An impact of tropical cyclone on meiobenthic fauna of Chennai coast, Tamil Nadu, India: A case study of cyclone Mandous.

The meiofaunal diversity is used as an indicator to assess the complex and diverse impacts on the coastal environment during the natural calamities. The present study evaluates the effects of Mandous cyclone on ecologically two different stations, Pattinampakkam beach and Adyar estuary, which are located on Chennai coast, Tamil Nadu, India. The impact of the Mandous cyclone on physico-chemical parameters and meiobenthic faunal composition was investigated during, prior to, and after the cyclone. Thirty-nine species of meiofauna belonging to 15 taxa were recorded in both the stations. Nematoda, Oligochaeta and Harpacticoida taxa occurred with higher diversity and abundance than other meiofaunal taxa. Among these taxa, Polygastrophora sp. of Nematoda, Grania pusilla of Oligochaeta, and Arenosetella indica of Harpacticoida were the predominant species recorded during the study period. There was a prominent decline in the population density of meiofauna due to the Mandous cyclone, and thereafter, it took three weeks for recolonization and restoration to normalcy. Statistically, significant impact of the Mandous cyclone on the diversity, density, and evenness of the meiofaunal community with abiotic factors were observed through the Ecological indices and Canonical Correspondence Analysis. The Mandous cyclone assessment with special emphasis on meiofaunal communities allowed to fill the gap with knowledge regarding the diversity, abundance, composition, and distribution of meiofauna between pre- and post-Mandous cyclone, which helped in understanding the physico-chemical changes and response of meiofauna in a sandy beach and estuary.

Studies on the zooplankton biodiversity and density in Adyar estuary, Chennai, India.

The Adyar estuary was once known for its unique ecology and endemic flora and fauna, has lost its pristine condition due to urbanization, discharge of untreated domestic wastes, industrial effluents and encroachments. Zooplankton were monitored for a period of one year from July 2009 to June 2010, following standard methods to evaluate the seasonal variations in diversity and density in relation to environmental parameters like temperature (28.6-33.6 degrees C), salinity (23.3-30.3 per thousand), pH (7.3-7.8) and DO (4.4-7.1 mg l(-1)). Highest diversity was observed during post-monsoon (20 species) and pre-monsoon (19 species), followed by summer (9 species) and monsoon (9 species). The zooplankton density was maximum during summer (1887167 m(-3)) followed by pre-monsoon (1843832 m(-3)), post-monsoon (1153333 m(-3)) and monsoon (182334 m(-3)). Zooplankton community structure and dynamics showed a differential pattern with dominance of harpacticoids and rotifers in pre-monsoon; cyclopoids and rotifers during post-monsoon and summer. The significance of monitoring zooplankton biodiversity as a base-line study for future investigations on environmental changes in this area is discussed.

The putative iron transport system SitABCD encoded on SPI1 is required for full virulence of Salmonella typhimurium.

Salmonella typhimurium is an invasive pathogen that causes diseases ranging from mild gastroenteritis to enteric fever. During the infection process, S. typhimurium induces a number of virulence genes required to circumvent host defences and/or acquire nutrients in the host. We have used the in vivo expression technology (IVET) system to select for S. typhimurium genes that are induced after invasion of a murine cultured cell line. We have characterized a putative iron transporter in Salmonella pathogenicity island 1, termed sitABCD. The sitABCD operon is induced under iron-deficient conditions in vitro and is repressed by Fur. This locus is induced in the animal specifically after invasion of the intestinal epithelium. We show that a sit null mutant is significantly attenuated in BALB/c mice, suggesting that SitABCD plays an important role in iron acquisition in the animal.