Climate drivers alter nitrogen availability in surface peat and decouple N2 fixation from CH4 oxidation in the Sphagnum moss microbiome

Peat mosses (Sphagnum spp.) are keystone species in boreal peatlands, where they dominate net primary productivity and facilitate the accumulation of carbon in thick peat deposits. Sphagnum mosses harbor a diverse assemblage of microbial partners, including N₂-fixing (diazotrophic) and CH₄-oxidizing (methanotrophic) taxa that support ecosystem function by regulating transformations of carbon and nitrogen. Here, we investigate the response of the Sphagnum phytobiome (plant + constituent microbiome + environment) to a gradient of experimental warming (+0°C to +9°C) and elevated CO₂ (+500 ppm) in an ombrotrophic peatland in northern Minnesota (USA). By tracking changes in carbon (CH₄, CO₂) and nitrogen (NH₄-N) cycling from the belowground environment up to Sphagnum and its associated microbiome, we identified a series of cascading impacts to the Sphagnum phytobiome triggered by warming and elevated CO₂. Under ambient CO₂, warming increased plant-available NH₄-N in surface peat, excess N accumulated in Sphagnum tissue, and N₂ fixation activity decreased. Elevated CO₂ offset the effects of warming, disrupting the accumulation of N in peat and Sphagnum tissue. Methane concentrations in porewater increased with warming irrespective of CO₂ treatment, resulting in a ~10× rise in methanotrophic activity within Sphagnum from the +9°C enclosures. Warming's divergent impacts on diazotrophy and methanotrophy caused these processes to become decoupled at warmer temperatures, as evidenced by declining rates of methane-induced N₂ fixation and significant losses of keystone microbial taxa. In addition to changes in the Sphagnum microbiome, we observed ~94% mortality of Sphagnum between the +0°C and +9°C treatments, possibly due to the interactive effects of warming on N-availability and competition from vascular plant species. Collectively, these results highlight the vulnerability of the Sphagnum phytobiome to rising temperatures and atmospheric CO₂ concentrations, with significant implications for carbon and nitrogen cycling in boreal peatlands.     

Microcalorimetric studies of the growth of sulfate-reducing bacteria: comparison of the growth parameters of some Desulfovibrio species.

We performed a comparative study of the growth energetics of some species of Desulfovibrio by measuring microcalorimetric and molar growth yield values. Lactate and pyruvate were used as energy sources for sulfate reduction. On lactate-sulfate media Desulfovibrio desulfuricans Norway, Desulfovibrio gigas, and Desulfovibrio africanus exhibited molar growth yields of 4.1 +/- 0.6, 3.7 +/- 1.7, and 1.8 +/- 0.1 g/mol, respectively, whereas on pyruvate-sulfate media the molar growth yields were higher (8.5 +/- 0.8, 7.7 +/- 1.6, and 3.5 +/- 0.5 g/mol, respectively). Thus, we found that D. africanus was the least efficient species in converting energy into cell material. The uncoupling of energy in this strain was obvious since its catabolic activities were high compared with those of the two other strains. The enthalpy changes associated with lactate and pyruvate metabolism were -49 +/- 0.7 and -70.2 +/- 6.0 jK/mol, respectively, for D. desulfuricans, -76.6 +/- 1.8 and -91.2 +/- 1.1 kJ/mol, respectively, for D. gigas, and -78.8 +/- 7.2 and -88.0 +/- 6.2 kJ/mol, respectively, for D. africanus. D. gigas and D. africanus produced only acetate, CO2 and hydrogen sulfide as metabolic end products. In addition to these normal end products, D. desulfuricans Norway produced a small amount of butanol. This butanol production was interpreted as reflecting a regulatory system of electron flow during the catabolism of both substrates. Such metabolism was comparable to that reported for D. vulgaris, which lost part of the reducing power of its energy sources through hydrogen evolution.     

Profil spermiologique des hommes infertiles au Mali

Infertility remains a major sociocultural problem in view of the fact that in Africa, in general, and in Mali, in particular, the main purpose of marriage remains procreation. The birth of a child is a source of joy and contributes to maintenance of a certain harmony in the home. In Africa, infertility is a dramatic problem that is difficult to bear for the couple. It is the leading cause of marital discord or divorce. It is considered to be due to fate, or a curse inflicted on the couple. For the woman, it represents a divine punishment, as it is usually the woman who is blamed for the problem male responsibility is only discovered during assessment of the couple’s infertility. Sperm count and sperm cytology are the basic examinations performed on semen. These examinations constitute key elements to evaluate the quality of semen. In Mali, the Cytogenetics and Reproduction Biology laboratory performs the greatest number of semen examinations in the country. The purpose of this study was to present the sperm profile of infertile men in Mali based on a 5-year retrospective study. Male infertility is a public health problem in Mali. The age-group most frequently affected is between 30 and 39 years. Primary sterility was the predominant form, observed in 70% of the subjects studied. Schistosomiasis plays a predominant role in the infectious history. The sperm count results show that cases of oligoasthenozoospermia and azoospermia represent 49.5% and 23.7% of the study population, respectively.     

Cryptic plasmids isolated from Campylobacter strains represent multiple, novel incompatibility groups

Three small, cryptic plasmids from the multi-drug-resistant (MDR) Campylobacter coli strain RM2228 and one small, cryptic plasmid from the MDR Campylobacter jejuni strain RM1170 were sequenced and characterized. pCC2228-1 has some similarity to Firmicutes RepL family plasmids that replicate via a rolling-circle mechanism. pCC2228-2 is a theta-replicating, iteron-containing plasmid (ICP) that is a member of the same incompatibility (Inc) group as previously described Campylobacter shuttle vectors. The other two ICPs, pCC2228-3 and pCJ1170, represent a second novel Inc group. Comparison of the four plasmids described in this study with other characterized plasmids from C. jejuni, C. coli, C. lari, and C. hyointestinalis suggests that cryptic plasmids in Campylobacter may be classified into as many as nine Inc groups. The plasmids characterized in this study have several unique features suitable for the construction of novel Campylobacter shuttle vectors, e.g., small size, absence of many common multiple-cloning site restriction sites, and Inc groups not represented by current Campylobacter shuttle plasmids. Thus, these plasmids may be used to construct a new generation of Campylobacter shuttle vectors that would permit transformation of environmental Campylobacter isolates with an existing repertoire of native plasmids.     

Porphobilinogen deaminase gene in African and Afro-Caribbean ethnic groups: mutations causing acute intermittent porphyria and specific intragenic polymorphisms

Acute intermittent porphyria (AIP), the most common acute hepatic porphyria, is a low-penetrant autosomal dominant disorder caused by mutations in the porphobilinogen deaminase (PBGD) or hydroxymethylbilane synthase (HMBS) gene. Although AIP has been identified in all the main ethnic groups, little is known about PBGD gene defects in Africans, Afro-Caribbean and Afro-Americans. We have carried out PBGD gene screening among seven unrelated AIP families and 98 controls belonging to the Afro-Caribbean (French West Indies) and the sub-Saharan African (Morocco, Algeria, Cameroon, Mali, and Burkina Faso) populations. Using denaturing-gradient gel electrophoresis (DGGE) and direct sequencing we characterized six different mutations, including four novel, from the seven AIP families: three splicing defects (IVS 5+2 Ins G; IVS 7+1 G to A in two families; IVS 10-1 G to T); a small deletion (1004 Del G); and two missense mutations (R116 W; A270G). The allele frequencies of the 14 polymorphic sites, previously known in the normal Caucasian population, were similar in Africans and Afro-Caribbean control populations. Interestingly, two common new intragenic polymorphic sites, close to intron/junction boundaries, were identified only in blacks: 1) in intron 2, a single base-pair G deletion at position 3167 (G:0.88; delG:0.12); 2) in intron 10, a A/G dimorphism at position 7052 (A:0.56; G:0.44). These two single nucleotide polymorphisms (SNPs) were never encountered in 750 unrelated Caucasian subjects. The allele frequency distributions of populations within black ethnic groups (Africans and Afro-Caribbean) are similar. This study highlights differences both in PBGD gene mutations causing AIP and in SNPs between white and black peoples; the allele frequencies provided contribute to a better knowledge of the variability of these markers among the major population groups, especially in sub-Saharan West African and Afro-Caribbean populations.     

The Use of a Mercury Biosensor to Evaluate the Bioavailability of Mercury-Thiol Complexes and Mechanisms of Mercury Uptake in Bacteria

As mercury (Hg) biosensors are sensitive to only intracellular Hg, they are useful in the investigation of Hg uptake mechanisms and the effects of speciation on Hg bioavailability to microbes. In this study, bacterial biosensors were used to evaluate the roles that several transporters such as the glutathione, cystine/cysteine, and Mer transporters play in the uptake of Hg from Hg-thiol complexes by comparing uptake rates in strains with functioning transport systems to strains where these transporters had been knocked out by deletion of key genes. The Hg uptake into the biosensors was quantified based on the intracellular conversion of inorganic mercury (Hg(II)) to elemental mercury (Hg(0)) by the enzyme MerA. It was found that uptake of Hg from Hg-cysteine (Hg(CYS)₂) and Hg-glutathione (Hg(GSH)₂) complexes occurred at the same rate as that of inorganic complexes of Hg(II) into Escherichia coli strains with and without intact Mer transport systems. However, higher rates of Hg uptake were observed in the strain with a functioning Mer transport system. These results demonstrate that thiol-bound Hg is bioavailable to E. coli and that this bioavailability is higher in Hg-resistant bacteria with a complete Mer system than in non-resistant strains. No difference in the uptake rate of Hg from Hg(GSH)₂ was observed in E. coli strains with or without functioning glutathione transport systems. There was also no difference in uptake rates between a wildtype Bacillus subtilis strain with a functioning cystine/cysteine transport system, and a mutant strain where this transport system had been knocked out. These results cast doubt on the viability of the hypothesis that the entire Hg-thiol complex is taken up into the cell by a thiol transporter. It is more likely that the Hg in the Hg-thiol complex is transferred to a transport protein on the cell membrane and is subsequently internalized.     

Exceptional diversity, maintenance of polymorphism, and recent directional selection on the APL1 malaria resistance genes of Anopheles gambiae

The three-gene APL1 locus encodes essential components of the mosquito immune defense against malaria parasites. APL1 was originally identified because it lies within a mapped QTL conferring the vector mosquito Anopheles gambiae natural resistance to the human malaria parasite, Plasmodium falciparum, and APL1 genes have subsequently been shown to be involved in defense against several species of Plasmodium. Here, we examine molecular population genetic variation at the APL1 gene cluster in spatially and temporally diverse West African collections of A. gambiae. The locus is extremely polymorphic, showing evidence of adaptive evolutionary maintenance of genetic variation. We hypothesize that this variability aids in defense against genetically diverse pathogens, including Plasmodium. Variation at APL1 is highly structured across geographic and temporal subpopulations. In particular, diversity is exceptionally high during the rainy season, when malaria transmission rates are at their peak. Much less allelic diversity is observed during the dry season when mosquito population sizes and malaria transmission rates are low. APL1 diversity is weakly stratified by the polymorphic 2La chromosomal inversion but is very strongly subdivided between the M and S "molecular forms." We find evidence that a recent selective sweep has occurred at the APL1 locus in M form mosquitoes only. The independently reported observation of a similar M-form restricted sweep at the Tep1 locus, whose product physically interacts with APL1C, suggests that epistatic selection may act on these two loci causing them to sweep coordinately.     

Minimally Invasive Detection of Piscirickettsia salmonis in Cultivated Salmonids via the PCR

The attributes of the PCR allowed implementation of an assay for specific detection of Piscirickettsia salmonis from a few microliters of fish serum. This opens the way to less invasive modes of sampling for this microbial pathogen in salmonids.