Isolation and characterization of some aquatic bacteria from Qurug?l lake in Azerbaijan under aerobic conditions

Abstract

Aquatic bacteria play crucial roles in environmental biology. They are a rich source of new genes; unfortunately most of them are left unknown and regarding the ones which have been recognized and known there is not enough and efficient information considering their applications. Considering the geographical conditions of Qurug?l Lake that is mostly frozen during the cold seasons and also lack of published papers on the presence of aquatic bacteria of this lake, the present study aimed to investigate the bacterial community in the lake. In so doing, samples were taken from four different parts and at each part they were taken from three different depths 0.25, 1 and 8 meter, respectively. The taken samples were grown on special media including: modified marine agar and sea water medium (SWM). Biochemical tests consisted of determination of oxidase and catalase activity, gelatin liquefaction, ability to hydrolyze starch and casein, production of indole, H2S and nitrate reduction tests were carried out. Thirty two isolates recognized. Most of isolated strains were Gramnegative (21) and mostly were psychrophilic bacteria. According to the results obtained from the analysis of extra-cellular enzymes it was found that the isolated bacteria have high variety hydrolytic enzyme activity. In a way that few of the isolated bacteria could produce a mixture of the mentioned enzymes, but all in all Grampositive bacteria in comparison with Gram-negative bacteria tested showed more hydrolytic activities, also revealed that the capability of Gram-negative bacteria in production of lipase enzyme is more than Grampositive bacteria. On the basis of phylogenetic results, it is recommended that the isolates belong to Aeromonas, Alishewanella, Alteromonas, Jeotgalicoccus, Bacillus, Marinobacter, Marinococcus, Paracoccus, Pseudoalteromonas, Rheinheimera, Rodobacter, Prophyrobacter and Shewanella. Moreover, several members of the Alishewanella, Jeotgalicoccus, Bacillus, Marinococcus and Shewanella clades were recovered. In a way that Alishewanella clade was dominant.