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Novel HNPP/Fast Red TR in situ hybridization method was used to study the response of river water microbial communities to aniline, as a model chemical pollutant , in two biodegradation test systems: a river die-away (TOC-HANDAI) test and a cultivation (HANDAI) test. Pseudomonas rRNA group I and Acinetobacter were the most abundant groups during peak biodegradation activity in both test systems in spite of the differences in test conditions and initial community structures. Burkholderia-Pseudomonas rRNA III-authentic Alcaligenes group were significant only in the cultivation test under highly polluted conditions. Vibrio-Aeromonas and Flavobacterium-Cytophaga groups were adversely affected by aniline in both test systems.

The present study was conducted to isolate and identify endophytic diazotrophic bacteria in two Sri Lankan rice (Oryza Sativa L.) varieties; Suwandel and Bg 358 and to evaluate their potential to promote rice plant growth. A total of 15 putative endophytic diazotrophic bacterial isolates were obtained from shoots and roots of Suwandel and Bg 358 rice varieties out of which 7 isolates were selected based on their ability to produce IAA and phosphate solubilization. According to the morphological characters and biochemical tests, these bacteria were identified belong to genera Bacillus (IN003, IN006, and IN007), Klebsiella (IN008 and IN018), Pantoea (IN009), and Enterobacter (IN015). All selected bacterial isolates produced IAA (7.1µmgl -1 to 30.9 µ mgl -1 ) in the tryptophan supplemented medium. Five out of seven bacterial isolates (IN006, IN007, IN008, IN015, and IN018) were able to solubilize inorganic phosphate on Pikovskaya's agar medium. Rice seeds (Suwandel variety) treated with these endophytic diazotrophic bacteria with plant growth-promoting ability showed significantly enhanced shoot length, root length, shoot fresh weight, shoot dry weight and root fresh weight compared to the uninoculated control. Plant inoculation experiment indicated that Enterobacter sp. (IN015) was most effective in rice plant growth promotion among seven bacterial isolates tested. These results strongly suggest that endophytic diazotrophic bacteria characterized in this study could be successfully used to promote rice plant growth.