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  • Author or Editor: P. Vass x
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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 markedly 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, moderately 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 several 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 candidates for biosensing applications for detection of Ni 2+ and arsenic pollutants, respectively.

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