Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1

Persistent Link:
http://hdl.handle.net/10150/610053
Title:
Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1
Author:
He, Minyan; Li, Xiangyang; Guo, Liang; Miller, Susan; Rensing, Christopher; Wang, Gejiao
Affiliation:
State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China; Department of Soil, Water and Environmental Science, The University of Arizona, Tucson, AZ 85721, USA; Biotechnology Computing Facility, Arizona Research Laboratories, The University of Arizona, Tucson, AZ 85721, USA
Issue Date:
2010
Publisher:
BioMed Central
Citation:
He et al. BMC Microbiology 2010, 10:221 http://www.biomedcentral.com/1471-2180/10/221
Journal:
BMC Microbiology
Rights:
© 2010 He et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0)
Collection Information:
This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at repository@u.library.arizona.edu.
Abstract:
BACKGROUND:Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by Bacillus cereus SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence.RESULTS:Bacillus cereus SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, chrIA1, and two additional chrA genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene azoR and four nitroreductase genes nitR possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes chrA1 and chrI was induced in response to Cr(VI) but expression of the other two chromate transporter genes chrA2 and chrA3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of chrIA1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of chrIA1 in B. cereus SJ1 implied the possibility of recent horizontal gene transfer.CONCLUSION:Our results indicate that expression of the chromate transporter gene chrA1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the chrIA1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of B. cereus SJ1.
EISSN:
1471-2180
DOI:
10.1186/1471-2180-10-221
Version:
Final published version
Additional Links:
http://www.biomedcentral.com/1471-2180/10/221

Full metadata record

DC FieldValue Language
dc.contributor.authorHe, Minyanen
dc.contributor.authorLi, Xiangyangen
dc.contributor.authorGuo, Liangen
dc.contributor.authorMiller, Susanen
dc.contributor.authorRensing, Christopheren
dc.contributor.authorWang, Gejiaoen
dc.date.accessioned2016-05-20T08:57:30Z-
dc.date.available2016-05-20T08:57:30Z-
dc.date.issued2010en
dc.identifier.citationHe et al. BMC Microbiology 2010, 10:221 http://www.biomedcentral.com/1471-2180/10/221en
dc.identifier.doi10.1186/1471-2180-10-221en
dc.identifier.urihttp://hdl.handle.net/10150/610053-
dc.description.abstractBACKGROUND:Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by Bacillus cereus SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence.RESULTS:Bacillus cereus SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, chrIA1, and two additional chrA genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene azoR and four nitroreductase genes nitR possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes chrA1 and chrI was induced in response to Cr(VI) but expression of the other two chromate transporter genes chrA2 and chrA3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of chrIA1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of chrIA1 in B. cereus SJ1 implied the possibility of recent horizontal gene transfer.CONCLUSION:Our results indicate that expression of the chromate transporter gene chrA1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the chrIA1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of B. cereus SJ1.en
dc.language.isoenen
dc.publisherBioMed Centralen
dc.relation.urlhttp://www.biomedcentral.com/1471-2180/10/221en
dc.rights© 2010 He et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0)en
dc.titleCharacterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1en
dc.typeArticleen
dc.identifier.eissn1471-2180en
dc.contributor.departmentState Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, Chinaen
dc.contributor.departmentDepartment of Soil, Water and Environmental Science, The University of Arizona, Tucson, AZ 85721, USAen
dc.contributor.departmentBiotechnology Computing Facility, Arizona Research Laboratories, The University of Arizona, Tucson, AZ 85721, USAen
dc.identifier.journalBMC Microbiologyen
dc.description.collectioninformationThis item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at repository@u.library.arizona.edu.en
dc.eprint.versionFinal published versionen
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