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Close association of active nitrifiers with B eggiatoa mats covering deep‐sea hydrothermal sediments
Author(s) -
Winkel Matthias,
Beer Dirk,
Lavik Gaute,
Peplies Jörg,
Mußmann Marc
Publication year - 2014
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12316
Subject(s) - nitrification , microbial mat , environmental chemistry , ammonia monooxygenase , biology , water column , nitrate , biogeochemical cycle , nitrogen cycle , nitrospira , chemocline , hydrothermal vent , hydrothermal circulation , nitrogen , ecology , nitrite , bacteria , chemistry , cyanobacteria , organic chemistry , genetics , paleontology
Summary Hydrothermal sediments in the G uaymas B asin are covered by microbial mats that are dominated by nitrate‐respiring and sulphide‐oxidizing B eggiatoa . The presence of these mats strongly correlates with sulphide‐ and ammonium‐rich fluids venting from the subsurface. Because ammonium and oxygen form opposed gradients at the sediment surface, we hypothesized that nitrification is an active process in these B eggiatoa mats. Using biogeochemical and molecular methods, we measured nitrification and determined the diversity and abundance of nitrifiers. Nitrification rates ranged from 74 to 605 μmol N l −1 mat day −1 , which exceeded those previously measured in hydrothermal plumes and other deep‐sea habitats. Diversity and abundance analyses of archaeal and bacterial ammonia monooxygenase subunit A genes, archaeal 16 S ribosomal RNA pyrotags and fluorescence in situ hybridization confirmed that ammonia‐ and nitrite‐oxidizing microorganisms were associated with B eggiatoa mats. Intriguingly, we observed cells of bacterial and potential thaumarchaeotal ammonia oxidizers attached to narrow, B eggiatoa ‐like filaments. Such a close spatial coupling of nitrification and nitrate respiration in mats of large sulphur bacteria is novel and may facilitate mat‐internal cycling of nitrogen, thereby reducing loss of bioavailable nitrogen in deep‐sea sediments.