Dynamics of fungal communities in bulk and maize rhizosphere soil in the tropics

The fungal population dynamics in soil and in the rhizospheres of two maize cultivars grown in tropical soils were studied by a cultivation-independent analysis of directly extracted DNA to provide baseline data. Soil and rhizosphere samples were taken from six plots 20, 40, and 90 days after planting in two consecutive years. A 1.65-kb fragment of the 18S ribosomal DNA (rDNA) amplified from the total community DNA was analyzed by denaturing gradient gel electrophoresis (DGGE) and by cloning and sequencing. A rhizosphere effect was observed for fungal populations at all stages of plant development. In addition, pronounced changes in the composition of fungal communities during plant growth development were found by DGGE. Similar types of fingerprints were observed in two consecutive growth periods. No major differences were detected in the fungal patterns of the two cultivars. Direct cloning of 18S rDNA fragments amplified from soil or rhizosphere DNA resulted in 75 clones matching 12 dominant DGGE bands. The clones were characterized by their HinfI restriction patterns, and 39 different clones representing each group of restriction patterns were sequenced. The cloning and sequencing approach provided information on the phylogeny of dominant amplifiable fungal populations and allowed us to determine a number of fungal phylotypes that contribute to each of the dominant DGGE bands. Based on the sequence similarity of the 18S rDNA fragment with existing fungal isolates in the database, it was shown that the rhizospheres of young maize plants seemed to select the Ascomycetes order Pleosporales, while different members of the Ascomycetes and basidiomycetic yeast were detected in the rhizospheres of senescent maize plants.     

Control of autogenous activation of Herbaspirillum seropedicae nifA promoter by the IHF protein

Analysis of the expression of the Herbaspirillum seropedicae nifA promoter in Escherichia coli and Herbaspirillum seropedicae, showed that nifA expression is primarily dependent on NtrC but also required NifA for maximal expression under nitrogen-fixing conditions. Deletion of the IHF (integration host factor)-binding site produced a promoter with two-fold higher activity than the native promoter in the H. seropedicae wild-type strain but not in a nifA strain, indicating that IHF controls NifA auto-activation. IHF is apparently required to prevent overexpression of the NifA protein via auto-activation under nitrogen-fixing conditions in H. seropedicae.     

Production and Regulation of Lipase Activity from <Emphasis Type="Italic">Penicillium restrictum</Emphasis> in Submerged and Solid-State Fermentations

Different carbon (C) sources, mainly carbohydrates and lipids, have been screened for their capacity to support growth and lipase production by Penicillium restrictum in submerged fermentation (SmF) and in solid-state fermentation (SSF). Completely different physiological behaviors were observed after the addition of easily (oleic acid and glucose) and complex (olive oil and starch) assimilable C sources to the liquid and solid media. Maximal lipolytic activities (12.1 U/mL and 17.4 U/g) by P. restrictum were obtained with olive oil in SmF and in SSF, respectively. Biomass levels in SmF (12.2–14.1 mg/mL) and SSF (7.0–8.0 mg/g) did not varied greatly with the distinct C sources used. High lipase production (12.3 U/g) using glucose was only attained in SSF, perhaps due to the ability of this fermentation process to minimize catabolite repression.     

High frequency of p16 promoter methylation in non-small cell lung carcinomas from Chile

The inactivation of tumour suppressor genes by aberrant methylation of promoter regions has been described as a frequent event in neoplasia development, including lung cancer. The p16 gene is a tumour suppressor gene involved in the regulation of cell cycle progression that has been reported to be inactivated by promoter methylation in lung carcinomas at variable frequencies around the world in a smoking habit dependent manner. The purpose of this study was to investigate the methylation status of the promoter region of the p16 gene in 74 non-small cell lung carcinomas from Chile. The frequency of p16 gene inactivation by promoter methylation was determined as 79.7% (59/74). When we considered histological type, we observed that p16 promoter methylation was significantly higher in squamous cell carcinomas (30/33, 91%) compared with adenocarcinomas (21/30, 70%) (p=0.029). In addition, no association between p16 promoter methylation and gender, age or smoking habit was found (p=0.202, 0.202 and 0.147 respectively). Our results suggest that p16 promoter hypermethylation is a very frequent event in non-small cell lung carcinomas from Chile and could be smoking habit-independent.     

Synthesis and anti-HCV activity of β-d-2′-deoxy-2′-α-chloro-2′-β-fluoro and β-d-2′-deoxy-2′-α-bromo-2′-β-fluoro nucleosides and their phosphoramidate prodrugs

We report herein the synthesis and evaluation of a series of β-d-2′-deoxy-2′-α-chloro-2′-β-fluoro and β-d-2′-deoxy-2′-α-bromo-2′-β-fluoro nucleosides along with their corresponding phosphoramidate prodrugs. Key intermediates, lactols 11 and 12, were obtained by a diastereoselective fluorination of protected 2-deoxy-2-chloro/bromo-ribonolactones 7 and 8. All synthesized nucleosides and prodrugs were evaluated with a hepatitis C virus (HCV) subgenomic replicon system.     

Can Butterflies Evade Fire? Pupa Location and Heat Tolerance in Fire Prone Habitats of Florida

Butterflies such as the atala hairstreak, Eumaeus atala Poey, and the frosted elfin, Callophrys irus Godart, are restricted to frequently disturbed habitats where their larval host plants occur. Pupae of these butterflies are noted to reside at the base of host plants or in the leaf litter and soil, which may allow them to escape direct mortality by fire, a prominent disturbance in many areas they inhabit. The capacity of these species to cope with fire is a critical consideration for land management and conservation strategies in the locations where they are found. Survival of E. atala pupae in relation to temperature and duration of heat pulse was tested using controlled water bath experiments and a series of prescribed fire field experiments. Survival of E. atala pupae was correlated to peak temperature and heat exposure in both laboratory and field trials. In addition, E. atala survival following field trials was correlated to depth of burial; complete mortality was observed for pupae at the soil surface. Fifty percent of E. atala survived the heat generated by prescribed fire when experimentally placed at depths ≥ 1.75cm, suggesting that pupation of butterflies in the soil at depth can protect from fatal temperatures caused by fire. For a species such as E. atala that pupates above ground, a population reduction from a burn event is a significant loss, and so decreasing the impact of prescribed fire on populations is critical.     

Cyano-metal complexes uptake by Aspergillus niger

Aspergillus niger was grown in an industrial gold mining solution containing cyano-metal complexes. Gold, silver, copper, iron and zinc were accumulated, and the major mechanism of metal uptake involved metal precipitation on the cell surface. This could be achieved by the extensive application of instrumental analyses combined to the study of the chemical composition of the solutions, before and after contact with the fungus.     

Subchronic microcystin-LR exposure increased hepatic apoptosis and induced compensatory mechanisms in mice

Acute lethal cytotoxicity of microcystin-LR (MC-LR), a toxin produced by fresh-water cyanobacteria, has been attributed to protein phosphatases type 1 and type 2A (PP1/PP2A) inhibition and reactive oxygen species (ROS) generation. However, the effects and molecular mechanisms of prolonged, sublethal MC-LR exposure are less known. We studied mice intraperitonealy injected with saline or 25 μg MC-LR/kg for 28 days (every 2 days). MC-LR induced apoptosis in liver and not in kidneys or heart of treated animals. Liver also showed decreased α-tubulin levels (45.56% ± 7.65% of controls) and activation of p38-MAPK and CaMKII pathways (137.93% ± 11.64% and 419.35% ± 67.83% of the control group, respectively). PP1/PP2A activity decreased from 1.82 ± 0.23 (controls) to 0.91 ± 0.98 mU/mg (MC-LR-treated mice); however, no difference in total Ser/Thr phosphatase activity was found between both the groups. The results demonstrated that apoptosis and cytoskeleton disruption contributed to the hepatic cytotoxic effects of subchronic MC-LR administration. These effects occurred in association with sustained activation of signaling cascades and development of compensatory mechanisms to maintain total Ser/Thr phosphatase activity.