Incipient speciation driven by hypertrophied lips in Midas cichlid fishes?

Sympatric speciation has been debated in evolutionary biology for decades. Although it has gained in acceptance recently, still only a handful of empirical examples are seen as valid (e.g. crater lake cichlids). In this study, we disentangle the role of hypertrophied lips in the repeated adaptive radiations of Nicaraguan crater lake cichlid fish. We assessed the role of disruptive selection and assortative mating during the early stages of divergence and found a functional trade‐off in feeding behaviour between thick‐ and thin‐lipped ecotypes, suggesting that this trait is a target of disruptive selection. Thick‐lipped fish perform better on nonevasive prey at the cost of a poorer performance on evasive prey. Using enclosures in the wild, we found that thick‐lipped fish perform significantly better in rocky than in sandy habitats. We found almost no mixed pairs during two breeding seasons and hence significant assortative mating. Genetic differentiation between ecotypes seems to be related to the time since colonization, being subtle in L. Masaya (1600 generations ago) and absent in the younger L. Apoyeque (<600 generations ago). Genome‐wide differentiation between ecotypes was higher in the old source lakes than in the young crater lakes. Our results suggest that hypertrophied lips might be promoting incipient sympatric speciation through divergent selection (ecological divergence in feeding performance) and nonrandom mating (assortative mating) in the young Nicaraguan crater lakes. Nonetheless, further manipulative experiments are needed in order to confirm the role of hypertrophied lips as the main cue for assortative mating.     

Suppression of alternative lengthening of telomeres by Sp100-mediated sequestration of the MRE11/RAD50/NBS1 complex

Approximately 10% of cancers overall use alternative lengthening of telomeres (ALT) instead of telomerase to prevent telomere shortening, and ALT is especially common in astrocytomas and various types of sarcomas. The hallmarks of ALT in telomerase-negative cancer cells include a unique pattern of telomere length heterogeneity, rapid changes in individual telomere lengths, and the presence of ALT-associated promyelocytic leukemia bodies (APBs) containing telomeric DNA and proteins involved in telomere binding, DNA replication, and recombination. The ALT mechanism appears to involve recombination-mediated DNA replication, but the molecular details are largely unknown. In telomerase-null Saccharomyces cerevisiae, an analogous survivor mechanism is dependent on the RAD50 gene. We demonstrate here that overexpression of Sp100, a constituent of promyelocytic leukemia nuclear bodies, sequestered the MRE11, RAD50, and NBS1 recombination proteins away from APBs. This resulted in repression of the ALT mechanism, as evidenced by progressive telomere shortening at 121 bp per population doubling, a rate within the range found in telomerase-negative normal cells, suppression of rapid telomere length changes, and suppression of APB formation. Spontaneously generated C-terminally truncated Sp100 that did not sequester the MRE11, RAD50, and NBS1 proteins failed to inhibit ALT. These findings identify for the first time proteins that are required for the ALT mechanism.     

CD4+ T lymphocytes expressing CD40 ligand help the IgM antibody response to soluble pneumococcal polysaccharides via an intermediate cell type

Streptococcus pneumoniae causes serious infections in children, the elderly, and immunocompromised patients. Protection against infections with S. pneumoniae is mediated through Abs against the capsular polysaccharides (caps-PS). We previously showed that the murine Ab response to caps-PS is dependent on CD40-CD40L interaction. In the present paper, we addressed the question of whether the CD40-CD40L-mediated modulation of the anti-caps-PS immune reaction is the result of a direct interaction between B lymphocytes and T lymphocytes or of an indirect interaction. SCID/SCID mice reconstituted with B lymphocytes from wild-type mice did not mount anti-caps-PS Abs. SCID/SCID mice reconstituted with B lymphocytes from wild-type mice and CD4+ T lymphocytes from wild-type mice but not CD4+ T lymphocytes from CD40L knockout mice stimulated the anti-caps-PS Ab response. This indicated that CD4+ T lymphocytes stimulated the anti-caps-PS Ab response in a CD40L-dependent manner. SCID/SCID mice reconstituted with B lymphocytes from CD40 knockout mice and CD4+ T lymphocytes from wild-type mice generated an anti-caps-PS Ab response that could be inhibited by MR1, a blocking anti-CD40L Ab. These data indicated that CD4+ T lymphocytes stimulated the anti-caps-PS Ab response in an indirect way. Finally, lethally irradiated CD40 knockout mice reconstituted with bone marrow from wild-type mice mounted an anti-caps-PS Ab response that was comparable to the Ab response in wild-type mice, revealing that the required CD40 was on hemopoietic cells. In conclusion, we provide evidence that CD4+ T lymphocytes expressing CD40L stimulate the Ab response to soluble caps-PS by interacting with CD40-expressing non-B cells.     

Effect of Temperature on Carbon and Electron Flow and on the Archaeal Community in Methanogenic Rice Field Soil

Temperature is an important factor controlling CH₄ production in anoxic rice soils. Soil slurries, prepared from Italian rice field soil, were incubated anaerobically in the dark at six temperatures of between 10 to 37°C or in a temperature gradient block covering the same temperature range at intervals of 1°C. Methane production reached quasi-steady state after 60 to 90 days. Steady-state CH₄ production rates increased with temperature, with an apparent activation energy of 61 kJ mol⁻¹. Steady-state partial pressures of the methanogenic precursor H₂ also increased with increasing temperature from <0.5 to 3.5 Pa, so that the Gibbs free energy change of H₂ plus CO₂-dependent methanogenesis was kept at −20 to −25 kJ mol of CH₄⁻¹ over the whole temperature range. Steady-state concentrations of the methanogenic precursor acetate, on the other hand, increased with decreasing temperature from <5 to 50 μM. Simultaneously, the relative contribution of H₂ as methanogenic precursor decreased, as determined by the conversion of radioactive bicarbonate to ¹⁴CH₄, so that the carbon and electron flow to CH₄ was increasingly dominated by acetate, indicating that psychrotolerant homoacetogenesis was important. The relative composition of the archaeal community was determined by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes (16S rDNA). T-RFLP analysis differentiated the archaeal Methanobacteriaceae, Methanomicrobiaceae, Methanosaetaceae, Methanosarcinaceae, and Rice clusters I, III, IV, V, and VI, which were all present in the rice field soil incubated at different temperatures. The 16S rRNA genes of Rice cluster I and Methanosaetaceae were the most frequent methanogenic groups. The relative abundance of Rice cluster I decreased with temperature. The substrates used by this microbial cluster, and thus its function in the microbial community, are unknown. The relative abundance of acetoclastic methanogens, on the other hand, was consistent with their physiology and the acetate concentrations observed at the different temperatures, i.e., the high-acetate-requiring Methanosarcinaceae decreased and the more modest Methanosaetaceae increased with increasing temperature. Our results demonstrate that temperature not only affected the activity but also changed the structure and the function (carbon and electron flow) of a complex methanogenic system.     

Complete Nucleotide Sequence of a 43-Kilobase Genomic Island Associated with the Multidrug Resistance Region of Salmonella enterica Serovar Typhimurium DT104 and Its Identification in Phage Type DT120 and Serovar Agona

This study describes the characterization of the recently described Salmonella genomic island 1 (SGI1) (D. A. Boyd, G. A. Peters, L.-K. Ng, and M. R. Mulvey, FEMS Microbiol. Lett. 189:285-291, 2000), which harbors the genes associated with the ACSSuT phenotype in a Canadian isolate of Salmonella enterica serovar Typhimurium DT104. A 43-kb region has been completely sequenced and found to contain 44 predicted open reading frames (ORFs) which comprised approximately 87% of the total sequence. Fifteen ORFs did not show any significant homology to known gene sequences. A number of ORFs show significant homology to plasmid-related genes, suggesting, at least in part, a plasmid origin for the SGI1, although some with homology to phage-related genes were identified. The SGI1 was identified in a number of multidrug-resistant DT120 and S. enterica serovar Agona strains with similar antibiotic-resistant phenotypes. The G+C content suggests a potential mosaic structure for the SGI1. Emergence of the SGI1 in serovar Agona strains is discussed.     

Deep soil flipping increases carbon stocks of New Zealand grasslands

Sequestration of soil organic carbon (SOC) has been recognized as an opportunity to off‐set global carbon dioxide (CO₂) emissions. Flipping (full inversion to 1–3 m) is a practice used on New Zealand's South Island West Coast to eliminate water‐logging in highly podzolized sandy soils. Flipping results in burial of SOC formed in surface soil horizons into the subsoil and the transfer of subsoil material low in SOC to the “new” topsoil. The aims of this study were to quantify changes in the storage and stability of SOC over a 20‐year period following flipping of high‐productive pasture grassland. Topsoils (0–30 cm) from sites representing a chronosequence of flipping (3–20 years old) were sampled (2005/07) and re‐sampled (2017) to assess changes in topsoil carbon stocks. Deeper samples (30–150 cm) were also collected (2017) to evaluate the changes in stocks of SOC previously buried by flipping. Density fractionation was used to determine SOC stability in recent and buried topsoils. Total SOC stocks (0–150 cm) increased significantly by 69 ± 15% (179 ± 40 Mg SOC ha^‐1) over 20 years following flipping. Topsoil burial caused a one‐time sequestration of 160 ± 14 Mg SOC ha^‐1 (30–150 cm). The top 0–30 cm accumulated 3.6 Mg SOC ha^‐1 year^‐1. The chronosequence and re‐sampling revealed SOC accumulation rates of 1.2–1.8 Mg SOC ha^‐1 year^‐1 in the new surface soil (0–15 cm) and a SOC deficit of 36 ± 5% after 20 years. Flipped subsoils contained up to 32% labile SOC (compared to <1% in un‐flipped subsoils) thus buried SOC was preserved. This study confirms that burial of SOC and the exposure of SOC depleted subsoil results in an overall increase of SOC stocks of the whole soil profile and long‐term SOC preservation.     

Protein Kinase B (AKT) Mediates Phospholipase D Activation via ERK1/2 and Promotes Respiratory Burst Parameters in Formylpeptide-stimulated Neutrophil-like HL-60 Cells

Phospholipase D (PLD), a major source of lipid second messengers (phosphatidic acid, diglycerides) in many cell types, is tightly regulated by protein kinases, but only a few of them have been identified. We show here that protein kinase B (AKT) is a novel major signaling effector of PLD activity induced by the formylpeptide f-Met-Leu-Phe (fMLP) in human neutrophil-like HL-60 cells (dHL-60 cells). AKT inhibition with the selective antagonist AKTib1/2 almost completely prevented fMLP-mediated activity of PLD, its upstream effector ERK1/2, but not p38 MAPK. Immunoprecipitation studies show that phosphorylated AKT, ERK, and PLD2 form a complex induced by fMLP, which can be prevented by AKTib1/2. In cell-free systems, AKT1 stimulated PLD activity via activation of ERK. AKT1 actually phosphorylated ERK2 as a substrate (K_m 1 μm). Blocking AKT activation with AKTib1/2 also prevented fMLP- but not phorbol 12-myristate 13-acetate-mediated NADPH oxidase activation (respiratory burst, RB) of dHL-60 cells. Impaired RB was associated with defective membrane translocation of NADPH oxidase components p67^phox and p47^phox, ERK, AKT1, AKT2, but not AKT3. Depletion of AKT1 or AKT2 with antisense oligonucleotides further indicates a partial contribution of both isoforms in fMLP-induced activation of ERK, PLD, and RB, with a predominant role of AKT1. Thus, formylpeptides induce sequential activation of AKT, ERK1/2, and PLD, which represents a novel signaling pathway. A major primarily role of this AKT signaling pathway also emerges in membrane recruitment of NOX2 components p47^phox, p67^phox, and ERK, which may contribute to assembly and activation of the RB motor system, NADPH oxidase.     

Subsurface microbiology and biogeochemistry of a deep, cold-water carbonate mound from the Porcupine Seabight (IODP Expedition 307)

The Porcupine Seabight Challenger Mound is the first carbonate mound to be drilled (∼270 m) and analyzed in detail microbiologically and biogeochemically. Two mound sites and a non-mound Reference site were analyzed with a range of molecular techniques [catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH), quantitative PCR (16S rRNA and functional genes, dsrA and mcrA ), and 16S rRNA gene PCR-DGGE] to assess prokaryotic diversity, and this was compared with the distribution of total and culturable cell counts, radiotracer activity measurements and geochemistry. There was a significant and active prokaryotic community both within and beneath the carbonate mound. Although total cell numbers at certain depths were lower than the global average for other subseafloor sediments and prokaryotic activities were relatively low (iron and sulfate reduction, acetate oxidation, methanogenesis) they were significantly enhanced compared with the Reference site. In addition, there was some stimulation of prokaryotic activity in the deepest sediments (Miocene, > 10 Ma) including potential for anaerobic oxidation of methane activity below the mound base. Both Bacteria and Archaea were present, with neither dominant, and these were related to sequences commonly found in other subseafloor sediments. With an estimate of some 1600 mounds in the Porcupine Basin alone, carbonate mounds may represent a significant prokaryotic subseafloor habitat.     

Interaction of S-layer proteins of Lactobacillus kefir with model membranes and cells

In previous works, it was shown that S-layer proteins from Lactobacillus kefir were able to recrystallize and stabilize liposomes, this feature reveling a great potential for developing liposomal-based carriers. Despite previous studies on this subject are important milestones, a number of questions remain unanswered. In this context, the feasibility of S-layer proteins as a biomaterial for drug delivery was evaluated in this work. First, S-layer proteins were fully characterized by electron microscopy, 2D-electrophoresis, and anionic exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). Afterward, interactions of S-layer proteins with model lipid membranes were evaluated, showing that proteins adsorb to the lipid surface following a non-fickean or anomalous diffusion, when positively charged lipid were employed, suggesting that electrostatic interaction is a key factor in the recrystallization process on these proteins. Finally, the interaction of S-layer coated liposomes with Caco-2 cell line was assessed: First, cytotoxicity of formulations was tested showing no cytotoxic effects in S-layer coated vesicles. Second, by flow cytometry, it was observed an increased ability to transfer cargo molecules into Caco-2 cells from S-layer coated liposomes in comparison to control ones. All data put together, supports the idea that a combination of adhesive properties of S-layer proteins concomitant with higher stability of S-layer coated liposomes represents an exciting starting point in the development of new drug carriers.     

Role of Wnt-5a in the Determination of Human Mesenchymal Stem Cells into Preadipocytes

Increasing adipocyte size as well as numbers is important in the development of obesity and type 2 diabetes, with adipocytes being generated from mesenchymal precursor cells. This process includes the determination of mesenchymal stem cells (MSC) into preadipocytes (PA) and the differentiation of PA into mature fat cells. Although the process of differentiation has been highly investigated, the determination in humans is poorly understood. In this study, we compared human MSC and human committed PA on a cellular and molecular level to gain further insights into the regulatory mechanisms in the determination process. Both cell types showed similar morphology and expression patterns of common mesenchymal and hematopoietic surface markers. However, although MSC were able to differentiate into adipocytes and osteocytes, PA were only able to undergo adipogenesis, indicating that PA lost their multipotency during determination. WNT-5a expression showed significantly higher levels in MSC compared with PA suggesting that WNT-5a down-regulation might be important in the determination process. Indeed, incubation of human MSC in medium containing neutralizing WNT-5a antibodies abolished their ability to undergo osteogenesis, although adipogenesis was still possible. An opposite effect was achieved using recombinant WNT-5a protein. On a molecular level, WNT-5a was found to promote c-Jun N-terminal kinase-dependent intracellular signaling in MSC. Activation of this noncanonical pathway resulted in the induction of osteopontin expression further indicating pro-osteogenic effects of WNT-5a. Our data suggest that WNT-5a is necessary to maintain osteogenic potential of MSC and that inhibition of WNT-5a signaling therefore plays a role in their determination into PA in humans.