skip to main content


Title: NifH-Harboring Bacterial Community Composition across an Alaskan Permafrost Thaw Gradient

Since nitrogen (N) is often limiting in permafrost soils, we investigated the N 2-fixing genetic potential and the inferred taxa harboring those genes by sequencing nifH gene fragments in samples taken along a permafrost thaw gradient in an Alaskan boreal soil. Samples from minimally, moderately and extensively thawed sites were taken to a depth of 79 cm to encompass zones above and below the depth of the water table. NifH reads were translated with frameshift correction and 112,476 sequences were clustered at 5% amino acid dissimilarity resulting in 1,631 OTUs. Sample depth in relation to water table depth was correlated to differences in the NifH sequence classes with those most closely related to group I nifH-harboring Alpha- and Beta-Proteobacteria in higher abundance above water table depth while those related to group III nifH-harboring Delta Proteobacteria more abundant below. The most dominant below water table depth NifH sequences, comprising 1/3 of the total, were distantly related to Verrucomicrobia-Opitutaceae. Overall, these results suggest that permafrost thaw alters the class-level composition of N 2-fixing communities in the thawed soil layers and that this distinction corresponds to the depth of the water table. These nifH data were also compared to nifH sequences obtained frommore » a study at an Alaskan taiga site, and to those of other geographically distant, non-permafrost sites. The two Alaska sites were differentiated largely by changes in relative abundances of the same OTUs, whereas the non-Alaska sites were differentiated by the lack of many Alaskan OTUs, and the presence of unique halophilic, sulfate- and iron-reducing taxa in the Alaska sites.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [3] ;  [3] ;  [3] ;  [3] ;  [5] ;  [6] ;  [4] ;  [7]
  1. Arizona State Univ., Mesa, AZ (United States); Arizona State Univ., Tempe, AZ (United States)
  2. Univ. of Oklahoma, Norman, OK (United States); Xiamen Univ., Xiamen (China)
  3. Univ. of Oklahoma, Norman, OK (United States)
  4. Michigan State Univ., East Lansing, MI (United States)
  5. Xiamen Univ., Xiamen (China)
  6. Northern Arizona Univ., Flagstaff, AZ (United States)
  7. Univ. of Oklahoma, Norman, OK (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tsinghua Univ., Beijing (China)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Frontiers in Microbiology
Additional Journal Information:
Journal Volume: 7; Journal Issue: NOV; Journal ID: ISSN 1664-302X
Frontiers Research Foundation
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES; nifH; nitrogen-fixing; permafrost; diazotroph; nitrogen; microbial
OSTI Identifier: