Characterization of the activity of heavy metal-responsive promoters in the cyanobacterium Synechocystis PCC 6803

Peca, Loredana and Kós, P. and Vass, I. (2007) Characterization of the activity of heavy metal-responsive promoters in the cyanobacterium Synechocystis PCC 6803. Acta Biologica Hungarica, 58 (Supple). pp. 11-22. ISSN 0236-5383

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Abstract

Aiming at developing cyanobacterial-based biosensors for heavy metal detection, expression of heavy metal inducible genes of the cyanobacterium Synechocystis PCC 6803 was investigated by quantitative RT-PCR upon 15 minutes exposure to biologically relevant concentrations of Co 2+ , Zn 2+ , Ni 2+ , Cd 2+ , Cr 6+ , As 3+ and As 5+ . The ziaA gene, which encodes a Zn 2+ -transporting P-type ATPase showed a marked- ly increased mRNA level after incubation with Cd 2+ and arsenic ions, besides the expected induction by Zn 2+ ions. The Co 2+ efflux system-encoding gene coaT was strongly induced by Co 2+ and Zn 2+ ions, mod- erately induced by As 3+ ions, and induced at a relatively low level by Cd 2+ and As 5+ ions. Expression of nrsB , which encodes a part of a putative Ni 2+ efflux system was highly induced by Ni 2+ salts and at a low extent by Co 2+ and Zn 2+ salts. The arsB gene, which encodes a putative arsenite-specific efflux pump was highly induced by As 3+ and As 5+ ions, while other metal salts provoked insignificant transcript level increase. The transcript of chrA , in spite of the high sequence similarity of its protein product with sev- eral bacterial chromate transporters, shows no induction upon Cr 6+ salt exposure. We conclude that due to the largely unspecific heavy metal response of the studied genes only nrsB and arsB are potential can- didates for biosensing applications for detection of Ni 2+ and arsenic pollutants, respectively.

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