Microbial populations and activity in two soils of Tanzania as influenced by mercury

Summary The influence of mercury on microbial populations and activity of two soils from Tanzania was studied. Aretan (2-methoxyethylmercury chloride) slightly affected the microbial population of the Morogoro (Oxisol) soil, which was 10⁷ c.f.u./g in control soil and 10⁶ c.f.u./g in the presence of 2000 mg Hg/kg soil. Mercuric chloride at >8 mg Hg/kg soil increased the population slightly, with a sharp decrease at >100 mg Hg/kg soil, dropping ultimately to 10³ c.f.u./g at 2000 mg Hg/kg soil. In the Arusha (Andept) soil, the microbial response to the two mercury compounds was the opposite of that for the Morogoro soil. Aretan sharply reduced the nitrogenase activity of aerobically incubated Morogoro soils at Hg levels >24 mg/kg, resulting in very low activity at >50 mg Hg/kg soil. Mercuric chloride increased the activity, which showed a peak at 24 mg Hg/kg soils, followed by a sharp drop at 30 mg Hg/kg and remained low thereafter. In the Arusha soil, the activity was reduced gradually by both Aretan and HgCl₂. The response of the activity under anaerobic incubation in the Morogoro soil was the opposite of that under aerobic incubation, in that it was Aretan which at first increased the activity. In the Arusha soil the activity under anaerobic incubation decreased gradually over the entire range of added Hg. Nitrification was decreased by HgCl₂ atlevels of <2 and <10 mg Hg/kg soil in the Arusha and Morogoro soils, respectively. The tolerance to Hg by microorganisms in this study was in the order: total population > nitrogen fixers > nitrifiers. This may be explained in terms of species diversity of the microorganisms, which may be expected to follow the same sequence.

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Population et activités microbiennes dans deux sols de Tanzanie sous l'influence du mercure

Résumé On étudie l'influence du mercure sur les populations et les activités microbiennes de deux sols en provenance de Tanzanie. L'Aretan (chlorure de 2-méthoxyéthylmercure) n'affecte que faiblement la population microbienne du sol de Morogoro (oxisol), qui compte 10⁷ individus par g dans le sol témoin et 10⁶ individus en présence de 2000 mg de mercure par kg de sol. Le chlorure mercurique, à une dose supérieure à 8 mg de mercure par kg de sol, augmente quelque peu la population. Celle-ci décroît brutalement au delà de 100 mg de mercure par kg de sol, pour tomber finalement à 10³ individus par g à 2000 mg de mercure par kg de sol. Dans le sol d'Arusha (Andept), la réponse microbienne aux deux composés mercuriels est l'inverse de celle obtenue avec le sol de Morogoro. L'Aretan réduit fortement l'activité de la nitrogénase de sols de Morogoro incubés en aérobiose à des teneurs en mercure au delà de 24 mg par kg. L'activité devient très faible au delà de 50 mg de mercure par kg de sol. Le chlorure mercurique augmente cette activité, avec un pic de 24 mg de mercure par kg de sol, suivi d'une chute sévère à 30 mg de mercure par kg. L'activité demeure faible aux doses plus fortes. Dans le sol d'Arusha, l'activité est réduite progressivement tant par l'Aretan que par HgCl₂. La réponse de l'activité en incubation anaérobie dans le sol de Morogoro est l'inverse de celle en incubation aérobie en ceci que c'est l'Aretan, cette fois-ci, qui augmente d'abord l'activité. Dans le sol d'Arusha, l'activité en incubation anaérobie décroît progressivement sur l'échelle entière des concentrations d'ajout de mercure. La nitrification est réduite par HgCl₂ à des seuils au dessous de 2 et 10 mg de mercure par kg de sol, respectivement pour les sols d'Arusha et de Morogoro. La tolérance des microorganismes au mercure dans cette étude est dans l'ordre: population totale > fixateurs d'azote > nitrificateurs. Ceci peut être expliqué en termes de diversité des espèces de microorganismes qui suit vraisemblablement la même séquence.

     

Membrane-trafficking RabA4c involved in the effect of glycine betaine on recovery from chilling stress in Arabidopsis

Glycine betaine (GB) can confer tolerance to several types of stress at low concentrations, either after application to plants or in transgenics engineered to overproduce GB. Based on earlier studies on levels of GB in plants and evidence for effects on gene expression, we hypothesized that at least part of this effect could be ascribed to the activation of the expression of stress tolerance genes. Using a strategy based on high-throughput gene expression analysis with microarrays followed by confirmation with northern blots, we identified Arabidopsis genes upregulated in roots that reinforce intracellular processes protecting cells from oxidative damage and others that appear to be involved in reinforcing a scavenging system for reactive oxygen species (ROS) in cell walls. Upregulated genes in roots include those for the membrane-trafficking RabA4c, the root-specific NADPH-dependent ferric reductase (FRO2) localized to the plasma membrane, mitochondrial catalase 2 and the cell wall peroxidase ATP3a. Comparative studies with wild-type Arabidopsis and knockout mutants for the membrane-trafficking RabA4c gene demonstrated that the mutants respond only slightly to GB, if at all, compared with wild-type in relation to root growth recovery after chilling stress, demonstrating the role of RabA4c in relation to the GB effect. The results point toward links between oxidative stress, gene expression, membrane trafficking and scavenging of ROS such as superoxide and hydrogen peroxide in relation to GB effects on chilling tolerance in plants.     

Further studies of the plasma alpha 1 B-glycoprotein polymorphism: two new alleles and allele frequencies in Caucasians and in American blacks

Two new alleles (A1 B*3 and A1 B*4) of human plasma alpha 1 B-glycoprotein (alpha 1 B) were reported. alpha 1 B phenotyping was done by using either a simple method of two-dimensional (2-D) agarose gel-horizontal polyacrylamide gel electrophoresis (PAGE) followed by protein staining or by one-dimensional horizontal PAGE and immunoblotting. Seven different alpha 1 B phenotypes (1-1, 1-2, 1-3, 1-4, 2-2, 2-3 and 3-3) were observed; phenotypes 1-3 and 1-4 were differentiated from each other only by the 2-D method. The respective frequencies Af A1 B*1, A1 B*2, A1 B*3 and A1 B*4 alleles in the studied populations were estimated as follows: American Blacks (New York) 0.732, 0.204, 0.064, 0; American Whites (New York) 0.947, 0.053; Czechs (M?lník) 0.964, 0.034, 0, 0.002; Slovaks (Bratislava and Trencin) 0.977, 0.023, 0, 0. The population of American Blacks showed a much higher degree of alpha 1 B polymorphism (polymorphism information content = 0.37) than the Caucasian populations that have been studied.     

Analysis of HLA and Disease Susceptibility: Chromosome 6 Genes and Sex Influence Long-QT Phenotype

The long-QT (LQT) syndrome is a genetically complex disorder that is characterized by syncope and fatal ventricular arrhythmias. LQT syndrome, as defined by a prolonged electrocardiographic QT interval, has a higher incidence in females than in males and does not exhibit Mendelian transmission patterns in all families. Among those families that are nearly consistent with Mendelian transmission, linkage between a locus for LQT syndrome and the H-ras-1 locus on the short arm of chromosome 11 has been reported in some families but not in others. Earlier analyses suggesting that LQT syndrome might be caused by a gene in the HLA region of chromosome 6 were not confirmed by standard linkage analyses. Here, we present an analysis of HLA haplotype sharing among affected pedigree members, showing an excess of haplotype sharing in a previously published Japanese pedigree and possibly also in 15 families of European descent. The haplotypes shared by affected individuals derive from both affected and unaffected parents. In an analysis of independent (unrelated) HLA haplotypes, we also found a nonrandom distribution of HLA-DR genes in LQT syndrome patients compared with controls, suggesting an association between the LQT phenotype and specific HLA-DR genes. Our data indicate that DR2 has a protective effect and, particularly in males, that DR7 may increase susceptibility to the LQT syndrome. Thus, LQT syndrome may be influenced by genes on chromosomes 11 and 6, possibly with a sex-specific effect. These results provide a model for an effect of HLA-region genes inherited from either parent on the expression of an illness that may be determined principally by alleles at loci not linked to HLA.     

Whole Genome Gene Expression Meta-Analysis of Inflammatory Bowel Disease Colon Mucosa Demonstrates Lack of Major Differences between Crohn's Disease and Ulcerative Colitis

Background

In inflammatory bowel disease (IBD), genetic susceptibility together with environmental factors disturbs gut homeostasis producing chronic inflammation. The two main IBD subtypes are Ulcerative colitis (UC) and Crohn’s disease (CD). We present the to-date largest microarray gene expression study on IBD encompassing both inflamed and un-inflamed colonic tissue. A meta-analysis including all available, comparable data was used to explore important aspects of IBD inflammation, thereby validating consistent gene expression patterns.

Methods

Colon pinch biopsies from IBD patients were analysed using Illumina whole genome gene expression technology. Differential expression (DE) was identified using LIMMA linear model in the R statistical computing environment. Results were enriched for gene ontology (GO) categories. Sets of genes encoding antimicrobial proteins (AMP) and proteins involved in T helper (Th) cell differentiation were used in the interpretation of the results. All available data sets were analysed using the same methods, and results were compared on a global and focused level as t-scores.

Results

Gene expression in inflamed mucosa from UC and CD are remarkably similar. The meta-analysis confirmed this. The patterns of AMP and Th cell-related gene expression were also very similar, except for IL23A which was consistently higher expressed in UC than in CD. Un-inflamed tissue from patients demonstrated minimal differences from healthy controls.

Conclusions

There is no difference in the Th subgroup involvement between UC and CD. Th1/Th17 related expression, with little Th2 differentiation, dominated both diseases. The different IL23A expression between UC and CD suggests an IBD subtype specific role. AMPs, previously little studied, are strongly overexpressed in IBD. The presented meta-analysis provides a sound background for further research on IBD pathobiology.     

The Role of Individual Traits and Environmental Factors for Diet Composition of Sheep

Large herbivore consumption of forage is known to affect vegetation composition and thereby ecosystem functions. It is thus important to understand how diet composition arises as a mixture of individual variation in preferences and environmental drivers of availability, but few studies have quantified both. Based on 10 years of data on diet composition by aid of microhistological analysis for sheep kept at high and low population density, we analysed how both individual traits (sex, age, body mass, litter size) linked to preference and environmental variation (density, climate proxies) linked to forage availability affected proportional intake of herbs (high quality/low availability) and Avenella flexuosa (lower quality/high availability). Environmental factors affecting current forage availability such as population density and seasonal and annual variation in diet had the most marked impact on diet composition. Previous environment of sheep (switch between high and low population density) had no impact on diet, suggesting a comparably minor role of learning for density dependent diet selection. For individual traits, only the difference between lambs and ewes affected proportion of A. flexuosa, while body mass better predicted proportion of herbs in diet. Neither sex, body mass, litter size, ewe age nor mass of ewe affected diet composition of lambs, and there was no effect of age, body mass or litter size on diet composition of ewes. Our study highlights that diet composition arises from a combination of preferences being predicted by lamb and ewes’ age and/or body mass differences, and the immediate environment in terms of population density and proxies for vegetation development.     

Divergent responses of Atlantic cod to ocean acidification and food limitation

In order to understand the effect of global change on marine fishes, it is imperative to quantify the effects on fundamental parameters such as survival and growth. Larval survival and recruitment of the Atlantic cod (Gadus morhua) were found to be heavily impaired by end‐of‐century levels of ocean acidification. Here, we analysed larval growth among 35–36 days old surviving larvae, along with organ development and ossification of the skeleton. We combined CO₂ treatments (ambient: 503 µatm, elevated: 1,179 µatm) with food availability in order to evaluate the effect of energy limitation in addition to the ocean acidification stressor. As expected, larval size (as a proxy for growth) and skeletogenesis were positively affected by high food availability. We found significant interactions between acidification and food availability. Larvae fed ad libitum showed little difference in growth and skeletogenesis due to the CO₂ treatment. Larvae under energy limitation were significantly larger and had further developed skeletal structures in the elevated CO₂ treatment compared to the ambient CO₂ treatment. However, the elevated CO₂ group revealed impairments in critically important organs, such as the liver, and had comparatively smaller functional gills indicating a mismatch between size and function. It is therefore likely that individual larvae that had survived acidification treatments will suffer from impairments later during ontogeny. Our study highlights important allocation trade‐off between growth and organ development, which is critically important to interpret acidification effects on early life stages of fish.     

Harvesting of males delays female breeding in a socially monogamous mammal; the beaver

Human exploitation may skew adult sex ratios in vertebrate populations to the extent that males become limiting for normal reproduction. In polygynous ungulates, females delay breeding in heavily harvested populations, but effects are often fairly small. We would expect a stronger effect of male harvesting in species with a monogamous mating system, but no such study has been performed. We analysed the effect of harvesting males on the timing of reproduction in the obligate monogamous beaver (Castor fiber). We found a negative impact of harvesting of adult males on the timing of parturition in female beavers. The proportion of normal breeders sank from over 80%, when no males had been shot in the territories of pregnant females, to under 20%, when three males had been shot. Harvesting of males in monogamous mammals can apparently affect their normal reproductive cycle.     

Positive short-term effects of sheep grazing on the alpine avifauna

Grazing by large herbivores may negatively affect bird populations. This is of great conservation concern in areas with intensive sheep grazing. Sheep management varies substantially between regions, but no study has been performed in less intensively grazed systems. In a fully replicated, landscape scale experiment with three levels of sheep grazing, we tested whether the abundance and diversity of an assemblage of mountain birds were negatively affected by grazing or if grazing facilitated the bird assemblage. Density of birds was higher at high sheep density compared with low sheep density or no sheep by the fourth grazing season, while there was no clear effect on bird diversity. Thus, agricultural traditions and land use politics determining sheep density may change the density of avifauna in either positive or negative directions.