The hydroxyectoine gene cluster of the nonhalophi

Authors: Katharina D Moritz Birgit Amendt Elisabeth M H J Witt Erwin A Galinski

Publish Date: 2014/08/21

Volume: 19, Issue: 1, Pages: 87-99

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Abstract

Acidiphilium cryptum is an acidophilic heterotrophic αProteobacterium which thrives in acidic metalrich environments eg 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 JF5 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 JF5 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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