Alok Kumar Sil

Antibacterial activity of long-chain fatty alcohols against mycobacteria

Tuberculosis is caused by the bacterium Mycobacterium tuberculosis and results in innumerable deaths across the world. The emergence of multidrug-resistant and extremely drug-resistant tuberculosis strains and its coinfection with HIV has made tuberculosis more difficult to treat. Therefore, new antimycobacterial agent(s) for both therapy and disinfection are urgently required. In this context the present study describes the antibacterial property of long-chain fatty alcohols against mycobacteria. The antimycobacterial activities of alcohols with chain length ranging from C(5) to C(13) were examined against Mycobacterium smegmatis mc(2) 155 and M. tuberculosis H(37)R(v). The best activity was found with one with a C(10) chain length. This bactericidal activity can partly be attributed to its ability to damage the robust and complex cell envelope of Mycobacteria. Moreover, our study reveals the ability of decanol to attenuate biofilm formation by M. smegmatis. This knowledge can be used to develop new therapeutics and disinfectants against mycobacteria.

Epicatechin ameliorates ionising radiation-induced oxidative stress in mouse liver

Abstract The current study was intended to evaluate the hepatoprotective effect of Epicatechin (EC) against radiation-induced oxidative stress, in terms of inflammation and lipid peroxidation. Swiss albino mice were administered with EC (15 mg/kg body weight) for three consecutive days before exposing them to a single dose of 5-Gy 60Co gamma (γ) irradiation. Mice were necropsied and livers were taken for immunohistochemistry, western blot analysis and biochemical tests for the detection of markers of hepatic oxidative stress. Nuclear translocation of nuclear factor kappa B (NF-κB) and lipid peroxidation were increased whereas the activities of superoxide dismutase (SOD) and catalase (CAT), reduced glutathione (GSH) content and ferric reducing antioxidant power (FRAP) were diminished upon radiation exposure compared to control. Translocation of NF-κB from cytoplasm to nucleus and lipid peroxidation were found to be inhibited whereas an increase in SOD, CAT, GSH and FRAP was observed in the mice treated with EC prior to irradiation. Thus, pre-treatment with EC offers protection against γ-radiation induced hepatic alterations.

Bioaugmentation of polyethylene succinate-contaminated soil with Pseudomonas sp. AKS2 results in increased microbial activity and better polymer degradation.

Pseudomonas sp. AKS2 isolated from soil degrades polyethylene succinate (PES) efficiently in the laboratory. However, this organism may not be able to degrade PES with similar efficiency in a natural habitat. Since in situ remediation is preferred for the effective removal of recalcitrant materials like plastic, in the current study, bioaugmentation potential of this organism was investigated. To investigate the potential of the AKS2 strain to bioaugment the PES-contaminated soil, a microcosm-based study was carried out wherein naturally attenuated, biostimulated, and AKS2-inoculated (bioaugmented) soil samples were examined for their ability to degrade PES. The results showed better degradation of PES by bioaugmented soil than other microcosms. Consistent with it, a higher number of PES-degrading organisms were found in the bioaugmented microcosm. The bioaugmented microcosm also exhibited a higher level of average well color development in BiOLOG ECO plate assay than the other two. The corresponding Shannon–Weaver index and Gini coefficient revealed a higher soil microbial diversity of bioaugmented microcosm than the others. This was further supported by community-level physiological profile of three different microcosms wherein we have observed better utilization of different carbon sources by bioaugmented microcosms. Collectively, these results demonstrate that bioaugmentation of PES-contaminated soil with AKS2 not only enhances polymer degradation but also increases microbial diversity. Bioaugmentation of soil with AKS2 enhances PES degradation without causing damage to soil ecology. Thus, Pseudomonas sp. AKS2 has the potential to be implemented as a useful tool for in situ bioremediation of PES.

Adaptation of Pseudomonas sp. AKS2 in biofilm on low-density polyethylene surface: an effective strategy for efficient survival and polymer degradation

BackgroundPseudomonas sp. AKS2 can efficiently degrade low-density polyethylene (LDPE). It has been shown that this degradation of LDPE by AKS2 is correlated to its ability to form biofilm on the polymer surface. However, the underlying mechanism of this biofilm-mediated degradation remains unclear. Since bioremediation potential of an organism is related to its adaptability in a given environment, we hypothesized that AKS2 cells undergo successful adaptation in biofilm on LDPE, which leads to higher level of LDPE degradation. To verify this, the current study investigated a number of parameters of AKS2 cells in biofilm that are known to be involved in adaptation process.ResultsSuccessful adaptation always develops a viable microbial population. So we examined the viability of AKS2 cells in biofilm. We observed the presence of viable population in the biofilm. To gain an insight, the growth of AKS2 cells in biofilm on LDPE at different time points was examined. Results showed a better reproductive competence and more colonization for AKS2 biofilm cells than planktonic cells, indicating the increased fitness of AKS2 biofilm cells than their planktonic counterpart. Towards understanding fitness, we determined the hydrolytic activity, different carbon source utilization potentials, functional diversity and homogeneity of AKS2 biofilm cells. Results showed increased hydrolytic activity (approximately 31%), higher metabolic potential, higher functional diversity (approximately 27%) and homogeneity for biofilm-harvested cells than planktonic cells. We also examined cellular surface hydrophobicity, which is important for cellular attachment to LDPE surface. Consistent with the above results, the cell surface hydrophobicity of biofilm-harvested AKS2 cells was found to be higher (approximately 26%) compared to that of their planktonic counterpart. All these results demonstrated the occurrence of physiological as well as structural adaptations of AKS2 cells in biofilm on LDPE surface that resulted in better attachment, better utilization of polymer and better growth of AKS2 cells, leading to the development of a stable colony on LDPE surface.ConclusionsThe present study shows that AKS2 cells in biofilm on LDPE surface undergo successful adaptation that leads to enhanced LDPE degradation, and thus, it helps us to understand the underlying mechanism of biofilm-mediated polymer degradation process by AKS2 cells.

Sewage treatment in a single pond system at East Kolkata Wetland, India

East Kolkata Wetland (EKW), a Ramsar site, greatly contributes towards purification of city sewage employing single pond system. However, the underlying mechanism remains unknown. Therefore to gain an insight, in this study efforts have been made to understand the rate of biodegradation and the time dependent changes of different physicochemical factors and their interactions that are involved in the process. For this purpose, different parameters such as BOD, COD, faecal coliforms etc. have been measured at different time intervals during the purification process. The results reveal that biodegradation rate at EKW pond is very high and wastewater gets stabilized within 10 days of retention. The higher rate of biodegradation in pond system at EKW (k = 0.7 day(-1)) than in laboratory based in vitro experiment (k = 0.12 day(-1)) reveals the important contribution from other environmental components that are unique for this system. The results also demonstrate the significant influence (P< or =0.01) of temperature, pH and dissolved oxygen on the purification of waste water. Thus the current study provides an insight about the optimal pathway of gradual improvement of wastewater quality in the single pond system at EKW and may serve to explore the inherent mechanism to a great extent.

Identification and Characterization of a FYVE Domain from the Early Diverging Eukaryote Giardia lamblia

The morphology of the endomembrane system of Giardia lamblia appears to be significantly different from higher eukaryotes. Therefore, the molecular mechanisms controlling vesicular trafficking are also likely to be altered. Since FYVE domain is a known regulator of endosomal trafficking, the authors used BLAST search to identify FYVE domain(s) in G. lamblia. A 990 amino acid long putative FYVE domain-containing ORF was identified, which contains all the conserved sequence elements in the ligand binding pocket. Phylogenetic analysis reveals that this domain is significantly diverged. The authors have shown that the corresponding gene is expressed in G. lamblia trophozoites and cysts. In spite of this phylogenetic divergence, in vitro biochemical assay indicates that this domain preferentially binds to phosphatidylinositol 3-phosphate {PtdIns(3)P}and in vivo expression of the GFP-tagged G. lamblia FYVE domain in S. cerevisiae, displays its selective localization to PtdIns(3)P-enriched endosomes. This is the first study to characterize a PtdIns(3)P effector protein in this early-diverged eukaryote.

Founder effect uncovers a new axis in polyethylene succinate bioremediation during biostimulation

Biostimulation is a method of in situ bioremediation wherein native soil microbes are stimulated by nutrient supplementation. In a previous report, we showed considerable polyethylene succinate (PES) degradation by biostimulation. To gain an insight into this, this study was undertaken to investigate the different facets of the microbial population present in both soil and PES-films during biostimulation-mediated PES degradation. It was observed that addition of PES-films to both nutrient-treated and untreated soil resulted in significant reduction of soil microbial counts compared with the corresponding control. It was observed that a small microbial population containing both PES degraders and non-degraders translocated to PES surface. Over time, the population adhering to PES films changed from having both PES degraders and non-degraders to being mainly PES degraders. This newly developed microbial community on PES-films exhibited low diversity with a distinct cluster of metabolic fingerprinting and higher evenness compared with parent soil microbial population. Thus the establishment of a new community on the PES surface is an exhibition of founder effect, which subsequently resulted in the emergence of a more efficient PES-degrading population and subsequently led to considerable PES degradation.

Bioactive compound from Pseudomonas synxantha inhibits the growth of Mycobacteria

Tuberculosis is a dreaded disease and the current situation demands new anti-tubercular agent(s) for the management of public health. Towards this direction, we obtained a contaminant organism on a Mycobacterium smegmatis lawn having growth inhibitory activity against the later. In the current study, efforts were targeted to identify this organism and characterize the bioactive compound from this isolate that inhibited the growth of Mycobacteria. The result revealed that the organism is a strain of Pseudomonas synxantha. Biophysical analyses including (1)H and (13)C NMR, ESI-mass spectroscopy, FTIR showed that the bioactive compound is a long chain aliphatic hydrocarbon with a terminal alyl bond and intermediate electronegative atom. The compound exhibited strong growth inhibitory activities against M. smegmatis and Mycobacterium tuberculosis strains H37Ra, H37Rv and BCG. Further experiments showed that both P. synxantha and its secretory metabolites are capable of inducing hemolysis of human blood. Thus the results of this study clearly indicate that the bioactive compound produced by P. Synxantha has biosurfactant activities as well as anti-myco-bacterial properties.

Vitamin C forestalls cigarette smoke induced NF-κB activation in alveolar epithelial cells.

Cigarette smoking causes cellular oxidative stress resulting in inflammatory diseases of lung wherein transcription factor NF-κB plays an important role. It is possible that vitamin C, an antioxidant, may prevent cigarette smoke (CS)-induced NF-κB activation that involves degradation of I-κBε and nuclear translocation of c-Rel/p50 in alveolar epithelial cells. Therefore, to examine the hypothesis, we verified the effect of vitamin C on CS-induced expression of NF-κB driven luciferase reporter and NF-κB binding at its target DNA by EMSA in alveolar epithelial A549 cells. We also examined the level of I-κBε and sub-cellular distribution of c-Rel by western blotting and immunofluorescence respectively in CSE-treated A549 cells with or without vitamin C pretreatment. We observed a significant reduction in CSE induced luciferase expression, NF-κB DNA binding, I-κBε degradation and c-Rel nuclear translocation in cells pretreated with vitamin C. To further validate the result, we examined sub-cellular distribution of c-Rel in lungs of CS-exposed guinea pigs treated or untreated with vitamin C. Result showed that vitamin C treatment resulted in markedly reduced c-Rel nuclear translocation. All these results demonstrate that vitamin C prevents CS(E)-induced NF-κB activation and thus it could be used for the prevention of CS-induced inflammatory diseases.

Nitrogen dynamics of the aquatic system is an important driving force for efficient sewage purification in single pond natural treatment wetlands at East Kolkata Wetland

At East Kolkata Wetlands, though the domestic city sewage is purified very rapidly, the mechanisms of treatment remains inadequately explored. In this context, the present study investigated nitrogen dynamics of the single pond treatment systems during purification and explored its potential role in sewage treatment. For this purpose the concentrations of different forms of nitrogen present both in water and soil at different time points of purification were measured. The organic nitrogen content decreased sharply, in the early phase, with an increase in ammonium concentration. Notably the reduction in organic nitrogen was significantly higher than the increase in NH4+ which can be attributed to the volatilization of NH4+ under alkaline pH. This volatilization results in reduced oxygen demand. The nitrate-N concentration decreased sharply from soil with a concomitant increase in water column. However the reduction of nitrate in soil was significantly higher than the increase in water column. It indicated the occurrence of denitrification under anoxic condition wherein nitrate serves as terminal electron acceptor. Additionally a part of the nitrate supported planktonic growth. Thus it describes another mechanism of reducing oxygen demand. The initial NH4+-N concentration in the soil was very low and it increased gradually during purification due to increasing soil cation exchange capacity. Thus by trapping NH4+ ion soil contributes towards preventing contamination of water. Thus at EKW, the cumulative activities in water and soil involved in nitrogen dynamics lead to overall reduction of the oxygen demand and contribute towards efficient sewage purification.