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Abstract:The North Eastern region of India is undergoing industrial development at a faster rate than expected. Roads form the main system of transportation and communication owing to the hilly topography of the region. Automobiles discharge a number of gaseous and trace metal contaminants. Human activities like stone grinding, road construction and sand milling also increase the atmospheric dust and heavy metal contaminant level. These contaminants get settled on leaf surfaces at roadsides and enter in contact with phylloplane microorganisms. This study compares microorganisms on leaf surfaces of alder (Alnus nepalensis (Betulaceae)) on roadside and non-roadside environments. Two sites dominated by alder were selected. One at a busy road intersection on the National Highway no. 44 in Shillong with high traffic density (8 000-9 000 heavy vehicles/day), taken as the polluted site and the other one in a forest approximately 500 m away from the roadside considered as the unpolluted site. Analysis of phylloplane microorganisms, lead, zinc, copper, cadmium and sulphur was carried out from leaves. The bacterial population was higher at the unpolluted site. Bacterial population showed a significant negative correlation with lead, zinc, copper, cadmium and sulphur. Similarly, fungal population was higher at the unpolluted site. A total of 29 fungal species were isolated from the phylloplane of A. nepalensis (polluted site 16 species; unpolluted site 28 species). Some fungal forms like Mortierella sp., Fusarium oxysporum and Aureobasidium pollulans were dominant in the polluted site. Numbers of phylloplane fungi and bacteria were significantly reduced in the polluted site. The correlation coefficient indicated a detrimental effect of metals like lead, zinc, copper, cadmium and sulphur on the microbial community of leaf surfaces. The specificity of certain fungi to the unpolluted site may be attributed to their sensitivity to pollution. The predominance of Aureobasidium pollulans, Fusarium oxysporum and Mortierella sp. in the polluted site may be due to their resistance to pollutants in roadside conditions. Rev. Biol. Trop. 56 (3): 1521-1529. Epub 2008 September 30.

Bacterial attachment is influenced by the cell surface, attachment media and other environmental factors. Bacterial community composition involved in biofilm formation in extremely high rainfall areas like Cherrapunjee has not been reported. The present study was undertaken to characterize bacteria involved in biofilm formation on different substrata in water bodies of Cherrapunjee, the highest rainfall receiving place on planet earth and to assess if the continuous rainfall has an effect on nature and colonization of biofilm bacteria. We developed the biofilm bacteria on stainless steel and glass surfaces immersed in water bodies of the study sites. Isolation of biofilm bacteria were performed on different culture media followed by estimation of protein and carbohydrate content of bacterial exopolysaccharides. 16S rRNA gene sequences were amplified for molecular characterization. The results showed that the biofilm bacterial diversity in water bodies of Cherrapunjee was influenced by substratum and was observed more in stainless steel than glass surface. Scanning electron microscopy images revealed that biofilm microstructure may represent a key determinant of biofilm growth and physiology of associated bacteria. The overall protein content of the extracted EPS of all the isolates were relatively higher than the carbohydrate content. Diverse bacteria proliferated on the substrata regardless of each other's presence, with more diverse bacteria colonizing the substrata on 7 th day compared to 15 th day of incubation. The biofilm bacteria compositions in the highest rainfall receiving habitat were not distinctly different from reports available, hence not unique from other water bodies.

Metal tolerant bacterium Chryseobacterium sp. PMSZPI previously isolated and characterized from uranium ore deposit was studied for elucidating the role of metal transporter genes belonging to the Cation Diffusion Facilitator (CDF), Root-Nodulation-Division (RND) and P IB -type ATPase family in cadmium and uranium tolerance. The bacterium showed tolerance towards cadmium (MIC~6mM) and uranium (MIC~2mM) and was found to harbor metal transporter genes belonging to CDF, RND and P IB -type ATPase family of proteins. Expression studies by real-time PCR showed an upregulation of czcA (RND), czcD (CDF) and cadA (P IB -type ATPase) genes in presence of cadmium or uranium. Higher expression of czcA and czcD was found when the bacterium was treated with cadmium and uranium respectively. This study provides significant insight into the molecular mechanism that plays a role in cadmium and uranium tolerance in bacteria.