Microbial Diversity of Soda Lake Habitats

Abstract

A molecular approach has been utilised for an analysis of the procaryotic diversity in sediment samples from Lake Magadi, an African soda lake in the Rift Valley, Kenya. The molecular analysis included: a) extraction of total DNA; b) PCR-amplification using 16S rDNA primers specific for Bacteria or Archaea; c) ligation-independent cloning of PCR-products; d) screening of the clone libraries using hybridisation probing, ARDRA and partial sequencing; e) sequence analysis of entire 16S rDNA. The analysis of bacterial clone libraries revealed the detection of 16S rDNA sequence types clustering, predominantly, with the taxa of Cyanobacteria, particularly the “Euhalothece”, as well as other taxa, including members of the Firmicutes (i.e., Bacilli and Clostridia), the Alpha-, Gamma-, and Delta- Proteobacteria and the Bacteroidetes. Screening of cloned sequence types of the archaeal 16S rDNA clone library detected different sequence types clustering within the Euryarchaeota, mainly, with organisms of the family Halobacteriaceae. Additionally, various haloalkaliphilic archaeal isolates of the halobacteria, derived from different saline and alkaline habitats, such as the Wadi Natrun (Egypt) and Owens Lake (California) were analysed by molecular, genotypic characterisation. These organisms were affiliated with three major lines of existing Halobacteria, i.e., the genera Natronomonas and Halorubrum, as well as the rather diffuse cluster of halobacteria including Natronobacterium gregoryi and relatives. These analyses enabled the detection and recognition of here-to-fore unknown archaeal and bacterial 16S rDNA sequence types and provided new insights into the procaryotic composition of the soda lake environment.