Insights into the prokaryotic communities of the abyssal-hadal benthic-boundary layer of the Kuril Kamchatka Trench

Susanna Gorrasi; Andrea Franzetti; Angelika Brandt; Ulrike Minzlaff; Marcella Pasqualetti; Massimiliano Fenice

doi:10.1186/s40793-023-00522-9

Insights into the prokaryotic communities of the abyssal-hadal benthic-boundary layer of the Kuril Kamchatka Trench

Environ Microbiome. 2023 Aug 2;18(1):67. doi: 10.1186/s40793-023-00522-9.

Authors

Susanna Gorrasi¹, Andrea Franzetti², Angelika Brandt^{3

4}, Ulrike Minzlaff⁴, Marcella Pasqualetti⁵, Massimiliano Fenice^{6

7}

Affiliations

¹ Laboratory of Microbiology, Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, 01100, Italy. gorrasi@unitus.it.
² Laboratory of Microbiology, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, 20126, Italy.
³ Senckenberg Research Institute and Natural History Museum, 60325, Frankfurt am Main, Germany.
⁴ Institute of Ecology, Diversity and Evolution, Goethe University, 60438, Frankfurt am Main, Germany.
⁵ Laboratory of Ecology of Marine Fungi - CoNISMa, Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, 01100, Italy.
⁶ Laboratory of Microbiology, Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, 01100, Italy. fenice@unitus.it.
⁷ Laboratory of Applied Marine Microbiology - CoNISMa, Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, 01100, Italy. fenice@unitus.it.

Abstract

Background: The Kuril-Kamchatka Trench (maximum depth 9604 m), located in the NW Pacific Ocean, is among the top seven deepest hadal trenches. The work aimed to investigate the unexplored abyssal-hadal prokaryotic communities of this fascinating, but underrated environment.

Results: As for the bacterial communities, we found that Proteobacteria (56.1-74.5%), Bacteroidetes (6.5-19.1%), and Actinobacteria (0.9-16.1%) were the most represented bacterial phyla over all samples. Thaumarchaeota (52.9-91.1%) was the most abundant phylum in the archaeal communities. The archaeal diversity was highly represented by the ammonia-oxidizing Nitrosopumilus, and the potential hydrocarbon-degrading bacteria Acinetobacter, Zhongshania, and Colwellia were the main bacterial genera. The α-diversity analysis evidenced that both prokaryotic communities were characterized by low evenness, as indicated by the high Gini index values (> 0.9). The β-diversity analysis (Redundancy Analysis) indicated that, as expected, the depth significantly affected the structure of the prokaryotic communities. The co-occurrence network revealed seven prokaryotic groups that covaried across the abyssal-hadal zone of the Kuril-Kamchatka Trench. Among them, the main group included the most abundant archaeal and bacterial OTUs (Nitrosopumilus OTU A2 and OTU A1; Acinetobacter OTU B1), which were ubiquitous across the trench.

Conclusions: This manuscript represents the first attempt to characterize the prokaryotic communities of the KKT abyssal-hadal zone. Our results reveal that the most abundant prokaryotes harbored by the abyssal-hadal zone of Kuril-Kamchatka Trench were chemolithotrophic archaea and heterotrophic bacteria, which did not show a distinctive pattern distribution according to depth. In particular, Acinetobacter, Zhongshania, and Colwellia (potential hydrocarbon degraders) were the main bacterial genera, and Nitrosopumilus (ammonia oxidizer) was the dominant representative of the archaeal diversity.

Keywords: 16S rRNA gene amplicon sequencing; Abyssal-hadal zone; Archaeal communities; Bacterial communities; Deep Sea; Kuril Kamchatka Trench.