Screening and characterization of aldehyde dehydrogenase gene from Halomonas salina strain AS11

A population survey was made of moderately halophilic bacteria in prawn pond sediment in the Songkla region of Thailand. Twenty-two isolated halophilic bacteria capable of growing on modified ATCC culture medium 1270 for halobacterium were then assayed for aldehyde dehydrogenase (ALDH) activity which might be involved in the metabolism of xenobiotic compounds. One isolate, designated AS11, was selected based on its high amount of ALDH activity. This organism can grow at sodium chloride concentrations ranging from 2.5 to 25%, although optimum growth occurs at 5% NaCl. Phenotypic and phylogenetic studies indicated that AS11 was an isolate of Halomonas salina. The aldh gene coding for this enzyme was then cloned. The open reading frame of the aldh gene was 1521-bp long and coded for a protein of 506 amino acid residues with a calculated molecular mass of 55 kDa. The aldh gene product proved to be 76% identical to the NAD-dependent acetaldehyde dehydrogenase gene from Pseudomonase aeruginosa.