Carbon isotopic composition of Frutexites in subseafloor ultramafic rocks

Micrometer sized stromatolitic structures called Frutexites are features observed in samples from the deep subsurface, and hot-spring environments. These structures are comprised of fine laminations, columnar morphology, and commonly consist of iron oxides, manganese oxides, and/or carbonates. Although a biological origin is commonly invoked, few reports have shown direct evidence of their association with microbial activity. Here, we report for the first time the occurrence of subsurface manganese-dominated Frutexites preserved within carbonate veins in ultramafic rocks. To determine the biogenicity of these putative biosignatures, we analyzed their chemical and isotopic composition using Raman spectroscopy and secondary ion mass spectroscopy (SIMS). These structures were found to contain macromolecular carbon signal and have a depleted ¹³C/¹²C carbon isotopic composition of – 35.4?±?0.50‰ relative to the entombing carbonate matrix. These observations are consistent with a biological origin for the observed Frutexites structures.

     

Organization of the ferret lateral cervical nucleus and cervicothalamic tract

To elucidate the organization of the ferret spinocervicothalamic pathway (SCTP), we examined the lateral cervical nucleus (LCN) and the termination of the cervicothalamic tract (CTT) in this species. In thionin-stained sections, the ferret LCN appeared as an easily delineated column of cells in the dorsolateral funiculus from about mid-C3 to the rostral end of C1, with most cells located in the C1 and C2 segments. In transverse sections, the LCN was elongated along a dorsolateral to ventromedial axis and in the rostral half of C2 and caudal half of C1 continuous with the neck of the dorsal horn. The number of ferret LCN cells was estimated to 2,500-3,700, with an average of 3,340. Substance P-like immunoreactive fibers located preferentially in the ventromedial part of the LCN, whereas serotonin-like immunoreactive fibers were found throughout the nucleus. Anterograde transport of wheat germ agglutinin-horseradish peroxidase conjugate and biotinylated dextran amine demonstrated that the ferret CTT terminates extensively in the peripheral parts of the ventral posterior lateral nucleus. Sparser termination was evident in the ventral posterior inferior nucleus, in the medial nucleus of the posterior complex, and in the medial part of the magnocellular medial geniculate nucleus. Thus, although the LCN is significantly smaller in ferrets than in cats and raccoons, the organization of the LCN and of the cervicothalamic tract is closely similar in the three species. These findings indicate a conserved general organization of the SCTP among carnivores.     

Identification of X-linked quantitative trait loci affecting cold tolerance in Drosophila melanogaster and fine mapping by selective sweep analysis

Drosophila melanogaster is a cosmopolitan species that colonizes a great variety of environments. One trait that shows abundant evidence for naturally segregating genetic variance in different populations of D. melanogaster is cold tolerance. Previous work has found quantitative trait loci (QTL) exclusively on the second and the third chromosomes. To gain insight into the genetic architecture of cold tolerance on the X chromosome and to compare the results with our analyses of selective sweeps, a mapping population was derived from a cross between substitution lines that solely differed in the origin of their X chromosome: one originates from a European inbred line and the other one from an African inbred line. We found a total of six QTL for cold tolerance factors on the X chromosome of D. melanogaster. Although the composite interval mapping revealed slightly different QTL profiles between sexes, a coherent model suggests that most QTL overlapped between sexes, and each explained around 5–14% of the genetic variance (which may be slightly overestimated). The allelic effects were largely additive, but we also detected two significant interactions. Taken together, this provides evidence for multiple QTL that are spread along the entire X chromosome and whose effects range from low to intermediate. One detected transgressive QTL influences cold tolerance in different ways for the two sexes. While females benefit from the European allele increasing their cold tolerance, males tend to do better with the African allele. Finally, using selective sweep mapping, the candidate gene CG16700 for cold tolerance colocalizing with a QTL was identified.     

Francisella tularensis Subspecies holarctica Occurs in Swedish Mosquitoes,Persists Through the Developmental Stages of Laboratory-Infected Mosquitoes and Is Transmissible During Blood Feeding

In Sweden, mosquitoes are considered the major vectors of the bacterium Francisella tularensis subsp. holarctica, which causes tularaemia. The aim of this study was to investigate whether mosquitoes acquire the bacterium as aquatic larvae and transmit the disease as adults. Mosquitoes sampled in a Swedish area where tularaemia is endemic (Örebro) were positive for the presence of F. tularensis deoxyribonucleic acid throughout the summer. Presence of the clinically relevant F. tularensis subsp. holarctica was confirmed in 11 out of the 14 mosquito species sampled. Experiments performed using laboratory-reared Aedes aegypti confirmed that F. tularensis subsp. holarctica was transstadially maintained from orally infected larvae to adult mosquitoes and that 25 % of the adults exposed as larvae were positive for the presence of F. tularensis-specific sequences for at least 2 weeks. In addition, we found that F. tularensis subsp. holarctica was transmitted to 58 % of the adult mosquitoes feeding on diseased mice. In a small-scale in vivo transmission experiment with F. tularensis subsp. holarctica-positive adult mosquitoes and susceptible mice, none of the animals developed tularaemia. However, we confirmed that there was transmission of the bacterium to blood vials by mosquitoes that had been exposed to the bacterium in the larval stage. Taken together, these results provide evidence that mosquitoes play a role in disease transmission in part of Sweden where tularaemia recurs.     

Mapping Quantitative Trait Loci onto a Phylogenetic Tree

Despite advances in genetic mapping of quantitative traits and in phylogenetic comparative approaches, these two perspectives are rarely combined. The joint consideration of multiple crosses among related taxa (whether species or strains) not only allows more precise mapping of the genetic loci (called quantitative trait loci, QTL) that contribute to important quantitative traits, but also offers the opportunity to identify the origin of a QTL allele on the phylogenetic tree that relates the taxa. We describe a formal method for combining multiple crosses to infer the location of a QTL on a tree. We further discuss experimental design issues for such endeavors, such as how many crosses are required and which sets of crosses are best. Finally, we explore the method's performance in computer simulations, and we illustrate its use through application to a set of four mouse intercrosses among five inbred strains, with data on HDL cholesterol.