A benzene-degrading nitrate-reducing microbial consortium displays aerobic and anaerobic benzene degradation pathways

All sequence data from this study were deposited at the European Bioinformatics Institute under the accession numbers ERS1670018 to ERS1670023. Further, all assigned genes, taxonomy, function, sequences of contigs, genes and proteins can be found in Table S3.In this study, we report transcription of genes involved in aerobic and anaerobic benzene degradation pathways in a benzene-degrading denitrifying continuous culture. Transcripts associated with the family Peptococcaceae dominated all samples (2136% relative abundance) indicating their key role in the community. We found a highly transcribed gene cluster encoding a presumed anaerobic benzene carboxylase (AbcA and AbcD) and a benzoate-coenzyme A ligase (BzlA). Predicted gene products showed >96% amino acid identity and similar gene order to the corresponding benzene degradation gene cluster described previously, providing further evidence for anaerobic benzene activation via carboxylation. For subsequent benzoyl-CoA dearomatization, bam-like genes analogous to the ones found in other strict anaerobes were transcribed, whereas gene transcripts involved in downstream benzoyl-CoA degradation were mostly analogous to the ones described in facultative anaerobes. The concurrent transcription of genes encoding enzymes involved in oxygenase-mediated aerobic benzene degradation suggested oxygen presence in the culture, possibly formed via a recently identified nitric oxide dismutase (Nod). Although we were unable to detect transcription of Nod-encoding genes, addition of nitrite and formate to the continuous culture showed indication for oxygen production. Such an oxygen production would enable aerobic microbes to thrive in oxygen-depleted and nitrate-containing subsurface environments contaminated with hydrocarbons.This study was supported by a grant of BE-Basic-FES funds from the Dutch Ministry of Economic Affairs. The research of A.J.M. Stams is supported by an ERC grant (project 323009) and the gravitation grant “Microbes for Health and Environment” (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science. F. Hugenholtz was supported by the same gravitation grant (project 024.002.002). B. Hornung is supported by Wageningen University and the Wageningen Institute for Environment and Climate Research (WIMEK) through the IP/OP program Systems Biology (project KB-17-003.02-023).info:eu-repo/semantics/publishedVersio

Understanding the factors that determine the emergence of anthroponotic cutaneous leishmaniasis due to Leishmania tropica in Morocco: Density and mitochondrial lineage of Phlebotomus sergenti in endemic and free areas of leishmaniasis

This study was funded by the University of Granada (Centro de Iniciativas de Cooperación al Desarrollo, CICODE, 2013). Funding for open access charge: Universidad de Granada/CBVA.Anthroponotic cutaneous leishmaniasis (ACL) due to Leishmania tropica is spreading to new areas in Morocco. Exposure to the vector, Phlebotomus sergenti, is the only proven risk factor. Our objective was to compare the densities and genetic characteristics of P. sergenti populations in two nearby localities in Morocco, one in an ACL endemic area (El Borouj) and another in a nonendemic area (Sidi Hajjaj). P. sergenti density was significantly higher in the endemic area than in the nonendemic town (p = 0.032). A different predominant P. sergenti mitochondrial lineage was evidenced in each one of the two localities, and for the first time, the P. sergenti lineage acting as a vector of L. tropica has been identified. Bioclimatic differences were detected between both localities. In conclusion we found differences in both the density and the mitochondrial lineage of P. sergenti populations that may explain the different epidemiological situation. Given that the density of P. sergenti in the locality without ACL cases seems sufficient to allow transmission, the main factor that would justify its nonendemic character could be the absence of P. sergenti Lineage IV, which seems to prefer warmer and drier climates.University of Granad

Methanogens: Syntrophic Metabolism

Syntrophy is a mutualistic interaction in which two metabolically different types of microorganisms are linked by the need to keep metabolites exchanged between the two partners at low concentrations to make the overall metabolism of both organisms feasible. In most cases, the cooperation is based on the transfer of hydrogen, formate, or acetate from fermentative bacteria to methanogens to make the degradation of electron-rich substrates thermodynamically favorable. Syntrophic metabolism proceeds at very low Gibbs’ free energy changes, close to the minimum free energy change needed to conserve energy biologically, which is the energy needed to transport one proton across the cytoplasmic membrane. Pathways for syntrophic degradation of fatty acids predict the net synthesis of about one-third of an ATP per round of catabolism. Syntrophic metabolism entails critical oxidation-reduction reactions in which H2 or formate production would be thermodynamically unfavorable unless energy is invested. Molecular insights into the membrane processes involved in ion translocation and reverse electron transport revealed that syntrophs harbor multiple systems for reverse electron transfer. While much evidence supports the interspecies transfer of H2 and formate, other mechanisms of interspecies electron transfer exist including cysteine cycling and possibly direct interspecies electron transfer as electric current via conductive pili or (semi)conductive minerals