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The hydroxyectoine gene cluster of the non-halophilic acidophile Acidiphilium cryptum

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Abstract

Acidiphilium cryptum is an acidophilic, heterotrophic α-Proteobacterium which thrives in acidic, metal-rich environments (e.g. acid mine drainage). Recently, an ectABCDask gene cluster for biosynthesis of the compatible solutes ectoine and hydroxyectoine was detected in the genome sequence of A. cryptum JF-5. We were able to demonstrate that the type strain A. cryptum DSM 2389T is capable of synthesizing the compatible solute hydroxyectoine in response to moderate osmotic stress caused by sodium chloride and aluminium sulphate, respectively. Furthermore, we used the A. cryptum JF-5 sequence to amplify the ectABCDask gene cluster from strain DSM 2389T and achieved heterologous expression of the gene cluster in Escherichia coli. Hence, we could for the first time prove metabolic functionality of the genes responsible for hydroxyectoine biosynthesis in the acidophile A. cryptum. In addition, we present information on specific enzyme activity of A. cryptum DSM 2389T ectoine synthase (EctC) in vitro. In contrast to EctCs from halophilic microorganisms, the A. cryptum enzyme exhibits a higher isoelectric point, thus a lower acidity, and has maximum specific activity in the absence of sodium chloride.

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Acknowledgments

The authors would like to thank Marlene Hecker for skilful technical assistance with the osmotic pressure measurements.

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The authors declare that they have no conflict of interest.

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The authors declare that the experiments comply with the current laws of the country in which they were performed.

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Correspondence to Katharina D. Moritz.

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Communicated by L. Huang.

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Moritz, K.D., Amendt, B., Witt, E.M.H.J. et al. The hydroxyectoine gene cluster of the non-halophilic acidophile Acidiphilium cryptum . Extremophiles 19, 87–99 (2015). https://doi.org/10.1007/s00792-014-0687-0

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  • DOI: https://doi.org/10.1007/s00792-014-0687-0

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