High-Sensitivity Monoclonal Antibodies Specific for Homoserine Lactones Protect Mice from Lethal Pseudomonas aeruginosa Infections

A number of bacteria, including pathogens like Pseudomonas aeruginosa, utilize homoserine lactones (HSLs) as quorum sensing (QS) signaling compounds and engage in cell-to-cell communication to coordinate their behavior. Blocking this bacterial communication may be an attractive strategy for infection control as QS takes a central role in P. aeruginosa biology. In this study, immunomodulation of HSL molecules by monoclonal antibodies (MAbs) was used as a novel approach to prevent P. aeruginosa infections and as tools to detect HSLs in bodily fluids as a possible first clue to an undiagnosed Gram-negative infection. Using sheep immunization and recombinant antibody technology, a panel of sheep-mouse chimeric MAbs were generated which recognized HSL compounds with high sensitivity (nanomolar range) and cross-reactivity. These MAbs retained their nanomolar sensitivity in complex matrices and were able to recognize HSLs in P. aeruginosa cultures grown in the presence of urine. In a nematode slow-killing assay, HSL MAbs significantly increased the survival of worms fed on the antibiotic-resistant strain PA058. The therapeutic benefit of these MAbs was further studied using a mouse model of Pseudomonas infection in which groups of mice treated with HSL-2 and HSL-4 MAbs survived, 7 days after pathogen challenge, in significantly greater numbers (83 and 67%, respectively) compared with the control groups. This body of work has provided early proof-of-concept data to demonstrate the potential of HSL-specific, monoclonal antibodies as theranostic clinical leads suitable for the diagnosis, prevention, and treatment of life-threatening bacterial infections.     

Caveolae-mediated endocytosis of the glucosaminoglycan-interacting adipokine tartrate resistant acid phosphatase 5a in adipocyte progenitor lineage cells

Adipogenesis depends on growth factors controlling proliferation/differentiation of mesenchymal stem cells (MSCs). Membrane binding and endocytosis of growth factors are often coupled to receptor activation and downstream signaling leading to specific cellular responses. The novel adipokine tartrate-resistant acid phosphatase (TRAP) 5a exhibits a growth factor-like effect on MSCs and pre-adipocytes and induces hyperplastic obesity in vivo. However its molecular interaction with pre-adipocytes remains unknown. Therefore, this study aimed to investigate membrane interaction of TRAP and its endocytosis routes in pre-adipocytes. Confocal and/or electron microscopy were used to detect TRAP in untreated or TRAP 5a/b treated pre-adipocytes under conditions that allow or inhibit endocytosis in combination with co-staining of endocytotic vesicles. TRAP interaction with heparin/heparan sulfate was verified by gel filtration. It could be shown that TRAP 5a, but not 5b, binds to the membrane of pre-adipocytes where it co-localizes with heparin-sulfate proteoglycan glypican-4. Also in vitro, TRAP 5a exhibited affinity for both heparin and heparan sulfate with heparin inhibiting its enzyme activity. Upon caveolae-mediated endocytosis of saturating levels of TRAP 5a, TRAP 5a co-localized intracellularly with glypican-4 and late endosomal marker Rab-7 positive vesicles. The protein was also located in multivesicular bodies (MVBs) but did not co-localize with lysosomal marker LAMP-1. TRAP 5a endocytosis was also detectable in pre-osteoblasts, but not fibroblasts, embryonic MSCs or mature adipocytes. These results indicate that TRAP 5a exhibits binding to cell surface, endocytosis and affinity to glucosaminoglycans (GAGs) in pre-adipocyte and pre-osteoblast lineage cells in a manner similar to other heparin-binding growth factors.     

Modern Hunting Practices and Wild Meat Trade in the Oil Palm Plantation-Dominated Landscapes of Sumatra,Indonesia

The ongoing expansion of plantation agriculture has changed the ecological, demographic, and social conditions of Southeast Asia’s forested areas, yet little is known about hunting practices in these novel landscapes. Using information from 73 in-depth interviews with hunters, agricultural workers and wild meat dealers in the Jambi province of Sumatra, Indonesia, we describe contemporary hunting practices, including how hunting methods, wildlife harvest and consumption rates vary between different indigenous and immigrant ethnic groups. Hunting is now primarily a commercial endeavor for harvesting wild boar (Sus scrofa) meat; over 7500 wild boars were sold in Jambi City alone in 2011. The Muslim majority avoids wild boar for religious reasons, but there is substantial local and export demand driven by Chinese and Christian Batak. We conclude that hunting within oil palm plantations may reduce crop damage from wild boar and also yield large amounts of wild meat with relatively little by-catch of threatened animals.     

Anti-herpesvirus bovine type 5 activities of extracts obtained from Plocamium brasiliense

Bovine herpesvirus type 5 (BoHV-5) is an important etiologic agent of meningoencephalitis in cattle and has been frequently identified in outbreaks of neurological disease in bovine in the southern hemisphere including Brazil. This study aimed to evaluate the cytotoxic effect and the antiviral properties of extracts obtained from Plocamium brasiliense (Greville) Howe and Taylor in BoHV-5 RJ42/01 replication. The cytotoxic effects were measured in Madin-Darbin bovine kidney cells (MDBK) and cytotoxic concentration (CC₅₀) values have been determined for acyclovir (ACV) (223 μg?±?2.0), ethyl acetate extract from P. brasiliense (2,109 μg?±?10), hexane extract from P. brasiliense (7.181 μg?±?5), dichloromethane extract from P. brasiliense (2.356 μg?±?6.5), and hydroalcoholic extract from P. brasiliense (1.408 μg?±?5.8). As a first approach to characterize the action of these extracts on BoHV-5 RJ42/01, a virucidal assay activity was performed. A virus suspension containing 1?×?10⁵ plaque-forming units (PFU) of the BoHV-5 RJ42/01 was mixed with 600 μg of extract and acyclovir and kept at room temperature (24 °C) for 3 h. Meanwhile, a control of untreated infected virus was performed in the same conditions. Then, treated virus suspension and untreated control were diluted, and percentage of inhibition of infectivity was determined by plaque assay: ethyl acetate extract (99 %), hexane extract (90 %), dichloromethane extract (99 %), and hydroalcoholic extract (27 %). Acyclovir had a slight virucidal activity on viral particle. The inhibition of attachment was performed in MDBK cells inoculated with 100 PFU of BoHV-5 RJ42/01 in the presence or absence of various concentrations of extracts (0.3, 0.9, and 1.5 μg mL^?1). Acyclovir was also assayed at 2.8 and 11.25 μg mL^?1. The inhibition of adsorption was also tested in MDBK cells treated with the same concentrations of the extracts before virus inoculation. Results: hexane extracts inhibited virus attachment in pre-treated cell 0.9 μg (55 %) and 1.5 μg (71 %) and untreated MDBK cell only with 1.5 μg (63 %). Ethyl acetate extract on cell pre-treated with 0.3 μg (67 %), 0.9 μg (81 %), and 1.5 μg (91 %). Ethyl acetate extract on pre-treated cell 0.3 μg (67 %), 0.9 μg (81 %), and 1.5 (91 %) but discrete inhibition on cell untreated. Dichloromethane extract and acyclovir slightly inhibited virus binding on MDBK cell.     

The genetics of gene expression in complex mouse crosses as a tool to study the molecular underpinnings of behavior traits

Complex Mus musculus crosses provide increased resolution to examine the relationships between gene expression and behavior. While the advantages are clear, there are numerous analytical and technological concerns that arise from the increased genetic complexity that must be considered. Each of these issues is discussed, providing an initial framework for complex cross study design and planning.     

Genetically distinct pathways guide effector export through the type VI secretion system

Bacterial secretion systems often employ molecular chaperones to recognize and facilitate export of their substrates. Recent work demonstrated that a secreted component of the type VI secretion system (T6SS), haemolysin co‐regulated protein (Hcp), binds directly to effectors, enhancing their stability in the bacterial cytoplasm. Herein, we describe a quantitative cellular proteomics screen for T6S substrates that exploits this chaperone‐like quality of Hcp. Application of this approach to the Hcp secretion island I‐encoded T6SS (H1‐T6SS) of Pseudomonas aeruginosa led to the identification of a novel effector protein, termed Tse4 (t ype VI s ecretion e xported 4), subsequently shown to act as a potent intra‐specific H1‐T6SS‐delivered antibacterial toxin. Interestingly, our screen failed to identify two predicted H1‐T6SS effectors, Tse5 and Tse6, which differ from Hcp‐stabilized substrates by the presence of toxin‐associated PAAR‐repeat motifs and genetic linkage to members of the valine‐glycine repeat protein G (vgrG) genes. Genetic studies further distinguished these two groups of effectors: Hcp‐stabilized effectors were found to display redundancy in interbacterial competition with respect to the requirement for the two H1‐T6SS‐exported VgrG proteins, whereas Tse5 and Tse6 delivery strictly required a cognate VgrG. Together, we propose that interaction with either VgrG or Hcp defines distinct pathways for T6S effector export.     

Phosphatase activity of the histidine kinases ensures pathway specificity of the ChrSA and HrrSA two‐component systems in Corynebacterium glutamicum

The majority of bacterial genomes encode a high number of two‐component systems controlling gene expression in response to a variety of different stimuli. The Gram‐positive soil bacterium Corynebacterium glutamicum contains two homologous two‐component systems (TCS) involved in the haem‐dependent regulation of gene expression. Whereas the HrrSA system is crucial for utilization of haem as an alternative iron source, ChrSA is required to cope with high toxic haem levels. In this study, we analysed the interaction of HrrSA and ChrSA in C. glutamicum. Growth of TCS mutant strains, in vitro phosphorylation assays and promoter assays of P_hrtBA and P_hmuO fused to eyfp revealed cross‐talk between both systems. Our studies further indicated that both kinases exhibit a dual function as kinase and phosphatase. Mutation of the conserved glutamine residue in the putative phosphatase motif DxxxQ of HrrS and ChrS resulted in a significantly increased activity of their respective target promoters (P_hmuO and P_hrtBA respectively). Remarkably, phosphatase activity of both kinases was shown to be specific only for their cognate response regulators. Altogether our data suggest the phosphatase activity of HrrS and ChrS as key mechanism to ensure pathway specificity and insulation of these two homologous systems.     

Factors affecting stress tolerance in recalcitrant embryonic axes from seeds of four Quercus (Fagaceae) species native to the USA or China

MethodsWater relations and survival of excised axes in response to water loss and cryo-exposure were compared for four Quercus species from subtropical China (Q. franchetii, Q. schottkyana) and temperate USA (Q. gambelii, Q. rubra).ConclusionsQuercus species adapted to arid and semi-humid climates still produce recalcitrant seeds. The ability to avoid freezing rather than drought may be a more important selection factor to increase desiccation tolerance. Cryopreservation of recalcitrant germplasm from temperate species is currently feasible, whilst additional protective treatments are needed for ex situ conservation of Quercus from tropical and subtropical areas.