Open AccessCultivation and isolation of N 2 ‐fixing bacteria from suboxic waters in the Baltic Sea
Author(s) -
BentzonTilia Mikkel,
Farnelid Hanna,
Jürgens Klaus,
Riemann Lasse
Publication year - 2014
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12304
Subject(s) - bacterioplankton , biology , diazotroph , anoxic waters , bacteria , water column , marine bacteriophage , seawater , nitrogenase , heterotroph , botany , nitrogen fixation , ecology , nutrient , phytoplankton , genetics
Nitrogenase genes ( nifH ) from heterotrophic dinitrogen (N 2 )‐fixing bacteria appear ubiquitous in marine bacterioplankton, but the significance of these bacteria for N cycling is unknown. Quantitative data on the N 2 ‐fixation potential of marine and estuarine heterotrophs are scarce, and the shortage of cultivated specimens currently precludes ecophysiological characterization of these bacteria. Through the cultivation of diazotrophs from suboxic (1.79 μmol O 2 L −1 ) Baltic Sea water in an artificial seawater medium devoid of combined N, we report the cultivability of a considerable fraction of the diazotrophic community in the Gotland Deep. Two nifH clades were present both in situ and in enrichment cultures showing gene abundances of up to 4.6 × 10 5 and 5.8 × 10 5 nifH gene copies L −1 within two vertical profiles in the Baltic Sea. The distributions of the two clades suggested a relationship with the O 2 concentrations in the water column as abundances increased in the suboxic and anoxic waters. It was possible to cultivate and isolate representatives from one of these prevalent clades, and preliminary analysis of their ecophysiology demonstrated growth optima at 0.5–15 μmol O 2 L −1 and 186–194 μmol O 2 L −1 in the absence of combined N.