Soil microbial community response to hexavalent chromium in planted and unplanted soil

Ioannis Ipsilantis, Mark S. Coyne

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Theories suggest that rapid microbial growth rates lead to quicker development of metal resistance. We tested these theories by adding hexavalent chromium [Cr(VI)] to soil, sowing Indian mustard (Brassica juncea), and comparing rhizosphere and bulk soil microbial community responses. Four weeks after the initial Cr(VI) application we measured Cr concentration, microbial biomass by fumigation extraction and soil extract ATP, tolerance to Cr and growth rates with tritiated thymidine incorporation, and performed community substrate use analysis with BIOLOG GN plates. Exchangeable Cr(VI) levels were very low, and therefore we assumed the Cr(VI) impact was transient. Microbial biomass was reduced by Cr(VI) addition. Microbial tolerance to Cr(VI) tended to be higher in the Cr-treated rhizosphere soil relative to the non-treated systems, while microorganisms in the Cr-treated bulk soil were less sensitive to Cr(VI) than microorganisms in the non-treated bulk soil. Microbial diversity as measured by population evenness increased with Cr(VI) addition based on a Gini coefficient derived from BIOLOG substrate use patterns. Principal component analysis revealed separation between Cr(VI) treatments, and between rhizosphere and bulk soil treatments. We hypothesize that because of Cr(VI) addition there was indirect selection for fast-growing organisms, alleviation of competition among microbial communities, and increase in Cr tolerance in the rhizosphere due to the faster turnover rates in that environment.

Original languageEnglish
Pages (from-to)638-645
Number of pages8
JournalJournal of Environmental Quality
Issue number3
StatePublished - May 2007

ASJC Scopus subject areas

  • Environmental Engineering
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution
  • Management, Monitoring, Policy and Law


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