Dental caries is the most common chronic disease. Tetracycline is commonly used in dental practice as a prophylactic agent and for treatment of oral infections. The wide use of tetracycline had resulted in a major increase in the rate of tetracycline resistance among bacteria. Substantial epidemiologic evidence links Streptococcus mutans to caries; the pathobiology of caries may involve more complex communities of bacterial species. Molecular methods for bacterial identification and enumeration now make it possible to more precisely study the micro biota associated with dental caries. The purpose of this study was to characterize the tetracycline resistant microorganism associated with the dental caries using cultural & molecular method. The first step involved 20 samples from patients with different level of dental caries. From which 33 different isolates were obtained, out of which 12 showed resistances to tetracycline and 5 were having maximum MIC indicating that they are highly resistant. These resistant microorganisms were identified to the species level by growing them on a suitable medium using the antibiotic tetracycline and were analyzed with the help of FAME analysis, which indicated that different strains of the Pseudomonas aeruginosa and Bacillus subtilis were present.The second step involved identifying the tet k gene in the cultures. Tet k was amplified under standard conditions by using specific primers results. Interestingly, the results showed that tet k gene was present in all the sample. Tet k gene is involved in imparting the resistant to the tetracycline by acting as a efflux pump. RFLP analyses were used in order to identify the polymorphic forms of the tet k. The HindIII digest suggest that high resistance to tetracycline was acquired due to some mutations in the genome.

RNA interference (RNAi) is a naturally occurring phenomenon of RNA-mediated gene silencing that is highly conserved among multicellular organisms. In the first step of the pathway, long doublestranded RNA molecules are chopped into shorter duplexes with 2 nucleotide overhangs at both 3’ ends by an endonuclease dubbed Dicer, the structure of which has been solved only recently. This results in the formation of small 21 nucleotide long RNAs, aptly named small or short interfering RNAs (siRNAs), which are incorporated into a multimeric protein complex, the RNA-induced silencing complex (RISC). One of the two-siRNA strands guides RISC to a complementary RNA. After hybridization the endonucleolytic “slicer” activity of RISC cleaves the target RNA, thus preventing its translation. While long double-stranded RNA molecules can be employed to induce RNAi in lower eukaryotes, siRNAs being 21 nucleotides in length have to be used for gene silencing in mammalian cells in order to prevent the activation of an unspecific interferon response [1]. In contrast to siRNAs, however, miRNAs are capable of inhibiting translation of the targeted mRNA without degrading it (at least in mammalian cells)[2-4]. The need for in silico analysis of the components of the RNA interference pathway arises from the fact that very little is known about the structural and interacting properties of the components. With the above background the analysis was performed to identify putative catalytic motifs in the mRNA of the DICER enzyme.

The comet assay is a sensitive, reliable and rapid method for DNA double & single strand break, alkali-labile sites and delayed repair site detection in individual cells. In recent years, this method has been widely used for studies of DNA repair, genetic toxicology, environmental biomonitoring, and apoptosis. However, this technique serves as an important tool for detection of DNA damage in living organisms and is increasingly being used in genetic testing of industrial chemicals, agrochemicals & pharmaceuticals. This research paper helps to evaluate the health effects of exposure to organic pollutants by using comet assay technique by KOMET 3.1 software. This study used human biomonitoring to evaluate the genotoxic effects of exposure to organic pollutants. The experimental data suggest that the DNA damage parameters (OTM, % T-DNA and TL) were found higher value in exposed population when compared to the control healthy population. The percentage and distribution of cells in exposed population also increases with the increase in OTM values. This study demonstrates that, using sensitive techniques, it is possible to detect human health risks at an early stage when intervention is possible.