干旱区生态环境知识资源中心

The Great Rann of Kachchh, a vast expanse of salt desert in Western India is a unique hostile ecosystem posing an extreme environment to life forms due to high salt content, hyper-arid climate, seasonal water logging and extremes of temperature. In the virtual absence of natural vegetation, soils and sediments of Rann of Kachchh are microbially dominated ecosystems. In the present study microbial activity and the diversity of cultivated heterotrophic bacteria were investigated in the sediments collected along a 5-m exposed section at Khadir Island in the Great Rann of Kachchh. Microbial activity (as an index of sediment enzymes) was found to be high in the middle of the section (200-280 cm). Dehydrogenase (DHA), substrate-induced DHA and alkaline phosphatase activities revealed the oligotrophic nature of the basal portion (320-480 cm). Abundant bacterial isolates obtained from different depths were found to be clustered in 12 different phylogenetic groups by amplified ribosomal DNA restriction analysis. 16S rRNA gene sequencing revealed the dominant bacterial ribotypes to be affiliated to Firmicutes (Families Bacillaceae and Staphylococcaceae) and Actinobacteria (Family Brevibacteriaceae) with minor contribution of Proteobacteria (Families Phyllobacteriaceae and Bartonellaceae), pointing their endurance and adaptability to environmental stresses. Statistical analysis indicated that sediment organic carbon, salinity, total available nitrogen and total available phosphorous are most likely critical determinants of microbial activity in the Khadir Island sediments.