Niche-based prediction of establishment of biocontrol agents: an example with Gratiana boliviana and tropical soda apple

Successful establishment of a biological control agent is a prerequisite for effective reduction of an invasive weed. Niche-based species distribution models can generate valuable information about the potential spread of a biological control agent and help to predict its distribution. The Maximum Entropy Species Distribution Model was used in our study to predict distributions of the leaf beetle Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) and its target weed, tropical soda apple (TSA), Solanum viarum Dunal (Solanaceae). The specific objectives of this study were to (1) assess the climatic suitability for establishment of this insect across the invasive range of the weed by overlapping predicted current distributions and, (2) examine the niche-related restriction in distribution of the insect by visualising the predictive niche in multivariate space. Accuracy of predicted distributions was tested using binomial tests and area under the curve scores. The results of statistical tests confirmed that the predictions were significantly better than random. The predictions indicated that the potential distribution of G. boliviana in the USA will be more restricted than that of its host plant. Consequently, the beetle's ability to inflict damage to TSA will be geographically limited. Niche visualisation, using a PCA-based analysis, provided evidence of the niche imposed restriction on the distribution of G. boliviana. Overall, this study proposes a new approach for understanding the spatial limitations in establishment of biological control agents, allowing researchers to establish more realistic expectations of success.     

Potent Dengue Virus Neutralization by a Therapeutic Antibody with Low Monovalent Affinity Requires Bivalent Engagement

We recently described our most potently neutralizing monoclonal antibody, E106, which protected against lethal Dengue virus type 1 (DENV-1) infection in mice. To further understand its functional properties, we determined the crystal structure of E106 Fab in complex with domain III (DIII) of DENV-1 envelope (E) protein to 2.45 Å resolution. Analysis of the complex revealed a small antibody-antigen interface with the epitope on DIII composed of nine residues along the lateral ridge and A-strand regions. Despite strong virus neutralizing activity of E106 IgG at picomolar concentrations, E106 Fab exhibited a ∼20,000-fold decrease in virus neutralization and bound isolated DIII, E, or viral particles with only a micromolar monovalent affinity. In comparison, E106 IgG bound DENV-1 virions with nanomolar avidity. The E106 epitope appears readily accessible on virions, as neutralization was largely temperature-independent. Collectively, our data suggest that E106 neutralizes DENV-1 infection through bivalent engagement of adjacent DIII subunits on a single virion. The isolation of anti-flavivirus antibodies that require bivalent binding to inhibit infection efficiently may be a rare event due to the unique icosahedral arrangement of envelope proteins on the virion surface.     

A new nitrilase from Bradyrhizobium japonicum USDA 110. Gene cloning, biochemical characterization and substrate specificity

A nitrilase gene blr3397 from Bradyrhizobium japonicum USDA110 was cloned and over-expressed in Escherichia coli, and the encoded protein was purified to give a nitrilase with a single band of about 34.5kD on SDS-PAGE. The molecular weight of the holoenzyme was about 340kD as determined by light scattering analysis, suggesting that nitrilase blr3397 self-aggregated to an active form with the native structure being a decamer. The V(max) and K(m) for phenylacetonitrile were 3.15U/mg and 4.36mM, respectively. The catalytic constant k(cat) and specificity constant k(cat)/K(m) were 111min(-1) and 2.6x10(4)min(-1)M(-1). This nitrilase is most active toward the hydrolysis of hydrocinnamonitrile among the tested substrates (4.3 times that of phenylacetonitrile). The nitrilase blr3397 shows higher activity towards the hydrolysis of aliphatic nitriles than that for the aromatic counterparts, and can be characterized as an aliphatic nitrilase in terms of activity. This nitrilase also possesses distinct features from the nitrilase bll6402 of the same microbe.     

Genomic relations among 31 species of Mammillaria haworth (Cactaceae) using random amplified polymorphic DNA

Thirty-one species of Mammillaria were selected to study the molecular phylogeny using random amplified polymorphic DNA (RAPD) markers. High amount of mucilage (gelling polysaccharides) present in Mammillaria was a major obstacle in isolating good quality genomic DNA. The CTAB (cetyl trimethyl ammonium bromide) method was modified to obtain good quality genomic DNA. Twenty-two random decamer primers resulted in 621 bands, all of which were polymorphic. The similarity matrix value varied from 0.109 to 0.622 indicating wide variability among the studied species. The dendrogram obtained from the unweighted pair group method using arithmetic averages (UPGMA) analysis revealed that some of the species did not follow the conventional classification. The present work shows the usefulness of RAPD markers for genetic characterization to establish phylogenetic relations among Mammillaria species.     

Bioremediation of DDT in soil by genetically improved strains of soil fungus Fusarium solani

Bioremediation of DDT in soil by genetically improved recombinants of the soil fungus Fusarium solani was studied. The parent strains were isolated from soil enriched with DDD or DDE (immediate anaerobic and aerobic degradation products of DDT), as further degradation of these products are slow processes compared to the parent compound. These naturally occurring strains isolated from soil, however, are poor degraders of DDT and differed in their capability to degrade its metabolites such as DDD, DDE, DDOH and DBP and other organochlorine pesticides viz. kelthane and lindane. Synergistic effect was shown by some of these strains, when grown together in the medium containing DDD and kelthane under mixed culture condition. No synergism in DDE degradation was observed with the strains isolated from enriched soil. DDD-induced proteins extracted from individual culture filtrate (exo-enzyme) when subjected to SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) showed complementary polypeptide bands in these strains i.e., each strain produced distinct DDD degrading polypeptide bands and the recombinant or hybrid strains produced all of the bands of the two parents and degraded DDD better than the parental strains. Recombinant hybrid strains with improved dehalogenase activity were raised by parasexual hybridisation of two such complementary isolates viz. isolate 1(P-1) and 4(P-2) showing highest complementation and are compatible for hyphal fusion inducing heterokaryosis. These strains are genetically characterised as Kel⁺Ben^RDBP^-Lin^- and Kel^-Ben^rDBP⁺Lin⁺ respectively.Recombinants with mixed genotype, i.e., Kel⁺Ben^RDBP⁺Lin⁺ showing superior degradation quality for DDT were selected for bioremediation study. Recombination was confirmed by polypeptide band analysis of DDD induced exo-proteins from culture filtrate usingSDS-Polyacrylamide Gel Electrophoresis (PAGE) and RAPD (Random Amplified Polymorphic DNA) of genomic DNA using PCR (Polymerase Chain Reaction) technique. SDS-PAGE showed combination of DDD induced polypeptide bands characteristic of both the parents in the recombinants or the hybrids. PCR study showed the parent specific bands in the recombinant strains confirming gene transformation.     

Biofouling effects on the performance of microbial fuel cells and recent advances in biotechnological and chemical strategies for mitigation

The occurrence of biofouling in MFC can cause severe problems such as hindering proton transfer and increasing the ohmic and charge transfer resistance of cathodes, which results in a rapid decline in performance of MFC. This is one of the main reasons why scaling-up of MFCs has not yet been successfully accomplished. The present review article is a wide-ranging attempt to provide insights to the biofouling mechanisms on surfaces of MFC, mainly on proton exchange membranes and cathodes, and their effects on performance of MFC based on theoretical and practical evidence. Various biofouling mitigation techniques for membranes are discussed, including preparation of antifouling composite membranes, modification of the physical and chemical properties of existing membranes, and coating with antifouling agents. For cathodes of MFC, use of Ag nanoparticles, Ag-based composite nanoparticles, and antifouling chemicals is outlined in considerable detail. Finally, prospective techniques for mitigation of biofouling are discussed, which have not been given much previous attention in the field of MFC research. This article will help to enhance understanding of the severity of biofouling issues in MFCs and provides up-to-date solutions. It will be beneficial for scientific communities for further strengthening MFC research and will also help in progressing this cutting-edge technology to scale-up, using the most efficient methods as described here.     

DNA protection by histone-like protein HU from the hyperthermophilic eubacterium Thermotoga maritima

In mesophilic prokaryotes, the DNA-binding protein HU participates in nucleoid organization as well as in regulation of DNA-dependent processes. Little is known about nucleoid organization in thermophilic eubacteria. We show here that HU from the hyperthermophilic eubacterium Thermotoga maritima HU bends DNA and constrains negative DNA supercoils in the presence of topoisomerase I. However, while binding to a single site occludes approximately 35 bp, association of T. maritima HU with DNA of sufficient length to accommodate multiple protomers results in an apparent shorter occluded site size. Such complexes consist of ordered arrays of protomers, as revealed by the periodicity of DNase I cleavage. Association of TmHU with plasmid DNA yields a complex that is remarkably resistant to DNase I-mediated degradation. TmHU is the only member of this protein family capable of occluding a 35 bp nonspecific site in duplex DNA; we propose that this property allows TmHU to form exceedingly stable associations in which DNA flanking the kinks is sandwiched between adjacent proteins. We suggest that T. maritima HU serves an architectural function when associating with a single 35 bp site, but generates a very stable and compact aggregate at higher protein concentrations that organizes and protects the genomic DNA.     

Role of chromium supplementation in Indians with type 2 diabetes mellitus

Type 2 diabetes mellitus is a complex metabolic disorder with adverse cardiovascular risk. The role of micronutrients has not yet been well clarified in this condition, especially in India.THE OBJECTIVES OF THIS STUDY WERE TO: (1) evaluate chromium status in Indian subjects with type 2 diabetes mellitus, (2) assess the effect of chromium picolinate (200 &mgr;g trivalent chromium twice daily) administration on glycaemic control and lipid profile in these subjects and (3) comment on the possible mechanism of any beneficial effect noted above.Fifty subjects were studied in a double blind, placebo-controlled, crossover fashion, with each treatment arm (chromium/placebo) lasting 12 weeks and 4 weeks' wash-off period in between. 50 healthy age- and sex-matched volunteers served as controls. Serum chromium level appeared to be higher in the general population in our country compared to western countries (36.5-59.5 nmol/L as compared to 2.3-40.3 nmol/L) However, the local diabetics were found to have a lower serum chromium level than the healthy controls (32.3 nmol/L against 44.7 nmol/L; p < 0.0001) and a mean increase of 3.5 nmol/L was noted after 12 weeks of chromium supplementation that was, expectedly, not seen in the placebo phase (p < 0.0001).Significant improvement in glycaemic control was noted in the chromium-treated group (DeltaFasting serum glucose = 0.44 mmol/L, p < 0.001; DeltaPost-prandial serum glucose = 1.97 mmol/L, p < 0.001; Deltaglycated hemoglobin = 0.01; p = 0.04, in comparison to placebo) This was accompanied by a significant greater fall in fasting serum insulin in the chromium-treated group, p < 0.05.The change in lipid parameters (total serum cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol and triglycerides) did not show significant difference between the chromium and placebo groups.Clinically significant hematological, renal or hepatic toxicity were excluded by routine hemogram, serum urea, creatinine, alanine amino transferase (ALT) and alkaline phosphatase estimations.In conclusion, chromium supplementation seems to improve glycaemic control in type 2 diabetic patients, which appears to be due to an increase in insulin action rather than stimulation of insulin secretion.     

Study of properties of cholinephosphotransferase from fetal guinea pig lung mitochondria and microsomes

Summary We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochondria and microsomes of fetal guinea pig lung. This study was designed to compare the properties of mitochondrial and microsomal cholinephosphotransferase in fetal guinea pig lung. Various parameters, such as substrate specificity, K_m values, sensitivity to N-ethylmaleimide, dithiothreitol and trypsin were measured. Both showed significant preference for unsaturated diacylglycerols over saturated diacylglycerols. Data on K_m and V_max indicate that the affinity of this enzyme for different diacylglycerols varies between the two forms. The ID₅₀ values for N-ethylmaleimide were 20 mM and 12.5 mM for the mitochondrial and microsomal form of the enzyme, respectively. Dithiothreitol showed an inhibitory effect on both; however, the mitochondrial form was inhibited less than the microsomal form. The effects of N-ethylmaleimide and dithiothreitol on both forms of enzyme indicated that the microsomal cholinephosphotransferase requires a higher concentration of -SH for its activity than the mitochondrial enzyme does. The enzyme was inhibited by trypsin in both mitochondria and microsome under isotonic condition suggesting that this enzyme is on the outside of the membrane in both endoplasmic reticulum and mitochondria.     

The chondrocyte-intrinsic circadian clock is disrupted in human osteoarthritis

Peripheral clocks are essential for driving cell differentiation. In osteoarthritis, loss of the normal differentiated chondrocyte (cartilage cell) phenotype is causative of disease. We investigated whether clock gene expression differed in osteoarthritic compared to “healthy” chondrocytes and used RNAi to determine whether the differences observed could affect chondrocyte phenotype. Following serum shock, PER2 expression was significantly higher, whereas BMAL1 expression was significantly lower, in osteoarthritic chondrocytes. Knockdown of BMAL1 in “healthy” chondrocytes was associated with higher cell proliferation and MMP13 expression, features characteristic of the osteoarthritic chondrocyte phenotype. Chondrocyte-intrinsic clock disruption may be a critical early step in osteoarthritis development.