Adaptation of acidogenic sludge to increasing glycerol concentrations for biohydrogen production

Hydrogen is a promising alternative as an energetic carrier and its production by dark fermentation from wastewater has been recently proposed, with special attention to crude glycerol as potential substrate. In this study, two different feeding strategies were evaluated for replacing the glucose substrate by glycerol substrate: a one-step strategy (glucose was replaced abruptly by glycerol) and a step-by-step strategy (progressive decrease of glucose concentration and increase of glycerol concentration from 0 to 5 g L^?1), in a continuous stirred tank reactor (12 h of hydraulic retention time (HRT), pH 5.5, 35 °C). While the one-step strategy led to biomass washout and unsuccessful H₂ production, the step-by-step strategy was efficient for biomass adaptation, reaching acceptable hydrogen yields (0.4?±?0.1 mol_H2?mol^?1 _{glycerol consumed}) around 33 % of the theoretical yield independently of the glycerol concentration. Microbial community structure was investigated by single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) fingerprinting techniques, targeting either the total community (16S ribosomal RNA (rRNA) gene) or the functional Clostridium population involved in H₂ production (hydA gene), as well as by 454 pyrosequencing of the total community. Multivariate analysis of fingerprinting and pyrosequencing results revealed the influence of the feeding strategy on the bacterial community structure and suggested the progressive structural adaptation of the community to increasing glycerol concentrations, through the emergence and selection of specific species, highly correlated to environmental parameters. Particularly, this work highlighted an interesting shift of dominant community members (putatively responsible of hydrogen production in the continuous stirred tank reactor (CSTR)) according to the gradient of glycerol proportion in the feed, from the family Veillonellaceae to the genera Prevotella and Clostridium sp., putatively responsible of hydrogen production in the CSTR.     

Cerebral nitric oxide represses choroid plexus NFκB‐dependent gateway activity for leukocyte trafficking

Chronic neuroinflammation is evident in brain aging and neurodegenerative disorders and is often associated with excessive nitric oxide (NO) production within the central nervous system (CNS). Under such conditions, increased NO levels are observed at the choroid plexus (CP), an epithelial layer that forms the blood–cerebrospinal fluid barrier (BCSFB) and serves as a selective gateway for leukocyte entry to the CNS in homeostasis and following injury. Here, we hypothesized that elevated cerebral NO levels interfere with CP gateway activity. We found that induction of leukocyte trafficking determinants by the CP and sequential leukocyte entry to the CSF are dependent on the CP epithelial NFκB/p65 signaling pathway, which was inhibited upon exposure to NO. Examining the CP in 5XFAD transgenic mouse model of Alzheimer''s disease (AD-Tg) revealed impaired ability to mount an NFκB/p65-dependent response. Systemic administration of an NO scavenger in AD-Tg mice alleviated NFκB/p65 suppression at the CP and augmented its gateway activity. Together, our findings identify cerebral NO as a negative regulator of CP gateway activity for immune cell trafficking to the CNS.     

Immune risk phenotype is associated with nosocomial lung infections in elderly in-patients

Background

Nosocomial infections are extremely common in the elderly and may be related to ageing of the immune system. The Immune Risk Phenotype (IRP), which predicts shorter survival in elderly patients, has not been evaluated as a possible risk factor for nosocomial infection. Our aim was to assess the prevalence of nosocomial infections in elderly in-patients and to investigate potential relationships between nosocomial infections and the immunophenotype, including IRP parameters.

Results

We included 252 consecutive in-patients aged 70 years or over (mean age, 85 ± 6.2 years), between 2006 and 2008. Among them, 97 experienced nosocomial infections, yielding a prevalence rate of 38.5% (95% confidence interval, 32.5-44.5). The main infection sites were the respiratory tract (21%) and urinary tract (17.1%) When we compared immunological parameters including cell counts determined by flow cytometry in the groups with and without nosocomial infections, we found that the group with nosocomial infections had significantly lower values for the CD4/CD8 ratio and naive CD8 and CD4 T-cell counts and higher counts of memory CD8 T-cells with a significant increase in CD28-negative CD8-T cells. Neither cytomegalovirus status (positive in 193/246 patients) nor presence of the IRP was associated with nosocomial infections. However, nosocomial pneumonia was significantly more common among IRP-positive patients than IRP-negative patients (17/60 versus 28/180; p = 0.036).

Conclusion

Immunological parameters that are easy to determine in everyday practice and known to be associated with immune system ageing and shorter survival in the elderly are also associated with an elevated risk of nosocomial pneumonia in the relatively short term.     

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.      

Calcium is necessary for light excitation in barnacle photoreceptors

Summary Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca²⁺ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La³⁺), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca²⁺ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca²⁺, but not K⁺ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La³⁺. The EGTA experiments suggest that internal Ca²⁺ is necessary for light excitation of barnacle photoreceptors while the La³⁺ experiments suggest that La³⁺-sensitive inward current is necessary to maintain excitation during prolonged light.Abbreviations EGTA ethylenglyol-bis-(-aminoethylether) N, N, N¹, N¹-tetraacetate - BAPTA bis-(0-aminophenoxy)-ethane-N, N, N¹, N¹-tetraacetic acid - DMSO dimethyl sulfoxide - trp transient receptor potential - nss no steady state - ASW artificial sea water     

The pink-blue spot syndrome in Acropora eurystoma (Eilat, Red Sea): a possible marker of stress?

The appearance of pink-blue spots (termed here as pink-blue spot syndrome - PBSS) in the branching coral Acropora eurystoma from the Gulf of Eilat, Red Sea, is described. We monitored 18 transects (10 x 1 m2 each) in front of the H. Steinitz Marine Laboratory (Eilat), at 3, 6 and 9 m depth, during March and August in 2001 and 2002. Transect measurements revealed high frequencies of colonies with PBSS (up to 100% of colonies) between 3 and 9 m depth. Ten PBSS-affected colonies of A. eurystoma were labelled and monitored for the development of spots. From March to August 2001, the number of spots per colony increased and remained constantly high at both sampling dates in 2002. Spot size ranged between 7 and 149 mm2. Spots were primarily recorded in areas where coral tissues contacted foreign biological matter, either around regenerative wounds or when surrounded by encrusting organisms, in fast-growing areas and in allogeneic interactions. A preliminary biochemical examination suggested that the pink-blue pigment in A. eurystoma is part of a family of compounds (pocilloporin) responsible for the pink-blue colours in pocilloporid and acroporid corals. Pink-blue colour could be experimentally induced in A. eurystoma by tissue-to-tissue contacts between distressed and non-distressed allogeneic branches. PBSS was also induced in healthy coral tissue by contact with inert objects, e.g., by bandaging a branch with plastic strips. Any specific pink-blue colour spots faded within 1-3 months from onset. These results suggest that PBSS in A. eurystoma may not be considered a regular coral disease, but rather a locally induced syndrome caused by restricted environmental and/or biological stress conditions.     

Postglacial-period and Recent Invasions Shape the Population Genetics of Botryllid Ascidians along European Atlantic Coasts

The colonial urochordate Botryllus schlosseri is a sedentary species of Mediterranean origin that became cosmopolitan, probably because of postglacial-period dispersal and human-mediated invasions of colonies attached to ship hulls. Here we studied microsatellite allele diversity of Atlantic coast populations from an area ranging from European regions south of the last glacial front to regions that had been permanently ice-covered. Gene diversity levels varied dramatically among populations residing in areas subject to different glacial conditions. Five populations from the Iberian Peninsula, in an area south of the last glacial front, as well as two populations from presumed refugia in Brittany, expressed high gene diversity values (expected heterozygosity [He]: 0.76–0.80; average number of alleles per locus [A]: 7.25–8.75). Two populations inhabiting areas that experienced permafrost conditions (Helgoland Island, Germany, and Plymouth, England) had intermediate values (He: 0.40–0.42; A: 3.0–4.0), whereas the Auchenmalg, Scotland, population, from an area previously covered by ice, showed a remarkably low value (He: 0.17; A: 1.75). Therefore, most European populations of B. schlosseri mirrored the movement of the ice front in the last ice age. A second population from the area that was covered by permanent ice (Lossiemouth, Scotland), however, had a high He of 0.61 and an intermediate A of 3.67. Results were compared with recent invasions (populations less than 200 years old) in the United States and New Zealand that had a higher degree of genetic variation than the European native populations established thousands of years ago. Given the overall dearth of studies on this subject, we suggest that in contemporary established Botryllus populations, gene diversity is affected by ecological factors, some of which can be traced directly to the last ice age. Other parameters of gene diversity are influenced by selection pressure, which might be more intense in northern regions.