Analysis of the diversity of aerobic, thermophilic endospore-forming bacteria in two Algerian hot springs using cultural and non-cultural methods

Abstract

Terrestrial hot environments are important resources for isolation of thermophilic microorganisms. Few studies have been made on microbial diversity of Algerian geothermal sites. This paper reports the diversity of thermophilic, aerobic endospore-forming bacteria from water and sediment samples taken from Hammam Ouled Ali and Hammam Debagh, two hot springs with a wide range of temperatures and a very rich mineral composition, located in the region of Guelma, north-east of Algeria using culture-dependent and culture-independent approaches Sequences of the V4 region of the 16S rRNA gene from environmental DNA extracted from sediment samples were analyzed and a set of isolates from water and sediment have been characterized by phenotypic and molecular methods. Phylogenetic surveys using environmental DNA sequences indicated that three families dominated the two hot springs: Planococcaceae, Bacillaceae, and Paenibacillaceae. Phenotypic characterization revealed the morphological, biochemical, and physiological properties of these microorganisms, all of which exhibited a range of common extracellular enzymatic activities. Amplified ribosomal DNA restriction analysis (ARDRA) was used to cluster isolates into different phylotypic groups and phylogenetic analysis of 16S rRNA gene sequences of selected isolates showed that all were closely related to four genera of thermophilic Bacilli: Bacillus, Anoxybacillus, Geobacillus, and Brevibacillus. Our results provide important insights into the microbial ecology of Guelma hot springs. They showed that the phylogenetic diversity of bacterial communities within the two studied hot springs was mostly aerobic, with the presence of taxonomic groups of great biotechnological interest. Bioprospection of thermozymes and other biomolecules within these communities will probably provide a data basis for their industrial exploitation.