Identification of Collimonas gene loci involved in the biosynthesis of a diffusible secondary metabolite with broad-spectrum antifungal activity and plant-protective properties

In greenhouse and field trials, a bacterial mixture of Collimonas arenae Cal35 and Bacillus velezensis FZB42, but not Cal35 alone or FZB42 alone, was able to protect tomato plants from challenge with the soilborne fungal pathogen Fusarium oxysporum f.sp. lycopersici (Fol). To identify genes and mechanisms underlying this property in Cal35, we screened a random transposon insertion library for loss of function and identified two mutants that were impaired completely or partially in their ability to halt the growth of a wide range of fungal species. In mutant 46A06, the transposon insertion was located in a biosynthetic gene cluster that was predicted to code for a hybrid polyketide synthase–non-ribosomal peptide synthetase, while mutant 60C09 was impacted in a gene cluster for the synthesis and secretion of sugar repeat units. Our data are consistent with a model in which both gene clusters are necessary for the production of an antifungal compound we refer to as carenaemins. We also show that the ability to produce carenaemin contributed significantly to the observed synergy between Cal35 and FZB42 in protecting tomato plants from Fol. We discuss the potential for supplementing Bacillus-based biocontrol products with Collimonas bacteria to boost efficacy of such products.     

A novel role for snapin in dendrite patterning: interaction with cypin

Temporal and spatial assembly of signal transduction machinery determines dendrite branch patterning, a process crucial for proper synaptic transmission. Our laboratory previously cloned and characterized cypin, a protein that decreases PSD-95 family member localization and regulates dendrite number. Cypin contains zinc binding, collapsin response mediator protein (CRMP) homology, and PSD-95, Discs large, zona occludens-1 binding domains. Both the zinc binding and CRMP homology domains are needed for dendrite patterning. In addition, cypin binds tubulin via its CRMP homology domain to promote microtubule assembly. Using a yeast two-hybrid screen of a rat brain cDNA library with cypin lacking the carboxyl terminal eight amino acids as bait, we identified snapin as a cypin binding partner. Here, we show by affinity chromatography and coimmunoprecipitation that the carboxyl-terminal coiled-coil domain (H2) of snapin is required for cypin binding. In addition, snapin binds to cypin's CRMP homology domain, which is where tubulin binds. We also show that snapin competes with tubulin for binding to cypin, resulting in decreased microtubule assembly. Subsequently, overexpression of snapin in primary cultures of hippocampal neurons results in decreased primary dendrites present on these neurons and increased probability of branching. Together, our data suggest that snapin regulates dendrite number in developing neurons by modulating cypin-promoted microtubule assembly.     

Influence of HLA Class I and HLA-KIR Compound Genotypes on HIV-2 Infection and Markers of Disease Progression in a Manjako Community in West Africa

Overall, the time to AIDS after HIV-2 infection is longer than with HIV-1, and many individuals infected with HIV-2 virus remain healthy throughout their lives. Multiple HLA and KIR gene products have been implicated in the control of HIV-1, but the effect of variation at these loci on HIV-2 disease is unknown. We show here for the first time that HLA-B*1503 is associated significantly with poor prognosis after HIV-2 infection and that HLA-B*0801 is associated with susceptibility to infection. Interestingly, previous data indicate that HLA-B*1503 is associated with low viral loads in HIV-1 clade B infection but has no significant effect on viral load in clade C infection. In general, alleles strongly associated with HIV-1 disease showed no effect in HIV-2 disease. These data emphasize the unique nature of the effects of HLA and HLA/KIR combinations on HIV-2 immune responses relative to HIV-1, which could be related to their distinct clinical course.Since the first report of this virus in 1986, HIV-2 remains largely confined to West Africa (11). It shares between 30 and 60% nucleotide and amino acid homology with HIV-1 but differs greatly in pathogenicity and transmissibility (20). Studies on HIV-2 patients across West Africa have shown that some people remain uninfected despite repeated exposure (36), and a substantial proportion of infected people remain relatively healthy for a very long time with low plasma viral load and normal CD4⁺ T-cell counts, a characteristic of long-term nonprogressors (LTNPs) infected with HIV-1 (37). This is perhaps a reflection of an effective immune response mounted against the virus, including a vigorous CD8⁺ T-cell response (28), maintenance of HIV-specific CD4⁺ T-cell function (15), and the presence of a strong neutralizing antibody response in many subjects (4), features that are highly desirable for a successful HIV-1 vaccine. Thus, HIV-2 disease course provides a natural model for investigating mechanisms that control HIV infection, and a better understanding of these mechanisms might inform new strategies for HIV prevention and treatment.HLA class I molecules present antigenic epitopes to cytotoxic T cells and are central to the acquired immune response. A number of associations between HLA class I alleles and HIV disease outcomes have been reported (10), the most consistent being B*57 and B*27, which show strong protection across studies, and certain subtypes of B*35, which associate with more rapid progression (19). While several mother-infant studies have implicated sharing of certain HLA alleles in transmission of the virus from mother to infant (29, 30), there is no convincing data that particular HLA class I alleles protect against HIV infection in general.HLA class I allotypes also serve as ligands for killer cell immunoglobulin-like receptors (KIRs), which modulate natural killer (NK) cell function. KIRs are structurally similar to one another and can be divided into activating and inhibitory receptors. NK cells are key components of the innate immune system and constantly survey host cell surfaces for appropriate levels of HLA class I molecules through a network of NK cell receptors, including KIRs (26). Upon engagement with their ligand, inhibitory KIR suppress NK cell activity, but if the ligand is missing or has been downregulated on target cells, the threshold for NK cell activation is lowered, thus allowing for activation signals to dominate (23).HLA and KIR genes are found on chromosomes 6 and 19, respectively, so they segregate independently. As such, the genes/alleles for the corresponding receptor-ligand pair must be present to confer functionality, whereas presence of one without the other results in a null phenotype. A number of HLA and KIR gene products either individually or collectively has been implicated in the control of HIV-1 (9), but nothing is known of their role in HIV-2.Epidemiological data from Caio and other cohorts in West Africa (3, 39) indicate that HIV-2 infection in a substantial proportion of infected individuals is compatible with normal survival and without signs of immunodeficiency, suggesting distinct viral pathogenic mechanisms and protective host factors against HIV-2 relative to HIV-1. Here, we determined the HLA class I and KIR gene profiles of the Caio population (>95% Manjako) from Guinea-Bissau and investigated their effects on susceptibility to HIV-2 infection and disease progression.     

Etiologic profile and antimicrobial susceptibility of community-acquired urinary tract infection in two Cameroonian towns

ABSTRACT: BACKGROUND: Urinary tract infection (UTI) represents one of the most common diseases encountered in community medical practice. In resource poor settings, treatment is usually empiric due to the high cost and long duration required for reporting diagnosis by culture and antibiotic susceptibility testing. With the growing problem of drug resistance knowledge of antibiotic susceptibility pattern is pertinent for successful eradication of invading pathogens. Our study, the first of its kind in Cameroon, analyzed the distribution and antibiotic susceptibility of bacteria causing community-acquired urinary tract infection (CAUTI) in two towns (Bamenda and Buea) with a large number of young and middle aged persons, to provide data that could guide empiric treatment. FINDINGS: We cultured 235 urine specimens and analyzed the antibiotic susceptibility of isolates by the disc diffusion technique. Uropathogens were recovered from 137 (58.3%), with prevalence rates in Buea and Bamenda being 65.9% and 54% respectively. Predominant pathogens were Escherichia coli (31.4%), Klebsiella oxytoca (25.5%) and Staphylococcus spp (24.1%). Geographic variation in uropathogen distribution and antibiotic susceptibility was observed, and a significant difference in pathogen distribution with respect to gender. The 20-39 years age group had the highest prevalence of infection. All pathogens isolated were detected in this group. Isolates exhibited low susceptibility to antibiotics tested. Bamenda isolates generally exhibited lower susceptibility compared to those from Buea. CONCLUSION: Regional variation in etiology of CAUTI and antibiotic susceptibility observed in our study emphasizes the need to establish local and national antimicrobial resistance monitoring systems in Cameroon to provide information for the development of CAUTI treatment guidelines.