Bioactive molecules from Nocardia: diversity,bioactivities and biosynthesis

Journal of Industrial Microbiology & Biotechnology - Nocardia spp. are catalase positive, aerobic, and non-motile Gram-positive filamentous bacteria. Many Nocarida spp. have been reported as...     

Determination of community structure through deconvolution of PLFA-FAME signature of mixed population

Phospholipid fatty acids (PLFAs) as biomarkers are well established in the literature. A general method based on least square approximation (LSA) was developed for the estimation of community structure from the PLFA signature of a mixed population where biomarker PLFA signatures of the component species were known. Fatty acid methyl ester (FAME) standards were used as species analogs and mixture of the standards as representative of the mixed population. The PLFA/FAME signatures were analyzed by gas chromatographic separation, followed by detection in flame ionization detector (GC-FID). The PLFAs in the signature were quantified as relative weight percent of the total PLFA. The PLFA signatures were analyzed by the models to predict community structure of the mixture. The LSA model results were compared with the existing "functional group" approach. Both successfully predicted community structure of mixed population containing completely unrelated species with uncommon PLFAs. For slightest intersection in PLFA signatures of component species, the LSA model produced better results. This was mainly due to inability of the "functional group" approach to distinguish the relative amounts of the common PLFA coming from more than one species. The performance of the LSA model was influenced by errors in the chromatographic analyses. Suppression (or enhancement) of a component's PLFA signature in chromatographic analysis of the mixture, led to underestimation (or overestimation) of the component's proportion in the mixture by the model. In mixtures of closely related species with common PLFAs, the errors in the common components were adjusted across the species by the model.     

Effect of different biosynthetic precursors on the production of nargenicin A1 from metabolically engineered Nocardia sp. CS682

Nargenicin A1 is a 28-membered polyketide macrolide, with antibacterial activity against methicillin-resistant Staphylococcus aureus, produced by Nocardia sp. CS682. In this study, the production of nargenicin A1 was improved by enhancing the supply of different biosynthetic precursors. In Nocardia sp. CS682 (KCTC11297BP), this improvement was ~4.62-fold with the supplementation of 30 mM methyl oleate, 4.25-fold with supplementation of 15 mM sodium propionate, and 2.81-fold with supplementation of 15 mM sodium acetate. In Nocardia sp. metK18 and Nocardia sp. CS682 expressing S-adenosylmethionine synthetase (MetK), the production of nargenicin A1 was improved by ~5.57-fold by supplementation with 30 mM methyl oleate, 5.01-fold by supplementation with 15 mM sodium propionate, and 3.64-fold by supplementation with 15 mM sodium acetate. Furthermore, supplementing the culture broth of Nocardia sp. ACC18 and Nocardia sp. CS682 expressing the acetyl-CoA carboxylase complex (AccA2 and AccBE) with 30 mM methyl oleate, 15 mM sodium propionate, or 15 mM sodium acetate resulted in ~6.99-, 6.46-, and 5.58-fold increases, respectively, in nargenicin A1 production. Our overall results showed that among the supplements, methyl oleate was the most effective precursor supporting the highest titers of nargenicin A1 in Nocardia sp. CS682, Nocardia sp. metK18, and Nocardia sp. ACC18.     

Lipotropes promote immunobiochemical plasticity and protect fish against low-dose pesticide-induced oxidative stress

An experiment was conducted to evaluate the role of different lipotropes in modulating immunity and biochemical plasticity under conditions of sublethal low-dose pesticide-induced stress in fish. Labeo rohita fish fingerlings were divided in two sets with one set of fish continuously exposed to low-dose endosulfan (1/10th of 96-h LC₅₀) for 21 days, the other was unexposed, and both sets of fish were fed with practical diets supplemented with either 2 % lecithin, 0.5 % betaine, or 0.1 % choline and compared against unsupplemented diet. Low-dose endosulfan exposure had adverse effects (P < 0.05/P < 0.01) on hematological profile (erythrocyte count, hemoglobin, and hematocrit), serum protein (total protein, albumin, and globulin) and lipid profile (cholesterol and triglyceride), anti-oxidative status (ascorbic acid content of muscle, liver, brain, and kidney and activity of anti-oxidative enzymes: catalase and superoxide dismutase), neurotransmission (acetylcholinesterase activity in muscle and brain), immunological attributes (WBC count, albumin to globulin ratio, phagocytic activity, and serum cortisol), and metabolic plasticity as revealed from enzyme activities (muscle lactate dehydrogenase, liver and kidney glucose-6-phosphatase dehydrogenase-G6PDH activity). Dietary lipotropes prevented these effects completely or partially and the effects were lipotrope dependent. Kinetics (maximum velocity value V_max, catalytic efficiency and Michaelis constant K_m) of G6PDH enzyme from crude extracts of liver and kidney indicated inhibition due to endosulfan but lipotropes could protect enzyme and showed a stabilizing effect. The supplements also helped maintain integrity of histoarchitecture of the hepatocytes in endosulfan-exposed fish to a great extent. Feeding lipotropes to fish reared in endosulfan-free water also improved hematological and serum protein and lipid profiles and were immunostimulatory. In conclusion, dietary lipotropes, especially betaine and lecithin at the levels used, improve erythropoiesis, serum protein and lipid profile, anti-oxidant status, immunocompetence, neurotransmission, and protect the livers of L. rohita fingerlings even when continuously exposed to low-dose endosulfan.     

Epicatechin ameliorates ionising radiation-induced oxidative stress in mouse [corrected] liver

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 (60)Co 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.     

Health risk assessment of atmospheric polycyclic aromatic hydrocarbons over the Central Himalayas

Carcinogenic risk assessments of polycyclic aromatic hydrocarbons (PAHs) in four sites from the Central Himalayas (Bode, Lumbini, Pokhara, and Dhunche) were performed. Lifetime Average Daily Dose (LADD), Lifetime lung cancer risk (LLCR) and Incremental lifetime cancer risk (ILCR) were calculated in order to evaluate the cancer risk. PAHs levels were converted to BaP equivalent concentrations (B[a]Peq), and models of health risk assessment were applied. B[a]Peq concentrations exceeded the standard limited value (1 ng/m³) in all the four sites. The human health risk assessment (HHRA) demonstrated high carcinogenic risk on residents of Bode and Lumbini. Further, LLCR in all sites were over the acceptable range (1.15E-03, 7.90E-04, 1.40E-04 and 9.96E-05, respectively); however, ILCR ranking exhibited acceptable range in Lumbini, Pokhara, and Dhunche (7.10E-06, 1.26E-06, and 8.95E-07). The risk variation among the sites is due to the difference in pollution status. The study shows health risk due to atmospheric PAHs via inhalation prevails all the seasons throughout, differing only seasonally; nevertheless, the concentration and carcinogenic risk decreased remarkably from south-north transect of the central Himalaya. Keeping some uncertainties aside, this study provides noble insights and helps to formulate new advance assessment on the carcinogenic risk of atmospheric PAHs over the Central Himalayas.     

Single-walled carbon nanotubes modulate pulmonary immune responses and increase pandemic influenza a virus titers in mice

Background

Numerous toxicological studies have focused on injury caused by exposure to single types of nanoparticles, but few have investigated how such exposures impact a host’s immune response to pathogen challenge. Few studies have shown that nanoparticles can alter a host’s response to pathogens (chiefly bacteria) but there is even less knowledge of the impact of such particles on viral infections. In this study, we performed experiments to investigate if exposure of mice to single-walled carbon nanotubes (SWCNT) alters immune mechanisms and viral titers following subsequent influenza A virus (IAV) infection.

Methods

Male C57BL/6 mice were exposed to 20 μg of SWCNT or control vehicle by intratracheal instillation followed by intranasal exposure to 3.2?×?10⁴ TCID₅₀ IAV or PBS after 3 days. On day 7 mice were euthanized and near-infrared fluorescence (NIRF) imaging was used to track SWCNT in lung tissues. Viral titers, histopathology, and mRNA expression of antiviral and inflammatory genes were measured in lung tissue. Differential cell counts and cytokine levels were quantified in bronchoalveolar lavage fluid (BALF).

Results

Viral titers showed a 63-fold increase in IAV in SWCNT + IAV exposed lungs compared to the IAV only exposure. Quantitation of immune cells in BALF indicated an increase of neutrophils in the IAV group and a mixed profile of lymphocytes and neutrophils in SWCNT + IAV treated mice. NIRF indicated SWCNT remained in the lung throughout the experiment and localized in the junctions of terminal bronchioles, alveolar ducts, and surrounding alveoli. The dual exposure exacerbated pulmonary inflammation and tissue lesions compared to SWCNT or IAV single exposures. IAV exposure increased several cytokine and chemokine levels in BALF, but greater levels of IL-4, IL-12 (P70), IP-10, MIP-1, MIP-1α, MIP-1β, and RANTES were evident in the SWCNT?+?IAV group. The expression of tlr3, ifnβ1, rantes, ifit2, ifit3, and il8 was induced by IAV alone but several anti-viral targets showed a repressed trend (ifits) with pre-exposure to SWCNT.

Conclusions

These findings reveal a pronounced effect of SWCNT on IAV infection in vivo as evidenced by exacerbated lung injury, increased viral titers and several cytokines/chemokines levels, and reduction of anti-viral gene expression. These results imply that SWCNT can increase susceptibility to respiratory viral infections as a novel mechanism of toxicity.