The acylation state of surface lipoproteins of mollicute Acholeplasma laidlawii

Acylation of the N-terminal Cys residue is an essential, ubiquitous, and uniquely bacterial posttranslational modification that allows anchoring of proteins to the lipid membrane. In gram-negative bacteria, acylation proceeds through three sequential steps requiring lipoprotein diacylglyceryltransferase, lipoprotein signal peptidase, and finally lipoprotein N-acyltransferase. The apparent lack of genes coding for recognizable homologs of lipoprotein N-acyltransferase in gram-positive bacteria and Mollicutes suggests that the final step of the protein acylation process may be absent in these organisms. In this work, we monitored the acylation state of eight major lipoproteins of the mollicute Acholeplasma laidlawii using a combination of standard two-dimensional gel electrophoresis protein separation, blotting to nitrocellulose membranes, and MALDI-MS identification of modified N-terminal tryptic peptides. We show that for each A. laidlawii lipoprotein studied a third fatty acid in an amide linkage on the N-terminal Cys residue is present, whereas diacylated species were not detected. The result thus proves that A. laidlawii encodes a lipoprotein N-acyltransferase activity. We hypothesize that N-acyltransferases encoded by genes non-homologous to N-acyltransferases of gram-negative bacteria are also present in other mollicutes and gram-positive bacteria.     

Effects of temperature and water availability on light energy utilization in photosynthetic processes of Deschampsia antarctica

Regional climate change in Antarctica would favor the carbon assimilation of Antarctic vascular plants, since rising temperatures are approaching their photosynthetic optimum (10–19°C). This could be detrimental for photoprotection mechanisms, mainly those associated with thermal dissipation, making plants more susceptible to eventual drought predicted by climate change models. With the purpose to study the effect of temperature and water availability on light energy utilization and putative adjustments in photoprotective mechanisms of Deschampsia antarctica Desv., plants were collected from two Antarctic provenances: King George Island and Lagotellerie Island. Plants were cultivated at 5, 10 and 16°C under well‐watered (WW) and water‐deficit (WD, at 35% of the field capacity) conditions. Chlorophyll fluorescence, pigment content and de‐epoxidation state were evaluated. Regardless of provenances, D. antarctica showed similar morphological, biochemical and functional responses to growth temperature. Higher temperature triggered an increase in photochemical activity (i.e. electron transport rate and photochemical quenching), and a decrease in thermal dissipation capacity (i.e. lower xanthophyll pool, Chl a/b and β carotene/neoxanthin ratios). Leaf mass per unit area was reduced at higher temperature, and was only affected in plants exposed to WD at 16°C and exhibiting lower electron transport rate and amount of chlorophylls. D. antarctica is adapted to frequent freezing events, which may induce a form of physiological water stress. Photoprotective responses observed under WD contribute to maintain a stable photochemical activity. Thus, it is possible that short‐term temperature increases could favor the photochemical activity of this species. However, long‐term effects will depend on the magnitude of changes and the plant's ability to adjust to new growth temperature.     

Bioremediation of oil polluted aquatic systems and soils with novel preparation `Rhoder'

This paper summarises the experience accumulated duringthe field application of biopreparation `Rhoder' (solely or in a combinationwith preliminary mechanical collection of free oil) for remediation of oil polluted aquatic systems and soils in the Moscow region and Western Siberia during 1994–1999.It was demonstrated that `Rhoder' had a very high efficiency (>99%) for bioremediation of the open aquatic surfaces (100 m² bay of the River Chernaya, two 5,000 m² lakes in Vyngayakha) at initial level of oil pollution of 0.4–19.1 g/l. During remediation of the wetland (2,000 m²) in Urai (initial level of oil pollution of 10.5 g/l), a preliminary mechanical collection of oil was applied (75% removal) followed by a triple treatment with `Rhoder'. It resulted in an overall treatment efficiency of 94%. Relatively inferior results of bioremediation of the 10,000 m² wetland in Vyngayakha (65% removal) and the 1,000 m² marshy peat soil in Nizhnevartovsk (19% removal) can be attributed to the very high initial level of oil pollution (24.3 g/l and >750 g/g dry matter, respectively) aggravated by the fact that it was impossible to apply a preliminary mechanical collection of oil on these sites. A possible strategy for remediation of such heavily polluted sitesis discussed.     

Molecular study of genes involved in virulence regulatory pathways in Bacillus anthracis vaccine strain "Carbosap"

This study investigated the genetic bases of attenuation in the Bacillus anthracis vaccine strain "Carbosap" used in Italy against anthrax in cattle and sheep. Twelve genes involved in virulence regulatory pathways underwent sequence analysis in comparison with a B. anthracis virulent strain.     

Laccase and Lectin Activities of Intracellular Proteins Produced in a Submerged Culture of the Xylotrophic Basidiomycete Lentinus edodes

The white-rot fungus Lentinus edodes produced D: -melibiose-specific lectins and two laccase forms in a lignin-containing medium. The maxima of laccase and lectin activities coincided, falling within the period of active mycelial growth. The enzymes and lectins were isolated and purified by gel filtration followed by anion-exchange chromatography. The L. edodes lectins were found to be able to stabilize the activity of the fungus's own laccases. Lectin activity during the formation of lectin-enzyme complexes remained unchanged.     

Curcumin derivatives as new ligands of Aβ peptides

Curcumin derivatives with high chemical stability, improved solubility and carrying a functionalized appendage for the linkage to other entities, have been synthesized in a straightforward manner. All compounds retained Curcumin ability to bind Aβ peptide oligomers without inducing their aggregation. Moreover all Curcumin derivatives were able to stain very efficiently Aβ deposits.     

Range maps and species richness patterns: errors of commission and estimates of uncertainty

Range maps are often combined into “range overlap maps” to estimate spatial variation in species richness. Range maps are, in most cases, designed to represent a species’ maximum geographical extent and not patterns of occupancy within the range. As a consequence, range maps overestimate occupancy by presenting false occupancy (errors of commission) within the interior of the range. To assess the implications of errors of commission when developing and applying range overlap maps, we used neutral landscapes to simulate range maps and patterns of occupancy within ranges. We explored several scenarios based on combinations of six parameters defining biogeographical and cartographic factors typically encountered by investigators. Our results suggest that, in general, uncertainty is lowest when map resolutions are moderately fine, the majority of species have geographically restricted ranges, species occur throughout their range, patterns of occupancy within the range are not correlated among species, and geographically local and widespread species tend to occupy different regions. Several of these outcomes are associated with broad geographical extents, the scale at which range overlap maps are typically applied. Thus, under most circumstances, reasonably accurate and precise representation of species richness patterns can be achieved. However, these representations can be improved by enhancing occupancy data for widespread species – a primary source of uncertainty – and selecting a map resolution that captures relevant biological and environmental heterogeneity. Hence, by determining where a study is situated within the scenarios examined in our simulations, uncertainty and its sources and implications can be ascertained. With this knowledge, research goals, methods, and data sources can be reassessed and refined and, in the end, conclusions and recommendations can be qualified. Alternatively, unique regional, taxonomic, or cartographic factors could be included in future simulations to provide direct assessments of uncertainty.