Spinosad is an insecticide widely used for the control of insect pest species, including Mediterranean fruit fly, Ceratitis capitata . Its target site is the α6 subunit of the nicotinic acetylcholine receptors, and different mutations in this subunit confer resistance to spinosad in diverse insect species. The insect α6 gene contains 12 exons, with mutually exclusive versions of exons 3 (3a, 3b) and 8 (8a, 8b, 8c). We report here the selection of a medfly strain highly resistant to spinosad, JW-100 s, and we identify three recessive Ccα6 mutant alleles in the JW-100 s population: (i) Ccα6 3aQ68* containing a point mutation that generates a premature stop codon on exon 3a (3aQ68*); (ii) Ccα6 3aAG > AT containing a point mutation in the 5′ splicing site of exon 3a (3aAG > AT); and (iii) Ccα6 3aQ68*-K352* that contains the mutation 3aQ68* and another point mutation on exon 10 (K352*). Though our analysis of the susceptibility to spinosad in field populations indicates that resistance has not yet evolved, a better understanding of the mechanism of action of spinosad is essential to implement sustainable management practices to avoid the development of resistance in field populations.

Target site insensitivity and metabolic resistance mediated by esterases have been previously suggested to be involved in resistance to malathion in a field-derived strain (W) of Ceratitis capitata. In the present study, we have obtained the coding sequence for acetylcholinesterase (AChE) gene (Ccace) of C. capitata. An allele of Ccace carrying only a point mutation Gly328Ala (Torpedo numbering) adjacent to the glutamate of the catalytic triad was found in individuals of the W strain. Adult flies homozygotes for this mutant allele showed reduced AChE activity and less sensitivity to inhibition by malaoxon, showing that target site insensitivity is one of the factors of malathion resistance. In addition, all individuals from the resistant W strain showed reduced aliesterase activity, which has been associated with specific malathion resistance in higher Diptera. However, the alphaE7 gene (CcalphaE7), sequenced in susceptible and resistant individuals, did not carry any of the mutations associated with organophosphorus insecticide resistance in other Diptera. Another esterase mechanism, perhaps a carboxylesterase selective for malathion, in addition to mutant AChE, thus contributes to malathion resistance in C. capitata.

Infections caused by multidrug-resistant (MDR) bacteria, including Vancomycin-Resistant Enterococcus (VRE), have become one of the greatest clinical challenges of the 21 st century. Particularly, VRE strains of E. faecium, a natural member of the gastrointestinal consortia, have recently emerged as one of the most problematic cases of MDR nosocomial pathogens. It is widely known that the establishment of high-level intestinal colonization of this bacterium, triggered by antibiotic treatment of the host, potentially leads to bacteremia, endocarditis and surgical wound, urinary tract, and devicerelated infections in hospitalized patients. However, the unique determinants possessed by these strains, which enable them to benefit from the antibiotic-induced perturbations of the gut microbiota and host intestinal immune defenses, remain to be identified.Essentially, what needs to be revealed is the differential gene expression of E. faecium in its niche at different time points; before and during antibiotic treatment of the host, and very interestingly, in the presence of probiotic bacteria. Differentially expressed genes will highlight how and why E. faecium is able to dominate the gut, as well as how it interacts with its surroundings, possibly pinpointing its potential weaknesses, as well as provide hints on what specific properties should be prerequisites for bacteria to be used as probiotics.Since the global expression intended to be analyzed is that of E. faecium alone, a method to separate this bacteria from the rest of the gut microbiota is required. Failure to do so would result in the study of the gut microbiota's transcriptome as a whole: metatranscriptomics. In practice, the separation VRE. faecium from the rest of the commensal microbiota could be carried out by means of flow cytometry if the generation of a fluorescent E. faecium was achieved. Additionally, it would serve as a great tool to study a series of facets of VRE faecium colonization which remain virtually unknown. It would enable the monitorization of VRE infection through whole-body imaging of infected mice, fluorescence microscopy analysis of histological cuts to determine its most predominant locations, the use of FbFP as a translational or transcriptional reporter, etc.Consequently, the main objective of this Final Degree Project has been to attempt the generation of a Vancomycin-Resistant Enterococcus faecium clinical isolate (C68) expressing a fluorescent protein whose chromophore can form under the anaerobic conditions found in the guts of animals: (FMN)-based fluorescent protein (FbFP).In order to fulfill the main objective of this work, first, the FbFP gene was synthesized with the appropriate features for its expression in E. faecium and for its cloning. Next, the plasmid construction aimed to confer E. faecium fluorescent properties (pBT2-FbFP), was generated. This was done by inserting the FbFP gene into the pBT2 plasmid. As a previous step to the transformation of E. faecium, pBT2-FbFP was transformed into E.coli DH5a in or...

PKDREJ is a testis-specific protein thought to be located on the sperm surface. Functional studies in the mouse revealed that loss of PKDREJ has effects on sperm transport and the ability to undergo an induced acrosome reaction. Thus, PKDREJ has been considered a potential target of post-copulatory sexual selection in the form of sperm competition. Proteins involved in reproductive processes often show accelerated evolution. In many cases, this rapid divergence is promoted by positive selection which may be driven, at least in part, by post-copulatory sexual selection. We analysed the evolution of the PKDREJ protein in primates and rodents and assessed whether PKDREJ divergence is associated with testes mass relative to body mass, which is a reliable proxy of sperm competition levels. Evidence of an association between the evolutionary rate of the PKDREJ gene and testes mass relative to body mass was not found in primates. Among rodents, evidence of positive selection was detected in the Pkdrej gene in the family Cricetidae but not in Muridae. We then assessed whether Pkdrej divergence is associated with episodes of sperm competition in these families. We detected a positive significant correlation between the evolutionary rates of Pkdrej and testes mass relative to body mass in cricetids. These findings constitute the first evidence of post-copulatory sexual selection influencing the evolution of a protein that participates in the mechanisms regulating sperm transport and the acrosome reaction, strongly suggesting that positive selection may act on these fertilization steps, leading to advantages in situations of sperm competition.

The identification of allergy-causing mites is conventionally based on morphological characters. However, molecular taxonomy using ribosomal DNA (rDNA) may be particularly useful in the analysis of mite cultures and purified mite fractions in the production of allergenic extracts. Full-length internal transcribed spacers (ITS1 and ITS2) were obtained from Dermatophagoides farinae, Dermatophagoides pteronyssinus, Dermatophagoides microceras and Euroglyphus maynei (Astigmata: Pyroglyphidae), Glycyphagus domesticus and Lepidoglyphus destructor (Astigmata: Glycyphagidae), Tyrophagus fanetzhangorum, Tyrophagus putrescentiae, Tyrophagus longior, Tyrophagus neiswanderi, Acarus farris and Acarus siro (Astigmata: Acaridae), and Blomia tropicalis (Astigmata: Echymopodidae), using mite-specific primers. Polymerase chain reaction (PCR) products were digested with HpaII and RsaI restriction enzymes in order to produce species-specific PCR restricted fragment length polymorphism (RFLP) profiles. A semi-nested re-amplification step was introduced before the RFLP in order to apply the method to environmental samples. Results demonstrate that rDNA sequences can be used for the unambiguous identification of mite species. The PCR-RFLP system allows the identification of species in purified mite fractions when the availability of intact adult mite bodies for morphological identification is limited. This reliable and straightforward PCR-RFLP system and the rDNA sequences obtained can be of use in the identification of allergy-causing mite species.