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Applied and Environmental Microbiology, February 2009, p. 784-791, Vol. 75, No. 3
0099-2240/09/$08.00+0     doi:10.1128/AEM.02481-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Bioinformatic and Expression Analyses of Genes Mediating Zinc Homeostasis in Nostoc punctiforme{triangledown} ,{dagger}

Lee Hudek,1 L. C. Rai,2 David Freestone,1 Agnes Michalczyk,1 Maria Gibson,1 Y. F. Song,3 and M. Leigh Ackland1*

Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia,1 Molecular Biology Unit, Laboratory of Algal Biology, CAS in Botany, Banaras Hindu University, Varanasi 221005, India,2 Key Laboratory of Terrestrial Ecological Processes, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, People's Republic of China3

Received 29 October 2008/ Accepted 4 November 2008

Zinc homeostasis was investigated in Nostoc punctiforme. Cell tolerance to Zn2+ over 14 days showed that ZnCl2 levels above 22 µM significantly reduced cell viability. After 3 days in 22 µM ZnCl2, ca. 12% of the Zn2+ was in an EDTA-resistant component, suggesting an intracellular localization. Zinquin fluorescence was detected within cells exposed to concentrations up to 37 µM relative to 0 µM treatment. Radiolabeled 65Zn showed Zn2+ uptake increased over a 3-day period, while efflux occurred more rapidly within a 3-h time period. Four putative genes involved in Zn2+ uptake and efflux in N. punctiforme were identified: (i) the predicted Co/Zn/Cd cation transporter, putative CDF; (ii) the predicted divalent heavy-metal cation transporter, putative Zip; (iii) the ATPase component and Fe/Zn uptake regulation protein, putative Fur; and (iv) an ABC-type Mn/Zn transport system, putative zinc ZnuC, ZnuABC system component. Quantitative real-time PCR indicated the responsiveness of all four genes to 22 µM ZnCl2 within 3 h, followed by a reduction to below basal levels after 24 h by putative ZIP, ZnuC, and Fur and a reduction to below basal level after 72 h by putative CDF efflux gene. These results demonstrate differential regulation of zinc transporters over time, indicating a role for them in zinc homeostasis in N. punctiforme.

* Corresponding author. Mailing address: Deakin University, Burwood Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia. Phone: 613 925 17036. Fax: 613 925 17048. E-mail: leigha{at}deakin.edu.au

{triangledown} Published ahead of print on 14 November 2008.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, February 2009, p. 784-791, Vol. 75, No. 3
0099-2240/09/$08.00+0     doi:10.1128/AEM.02481-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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