Antibacterial activity of Coccinia grandis leaf extract on selective bacterial strains.

To assess the antibacterial activities of Coccinia grandis leaf extract on selective bacterial strains under in-vitro conditions. The antibacterial activity was tested against five bacterial strains by agar well diffusion method. The crude extract showed a broad spectrum of antibacterial activity by inhibiting both the gram positive and gram negative groups. The antibacterial activity of C.grandis leaf extract using solvents such as acetone, ethanol, methanol, aqueous and hexane was evaluated against five bacterial sp. Ethanol leaf extract of C.grandis showed high antibacterial activity against S.aureus, B.cereus, E.coli, K.pneumoniae and S.pyogens. Minimal inhibitory concentration of the leaf extract against each test organism was also studied by observing their growth on Mueller Hinton Agar containing the extract at various incremental levels, equivalent to 31.25μg/ml to 1000μg/ml of the extract. The highest activity was observed in ethanol extracts against S.aureus, E.coli, and K.pneumoniae with an inhibitory concentration below 31.5μg/ml. The significance of the study was conducted to investigate the invitro antibacterial activity of folklore medicinal plant and to evaluate scientific base of their applications.

Invitro assessment of antagonistic activity of trichoderma sp. against sarocladium oryzae causing sheath rot disease in paddy.

Invitro screening using the dual culture technique was undertaken to assess the potential of seven Trichoderma species. Trichoderma viride, Trichoderma lignorum, T.album, T.hamatum, T.harizanum, T.glaucum and T.koeningi as biological control agents against Sheath rot fungus Sarocladium oryzae. The test organisms were isolated from the paddy field where the disease occurred. Results revealed that all the test antagonists effectively checked the growth of the pathogen. The test antagonists grow faster than the pathogen and produced inhibition zones thereby limiting the growth of the pathogen. In solid medium, Trichoderma harizanum was the most antagonistic organism under the conditions of this study. The culture filtrates of the test fungi also inhibited the growth of Sarocladium oryzae with Trichoderma harizanum showing the highest percentage inhibition (79%) and T.viride and T.lignorum (78%). T.harizanum culture filtrate showed the highest percentage growth inhibition at 15% concentration in Sarocladium oryzae while T.viride and T.lignorum filtrates showed inhibition,at 25% respectively.

Studies on molecular characterization of Azospirillum spp. isolated from Thanjavur district.

Altogether 30 Azospirillum strains isolated from paddy rhizosphere soil were identified as nitrogen fixers. A preliminary screening of all the species isolated from soils were made for nitrogen fixing activity.Among 30 strains three species of Azospirillum showed promising activity. These strains were classified as a unique grass by RAPD fingerprinting restriction enzyme analysis and 16S rRNA gene sequencing. Phylogenetic analysis of the 16S rRNA gene indicated that these diazotrophic strains belonged to the genus Azospirillum and were closely related to A. brasilense (with 84% similarity), A.amazonense (78% similarity) and A. halopraferens (93% similarity).

Biological control of banana wilt caused by fusarium solani (Mart.) Sacc.

The population dynamics of fungi in banana field soil, antibiotic potentiality of the soil fungi and antifungal ability of some plant extracts against Fusarium solani was studied. Maximum number of colonies were isolated during the month of November. The genus Aspergillus, Pencillium, Trichoderma, and Fusarium were isolated most frequently. Antibiotic interaction of the soil fungi against F.solani was performed. The test pathogen varied in its sensitivity to the metabolic growth products of antagonistic fungi. The maximum percentage of inhibition of pathogen was 85% against T.viride and 75% of inhibition was against A.niger. Culture filtrate of the soil fungi and the suppression of F.solani was observed. The maximum percentage of suppression of pathogen was observed against T.viride and A.niger at 20 per cent concentration level. The leaves of medicinal plant extract such as Adathoda vasica, Azadirachta indica and Vitex negundo was more effective at 20% concentration against the pathogen was reported. The leaf extracts (Adathoda vasica, Azadirachta indica and Vitex negundo) with culture filtrate of Trichoderma viride in combination of 1:1 ratio was more effective at 20 per cent level against the F.solani. However, the combined treatment of A.vasica and T.viride was more effective in controlling the pathogen F.solani causing wilt disease of banana.

Preliminary evaluation of anopheles mosquito larvicidal efficacy of mangrove actinobacteria.

Totally 30 actinobacteria isolates were screened for their larvicidal activity against Anopheles mosquito larvae. Of them four isolates producing strong larvicidal activity. These isolates were morphologically characterized and identified as the isolate CC17, SM13 as Streptomyces sp, isolate SH15 as Streptosporangium, isolate S22 as Micropolyspora. The present investigation clearly reveals the larvaicidal potentials of selected actinobacterial isolates in the Muthupet mangrove soil and sediments. To exploit these findings for humanwelfare, it is necessary to carryout field trial and strategies for optimizing of large scale production of cellbiomass and larvicidal compounds are suggested as future course of action.

Glycemic level at the first visit and prediction of GDM.

OBJECTIVE: To evaluate the glycemic level at the first visit that is likely to predict gestational diabetes mellitus (GDM). METHODS: Consecutive pregnant women underwent a 75g oral glucose tolerance Test (OGTT) recommended by WHO and diagnosed GDM if 2hr post plasma glucose (PG) value > or = 140 mg/dl. Women with normal OGTT results at the first visit were screened again with an OGTT at the subsequent visits. RESULTS: A total of 4151 pregnant women from different trimesters underwent OGTT. Of them 739 women (17.8%) had GDM. Among the GDM women, 528 (71.4%) were detected at the first visit. On screening during subsequent visits, GDM was diagnosed in the remaining 211(28.6%) women who had normal OGTT in the first visit. We performed the analysis taking the glycemic level in the first visit of 211 pregnant women who manifested GDM in the subsequent visit. During normal pregnancy, 2hr PG level is < 120 mg/dl. Taking this value into consideration among the 211 women who turned to have GDM in the subsequent visits 119 women (56.4%) had 2hrPG > or = 120 mg/dl and the remaining 92(43.6%) had 2hrPG < 120 mg/dl. CONCLUSION: Pregnant women irrespective of 2 hr PG > or = or < 120 mg/dl at initial visit progressed to GDM in the subsequent visit. No glycemic level in the early weeks of pregnancy predicts GDM and at the same time at no statistically significant glycemic cut-off level could we say that a woman will not develop GDM. Hence rescreening in the subsequent trimester or visits is essential.