We examined diazotroph activity in controlled experiments containing natural populations of nitrogen (N2)fixing microbes collected offshore from Kane’ohe Bay, Hawai’i, and from Station ALOHA (A Long-term Oligotrophic Habitat Assessment) in the North Pacific subtropical gyre. Quantitative polymerase chain reaction and reverse transcription-polymerase chain reaction approaches showed that the abu...

A PCR-based assay (Mrnif) targeting the nifH gene of Methanobrevibacter ruminantium was developed to detect fecal pollution from domesticated ruminants in environmental water samples. The assay produced the expected amplification product only when the reaction mixture contained DNA extracted from M. ruminantium culture, bovine (80%), sheep (100%), and goat (75%) feces, and water samples from a ...

We herein report that Azorhizobium caulinodans PII and GlnK are not necessary for glutamine synthetase (GS) adenylylation whereas both proteins are required for complete GS deadenylylation. The disruption of both glnB and glnK resulted in a high level of GS adenylylation under the condition of nitrogen fixation, leading to ammonium excretion in the free-living state. PII and GlnK also controlle...

Two facultatively anaerobic, nitrogen-fixing bacteria (strains MSSRF30(T) and MSSRF31) were isolated from a mangrove-associated wild rice (Porteresia coarctata Tateoka). These strains were determined to be nitrogen-fixers using the acetylene reduction assay and by PCR detection of a nifH gene amplicon. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the novel strains were ...

The endophytic diazotroph Azoarcus sp. strain BH72 is capable of infecting rice roots and of expressing the nitrogenase (nif) genes there. In order to study the genetic background for nitrogen fixation in strain BH72, the structural genes of nitrogenase (nifHDK) were cloned and sequenced. The sequence analysis revealed an unusual gene organization: downstream of nifHDK, a ferredoxin gene (fdxN;...

Growth, protein amount, and activity levels of metabolic pathways in Trichodesmium are influenced by environmental changes such as elevated pCO(2) and temperature. This study examines changes in the expression of essential metabolic genes in Trichodesmium grown under a matrix of pCO(2) (400 and 900 µatm) and temperature (25 and 31°C). Using RT-qPCR, we studied 21 genes related to four metabolic...