Abstract
Over half of the organic carbon on Earth's surface is trapped in marine sediment as methane hydrates. Ocean warming causes hydrate dissociation and methane leakage to the water column, rendering the characterization of microbes from hydrate depositions a pressing matter. Through genomic, phylogenetic, and biochemical assays, we characterize the first microorganisms isolated from the Rio Grande Cone (Brazil), reservoir responsible for massive methane releases to the water column. From sediment harboring rich benthic communities, we obtained 43 strains of Brevibacillus sp., Paenibacillus sp. and groups of Bacillus sp. Methane-enriched samples yielded strains of the Pseudomonas fluorescens complex, exhibiting fluorescent siderophore production and broad multi-carbon catabolism. Genomic characterization of a novel Pseudomonas sp. strain indicated 32 genes not identified in the closest related type-species, including proteins involved with mercury resistance. Our results provide phylogenetic and genomic insights on the first bacterial isolates retrieved from a poorly explored region of the South Atlantic Ocean.
Highlights
Marine sediments of continental margins around the globe store considerable mass of methane (0.5 to 12.7 x 1021 g) in the form of gas hydrates (Dickens 2011; Piñero et al 2013; Ketzer et al 2019)
Our phylogenetic analysis categorized these bacteria into four groups (Fig. 2), three of which comprised species of high 16S rRNA similarity (>99%): the B. pumilus group (n = 19), the B. megaterium group (n = 7), and the B. cereus group (n = 4)
As such, characterizing deep-sea microbial communities in the Rio Grande Cone is essential for determining the baseline environmental functioning in the area before further hydrate dissociation changes these patterns
Summary
Marine sediments of continental margins around the globe store considerable mass of methane (0.5 to 12.7 x 1021 g) in the form of gas hydrates (Dickens 2011; Piñero et al 2013; Ketzer et al 2019). Increases in temperature or decreases in pressure (sea-level fall) lead to hydrate dissociation and consequential release of methane to the ocean (Giustiniani et al 2013; Hunter et al 2013). As these environmental changes could greatly impact the microbial basis of deep-sea communities, characterizing microbes directly associated with methane reservoirs is a pressing matter. While methane-oxidizing microbes, as primary producers of these communities, are at the center of most characterization efforts targeting cold seep environments, the metabolic potential of heterotrophic bacteria from these sites is often overlooked These heterotrophs represent an essential link between primary production and higher trophic levels, growing seafloor biofilms that feed benthic fauna and ciliates (Takishita et al 2010; Niemann et al 2013). The isolation and characterization of heterotrophs from methane-rich sediments could contribute for the understanding of associated microbial communities and future biotechnological applications
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
