A bifunctional chemical signature enabling RNA 4-thiouridine enrichment sequencing with single-base resolution

Both sequence enrichment and base resolution is essential for accurate sequencing analysis of low-abundance RNA. Yet it is hindered by the lack of molecular tools. Here we report a bifunctional...

Semiochemical signatures associated with differential attraction of Anopheles gambiae to human feet

Background Several human-produced volatiles have been reported to mediate the host-seeking process under laboratory conditions, yet no effective lure or repellent has been developed for field application. Previously, we found a gradation of the attractiveness of foot odors of different malaria free individuals to Anopheles gambiae sensu stricto Giles. In this study, foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was collected, analyzed and attractive blend components identified. Methods The foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was trapped on Porapak Q and analyzed by gas chromatography-linked mass spectrometry (GC-MS). Specific constituents perceived by the insect olfactory system were then identified by GC-linked to electro-antennography detector (GC-EAD) and characterized by GC-MS. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi-field conditions in a screen-house using Counter Flow Geometry (CFG traps) baited with (i) the blend of all the EAD-active and (ii) other blends containing all components with exclusion of one component at a time. The number of mosquitoes trapped in the baited CFG traps were compared with those in the control traps. Results Eleven major and minor constituents: 2 carboxylic acids, six aldehydes, two ketones and one phenolic compound, were confirmed to be EAD-active. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi- field conditions. Exclusion/ subtraction of one of the following compounds: i-butyric acid, i-valeric acid, n-octanal, n-nonanal, n-decanal, n-dodecanal, undecanal or n-tridecanal, from each blend led to reduction in the attractiveness of all the resulting blends, suggesting that all of them are critical/important for the attractiveness of the foot odor to An. gambiae mosquitoes. However, exclusion/subtraction of 4-ethoxyacetophenone, 4-ethylacetophenone and/or 2-methylphenol, led to significant enhancements in the attractiveness of the resulting blends, suggesting that each of these compounds had repellent effect on An. gambiae ss. Undecanal exhibited kairomonal activity at low natural concentrations under semi-field conditions but repellent activity at high unnatural conditions in the laboratory. Furthermore, the comparison of the mean mosquito catches in traps baited with the nine-component blend without 4-ethoxyacetophenone, 4-ethylacetophenone and the complete foot odor collection revealed that the former is significantly more attractive and confirmed the repellent effect of the two carbonyl compounds at low natural concentration levels. Conclusion These results suggest that differential attractiveness of An. gambiae to human feet is due to qualitative and/or qualitative differences in the chemical compositions of the foot odors from individual human beings and relative proportions of the two chemical signatures (attractants versus repellents) as observed from the ratios of the bioactive components in the foot odors of the most attractive and least attractive individuals. Chemical signature means the ensemble of the compounds released by the organism in a specific physiological state. The chemical signature is emitter-dependent, but does not depend on receiver response. Thus, there is only one chemical signature for one individual or species that may eventually include inactive, attractive and repellent components for another organism. The nine-component attractive blend has a potential as an effective field bait for trapping of malaria vectors in human dwellings.

Use of Chemical Signature to Trace the Impact of Emission Sources

The composition of organic fraction associated to particulate emissions depends on their nature as well as on contour conditions. Therefore, many Authors have investigated the chemical signature of airborne particulate matter and dusts with the goal of identifying the pollution sources and assessing their impact on the environment and health. Usually, Authors use three complementary tools for this goal; they are specific source markers, concentration ratios of pairs of congeners, and percent distributions of homologues within a group. After the presentation of the state-of-the-art about non-polar aliphatic (alkanes and alkenes), aromatic (PAHs, Nitro-PAHs) and polar (fatty acids, organic halides, polysaccharides) compounds associated to emissions, this paper provides new information with regard to chemical signature non-polar fraction, suitable to trace the impact of sources on airborne particulate matter and settled dust. Non-polar organic fraction comprises short/medium-chain alkenes and alkanes (with carbon numbers ranging from 12 to 23), which display distinct relative abundances in petrol-derived exhausts, microorganism residues and high vegetation leaf debris. Meanwhile, long-chain alkanes associated to tobacco smoke show a peculiar iso/anteiso/normal homologues fingerprint as well as n-hentriacontane percentages higher than other emissions. Based on this particular alkane distribution, two indexes (ATSR and AICR) have tentatively identified and tested though comparing their rates in some sets of particulate samples. Until now, the study of molecular signature has overall limited to qualitative purposes and seldom exploited to achieve quantitative estimates of contributions of sources to air pollution. Future investigations will reach this goal through further clarifying the nature and behavior of organic contaminants associated to airborne and settled particulate matters.

Nestmate recognition of early brood in ants

Brood is critically important in social insect colonies. It carries the colony fitness through delivering future reproductive adults as well as workers that will increase the colony's workforce. Adoption of non-nestmate brood can be a mean to increase colony's workforce but entails the risk of rearing unrelated sexuals or social parasites. For early brood (eggs and L1 larvae), this balance is less positive as young brood need a substantial amount of resource before becoming workers. Thus, it appears beneficial for ant workers to discriminate between nestmate and alien brood using the chemical cues displayed at the brood's surface. However, the chemical signature of ant early brood stages and its use by workers remains understudied. To fill this gap, we investigated the chemical basis of early brood nestmate and cross-species recognition in six Formicoid ants. We also tested the discrimination behaviour of workers in brood retrieval trials. We observed clear species-level cues and discrimination against heterospecific brood. We also found that eggs and most young larvae display a colony signature but that only some species discriminate against non-nestmate eggs and L1 larvae. Interestingly, these species appear to also be those belonging to genera subject to brood parasitism.

Indicators of Natural and Anthropogenic Emission Source Impact

The composition of organic fraction released in emissions varies with its nature and contour conditions; hence, the chemical signature of atmospheric particulate matter and dusts are investigated to identify the pollution sources and assess the respective aftermaths on environment and health. For this purpose, three complementary tools are usually adopted, i.e. specific source markers, concentration ratios of pairs of congeners, and percent distribution profiles of homologues (including derived “carbon preference indexes”). This paper provides an overview of investigations dealing with chemical signature of emission sources, applied to non-polar aliphatic (alkanes), aromatic (PAHs, Nitro-PAHs) and polar (fatty acids, organic halides, polysaccharides) organics affecting atmospheric particulate matter and deposition dust. Despite a rich literature is nowadays available, further investigations seem necessary to clarify the nature, sources and behaviors of mid-volatile, non-polar organic contaminants. More sophisticated investigations have gained importance recently (principal component analysis, source factorization modelling), nevertheless molecular fingerprints remain suitable to draw primary insights about the nature and impact of sources of environmental pollution.