Diversity, salinity adaptation, and role in carbon cycling of microbial communities inhabiting the oxic layer of intertidal hypersaline microbial mats

The main objective of this thesis was to study the diversity, salinity adaptation, and role in carbon cycling of microorganisms inhabiting the oxic layer of intertidal hypersaline microbial mats. For this purpose, mats from the Arabian Gulf coast of Abu Dhabi, United Arab Emirates (UAE), which are subjected to multiple harsh environmental conditions, were investigated. The mats possessed a high microbial diversity and the inhabiting microorganisms showed adaptation mechanisms to strong salinity fluctuations, desiccation, high UV and light intensities, and high temperatures. A new salinity-driven taxis of cyanobacteria in the mat from the upper tidal zone was discovered and termed as Halotaxis. Moreover, this study showed that mats from different tidal positions adjust the structure and function of their bacterial communities in response to the salinity range they experience. Furthermore, cyanobacterial cultures with associated bacteria, obtained from the mats, provided manifold, very complex, and highly specific interactions with a high potential for biotechnological purposes, e.g. for the discovery of new bioactive substances.