstract

Marine microbes provide the backbone for pelagic ecosystems by cycling and fixing nutrients and establishing the base of food webs. Microbial communities are often assumed to be highly connected and genetically mixed, with localized environmental filters driving minor changes in structure. Our study applied high-throughput Illumina 16S ribosomal RNA gene amplicon sequencing on whole-community bacterial samples to characterize geographic, environmental, and stochastic drivers of community diversity. DNA was extracted from seawater collected from the surface (N = 18) and at depth just below the deep chlorophyll-a maximum (DCM mean depth = 115.4 m; N = 22) in the Sargasso Sea and adjacent oceanographic regions. Discrete bacterioplankton assemblages were observed at varying depths in the North Sargasso Sea, with a signal for distance-decay of bacterioplankton community similarity found only in surface waters. Bacterial communities from different oceanic regions could be distinguished statistically but exhibited a low magnitude of divergence. Redundancy analysis identified temperature as the key environmental variable correlated with community structuring. The effect of dispersal limitation was weak, while variation partitioning and neutral community modeling demonstrated stochastic processes influencing the communities. This study advances understanding of microbial biogeography in the pelagic ocean and highlights the use of high-throughput sequencing methods in studying microbial community structure.

Psychromarinibacter sediminicola sp. nov., a novel salt-tolerant, metabolically diverse bacterium isolated from a solar saltern sediment, and comparison between members of family Roseobacteraceae

“…The obvious differences between M. alkaliphilus DSM 100037 T and M. lacisalsi X12M-4 T are mainly in the growth conditions, with M. alkaliphilus DSM 100037 T being extremely basophilic (optimum growth pH is 10.0), while M. lacisalsi X12M-4 T has similar pH requirements to Psychromarinibacter genus (optimum growth pH around 7.0). This may be related to the fact that Sargasso Sea (Atlantic Ocean) in which M. alkaliphilus DSM 100037 T was isolated has properties such as accumulation of alkaline substances in some water column and oligotrophic conditions (Gill et al, 2022;Lee et al, 2007). In the API and the BIOLOG tests, the two strains from genus Psychromarinibacter possessed more extensive substrate utilization than M. alkaliphilus DSM 100037 T , such as the utilization of substances such as dextrin, d-trehalose, d-cellobiose, β-hydroxy-d, l-butyric acid, and so on.…”