Inhibition of nitrate reduction by chromium (VI) in anaerobic soil microcosms.
Chromium is often found as a cocontaminant at sites polluted with organic compounds. For nitrate-respiring microbes, Cr(VI) may be not only directly toxic but may also specifically interfere with N reduction. In soil microcosms amended with organic electron donors, Cr(VI), and nitrate, bacteria oxidized added carbon, but relatively low doses of Cr(VI) caused a lag and then lower rates of CO(2) accumulation. Cr(VI) strongly inhibited nitrate reduction; it occurred only after soluble Cr(VI) could not be detected. However, Cr(VI) additions did not eliminate Cr-sensitive populations; after a second dose of Cr(VI), bacterial activity was strongly inhibited. Differences in microbial community composition (assayed by PCR-denaturing gradient gel electrophoresis) driven by different organic substrates (glucose and protein) were smaller than when other electron acceptors had been used. However, the selection of bacterial phylotypes was modified by Cr(VI). Nine isolated clades of facultatively anaerobic Cr(VI)-resistant bacteria were closely related to cultivated members of the phylum Actinobacteria or Firmicutes. In Bacillus cereus GNCR-4, the nature of the electron donor (fermentable or nonfermentable) affected Cr(VI) resistance level and anaerobic nitrate metabolism. Our results indicate that carbon utilization and nitrate reduction in these soils were contingent upon the reduction of added Cr(VI). The amount of Cr(VI) required to inhibit nitrate reduction was 10-fold less than for aerobic catabolism of the same organic substrate. We speculate that the resistance level of a microbial process is directly related to the diversity of microbes capable of conducting it.
Kourtev
Peter S
PS
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA. kourt1ps@cmich.edu
Nakatsu
Cindy H
CH
Konopka
Allan
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D044822:Biodiversity; D002244:Carbon / Q000378:metabolism; D002857:Chromium / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D009691:Nucleic Acid Denaturation; D010084:Oxidation-Reduction; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D009566:Nitrates; D002857:Chromium; C074702:chromium hexavalent ion; D002244:Carbon
Appl Microbiol Biotechnol. 2002 Oct;60(1-2):192-9
12382063
Biotechnol Bioeng. 1995 May 5;46(3):194-201
18623304
Appl Environ Microbiol. 1997 Dec;63(12):4679-85
16535749
J Hazard Mater. 2000 Dec 30;80(1-3):69-80
11080570
Appl Environ Microbiol. 2004 Jul;70(7):4230-41
15240306
Proc Natl Acad Sci U S A. 1999 Feb 16;96(4):1463-8
9990046
Appl Environ Microbiol. 2006 Jan;72(1):628-37
16391100
FEMS Microbiol Ecol. 2002 Oct 1;42(1):109-18
19709270
Microb Ecol. 2006 Feb;51(2):209-19
16463132
J Biol Chem. 1951 Nov;193(1):265-75
14907713
Biotechnol Bioeng. 2003 Sep 20;83(6):627-37
12889027
Mikrobiologiia. 2006 Mar-Apr;75(2):160-4
16758862
Rev Environ Contam Toxicol. 2003;178:93-164
12868782
Appl Environ Microbiol. 1999 Jan;65(1):61-6
9872760
Appl Environ Microbiol. 1999 Feb;65(2):529-33
9925578
FEMS Microbiol Ecol. 2005 Sep 1;54(1):35-46
16329970
FEMS Microbiol Ecol. 2001 Jun;36(1):11-19
11377769
Appl Environ Microbiol. 1991 May;57(5):1498-503
1854203
Appl Environ Microbiol. 1996 Aug;62(8):2970-7
16535383
Nucleic Acids Res. 1989 Oct 11;17(19):7843-53
2798131
Biodegradation. 2000;11(2-3):159-70
11440242
Appl Environ Microbiol. 2005 Dec;71(12):7679-89
16332740
Can J Microbiol. 2002 Apr;48(4):333-41
12030706
J Ind Microbiol Biotechnol. 2005 Sep;32(9):409-14
16091944
J Environ Qual. 2003 Jul-Aug;32(4):1228-33
12931876
Nucleic Acids Res. 1997 Sep 1;25(17):3389-402
9254694
Appl Environ Microbiol. 2003 Mar;69(3):1847-53
12620881
Appl Environ Microbiol. 2004 Aug;70(8):4756-65
15294812