Diversity, distribution, and expression of diazotroph nifH genes in oxygen-deficient waters of the Arabian Sea

Amal Jayakumar, Mamoon M.D. Al-Rshaidat, Bettie Ward, Margaret R. Mulholland

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

The Arabian Sea oxygen minimum zone (OMZ), the largest suboxic region in the world's oceans, is responsible for up to half of the global mesopelagic fixed nitrogen ( N ) loss from the ocean via denitrification and anammox. Dinitrogen ( N2 ) fixation is usually attributed to cyanobacteria in the surface ocean. Model prediction and physiological inhibition of N2 fixation by oxygen, however, suggest that N2 fixation should be enhanced near the oxygen-deficient zone (ODZ) of the Arabian Sea. N2 fixation and cyanobacterial nifH genes (the gene encoding dinitrogenase reductase) have been reported in surface waters overlying the Arabian Sea ODZ. Here, water samples from depths above and within the Arabian Sea ODZ were examined to explore the distribution, diversity, and expression of nifH genes. In surface waters, nifH DNA and cDNA sequences related to Trichodesmium, a diazotroph known to occur and fix N2 in the Arabian Sea, were detected. Proteobacterial nifH phylotypes (DNA but not cDNA) were also detected in surface waters. Proteobacterial nifH DNA and cDNA sequences, as well as nifH DNA and cDNA sequences related to strictly anaerobic N -fixers, were obtained from oxygen-deficient depths. This first report of nifH gene expression in subsurface low-oxygen waters suggests that there is potential for active N2 fixation by several phylogenetically and potentially metabolically diverse microorganisms in pelagic OMZs.

Original languageEnglish (US)
Pages (from-to)597-606
Number of pages10
JournalFEMS microbiology ecology
Volume82
Issue number3
DOIs
StatePublished - Dec 1 2012

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Ecology
  • Applied Microbiology and Biotechnology

Keywords

  • Arabian Sea
  • Nitrogen fixation
  • Oxygen deficient zone
  • nifH gene diversity and expression

Fingerprint Dive into the research topics of 'Diversity, distribution, and expression of diazotroph nifH genes in oxygen-deficient waters of the Arabian Sea'. Together they form a unique fingerprint.

  • Cite this