Impact of Oil on Bacterial Community Structure in Bioturbated Sediments

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions – with tidal cycles and natural seawater – was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities.     

MAIZEWALL. Database and developmental gene expression profiling of cell wall biosynthesis and assembly in maize

An extensive search for maize (Zea mays) genes involved in cell wall biosynthesis and assembly has been performed and 735 sequences have been centralized in a database, MAIZEWALL (http://www.polebio.scsv.ups-tlse.fr/MAIZEWALL). MAIZEWALL contains a bioinformatic analysis for each entry and gene expression data that are accessible via a user-friendly interface. A maize cell wall macroarray composed of a gene-specific tag for each entry was also constructed to monitor global cell wall-related gene expression in different organs and during internode development. By using this macroarray, we identified sets of genes that exhibit organ and internode-stage preferential expression profiles. These data provide a comprehensive fingerprint of cell wall-related gene expression throughout the maize plant. Moreover, an in-depth examination of genes involved in lignin biosynthesis coupled to biochemical and cytological data from different organs and stages of internode development has also been undertaken. These results allow us to trace spatially and developmentally regulated, putative preferential routes of monolignol biosynthesis involving specific gene family members and suggest that, although all of the gene families of the currently accepted monolignol biosynthetic pathway are conserved in maize, there are subtle differences in family size and a high degree of complexity in spatial expression patterns. These differences are in keeping with the diversity of lignified cell types throughout the maize plant.     

Residue R120 is essential for the quaternary structure and functional integrity of human alphaB-crystallin

The missense mutation Arg-120 to Gly (R120G) in the human alphaBeta-crystallin sequence has been reported to be associated with autosomal dominant myopathy, cardiomyopathy, and cataract. Previous studies of the mutant showed a significant ability to aggregate in cultured cells and an increased oligomeric size coupled to an important loss of the chaperone-like activity in vitro. The aim of this study was to further analyze the role of the R120 residue in the structural and functional properties of alphaBeta-crystallin. The following mutants were generated, Arg-120 to Gly (R120G), Cys (R120C), Lys (R120K), and Asp (R120D). In cellulo, after expression in two cultured cell lines, NIH-3T3 and Cos-7, the capacity of the wild-type and mutant crystallins to aggregate was evaluated and the protein location was determined by immunofluorescence. In vitro, the wild-type and mutant crystallins were expressed in Escherichia coli cells, purified by size exclusion chromatography, and characterized using dynamic light scattering, electron microscopy, and chaperone-like activity assays. Aggregate sizes in cellulo and in vitro were analyzed. The whole of the data showed that the preservation of an Arg residue at position 120 of alphaBeta-crystallin is critical for the structural and functional integrity of the protein and that each mutation results in specific changes in both structural and functional characteristics.     

Expression and purification in high yield of a functionally active recombinant human Type I inositol(1,4,5)P3 5-phosphatase

Inositol polyphosphates are the most widespread second messenger molecules in eukaryotic cells. Human Type I inositol 1,4,5-triphosphate (Ins(1,4,5)P(3)) 5-phosphatase removes the D-5 position phosphate from soluble Ins(1,4,5)P(3,) a key event in cell signaling particularly in Ca(2+) homeostasis. In this study, the cDNA encoding human Type I Ins(1,4,5)P(3) 5-phosphatase was subcloned into a modified pMAL expression vector. This plasmid produces a recombinant protein in fusion with affinity tags located at its N-terminus, consisting in a maltose binding protein (MPB) and an octa-histidine stretch. The construction was transformed into Escherichia coli BL21 (DE3) expression strain. This dual tag strategy allows the purification of milligrams of highly purified protein. The recombinant human Type I Ins(1,4,5)P(3) 5-phosphatase is active and can thus be used for functional and structural studies.     

Cortical‐layer‐specific effects of PACAP and tPA on interneuron migration during post‐natal development of the cerebellum

During early post‐natal development of the cerebellum, granule neurons (GN) execute a centripetal migration toward the internal granular layer, whereas basket and stellate cells (B/SC) migrate centrifugally to reach their final position in the molecular layer (ML). We have previously shown that pituitary adenylate cyclase‐activating polypeptide (PACAP) stimulates in vitro the expression and release of the serine protease tissue‐type plasminogen activator (tPA) from GN, but the coordinated role of PACAP and tPA during interneuron migration has not yet been investigated. Here, we show that endogenous PACAP is responsible for the transient arrest phase of GN at the level of the Purkinje cell layer (PCL) but has no effect on B/SC. tPA is devoid of direct effect on GN motility in vitro, although it is widely distributed along interneuron migratory routes in the ML, PCL, and internal granular layer. Interestingly, plasminogen activator inhibitor 1 reduces the migration speed of GN in the ML and PCL, and that of B/SC in the ML. Taken together, these results reveal for the first time that tPA facilitates the migration of both GN and fast B/SC at the level of their intersection in the ML through degradation of the extracellular matrix.

     

Development of Composite Indices to Measure the Adoption of Pro-Environmental Behaviours across Canadian Provinces

Objective

The adoption of pro-environmental behaviours reduces anthropogenic environmental impacts and subsequent human health effects. This study developed composite indices measuring adoption of pro-environmental behaviours at the household level in Canada.

Methods

The 2007 Households and the Environment Survey conducted by Statistics Canada collected data on Canadian environmental behaviours at households'' level. A subset of 55 retained questions from this survey was analyzed by Multiple Correspondence Analysis (MCA) to develop the index. Weights attributed by MCA were used to compute scores for each Canadian province as well as for socio-demographic strata. Scores were classified into four categories reflecting different levels of adoption of pro-environmental behaviours.

Results

Two indices were finally created: one based on 23 questions related to behaviours done inside the dwelling and a second based on 16 questions measuring behaviours done outside of the dwelling. British Columbia, Quebec, Prince-Edward-Island and Nova-Scotia appeared in one of the two top categories of adoption of pro-environmental behaviours for both indices. Alberta, Saskatchewan, Manitoba and Newfoundland-and-Labrador were classified in one of the two last categories of pro-environmental behaviours adoption for both indices. Households with a higher income, educational attainment, or greater number of persons adopted more indoor pro-environmental behaviours, while on the outdoor index, they adopted fewer such behaviours. Households with low-income fared better on the adoption of outdoors pro-environmental behaviours.

Conclusion

MCA was successfully applied in creating Indoor and Outdoor composite Indices of pro-environmental behaviours. The Indices cover a good range of environmental themes and the analysis could be applied to similar surveys worldwide (as baseline weights) enabling temporal trend comparison for recurring themes. Much more than voluntary measures, the study shows that existing regulations, dwelling type, households composition and income as well as climate are the major factors determining pro-environmental behaviours.     

Developmental Instability in Incipient Colonies of Social Insects

Social insect colonies can provide homeostatic conditions that buffer the incidence of environmental fluctuations on individuals, which have contributed to their ecological success. Coptotermes (Isoptera: Rhinotermitidae) is a highly invasive termite genus and several species have important economic impact in many areas of the world. Mature Coptotermes colonies with millions of individuals can provide optimal environmental condition and nurturing capacity for the developing brood. However, it was previously suggested that contrary to mature colonies, incipient colonies may be exposed to critical stress, which may explain for the low success rate of establishment within the first year of the life of a termite colony. We here investigated the stress imposed on individuals of incipient colonies by comparing the developmental instability of individuals between incipient and mature colonies of two Coptotermes species, C. formosanus Shiraki and C. gestroi (Wasmann). We assessed the developmental instability by measuring the asymmetry of morphological traits from the head capsule of the soldier caste. Soldiers from incipient colonies of both species displayed strong asymmetrical traits in comparison to soldiers from mature colonies. We suggest that homeostatic conditions for optimal development are reached as the colony matures, and confirmed that the incipient colony remains a critical bottleneck where individuals are exposed to high developmental stress.     

HIV-Associated Histoplasmosis Early Mortality and Incidence Trends: From Neglect to Priority

Background

Histoplasmosis is an endemic fungal infection in French Guiana. It is the most common AIDS-defining illness and the leading cause of AIDS-related deaths. Diagnosis is difficult, but in the past 2 decades, it has improved in this French overseas territory which offers an interesting model of Amazonian pathogen ecology. The objectives of the present study were to describe the temporal trends of incidence and mortality indicators for HIV-associated histoplasmosis in French Guiana.

Methods

A retrospective study was conducted to describe early mortality rates observed in persons diagnosed with incident cases of HIV-associated Histoplasma capsulatum var. capsulatum histoplasmosis admitted in one of the three main hospitals in French Guiana between 1992 and 2011. Early mortality was defined by death occurring within 30 days after antifungal treatment initiation. Data were collected on standardized case report forms and analysed using standard statistical methods.

Results

There were 124 deaths (45.3%) and 46 early deaths (16.8%) among 274 patients. Three time periods of particular interest were identified: 1992–1997, 1998–2004 and 2005–2011. The two main temporal trends were: the proportion of early deaths among annual incident histoplasmosis cases significantly declined four fold (χ2, p<0.0001) and the number of annual incident histoplasmosis cases increased three fold between 1992–1997 and 1998–2004, and subsequently stabilized.

Conclusion

From an occasional exotic diagnosis, AIDS-related histoplasmosis became the top AIDS-defining event in French Guiana. This was accompanied by a spectacular decrease of early mortality related to histoplasmosis, consistent with North American reference center mortality rates. The present example testifies that rapid progress could be at reach if awareness increases and leads to clinical and laboratory capacity building in order to diagnose and treat this curable disease.