title: Arsenate reduction and expression of multiple chromosomal ars operons in Geobacillus kaustophilus A1.
abstract: Geobacillus kaustophilus strain A1 was previously isolated from a geothermal environment for its ability to grow in the presence of high arsenate levels. In this study, the molecular mechanisms of arsenate resistance of the strain were investigated. As(V) was reduced to As(III), as shown by HPLC analysis. Consistent with the observation that the micro-organism is not capable of anaerobic growth, no respiratory arsenate reductases were identified. Using specific PCR primers based on the genome sequence of G. kaustophilus HTA426, three unlinked genes encoding detoxifying arsenate reductases were detected in strain A1. These genes were designated arsC1, arsC2 and arsC3. While arsC3 is a monocistronic locus, sequencing of the regions flanking arsC1 and arsC2 revealed the presence of additional genes encoding a putative arsenite transporter and an ArsR-like regulator upstream of each arsenate reductase, indicating the presence of sequences with putative roles in As(V) reduction, As(III) export and arsenic-responsive regulation. RT-PCR demonstrated that both sets of genes were co-transcribed. Furthermore, arsC1 and arsC2, monitored by quantitative real-time RT-PCR, were upregulated in response to As(V), while arsC3 was constitutively expressed at a low level. A mechanism for regulation of As(V) detoxification by Geobacillus that is both consistent with our findings and relevant to the biogeochemical cycle of arsenic and its mobility in the environment is proposed.
authors.affiliation: Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, 76 Lipman Drive, New Brunswick, NJ 08901-0231, USA.
authors.forename: Mariola
authors.initials: M
authors.lastname: Cuebas
authors.affiliation: Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, 76 Lipman Drive, New Brunswick, NJ 08901-0231, USA.
authors.forename: Aramis
authors.initials: A
authors.lastname: Villafane
authors.affiliation: Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, 76 Lipman Drive, New Brunswick, NJ 08901-0231, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: McBride
authors.affiliation: Department of Environmental Sciences, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901-8551, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Yee
authors.affiliation: Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, 76 Lipman Drive, New Brunswick, NJ 08901-0231, USA.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bini
mesh_terms: D053502:Arsenate Reductases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D001149:Arsenates / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D056506:Geobacillus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D009876:Operon; D010084:Oxidation-Reduction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017423:Sequence Analysis, RNA
chemical_list: D001149:Arsenates; D001426:Bacterial Proteins; D053502:Arsenate Reductases; C025657:arsenic acid