Bacterial viability assessment by flow cytometry analysis in soil

Soil microhabitats and their heterogeneity are often considered to be among the most important factors affecting soil biotic communities. The microbial commu-nity has become one of the most important links in soil nutrient cycles and trophic components due to its role in biological processes, spatial and temporal dynamics, and physiological adaptation. Sandy-soil desert systems are characterized by fast water infiltration during the rainy season, high salinity, and low moisture availability in the upper soil layers. Plants have developed different ecophy-siological adaptations in order to cope with this harsh environment. The Tamarix aphylla is known to be one of the most commonly adapted plants, exhibiting a mechan-ism for secretion of excess salts as aggregates through its leaves. These leaves aggregate beneath the plant, creating 'islands of salinity'. Soil biotic components are, therefore, exposed to extreme abiotic stress conditions in this niche. The goal of this study was to examine the effect of T. aphylla on the live/dead bacterial population ratio on a spatial and temporal scale. The results emphasize the effect of abiotic factors, which changed on temporal as well as spatial scales, and also on the size of the active soil bacterial community, which fluctuated between 1.44% and 25.4% in summer and winter, respectively. The results of this study elucidate the importance of moisture availability and the 'island-of-salinity' effect on the active microbial community in a sandy desert system.