Genetic evidence of fragmented populations and inbreeding in the Colombian endemic Dahl’s toad-headed turtle (<Emphasis Type="Italic">Mesoclemmys dahli</Emphasis>)

Population fragmentation is one of the most concerning consequences of habitat fragmentation, as small and isolated populations suffer increased genetic drift and inbreeding. However, the extent to which habitat fragmentation leads to population fragmentation depends not only on the landscape structure, but also on the response of organisms to it. This behavioral component makes it difficult to detect population fragmentation even if the habitat is fragmented, unless appropriate tools are used. In this study, we used a molecular approach to evaluate if Dahl’s toad-headed turtle (Mesoclemmys dahli) population was fragmented, given that it occurs in a very restricted area within the most degraded biome of Colombia, the tropical dry forest. We developed a panel of 15 microsatellite loci in order to perform the first genetic assessment of M. dahli across its complete geographic range. We found that M. dahli has significant genetic structure with at least four subpopulations, with surprisingly moderate to high levels of genetic diversity. Despite high levels of genetic diversity, subpopulations are very small (effective population sizes?<?50) and isolated, with little to no contemporary gene flow among them. As a consequence, mating among related individuals has been occurring, and all four populations are showing high degrees of inbreeding. To counteract this threat, we recommend an urgent genetic rescue strategy accompanied by habitat restoration, and advocate for a new conservation status assessment, not based on geographic range, but on adult population size and level of fragmentation.     

Evolutionary history of the European free-tailed bat,a tropical affinity species spanning across the Mediterranean Basin

The Mediterranean Basin is a global biodiversity hotspot, hosting a number of native species belonging to families that are found almost exclusively in tropical climates. Yet, whether or not these taxa were able to survive in the Mediterranean region during the Quaternary climatic oscillations remains unknown. Focusing on the European free-tailed bat (Tadarida teniotis), we aimed to (a) identify potential ancient populations and glacial refugia; (b) determine the post-glacial colonization routes across the Mediterranean; and (c) evaluate current population structure and demography. Mitochondrial and nuclear markers were used to understand T. teniotis evolutionary and demographic history. We show that T. teniotis is likely restricted to the Western Palearctic, with mitochondrial phylogeny suggesting a split between an Anatolian/Middle East clade and a European clade. Nuclear data pointed to three genetic populations, one of which is an isolated and highly differentiated group in the Canary Islands, another distributed across Iberia, Morocco, and France, and a third stretching from Italy to the east, with admixture following a pattern of isolation by distance. Evolutionary and demographic reconstruction supports a pre-Last Glacial Maximum (LGM) colonization of Italy and the Anatolian/Middle East, while the remaining populations were colonized from Italy after the Younger Dryas. We also found support for demographic expansion following the Iberian colonization. The results show that during the LGM T. teniotis persisted in Mediterranean refugia and has subsequently expanded to its current circum-Mediterranean range. Our findings raise questions regarding the physiological and ecological traits that enabled species with tropical affinities to survive in colder climates.     

Detection of Aeromonas hydrophila in food with an enzyme-linked immunosorbent assay

A microtitration plate, antibody capture, enzyme-linked immunosorbent assay was developed for the detection of Aeromonas hydrophila serotype O : 11 (highly virulent strains). The assay utilizes a detector antibody which shows no cross-reactions with Aeromonas strains other than serotype O : 11 or non- Aeromonas competing organisms. The detector antibody is mixed with the sample and incubated for 1 h, microcentrifuged and the supernatant fluid (unadsorbed antibody) titred in a microtitre plate coated with A. hydrophila cells from serotype O : 11. All the A. hydrophila strains from serotype O : 11 tested reacted strongly with the detector antibody. Also by culturing and performing the immunoassay with the detector antibody we established and quantified the presence of A. hydrophila O : 11 in different foods.     

Properties of a Novel PBP2A Protein Homolog from Staphylococcus aureus Strain LGA251 and Its Contribution to the ��-Lactam-resistant Phenotype

Methicillin-resistant Staphylococcus aureus (MRSA) strains show strain-to-strain variation in resistance level, in genetic background, and also in the structure of the chromosomal cassette (SCCmec) that carries the resistance gene mecA. In contrast, strain-to-strain variation in the sequence of the mecA determinant was found to be much more limited among MRSA isolates examined so far. The first exception to this came with the recent identification of MRSA strain LGA251, which carries a new homolog of this gene together with regulatory elements mecI/mecR that also have novel, highly divergent structures. After cloning and purification in Escherichia coli, PBP2A_LGA, the protein product of the new mecA homolog, showed aberrant mobility in SDS-PAGE, structural instability and loss of activity at 37 °C, and a higher relative affinity for oxacillin as compared with cefoxitin. The mecA homolog free of its regulatory elements was cloned into a plasmid and introduced into the background of the β-lactam-susceptible S. aureus strain COL-S. In this background, the mecA homolog expressed a high-level resistance to cefoxitin (MIC = 400 μg/ml) and a somewhat lower resistance to oxacillin (minimal inhibitory concentration = 200 μg/ml). Similar to PBP2A, the protein homolog PBP2A_LGA was able to replace the essential function of the S. aureus PBP2 for growth. In contrast to PBP2A, PBP2A_LGA did not depend on the transglycosylase activity of the native PBP2 for expression of high level resistance to oxacillin, suggesting that the PBP2A homolog may preferentially cooperate with a monofunctional transglycosylase as the alternative source of transglycosylase activity.     

Carotenoid supplementation and GnRH challenges influence female endocrine physiology, immune function, and egg-yolk characteristics in Japanese quail (Coturnix japonica)

Androgens and carotenoids circulating in plasma affect the physiology and behavior of vertebrates. Much is known about control mechanisms and functions of each of these substances, yet their interactive effects are not well understood. Here we examine possible additive, multiplicative, and interactive effects of testosterone and carotenoids on female endocrine physiology, immunocompetence, and investment in eggs by simultaneously manipulating levels of testosterone [via gonadotropin releasing hormone (GnRH) challenges] and carotenoids (via diet supplementation) in captive female Japanese quail (Coturnix japonica). Females were randomly assigned to one of four treatments: carotenoid supplementation, GnRH challenge, GnRH challenge?+?carotenoid supplementation, or control. Carotenoid supplementation significantly increased circulating plasma carotenoid levels and acquired immune system performance, but not innate immunity. GnRH challenges elevated circulating testosterone and carotenoid levels, and induced immunosuppression in females. However, females in the GnRH challenge?+?carotenoid supplementation treatment had higher cell-mediated immune responses than control females and similar responses to those of carotenoid-supplemented females. Hence, availability of carotenoids in female quail seemed to counteract immunosuppressive effects of GnRH challenges. Our results provide further evidence for synergistic effects of carotenoids and testosterone on endocrine physiology and immune function in female birds. Elevated plasma testosterone or carotenoids levels resulted in increased deposition of those compounds to eggs, respectively. Furthermore, because we found that concentrations of testosterone and carotenoids in yolks were correlated within each treatment group, differential deposition of hormones and carotenoids in eggs may not only respond to surrounding social and environmental conditions, but also to other components of the egg.     

Glutathione-mediated Antioxidative Mechanisms in Sunflower (<Emphasis Type="Italic">Helianthus Annuus</Emphasis> L.) Cells in Response to Cadmium Stress

Cadmium (Cd) homeostasis and detoxification in sunflower (Helianthus annuus L.) cells differing in Cd sensitivity/tolerance were studied by analyzing the glutathione-mediated antioxidant mechanism vis-à-vis phytochelatin biosynthesis in vitro. Calluses exposed to Cd-shock/-acclimatization (150μM) were assayed for oxidative stress, reduced glutathione (GSH), glutathione disulfide (GSSG), phytochelatins (PCs) and reactive oxygen species (ROS). Although Cd did not induce any oxidative stress in Cd-tolerant callus (TCd), it generated oxidative stress in Cd-shock callus (SCd) both in terms of lipid peroxidation and protein oxidation. GSH/GSSG ratio remained similar to control values in the cadmium-acclimatized calluses. However, after acute treatment, there was a decline in both GSH and GSSG levels in SCd with concomitant reduction in the GSH/GSSG ratio. Analysis of PCs was performed using HPLC and mass spectrometry methods. PC concentration in TCd were approximately twice those that in SCd, showing in both cases a 1:2:1 relative proportion for PC n = 2 (PC2): PC n = 3 (PC3): PC n = 4 (PC4). Calluses growing in the presence of Cd developed an increased resistance to paraquat oxidative stress generation. These results indicated that PCs synthesis was an important mechanism for Cd detoxification in sunflower calluses, but the capacity to grow in the presence of Cd is related to the tissues ability to maintain high intracellular levels of GSH.     

Effect of ice melting on bacterial carbon fluxes channelled by viruses and protists in the Arctic Ocean

During the last few years, extensive sea ice melting in the Arctic due to climate change has been detected, which could potentially modify the organic carbon fluxes in these waters. In this study, the effect of sea ice melting on bacterial carbon channelling by phages and protists has been evaluated in the northern Greenland Sea and Arctic Ocean. Grazing on bacteria by protists was evaluated using the FLB disappearance method. Lysis of bacteria due to viral infections was measured using the virus reduction approach. Losses of bacterial production caused by protists (PMM_BP) dominated losses caused by viruses (VMM_BP) throughout the study. Lysogenic viral production was detected in 7 out of 21 measurements and constituted from 33.9 to 100.0% of the total viral production. Significantly higher PMM_BP and lower VMM_BP were detected in waters affected by ice melting compared with unaffected waters. Consequently, significantly more bacterial carbon was channelled to the higher trophic levels in affected waters (13.05 ± 5.98 μgC l⁻¹ day⁻¹) than in unaffected waters (8.91 ± 8.33 μgC l⁻¹ day⁻¹). Viruses channelled 2.63 ± 2.45 μgC l⁻¹ day⁻¹ in affected waters and 4.27 ± 5.54 μgC l⁻¹ day⁻¹ in unaffected waters. We conclude that sea ice melting in the Arctic could modify the carbon flow through the microbial food web. This process may be especially important in the case of massive sea ice melting due to climate change.