Limited carbon cycling due to high-pressure effects on the deep-sea microbiome

Mon, 28 Nov 2022 00:00:00 +0000

Deep-sea microbial communities are exposed to high-pressure conditions, which has a variable impact on prokaryotes depending on whether they are piezophilic (that is, pressure-loving), piezotolerant or piezosensitive. While it has been suggested that elevated pressures lead to higher community-level metabolic rates, the response of these deep-sea microbial communities to the high-pressure conditions of the deep sea is poorly understood. Based on microbial activity measurements in the major oceanic basins using an in situ microbial incubator, we show that the bulk heterotrophic activity of prokaryotic communities becomes increasingly inhibited at higher hydrostatic pressure. At 4,000 m depth, the bulk heterotrophic prokaryotic activity under in situ hydrostatic pressure was about one-third of that measured in the same community at atmospheric pressure conditions. In the bathypelagic zone—between 1,000 and 4,000 m depth—~85% of the prokaryotic community was piezotolerant and ~5% of the prokaryotic community was piezophilic. Despite piezosensitive-like prokaryotes comprising only ~10% (mainly members of Bacteroidetes, Alteromonas ) of the deep-sea prokaryotic community, the more than 100-fold metabolic activity increase of these piezosensitive prokaryotes upon depressurization leads to high apparent bulk metabolic activity. Overall, the heterotrophic prokaryotic activity in the deep sea is likely to be substantially lower than hitherto assumed, with major impacts on the oceanic carbon cycling.

Impact of hydrostatic pressure on organic carbon cycling of the deep-sea microbiome

Thu, 31 Mar 2022 00:00:00 +0000

Deep-sea microbial communities are exposed to high hydrostatic pressure. While some of these deep-sea prokaryotes are adapted to high-pressure conditions, the contribution of piezophilic (i.e., pressure-loving) and piezotolerant prokaryotes to the total deep-sea prokaryotic community remains unknown. Here we show that the metabolic activity of prokaryotic communities is increasingly inhibited with increasing hydrostatic pressure. At 4,000 m depth, the bulk heterotrophic prokaryotic activity under in sit u hydrostatic pressure was only about one-third of that measured on the same community at atmospheric pressure conditions. Only ∼5% of the bathypelagic prokaryotic community are piezophilic while ∼85% of the deep-sea prokaryotes are piezotolerant. A small fraction (∼10%) of the deep-sea prokaryotes is piezosensitive (mainly members of Bacteroidetes, Alteromonas) exhibiting specific survival strategies at meso- and bathypelagic depths. These piezosensitive bacteria elevated their activity by more than 100-fold upon depressurization. Hence, the consistently higher bulk metabolic activity of the deep-sea prokaryotic community measured upon depressurization is due to a rather small fraction of the prokaryotic community. Overall, the heterotrophic prokaryotic activity in the deep-sea is substantially lower than hitherto assumed with major impacts on the oceanic carbon cycling.

Murat Kisadur | Amano Lab | Hokkaido University

Limited carbon cycling due to high-pressure effects on the deep-sea microbiome

Impact of hydrostatic pressure on organic carbon cycling of the deep-sea microbiome