Diversity of hydrolytic enzymes in haloarchaeal strains isolated from salt lake

ABSTRACT

Production of ten hydrolytic enzymes was qualitatively studied on the haloarchaeal strains isolated from Aran-Bidgol hypersaline lake in the central desert area of Iran. A total of 293 haloarchea strains were selected among 300 extremely halophilic isolated prokaryotes. Accordingly, 142, 141, 128, 64, 38, 16, 7, 3 and 1 archaeal isolates were able to produce DNase, amylase, lipase, inulinase, pullulanase, protease, cellulase, chitinase and xylanase, respectively. None was able to produce pectinase activity. Combined hydrolytic activity was also detected in many strains. A total of 0.3% of the strains showed 6 hydrolytic activities, 0.3% of the strains had 5 hydrolytic activities, 5.4% of the strains presented 4 hydrolytic activities, 25% of the strains presented 3 hydrolytic activities, 28% of the strains presented 2 hydrolytic activities and 18% of the strains presented 1 hydrolytic activity. According to their phenotypic characteristics and comparative partial 16S rRNA sequence analysis, the halophilic strains were all identified as members of family Halobacteriaceae within 12 different taxa from the following genera Halorubrum, Haloarcula, Natrinema, Halovivax and Natronomonas. Most enzymes production rate was observed in the genera Halorubrum, Haloarcula and Natrinema whereas; there was not any detectable amount of enzyme production in the genera Halovivax and Natronomonas. The most hydrolytic isolate with 6 combinatorial enzyme production belonged to the genus Natrinema. This investigation showed that the extreme halophilic archaea from Aran-Bidgol lake are a potential source of hydrolytic enzyme under stress conditions and may have possess commercial value