Bacterial community structure and enzyme activities in a membrane bioreactor (MBR) using pure oxygen as an aeration source

A pilot-scale membrane bioreactor was used to treat urban wastewater using pure oxygen instead of air as a source of aeration, to study its influence on bacterial diversity and levels of enzyme activities (acid and alkaline phosphatases, glucosidase, protease, and esterase) in the sludge. The experimental work was developed in two stages influenced by seasonal temperature. Operational parameters (temperature, pH, BOD₅, COD, total and volatile suspended solids) were daily monitored, and enzyme activities measured twice a week. Redundancy analysis (RDA) was used to reveal relationships between the level of enzyme activities and the variation of operational parameters, demonstrating a significant effect of temperature and volatile suspended solids. Bacterial diversity was analyzed by temperature-gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes. Significant differences in community structure were observed between both stages. Sequence analysis revealed that the prevalent Bacteria populations were evolutively close to Alphaproteobacteria (44%), Betaproteobacteria (25%) and Firmicutes (17%).     

Isolation, characterization and lipid-binding properties of the recalcitrant FtsA division protein from Escherichia coli

We have obtained milligram amounts of highly pure Escherichia coli division protein FtsA from inclusion bodies with an optimized purification method that, by overcoming the reluctance of FtsA to be purified, surmounts a bottleneck for the analysis of the molecular basis of FtsA function. Purified FtsA is folded, mostly monomeric and interacts with lipids. The apparent affinity of FtsA binding to the inner membrane is ten-fold higher than to phospholipids, suggesting that inner membrane proteins could modulate FtsA-membrane interactions. Binding of FtsA to lipids and membranes is insensitive to ionic strength, indicating that a net contribution of hydrophobic interactions is involved in the association of FtsA to lipid/membrane structures.     

Soil seed bank,fire season,and temporal patterns of germination in a seeder-dominated Mediterranean shrubland

Soil seed banks play a major role in the post-fire regeneration of Mediterranean shrublands. They vary throughout the year in species composition, abundance, and readiness to germinate. After fire, germination occurs mainly during the following fall to spring. Time of germination can determine recruitment success. It is unclear what factors control post-fire germination and its timing. We tested the effects of season and fire on the readily germinable soil seed bank of a seeder-dominated shrubland. Plots were burned early and late in the summer season (ES, LS). Soil samples were collected before and after fire, and germinated in a chamber simulating successively autumn, winter, and spring conditions. Samples were kept moistened at all times. Fire intensity was similar between ES and LS. Several species of Cistus and herbs, mostly annuals, were dominant. Most germination occurred during the simulated-autumn period, with little subsequent germination during the following two periods. Germination speed (T ₅₀) during simulated-autumn was similar for shrubs and herbs, and independent of season or fire. Germination was lower for two shrubs (Rosmarinus officinalis, Cistus salvifolius) and higher for herbaceous dicots in LS than in ES soils. Fire reduced monocots and enhanced Cistus. Germination period significantly interacted with fire and season in some groups or species, altering the simulated-autumn germination peak. We demonstrate that the seed bank can germinate swiftly under simulated-autumn conditions. Hence, water availability is the main controlling factor of germination. Fire season differentially affected some species or groups, and could affect the post-fire regeneration.     

Gene Expression Profiles of Spleen, Liver, and Head Kidney in Turbot (Scophthalmus maximus) Along the Infection Process with Philasterides dicentrarchi Using an Immune-Enriched Oligo-Microarray

We evaluated the expression profiles of turbot in spleen, liver, and head kidney across five temporal points of the Philasterides dicentrarchi infection process using an 8x15K Agilent oligo-microarray. The microarray included 2,176 different fivefold replicated gene probes designed from a turbot 3' sequenced EST database. We were able to identify 221 differentially expressed (DE) genes (8.1% of the whole microarray), 113 in spleen, 83 in liver, and 90 in head kidney, in at least 1 of the 5 temporal points sampled for each organ. Most of these genes could be annotated (83.0%) and functionally categorized using GO terms (69.1%) after the additional sequencing of DE genes from the 5' end. Many DE genes were related to innate and acquired immune functions. A high proportion of DE genes were organ-specific (70.6%), although their associated GO functions showed notable similarities in the three organs. The most striking difference in functional distribution was observed between the up- and downregulated gene groups. Upregulated genes were mostly associated to immune functions, while downregulated ones mainly involved metabolism-related genes. Genetic response appeared clustered in a few groups of genes with similar expression profiles along the temporal series. The information obtained will aid to understand the turbot immune response and will specifically be valuable to develop strategies of defense to P. dicentrarchi to achieve more resistant broodstocks for turbot industry.     

Gene functionalities and genome structure in Bathycoccus prasinos reflect cellular specializations at the base of the green lineage

ABSTRACT: BACKGROUND: Bathycoccus prasinos is an extremely small cosmopolitan marine green alga whose cells are covered with intricate spider's web patterned scales that develop within the Golgi cisternae before their transport to the cell surface. The objective of this work is to sequence and analyze its genome, and to present a comparative analysis with other known genomes of the green lineage. RESULTS: Its small genome of 15Mb consists of 19 chromosomes and lacks transposons. Although 70% of all B. prasinos genes share similarities with other Viridiplantae genes, up to 428 genes were probably acquired by horizontal gene transfer, mainly from other eukaryotes. Two chromosomes, one big and one small, are atypical, an unusual synapomorphic feature within the Mamiellales. Genes on these atypical outlier chromosomes show lower GC content and a significant fraction of putative horizontal gene transfer genes. Whereas the small outlier chromosome lacks colinearity with other Mamiellales and contains many unknown genes without homologs in other species, the big outlier shows a higher intron content, increased expression levels and a unique clustering pattern of housekeeping functionalities. Four gene families are highly expanded in B. prasinos, including sialyltransferases, sialidases, ankyrin repeats and zinc ion-binding genes, and we hypothesize that these genes are associated with the process of scale biogenesis. CONCLUSION: The minimal genomes of the Mamiellophyceae provide a baseline for evolutionary and functional analyses of metabolic processes in green plants.     

Anti-Mullerian hormone plasma concentration in prepubertal ewe lambs as a predictor of their fertility at a young age

ABSTRACT: BACKGROUND: In mammals, the ovarian follicular reserve is highly variable between individuals and impacts strongly on ovarian function and fertility. Nowadays, the best endocrine marker of this reserve in human, mouse and cattle is the anti-Mullerian hormone (AMH). The objectives of this work were to determine whether AMH could be detected in the plasma of prepubertal ewe lambs and to assess its relationship with their fertility at a young age. RESULTS: Plasma was taken from 76 Rasa Aragonesa ewe lambs at 3.6 months of age for AMH determination. Simultaneously, 600 IU equine chorionic gonadotropin (eCG) was administered and the number of ovulations recorded 6 days later. AMH was detected in 93 % of the lambs, and the concentrations were about 3-4-fold higher in ovulating than in non-ovulating lambs (P < 0.004). Ewes aged around 10 months were mated, giving an overall fertility of 29 %, and those failing to conceive were mated again 4 months later. Fertility at first mating was significantly correlated with plasma AMH concentration at 3.6 months (Spearman's rho = 0.34; P < 0.01). To use plasma AMH concentration as a screening test, a value of 97 pg/mL was determined as the optimum cutoff value to predict fertility at first mating (sensitivity = 68.2 %; specificity = 72.2 %). Fertility at first mating was 34.8 percentage points higher in ewe lambs with an AMH [greater than or equal to] 97 pg/mL than in those with lower AMH concentrations (50 % vs. 15 %; P < 0.001). CONCLUSIONS: Plasma AMH concentration might be a reliable marker of the ovarian status of prepubertal ewe lambs, reflecting their ability to respond to eCG stimulation. A single AMH measurement performed on ewe lambs early in age could be useful to select for replacement ewes with a higher predicted fertility at first mating.     

Naturally prion resistant mammals: A utopia?

Each known abnormal prion protein (PrP^Sc) is considered to have a specific range and therefore the ability to infect some species and not others. Consequently, some species have been assumed to be prion disease resistant as no successful natural or experimental challenge infections have been reported. This assumption suggested that, independent of the virulence of the PrP^Sc strain, normal prion protein (PrP^C) from these ‘resistant’ species could not be induced to misfold. Numerous in vitro and in vivo studies trying to corroborate the unique properties of PrP^Sc have been undertaken. The results presented in the article “Rabbits are not resistant to prion infection” demonstrated that normal rabbit PrP^C, which was considered to be resistant to prion disease, can be misfolded to PrP^Sc and subsequently used to infect and transmit a standard prion disease to leporids. Using the concept of species resistance to prion disease, we will discuss the mistake of attributing species specific prion disease resistance based purely on the absence of natural cases and incomplete in vivo challenges. The BSE epidemic was partially due to an underestimation of species barriers. To repeat this error would be unacceptable, especially if present knowledge and techniques can show a theoretical risk. Now that the myth of prion disease resistance has been refuted it is time to re-evaluate, using the new powerful tools available in modern prion laboratories, whether any other species could be at risk.