Avoidance of protein oxidation correlates with the desiccation and radiation resistance of hot and cold desert strains of the cyanobacterium Chroococcidiopsis

To investigate the relationship between desiccation and the extent of protein oxidation in desert strains of Chroococcidiopsis a selection of 10 isolates from hot and cold deserts and the terrestrial cyanobacterium Chroococcidiopsis thermalis sp. PCC 7203 were exposed to desiccation (air-drying) and analyzed for survival. Strain CCMEE 029 from the Negev desert and the aquatic cyanobacterium Synechocystis sp. PCC 6803 were further investigated for protein oxidation after desiccation (drying over silica gel), treatment with H₂O₂ up to 1 M and exposure to γ-rays up to 25 kGy. Then a selection of desert strains of Chroococcidiopsis with different survival rates after prolonged desiccation, as well as Synechocystis sp. PCC 6803 and Chroococcidiopsis thermalis sp. PCC 7203, were analyzed for protein oxidation after treatment with 10 and 100 mM of H₂O₂. Results suggest that in the investigated strains a tight correlation occurs between desiccation and radiation tolerance and avoidance of protein oxidation.

     

Paleoenvironmental study of the Carquefou site (Massif Armoricain, France) from the end of the Sub-boreal

The town of Carquefou, some 10 km northeast of Nantes on the left bank of the river Erdre, occupies a site long associated with human activity. During road construction east of the town, ditches, enclosures and post holes characteristic of the late la Tène were discovered at the locality of “Le Clouet”, which led us to obtain core samples from a nearby peat bog. These investigations indicated the changes in vegetation since 3915±95 uncal B.P., [2828 (2459) 2074 cal B.C.]. The slopes in the surroundings of the bog have been relatively treeless since the Bronze Age, but a very open woodland vegetation composed of Tilia, Corylus and Quercus has been maintained until the present day. In the area around the bog, and Alnus wood with an undergrowth of Cyperaceae was the dominant vegetation, despite some changes probably related to human occupation since the Bronze Age. Beginning at 955±35 uncal B.P. [1004 (1036, 1144, 1146) 1181 cal A.D.], in the Middle Ages, the alders disappeared almost totally, apparently because of clearance or an increase in water level. Human presence led to intensified cultivation of different crops including Cannabis and especially Cerealia. Finally, the presence of a variety of anthropogenic indicator plants (Cichorioideae, Asteraceae, Plantago lanceolata, etc.) suggests that cattle were reared in the vicinity of the site. Received May 22, 2000 / Accepted March 29, 2001     

Planting position and shade enhance native seedling performance in forest restoration for an endangered malagasy plant

The critically endangered tree Schizolaena tampoketsana is confined to a few diminished and degraded forest fragments on the Malagasy highlands. This habitat is vulnerable to loss due to frequent fires in the surrounding grassland that threaten to spread into the forest. One of these fragments is the focus a conservation project and here the managers aim to conserve S. tampoketsana by restoring its forest habitat to its former extent as evidenced by remnant woody plants. To inform this activity the survival and early-stage growth of seedlings of four locally native tree species were compared under contrasting conditions of proximity to the remaining forest and shade. After 12 months, seedlings of three species(Baronia taratana, Eugenia pluricymosa, Uapaca densifolia) survived better and experienced improved growth in height in grassland close to the existing forest rather than distant from it, and two survived better with shade rather than unshaded. A number of mechanisms could explain these results including reduced exposure to desiccating sunlight and winds and better soil and greater water availability close to the forest. The seedlings of one species(Nuxia capitata) survived well under all conditions. This study suggests that reforestation in these dry highlands is most feasible adjacent to remnant forest fragments and in microhabitats that minimize water loss, though young plants of some tree species may be capable of surviving in harsher conditions.     

High prevalence of Giardia duodenalis Assemblage B infection and association with underweight in Rwandan children

Background

Giardia duodenalis is highly endemic in East Africa but its effects on child health, particularly of submicroscopic infections, i.e., those below the threshold of microscopy, and of genetic subgroups (assemblages), are not well understood. We aimed at addressing these questions and at examining epidemiological characteristics of G. duodenalis in southern highland Rwanda.

Methodology/Principal Findings

In 583 children <5 years of age from communities and health facilities, intestinal parasites were assessed by triplicate light microscopy and by PCR assays, and G. duodenalis assemblages were genotyped. Cluster effects of villages were taken into account in statistical analysis. The prevalence of G. duodenalis as detected by microscopy was 19.8% but 60.1% including PCR results. Prevalence differed with residence, increased with age, and was reduced by breastfeeding. In 492 community children without, with submicroscopic and with microscopic infection, underweight (weight-for-age z-score <−2 standard deviations) was observed in 19.7%, 22.1%, and 33.1%, respectively, and clinically assessed severe malnutrition in 4.5%, 9.5%, and 16.7%. Multivariate analysis identified microscopically detectable G. duodenalis infection as an independent predictor of underweight and clinically assessed severe malnutrition. Submicroscopic infection showed respective trends. Overall, G. duodenalis was not associated with gastrointestinal symptoms but assemblages A parasites (proportion, 13%) were increased among children with vomiting and abdominal pain.

Conclusions/Significance

The prevalence of G. duodenalis in high-endemicity areas may be greatly underestimated by light microscopy, particularly when only single stool samples are analysed. Children with submicroscopic infections show limited overt manifestation, but constitute unrecognized reservoirs of transmission. The predominance of assemblage B in Rwanda may be involved in the seemingly unimposing manifestation of G. duodenalis infection. However, the association with impaired child growth points to its actual relevance. Longitudinal studies considering abundant submicroscopic infections are needed to clarify the actual contribution of G. duodenalis to morbidity in areas of high endemicity.     

Evidence of variability in the structure and recruitment of rhizospheric and endophytic bacterial communities associated with arable sweet sorghum (Sorghum bicolor (L) Moench)

Background and aims

Sorghum is the second most cultivated crop in Africa and is a staple food source in many African communities. Exploiting the associated plant growth-promoting bacteria (PGPB) has potential as an agricultural biotechnology strategy to enhance sorghum growth, yield and nutritional properties. Therefore this study aimed to evaluate factors that shape bacterial communities associated with sorghum farmed in South Africa, and to detect bacteria consistently associated with sorghum which may impart PGP activities.

Methods

Terminal-Restriction Fragment Length Polymorphism (T-RFLP) was used to assess factors that potentially shape rhizospheric (rhizosphere and rhizoplane) and endophytic (root, shoot, stem) bacterial communities associated with South African sorghum, and together with Denaturing Gradient Gel Electrophoresis (DGGE) to identify consistently sorghum-associated bacterial taxa.

Results

The sorghum rhizospheric communities were less variable than the endophytic ones. Geographical location was the main driver in describing bacterial community assemblages found in rhizospheric sorghum-linked niches, with total NO₃-N, NH₄-N, nitrogen, carbon, pH and, to a lesser extent, clay content identified as the main abiotic factors shaping sorghum-associated soil communities. Endophytic communities presented rather stochastic assemblages, with pH being the main variable explaining their structures. Despite community variations, specific bacterial taxa were consistently detected in sorghum-created rhizospheric and endophytic environments, irrespective of environmental factor effects.

Conclusions

Soil structure and composition, which are influenced by agricultural practices, played major roles in shaping sorghum-associated edaphic bacterial communities. In contrast, endophytic bacterial communities displayed more variation. Nevertheless, potentially agronomically relevant (cyano)bacterial taxa constantly associated with sorghum were identified which is suggestive of their deterministic recruitment.     

Comparison of family 9 cellulases from mesophilic and thermophilic bacteria

Cellulases containing a family 9 catalytic domain and a family 3c cellulose binding module (CBM3c) are important components of bacterial cellulolytic systems. We measured the temperature dependence of the activities of three homologs: Clostridium cellulolyticum Cel9G, Thermobifida fusca Cel9A, and C. thermocellum Cel9I. To directly compare their catalytic activities, we constructed six new versions of the enzymes in which the three GH9-CBM3c domains were fused to a dockerin both with and without a T. fusca fibronectin type 3 homology module (Fn3). We studied the activities of these enzymes on crystalline cellulose alone and in complex with a miniscaffoldin containing a cohesin and a CBM3a. The presence of Fn3 had no measurable effect on thermostability or cellulase activity. The GH9-CBM3c domains of Cel9A and Cel9I, however, were more active than the wild type when fused to a dockerin complexed to scaffoldin. The three cellulases in complex have similar activities on crystalline cellulose up to 60°C, but C. thermocellum Cel9I, the most thermostable of the three, remains highly active up to 80°C, where its activity is 1.9 times higher than at 60°C. We also compared the temperature-dependent activities of different versions of Cel9I (wild type or in complex with a miniscaffoldin) and found that the thermostable CBM is necessary for activity on crystalline cellulose at high temperatures. These results illustrate the significant benefits of working with thermostable enzymes at high temperatures, as well as the importance of retaining the stability of all modules involved in cellulose degradation.     

Understanding Private Sector Antimalarial Distribution Chains: A Cross-Sectional Mixed Methods Study in Six Malaria-Endemic Countries

Background

Private for-profit outlets are important treatment sources for malaria in most endemic countries. However, these outlets constitute only the last link in a chain of businesses that includes manufacturers, importers and wholesalers, all of which influence the availability, price and quality of antimalarials patients can access. We present evidence on the composition, characteristics and operation of these distribution chains and of the businesses that comprise them in six endemic countries (Benin, Cambodia, Democratic Republic of Congo, Nigeria, Uganda and Zambia).

Methods and Findings

We conducted nationally representative surveys of antimalarial wholesalers during 2009–2010 using an innovative sampling approach that captured registered and unregistered distribution channels, complemented by in-depth interviews with a range of stakeholders. Antimalarial distribution chains were pyramidal in shape, with antimalarials passing through a maximum of 4–6 steps between manufacturer and retailer; however, most likely pass through 2–3 steps. Less efficacious non-artemisinin therapies (e.g. chloroquine) dominated weekly sales volumes among African wholesalers, while volumes for more efficacious artemisinin-based combination therapies (ACTs) were many times smaller. ACT sales predominated only in Cambodia. In all countries, consumer demand was the principal consideration when selecting products to stock. Selling prices and reputation were key considerations regarding supplier choice. Business practices varied across countries, with large differences in the proportions of wholesalers offering credit and delivery services to customers, and the types of distribution models adopted by businesses. Regulatory compliance also varied across countries, particularly with respect to licensing. The proportion of wholesalers possessing any up-to-date licence from national regulators was lowest in Benin and Nigeria, where vendors in traditional markets are important antimalarial supply sources.

Conclusions

The structure and characteristics of antimalarial distribution chains vary across countries; therefore, understanding the wholesalers that comprise them should inform efforts aiming to improve access to quality treatment through the private sector.     

Stickiness--some fundamentals of adhesion

We review some adhesion mechanisms that have been understoodin the field of synthetic adhesives, and more precisely foradhesives that adhere instantaneously (a property named tackiness)and whose adhesive strength usually depends on the applied pressure(pressure-sensitive adhesives). The discussion includes effectsof surface roughness, elasticity, cavitation, viscous and elasticfingering, substrate flexibility.