|Title||Identification of free-living and particle-associated microbial communities present in hadal regions of the Mariana Trench|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Tarn J., Peoples L.M, Hardy K., Cameron J., Bartlett DH|
|Journal||Frontiers in Microbiology|
|Type of Article||Article|
|Keywords||archaea; arctic-ocean; bacterial communities; dark biosphere; deep-sea microbiology; deep-sea sediments; diversity; gen. nov.; hadal; hydrothermal vent plumes; marine microbial; marine planktonic; pacific subtropical gyre; particulate organic-matter; piezophile; puerto-rico; sp-nov.; trench|
Relatively few studies have described the microbial populations present in ultra-deep hadal environments, largely as a result of difficulties associated with sampling. Here we report Illumina-tag V6 16S rRNA sequence-based analyses of the free-living and particle-associated microbial communities recovered from locations within two of the deepest hadal sites on Earth, the Challenger Deep (10,918 meters below surface-mbs) and the Sirena Deep (10,667 mbs) within the Mariana Trench, as well as one control site (Ulithi Atoll, 761 mbs). Seawater samples were collected using an autonomous lander positioned similar to 1 m above the seafloor. The bacterial populations within the Mariana Trench bottom water samples were dissimilar to other deep-sea microbial communities, though with overlap with those of diffuse flow hydrothermal vents and deep subsurface locations. Distinct particle-associated and free-living bacterial communities were found to exist. The hadal bacterial populations were also markedly different from one another, indicating the likelihood of different chemical conditions at the two sites. In contrast to the bacteria, the hadal archaeal communities were more similar to other less deep datasets and to each other due to an abundance of cosmopolitan deep-sea taxa. The hadal communities were enriched in 34 bacterial and 4 archaeal operational taxonomic units (OTUs) including members of the Gammaproteobacteria, Epsilonproteobacteria, Marinimicrobia, Cyanobacteria, Deltaproteobacteria, Gemmatimonadetes, Atribacteria, Spirochaetes, and Euryarchaeota. Sequences matching cultivated piezophiles were notably enriched in the Challenger Deep, especially within the particle-associated fraction, and were found in higher abundances than in other hadal studies, where they were either far less prevalent or missing. Our results indicate the importance of heterotrophy, sulfur-cycling, and methane and hydrogen utilization within the bottom waters of the deeper regions of the Mariana Trench, and highlight novel community features of these extreme habitats.
The benthic boundary layer bottom water microbial communities of two hadal regions of the Mariana Trench have been shown to be surprisingly distinct, particularly among the bacteria. However, both deep trench sites were dominated by heterotrophic Gammaproteobacteria, as well as Nitrosopumilus and Euryarchaetoa. Other abundant taxa included Alpha- Beta- Delta- and Epsilonproteobacteria and anaerobic methane oxidizing archaea. Bacterial and archaeal communities in our samples showed different patterns of enrichment, with bacteria typically clustering based on sampling site and archaea according to the filter pore size fraction. Many of the analyses indicate connections between the Mariana Trench hadal samples and subsurficial and vent-derived communities and taxa. This was most evident in the case of the Sirena Deep, which harbored a distinct Pseudoalteromonas-dominated microbial community. Clear patterns of hadal enrichment were identified in specific OTUs belonging to a number of phyla and subphyla, including Gammaproteobacteria, Epsilonproteobacteria, Marinimicrobia, Cyanobacteria, Deltaproteobacteria, Gemmatimonadetes, Atribacteria, Spirochaetes, and Euryarchaeota. Additional studies will be needed to assess the significance of the microbes identified to biogeochemical processes occurring at great depth as well as the generality of our results over time and in additional hadal locations.