Investigation of microbial community in extreme saline environments

In Germany, three kinds of potential host rock systems (clay, crystalline and rock salt) are considered for the long-term storage of highly radioactive waste in a deep geological repository. In this study the focus is on the habitat rock salt to get a more detailed understanding of the way of life of the microorganisms occurring there. Next to bacteria and fungi, extreme halophilic archaea are dominating this habitat. It is of interest to know what kind of microorganisms are living there, how active they are under repository relevant conditions and how these microorganisms can influence the safe storage of the waste. The microbial diversity of two different types of samples (rock salt from Germany & saline soil sample from Israel) was investigated with a combination of culture-dependent and -independent methods. From the two samples DNA was extracted, purified for PCR amplifications of 16S rRNA genes and finally sequenced with Illumina MiSeq by RTL Genomics. Additionally, a specific portion of each sample was incubated in three different sodium chloride concentrations of modified R2A resuscitation buffer and subsequently spread on corresponding agar plates (37°C) to get isolates which were further characterized. Different halophilic microorganisms could be isolated from both kinds of samples. The isolates from rock salt can all be assigned to different Halobacterium species. Whereas from the saline soil samples different archaeal genera such as Natrinema, Halorubrum as well as Halobacterium could be isolated. Bacterial isolates were related to different Bacilli such as Halobacillus and Aquibacillus species. The obtained isolates can be further used for investigations e.g. regarding their activity under repository relevant conditions.