Phenotypic characterization and molecular taxonomic studies on Bacillus and related isolates from Phragmites australis periphyton

Reeds may play important role in the self-purification of aquatic habitats due to the filtration capacity and their periphyton communities developing on the underwater plant surfaces. The efficiency of this process and the transformation of organic substances can be influenced by the species composition and activity of microbial communities, including Bacillus and related species. For cultivation based bacteriological examinations reed periphyton samples were collected from 30 cm beneath the water surface of Lake Velencei and the Soroksar Danube branch (Hungary). After a primary selection 40 Bacillus and related strains were investigated by traditional morphological, biochemical tests, API 20E, API 50CHB and BIOLOG GP2 systems, and identified by 16S rDNA sequence comparison. The isolated strains were characterized by wide biochemical activity spectrum (i.e., the metabolism of carbohydrates and biopolymers) as well as widespread ecological tolerance based on their NaCl and pH range investigations. Species with facultative alkaliphilic features (Marinibacillus marinas, Bacillus firmus) were detected only from the reed biofilm of Lake Velencei, while alkalitolerant Bacillus and related species from both sampling sites. 22 endospore-forming strains were identified as members of species B. cereus, B. firmus, B. flexus, B. licheniformis, B. megaterium, B. muralis, B. pumilus, B. subtilis and Marinibacillus marinus. Only one species, with 95-96% sequence similarities to B. pumilus was found to be common among the strains from Lake Velencei and the Soroksar Danube branch. Altogether, 18 strains could not be identified as known species of Bacillus, Brevibacillus and Paenibacillus, hence they may represent new bacterial taxa. (c) 2006 Elsevier B.V. All rights reserved.