Starch-hydrolyzing bacteria from Ethiopian soda lakes

Alkaliphilic bacteria were isolated from soil and water samples obtained fr om Ethiopian soda lakes in the Rift Valley area - Lake Shala, Lake Abijata, and Lake Arenguadi. Starch-hydrolyzing isolates were selected on the basis of their activity on starch agar plate assay. Sixteen isolates were chosen , characterized, and subjected to 16S rRNA gene sequence analysis. All the isolates were gram positive and catalase- and beta -galactosidase positive. All isolates except one were motile endospore-forming rods and were found to be closely related to the Bacillus cluster. being grouped with Bacillus pseudofirmus, Bacillus cohnii, Bacillus vedderi, and Bacillus agaradhaerens . The one exception had nonmotile coccoid cells and was closely related to Nesterenkonia halobia. The majority of the isolates showed optimal growth a t 37 degreesC and tolerated salinity up to 10% (w/v) NaCl, Both extracellul ar and cell-bound amylase activity was detected among the isolates. The amy lase activity of two isolates, related to B. vedderi and B. cohnii, was sti mulated by ethylenediaminetetraacetic acid (EDTA) and inhibited in the pres ence of calcium ions. Pullulanase activity was expressed by isolates groupe d with B. vedderi and also most of the isolates clustered with B. cohnii; c yclodextrin glycosyltransferase was expressed by most of the B. agaradhaere ns-related strains. Minor levels of alpha -glucosidase activity were detect ed in all the strains.