Diversity and biogeography of bacterial assemblages in surface sediments across the San Pedro Basin, Southern California Borderlands

Sediment bacteria play important roles in the biogeochemistry of ocean sediments; however, factors influencing assemblage composition have not been extensively studied. We examined extractable sediment bacterial abundance, the composition of bacterial assemblages using a high-throughput molecular fingerprinting approach, and several sediment biogeochemical parameters (organic matter content and alkaline phosphatase activity), along a 35 km transect from Point Fermin, Southern California, to Santa Catalina Island, across the approximately 900-m-deep San Pedro Basin. Automated rRNA intergenic spacer analysis (ARISA) demonstrated that in two spatially isolated shallow (approximately < 60 m, on opposite sides of the channel) sediment environments, assemblages were more similar to each other than to deeper communities. Distinct communities existed in deeper and shallower sediments, and stations within the deep basin over 2 km apart contained remarkably similar assemblage fingerprints. The relative contribution to total amplified DNA fluorescence of operational taxonomic units (OTUs) was significantly correlated to that of other OTUs in few comparisons (2.7% of total), i.e. few bacterial types were found together or apart consistently. The relative proportions within assemblages of only a few OTU were significantly correlated to measured physicochemical parameters (organic matter content and wet/dry weight ratio of sediments) or enzyme (alkaline phosphatase) activities. A low percentage of shared OTU between shallow and deep sediments, and the presence of similar, but spatially isolated assemblages suggests that bacterial OTU may be widely dispersed over scales of a few kilometres, but that environmental conditions select for particular assemblages.     

Zika virus disrupts gene expression in human myoblasts and myotubes: Relationship with susceptibility to infection

The tropism of Zika virus (ZIKV) has been described in the nervous system, blood, placenta, thymus, and skeletal muscle. We investigated the mechanisms of skeletal muscle susceptibility to ZIKV using an in vitro model of human skeletal muscle myogenesis, in which myoblasts differentiate into myotubes. Myoblasts were permissive to ZIKV infection, generating productive viral particles, while myotubes controlled ZIKV replication. To investigate the underlying mechanisms, we used gene expression profiling. First, we assessed gene changes in myotubes compared with myoblasts in the model without infection. As expected, we observed an increase in genes and pathways related to the contractile muscle system in the myotubes, a reduction in processes linked to proliferation, migration and cytokine production, among others, confirming the myogenic capacity of our system in vitro. A comparison between non-infected and infected myoblasts revealed more than 500 differentially expressed genes (DEGs). In contrast, infected myotubes showed almost 2,000 DEGs, among which we detected genes and pathways highly or exclusively expressed in myotubes, including those related to antiviral and innate immune responses. Such gene modulation could explain our findings showing that ZIKV also invades myotubes but does not replicate in these differentiated cells. In conclusion, we showed that ZIKV largely (but differentially) disrupts gene expression in human myoblasts and myotubes. Identifying genes involved in myotube resistance can shed light on potential antiviral mechanisms against ZIKV infection.     

Mineral stabilization of soil carbon is suppressed by live roots,outweighing influences from litter quality or quantity

Biogeochemistry - Conserving soil carbon (C) and harnessing the potential for soil C sequestration requires an improved understanding of the processes through which organic material accumulates in...     

Repertoire, genealogy and genomic organization of cruzipain and homologous genes in Trypanosoma cruzi, T. cruzi-like and other trypanosome species

Trypanosoma cruzi, the agent of Chagas disease, is a complex of genetically diverse isolates highly phylogenetically related to T. cruzi-like species, Trypanosoma cruzi marinkellei and Trypanosoma dionisii, all sharing morphology of blood and culture forms and development within cells. However, they differ in hosts, vectors and pathogenicity: T. cruzi is a human pathogen infective to virtually all mammals whilst the other two species are non-pathogenic and bat restricted. Previous studies suggest that variations in expression levels and genetic diversity of cruzipain, the major isoform of cathepsin L-like (CATL) enzymes of T. cruzi, correlate with levels of cellular invasion, differentiation, virulence and pathogenicity of distinct strains. In this study, we compared 80 sequences of genes encoding cruzipain from 25 T. cruzi isolates representative of all discrete typing units (DTUs TcI-TcVI) and the new genotype Tcbat and 10 sequences of homologous genes from other species. The catalytic domain repertoires diverged according to DTUs and trypanosome species. Relatively homogeneous sequences are found within and among isolates of the same DTU except TcV and TcVI, which displayed sequences unique or identical to those of TcII and TcIII, supporting their origin from the hybridization between these two DTUs. In network genealogies, sequences from T. cruzi clustered tightly together and closer to T. c. marinkellei than to T. dionisii and largely differed from homologues of T. rangeli and T. b. brucei. Here, analysis of isolates representative of the overall biological and genetic diversity of T. cruzi and closest T. cruzi-like species evidenced DTU- and species-specific polymorphisms corroborating phylogenetic relationships inferred with other genes. Comparison of both phylogenetically close and distant trypanosomes is valuable to understand host-parasite interactions, virulence and pathogenicity. Our findings corroborate cruzipain as valuable target for drugs, vaccine, diagnostic and genotyping approaches.     

Precise direct tracking and remote sensing reveal the use of forest islands as roost sites by Purple Martins during migration

Direct tracking methods in combination with remote sensing data allow examination of habitat use by birds during migration. Species that roost communally during migration, such as some swallows, form large aggregations that can attract both avian and terrestrial predators. However, the extent to which they might use patchy habitats that could reduce predation risk during migration is unknown. We tested the hypothesis that Purple Martins (Progne subis) use forest islands (patches of suitable forest habitat surrounded by unsuitable habitat) as roost sites during migration between breeding sites in North America and overwintering sites in South America. We used high‐precision (< 10 m), archival GPS units deployed and retrieved during the 2015 and 2016 breeding seasons, respectively, at 12 colonies located across eastern North America. We found that Purple Martins roosted in forest islands more often than expected based on availability during both spring and fall migration. Despite an apparent association with urban habitats by Purple Martins based on observational and radar data in North America during the fall, the roost locations we identified during spring and fall migration were not more closely associated with urban areas than random locations. The use of forest islands during both spring and fall migration suggest that Purple Martins may use these habitats to reduce predation risk during migration. Our results suggest that some species of birds may use similar habitats as stopover sites during migration and that patches of forest habitat may be important conservation targets for Purple Martins and other species. Identifying habitat use during migration represents an important advance in support of full annual‐cycle conservation of Purple Martins and other migratory species with declining populations.     

Cell Wall Glycoproteins Participate in the Adhesion of <Emphasis Type="Italic">Sporothrix schenckii</Emphasis> to Epithelial Cells

Sporothrix schenckii is the etiologic agent of sporotrichosis. This fungal infection is an emerging disease potentially fatal in immunocompromised patients. The adhesion to host cells is a crucial early event related with the dissemination of pathogens. In order to clarify the mechanisms of adhesion of S. schenckii yeast cell to epithelial cells, we studied the biochemical basis of this process. The electrophoretic analysis of cell wall protein from S. schenckii coupled at ConA and stained with HRP, revealed nine different proteins with MW ≥ 180, 115, 90, 80, 58, 40, 36, 22 and 18 kDa. Using ligand-like assay with biotinylated S. schenckii surface proteins, five proteins with MW ≥ 190, 180, 115, 90 and 80 kDa which have affinity to epithelial cells were identified. The adhesion of yeast to epithelial monolayer was significantly inhibited when S. schenckii was pretreated with concanavalinA (ConA) and wheat germ agglutinin (WGA) lectins, alkali, periodate, trypsin, endoglycosidase H (EndoH), salt solutions and detergents. The ability of adhesion of S. schenckii yeast was recovered by blocking the lectin with sugar complementary. These data suggest that surface glycoprotein with mannose and glucose residue could be participate in the process of fungal adhesion to epithelial cells.     

Identification and phylogenetic analysis of heme synthesis genes in trypanosomatids and their bacterial endosymbionts

It has been known for decades that some insect-infecting trypanosomatids can survive in culture without heme supplementation while others cannot, and that this capability is associated with the presence of a betaproteobacterial endosymbiont in the flagellate's cytoplasm. However, the specific mechanisms involved in this process remained obscure. In this work, we sequence and phylogenetically analyze the heme pathway genes from the symbionts and from their hosts, as well as from a number of heme synthesis-deficient Kinetoplastida. Our results show that the enzymes responsible for synthesis of heme are encoded on the symbiont genomes and produced in close cooperation with the flagellate host. Our evidence suggests that this synergistic relationship is the end result of a history of extensive gene loss and multiple lateral gene transfer events in different branches of the phylogeny of the Trypanosomatidae.     

Early IFN-Gamma Production after YF 17D Vaccine Virus Immunization in Mice and Its Association with Adaptive Immune Responses

Yellow Fever vaccine is one of the most efficacious human vaccines ever made. The vaccine (YF 17D) virus induces polyvalent immune responses, with a mixed T_H1/T_H2 CD4⁺ cell profile, which results in robust T CD8⁺ responses and high titers of neutralizing antibody. In recent years, it has been suggested that early events after yellow fever vaccination are crucial to the development of adequate acquired immunity. We have previously shown that primary immunization of humans and monkeys with YF 17D virus vaccine resulted in the early synthesis of IFN-γ. Herein we have demonstrated, for the first time that early IFN-γ production after yellow fever vaccination is a feature also of murine infection and is much more pronounced in the C57BL/6 strain compared to the BALB/c strain. Likewise, in C57BL/6 strain, we have observed the highest CD8⁺ T cells responses as well as higher titers of neutralizing antibodies and total anti-YF IgG. Regardless of this intense IFN-γ response in mice, it was not possible to see higher titers of IgG2a in relation to IgG1 in both mice lineages. However, IgG2a titers were positively correlated to neutralizing antibodies levels, pointing to an important role of IFN-γ in eliciting high quality responses against YF 17D, therefore influencing the immunogenicity of this vaccine.