Effect of nitrogen supplementation on the longevity of antibiotic production by immobilized cells of Penicillium urticae

Summary Conidia of Penicillium urticae were immobilized in Kappa-Carrageenan beads (2–3 mm) by a previously described procedure to yield an in situ grown immobilized cell population which could be induced to produce the antibiotic and mycotoxin, patulin. When repeatedly transferred into a nitrogen-free production medium every 2 days, the patulin productivity of these cells gradually decreased to 50% within 14 days while the total cell protein remained constant. This decline was due to the gradual loss of the cells' catalytic capacity for converting glucose to 6-methylsalicylic acid (6-MSA), the first metabolite of the patulin pathway, as well as for converting 6-MSA to patulin. When these 14 day-old cells were incubated in a nutrient rich growth medium for 2 days their patulin producing activity increased from 50% to 130%. On the other hand the addition of a protein synthesis inhibitor, cycloheximide, to the N-free production medium drastically reduced the patulin producing activity of the immobilized cells; in particular, their capacity for converting 6-MSA to patulin. The cells' patulin producing activity was maintained at >100% for longer than 15 days when the cells were repeatedly transferred into a yeast extract supplemented production medium or when they were occasionally transferred into 10 or 20% strength growth medium. Repeated transfers to a 10% strength growth medium appeared to stabilize the cells' capacity for converting 6-MSA to patulin.     

Competitive binding assay using fluorescence resonance energy transfer for the identification of calmodulin antagonists

The ubiquitous calcium regulating protein calmodulin (CaM) has been utilized as a model drug target in the design of a competitive binding fluorescence resonance energy transfer assay for pharmacological screening. The protein was labeled by covalently attaching the thiol-reactive fluorophore, N-[2-(1-maleimidyl)ethyl]-7-(diethylamino)coumarin-3-carboxamide (MDCC) to an engineered C-terminal cysteine residue. Binding of the environmentally sensitive hydrophobic probe 2,6-anilinonaphthalene sulfonate (2,6-ANS) to CaM could be monitored by an increase in the fluorescence emission intensity of the 2,6-ANS. Evidence of fluorescence resonance energy transfer (FRET) from 2,6-ANS (acting as a donor) to MDCC (the acceptor in this system) was also observed; fluorescence emission representative of MDCC could be seen after samples were excited at a wavelength specific for 2,6-ANS. The FRET signal was monitored as a function of the concentration of calmodulin antagonists in solution. Calibration curves for both a selection of small molecules and a series of peptides based upon known CaM-binding domains were obtained using this system. The assay demonstrated dose-dependent antagonism by analytes known to hinder the biological activity of CaM. These data indicate that the presence of molecules known to bind CaM interfere with the ability of FRET to occur, thus leading to a concentration-dependent decrease of the ratio of acceptor:donor fluorescence emission. This assay can serve as a general model for the development of other protein binding assays intended to screen for molecules with preferred binding activity.     

The impact of land use and land cover change on biodiversity within and adjacent to Kibasira Swamp in Kilombero Valley,Tanzania

Wetlands are crucial ecosystems with multiple values and functions to a range of different stakeholders. The future of wetlands depends both on the legacy of the past and how they are currently used. Using 48 vegetation survey plots (0.08 ha) combined with Landsat 5 and 7 TM imagery, we assessed the influence of long‐term (1990–2011) land use and land cover change on the biodiversity of the Kibasira Swamp. Information on perceptions of adjacent communities on historical changes and drivers for the changes were also collected. Results showed an increase in the area covered by open water by 1% and forest by 4% between 1990 and 1998 whilst Cyperus papyrus L and cultivated land area decreased by 8% and 3%, respectively on the same period. Between 1998 and 2011, there was a decrease in areas covered by water by 35% and forest by 9% whereas C. papyrus L increased by 40% and cultivated land increased by 8%. These changes have affected the biodiversity of the swamp and adjacent to it as numbers of mammals have declined. However, the Swamp still provides extensive habitat for plants and bird species despite the ongoing human pressure. Interventions may be necessary to maintain biodiversity in Kibasira Swamp to ensure sustainable ecosystem services.     

Use of Quantal Method for Estimation of Agricultural Production

The usual analysis of quantal response data occurring in diverse fields such as economics, medicine, psychology and toxicology use probit and logit models or their extensions with generalised least squares or the principle of likelihood as the method of statistical inference. The quantal method was first used for estimation of agricultural production by S. M. Vidwans (1991). He has collected the data on yield rate of rabi jowar from the farmers for year 1981 in four villages in Shirur taluka and three villages in Daund taluka of Pune district of Maharashtra in India. The probit regression line is fitted. The fit is not good. The estimation is done using truncation of data. Here we observed that a second degree polynomial is a good fit to the data. This will give correct prediction of agricultural production with smaller standard error.