Biology subjects

Pund, A.

Publications and source records attributed to Pund, A..

3 recordsLinked to original sources

bioRxiv2020

Diversity of culturable actinobacteria producing protease inhibitors from the intertidal zones of Maharashtra, India

Phylogenetic diversity of culturable actinobacteria isolated from the intertidal regions of west coast of Maharashtra, India was studied using 16S rRNA gene sequencing. Total of 140 actinobacterial isolates were obtained, which belonged to 14 genera, 10 families and 65 putative species with Streptomyces being the most dominant (63%) genus followed by Nocardiopsis and Micromonospora. They were screened for production of extracellular protease inhibitors (PI) against three pure proteases viz. chymotrypsin, trypsin, subtilisin and one crude extracellular protease from Pseudomonas aeruginosa. Eighty percent of the isolates showed PI activity against at least one of the four proteases, majority of them belonged to genus Streptomyes. Actinobacterial diversity from two sites Ade (17{degrees}52' N, 73{degrees}04' E) and Harnai (17{degrees}48' N, 73{degrees}05' E) with varying degree of anthropological pressure showed that more putative species diversity was obtained from site with lower human intervention i.e Ade (Shannons H 3.45) than from Harnai (Shannons H 2.83), a site with more human intervention. Further, in Ade percentage of isolates not showing PI activity against any of the proteases was close to 21% and that in Harnai was close to 9%. Considering human activities in the coastal region might be contributing to increasing the organic load and in turn increasing the presence of extracellular enzymes in the intertidal environments it would be interesting to look at the association of PI production and organic load in these habitats.

microbiology↗

bioRxiv2019

Predator prey and the third beneficiary

All bacterial epibiotic predators are rich in secondary metabolites and most genera rich in secondary metabolites have demonstrable predatory abilities. Therefore it is likely that an antibiotic resistant and thereby predation resistant species may benefit not only by escaping predation but also by utilizing nutrients released by lysis of prey cells by predatory bacteria. The resistant organisms may enjoy greater fitness benefits than the predator since they get the benefit without investing in the predation machinery. In our experiment, a marine isolate of Streptomyces atrovirens showed good predatory activity on a range of species including Staphylococcus aureus and Proteus vulgaris. Escherichia coli was resistant to predation by this species. On slide culture with water agar when the predator, S. aureus and E. coli were grown together S. aureus population declined whereas the predation resistant E. coli increased their population as compared to controls. However the growth of E. coli did not affect growth of the predator unfavorably. This strengthens the possibility that evolution of antibiotic resistance not only gave a selective advantage of escaping predation, it also would have increased the fitness of the resistant organism by promoting growth on nutrients released from the prey cells lysed by the predator. When the predator was grown with S. aureus and P. vulgaris as prey, S. aureus declined rapidly whereas P. vulgaris was spared. This suggests that the predator appears to show preference towards prey and in that case even a partial or relative resistance may give substantial advantage to a population.

microbiology↗

bioRxiv2018

Inferring causal pathways among three or more variables from steady-state correlations in a homeostatic system

Cross-sectional correlations between two variables have limited implications for causality. We show here that in a homeostatic system with three or more inter-correlated variables, it is possible to make causal inferences from steady-state data. Every putative pathway between three variables makes a set of differential predictions that can be tested with steady state data. For example, among 3 variables, A, B and C, the coefficient of determination, [Formula] is predicted by the product of [Formula] and [Formula] for some pathways, but not for others. Residuals from a regression line are independent of residuals from another regression for some pathways, but positively or negatively correlated for certain other pathways. Different pathways therefore have different prediction signatures, which can be used to accept or reject plausible pathways. We apply these principles to test the classical pathway leading to a hyperinsulinemic normoglycemic insulin-resistant, or pre-diabetic state using four different sets of epidemiological data. Currently, a set of indices called HOMA-IR and HOMA-{beta} are used to represent insulin resistance and glucose-stimulated insulin response by {beta} cells respectively. Our analysis shows that if we assume the HOMA indices to be faithful indicators, the classical pathway must in turn, be rejected. Among the populations sampled, the classical pathway and faithfulness of the HOMA indices cannot be simultaneously true. The principles and tools described here can find wide application in inferring plausible regulatory mechanisms in homeostatic systems based on epidemiological data.

physiology↗