Do diversity of plants,soil fungi and bacteria influence aggregate stability on ultramafic Ferralsols? A metagenomic approach in a tropical hotspot of biodiversity

Plant and Soil - Understanding how soil aggregate stability (MWD) is influenced by microbial diversity and abundance can be crucial for ecological restoration in severely disturbed areas. We...     

Agouti reintroduction recovers seed dispersal of a large-seeded tropical tree

The aim of animal reintroductions has mainly been species recovery; only few reintroduction initiatives focus on ecosystem restoration. Therefore, reintroduction consequences on ecological interactions are seldom assessed. We used the interaction between a reintroduced population of agoutis (Dasyprocta leporina) and a vulnerable tropical endemic tree (Joannesia princeps) to examine reintroduction effects on seed dispersal and seedling establishment. To test the outcomes of this interaction, we tracked seeds of J. princeps in two adjacent forest areas with and without reintroduced agoutis. We also assessed if dispersal distances affected seedling survival. To determine seed fate and dispersal distance, we used spool-and-line tracking, together with camera traps to identify dispersers. Agoutis were the only species removing J. princeps seeds, thus dispersal only occurred where agoutis had been reintroduced; in the area without agoutis, all seeds remained intact on the soil, even one year after the experiment's beginning. At the reintroduction area, most seeds were preyed upon by agoutis but 7% remained dispersed and 2% germinated after ten months. Only seeds buried by agoutis were able to germinate. Most dispersed seeds were dispersed 15 m or farther and longer dispersal distances benefited J. princeps, since seedlings farther from a conspecific adult tree had greater survival probability. Agoutis were also seen burying seeds of two other plant species; these mammals have the potential to benefit dozens of large-seeded species in our study system. Agouti reintroduction thus exemplifies the value of trophic rewilding programs to re-establish ecological interactions and restore ecosystem functioning.     

Human T Lymphotropic Virus Type 1 SU Residue 195 Plays a Role in Determining the Preferential CD4+ T Cell Immortalization/Transformation Tropism

Human T lymphotropic virus type 1 (HTLV-1) mainly causes adult T cell leukemia and predominantly immortalizes/transforms CD4⁺ T cells in culture. HTLV-2 is aleukemic and predominantly immortalizes/transforms CD8⁺ T cells in culture. We have shown previously that the viral envelope is the genetic determinant of the differential T cell tropism in culture. The surface component (SU) of the HTLV-1 envelope is responsible for binding to the cellular receptors for entry. Here, we dissect the HTLV-1 SU further to identify key domains that are involved in determining the immortalization tropism. We generated HTLV-1 envelope recombinant virus containing the HTLV-2 SU domain. HTLV-1/SU2 was capable of infecting and immortalizing freshly isolated peripheral blood mononuclear cells in culture. HTLV-1/SU2 shifted the CD4⁺ T cell immortalization tropism of wild-type HTLV-1 (wtHTLV-1) to a CD8⁺ T cell preference. Furthermore, a single amino acid substitution, N195D, in HTLV-1 SU (Ach.195) resulted in a shift to a CD8⁺ T cell immortalization tropism preference. Longitudinal phenotyping analyses of the in vitro transformation process revealed that CD4⁺ T cells emerged as the predominant population by week 5 in wtHTLV-1 cultures, while CD8⁺ T cells emerged as the predominant population by weeks 4 and 7 in wtHTLV-2 and Ach.195 cultures, respectively. Our results indicate that SU domain independently influences the preferential T cell immortalization tropism irrespective of the envelope counterpart transmembrane (TM) domain. We further showed that asparagine at position 195 in HTLV-1 SU is involved in determining this CD4⁺ T cell immortalization tropism. The slower emergence of the CD8⁺ T cell predominance in Ach.195-infected cultures suggests that other residues/domains contribute to this tropism preference.     

Transient Receptor Potential Channel 6 (TRPC6) Protects Podocytes during Complement-mediated Glomerular Disease

Gain-of-function mutations in the calcium channel TRPC6 lead to autosomal dominant focal segmental glomerulosclerosis and podocyte expression of TRPC6 is increased in some acquired human glomerular diseases, particularly in membranous nephropathy. These observations led to the hypothesis that TRPC6 overactivation is deleterious to podocytes through pathological calcium signaling, both in genetic and acquired diseases. Here, we show that the effects of TRPC6 on podocyte function are context-dependent. Overexpression of TRPC6 alone did not directly affect podocyte morphology and cytoskeletal structure. Unexpectedly, however, overexpression of TRPC6 protected podocytes from complement-mediated injury, whereas genetic or pharmacological TRPC6 inactivation increased podocyte susceptibility to complement. Mechanistically, this effect was mediated by Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation. Podocyte-specific TRPC6 transgenic mice showed stronger CaMKII activation, reduced podocyte foot process effacement and reduced levels of proteinuria during nephrotoxic serum nephritis, whereas TRPC6 null mice exhibited reduced CaMKII activation and higher levels of proteinuria compared with wild type littermates. Human membranous nephropathy biopsy samples showed podocyte staining for active CaMKII, which correlated with the degree of TRPC6 expression. Together, these data suggest a dual and context dependent role of TRPC6 in podocytes where acute activation protects from complement-mediated damage, but chronic overactivation leads to focal segmental glomerulosclerosis.     

Fecal Shedding of Zoonotic Food-Borne Pathogens by Wild Rodents in a Major Agricultural Region of the Central California Coast

Recent outbreaks of food-borne illness associated with the consumption of produce have increased concern over wildlife reservoirs of food-borne pathogens. Wild rodents are ubiquitous, and those living close to agricultural farms may pose a food safety risk should they shed zoonotic microorganisms in their feces near or on agricultural commodities. Fecal samples from wild rodents trapped on 13 agricultural farms (9 produce, 3 cow-calf operations, and 1 beef cattle feedlot) in Monterey and San Benito Counties, CA, were screened to determine the prevalence and risk factors for shedding of several food-borne pathogens. Deer mice (Peromyscus maniculatus) were the most abundant rodent species trapped (72.5%). Cryptosporidium species (26.0%) and Giardia species (24.2%) were the predominant isolates from rodent feces, followed by Salmonella enterica serovars (2.9%) and Escherichia coli O157:H7 (0.2%). Rodent trap success was significantly associated with detection of Salmonella in rodent feces, while farm type was associated with fecal shedding of Cryptosporidium and Giardia. Seasonal shedding patterns were evident, with rodents trapped during the spring and summer months being significantly less likely to be shedding Cryptosporidium oocysts than those trapped during autumn. Higher rodent species diversity tended to correlate with lower fecal microbial prevalence, and most spatiotemporal pathogen clusters involved deer mice. Rodents in the study area posed a minimal risk as environmental reservoirs of E. coli O157:H7, but they may play a role in environmental dissemination of Salmonella and protozoa. Rodent control efforts that potentially reduce biodiversity may increase pathogen shedding, possibly through promotion of intraspecific microbial transmission.     

Habitat selection for resting sites by the water opossum (Chironectes minimus) in the Brazilian Atlantic Forest

We evaluated the selection of resting sites occupied by the water opossum Chironectes minimus, between 2004 and 2010, in streams of the Brazilian Atlantic Forest. Fourteen radio-tracked adult (males and females) opossums used natural cavities as resting sites. Opossums selected narrow river stretches and selected their resting sites mainly according to characteristics favoring protection against adverse weather conditions. Likewise, opossums avoided disturbed habitats and established their resting sites in well-preserved riparian forest sites, selecting river sections containing a high density of trees and a high proportion of forest cover between the river banks and 50 m from the river. Besides increasing our knowledge on this species habitat selection, such findings further highlight this species’ sensitivity to human disturbance.     

Pollen Contamination of Honey by Bees inside the Hive

This paper aims to assess to what degree and in what way the brood chamber affects the pollen content of the honey. Twenty-nine pieces of comb containing only honey were cut from different frames of hives. The percentage of cells in each frame occupied by the brood chamber and the distance between these cells and the cut piece were recorded. A honey sample was extracted from each comb piece, avoiding any contamination with pollen, its sediment examined under the microscope and its botanical constituents identified and counted. The results show that the pollen content of honey was higher in samples from frames containing brood or pollen cells; in these samples the pollen content was positively correlated with the amount of these cells in the frame and the proximity of the honey to them. The proportion of pollen grains from principally nectariferous plants was lower in honeys with a high pollen content.     

Identification and characterization of autotransporter proteins of Yersinia pestis KIM

Yersinia pestis is a Gram-negative bacterium that causes plague. Currently, plague is considered a re-emerging infectious disease and Y. pestis a potential bioterrorism agent. Autotransporters (ATs) are virulence proteins translocated by a variety of pathogenic Gram-negative bacteria across the cell envelope to the cell surface or extracellular environment. In this study, we screened the genome of Yersinia pestis KIM for AT genes whose expression might be relevant for the pathogenicity of this plague-causing organism. By in silico analyses, we identified ten putative AT genes in the genomic sequence of Y. pestis KIM; two of these genes are located within known pathogenicity islands. The expression of all ten putative AT genes in Y. pestis KIM was confirmed by RT-PCR. Five genes, designated yapA, yapC, yapG, yapK and yapN, were subsequently cloned and expressed in Escherichia coli K12 for protein secretion studies. Two forms of the YapA protein (130 kDa and 115 kDa) were found secreted into the culture medium. Protease cleavage at the C terminus of YapA released the protein from the cell surface. Outer membrane localization of YapC (65 kDa), YapG (100 kDa), YapK (130 kDa), and YapN (60 kDa) was established by cell fractionation, and cell surface localization of YapC and YapN was demonstrated by protease accessibility experiments. In functional studies, YapN and YapK showed hemagglutination activity and YapC exhibited autoagglutination activity. Data reported here represent the first study on Y. pestis ATs.     

Conservation of Protein Structure over Four Billion Years

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