Poly-γ-d-Glutamic Acid Capsule Interferes with Lytic Infection of Bacillus anthracis by B. anthracis-Specific Bacteriophages

The poly-γ-d-glutamic acid capsule of Bacillus anthracis is a barrier to infection by B. anthracis-specific bacteriophages. Capsule expression was found to completely inhibit lytic infection by γ phage, an observation supported by the demonstration that this phage does not elaborate a hydrolase that would facilitate penetration through the protective capsule outer layer.     

No sitting on the fence: protecting wetlands from feral pig damage by exclusion fences requires effective fence maintenance

Feral pigs damage the significant ecological and cultural values of tropical Australian wetlands. Control measures such as culling, baiting, and trapping can reduce overall pig populations, but do not eliminate the substantial physical damage to wetlands that can occur from just a few individuals. Exclusion fences have been adopted as a potential technique to prevent damage to selected wetlands. To test the effectiveness of exclusion fences we measured the physical damage caused by pigs to multiple wetlands in the Archer River catchment of tropical northern Australia. Wetlands were fenced using a typical cattle exclusion fence, a specific pig exclusion fence or had no fence. Initial analyses of these fence treatments showed no significant difference in the intensity of physical pig damage to exposed wetland sediments and fringing vegetation. However, several of the pig exclusion fences were found to have been compromised. Reanalysis indicated wetlands with functioning pig exclusion fences had no physical pig damage and this was significantly less damage than in all other treatments. In contrast, wetlands with compromised pig exclusion fences had damage that was statistically equivalent to sites without fences or with cattle exclusion fences, but in individual cases had the worst damage recorded in any of the treatments. Compromised pig exclusion fencing of wetlands can thus be worse than having no fencing at all. This suggests that the successful prevention of pig damage to wetlands by exclusion fences requires ongoing and effective fence monitoring and maintenance regimes.

     

The impact of asymptomatic helminth co-infection in patients with newly diagnosed tuberculosis in north-west ethiopia

Background

Areas endemic of helminth infection, tuberculosis (TB) and HIV are to a large extent overlapping. The aim of this study was to assess the impact of asymptomatic helminth infection on the immunological response among TB patients with and without HIV, their house hold contacts and community controls.

Methodology

Consecutive smear positive TB patients (n = 112), their household contacts (n = 71) and community controls (n = 112) were recruited in Gondar town, Ethiopia. Stool microscopy, HIV serology, serum IgE level, eosinophil and CD4 counts were performed and tuberculosis patients were followed up for 3 months after initiation of anti-TB treatment.

Results

Helminth co-infection rate was 29% in TB patients and 21% in both community control and household contacts (p = 0.3) where Ascaris lumbricoides was the most prevalent parasite. In TB patients the seroprevalence of HIV was 47% (53/112). Eosinophilia and elevated IgE level were significantly associated with asymptomatic helminth infection. During TB treatment, the worm infection rate of HIV+/TB patients declined from 31% (10/32) at week 0 to 9% (3/32) at week 2 of TB treatment, whereas HIV−/TB patients showed no change from baseline to week 2, 29% (13/45) vs. 22.2% (10/45). This trend was stable at week 8 and 12 as well.

Conclusion

One third of smear positive TB patients were infected with helminths. Eosinophilia and elevated IgE level correlated with asymptomatic worm infection, indicating an effect on host immunity. The rate of worm infection declined during TB treatment in HIV+/TB co-infected patients whereas no decline was seen in HIV−/TB group.     

Assessment of genetic diversity in Ethiopian cowpea [<Emphasis Type="Italic">Vigna unguiculata</Emphasis> (L.) Walp.] germplasm using simple sequence repeat markers

The genetic diversity of cowpea (Vigna unguiculata L. Walp.) in Ethiopia was analyzed using 19 uniform accessions, 62 variable accessions (yielding 185 sub-types), and two mungbean (Vigna radiata) accessions (four subtypes) as outgroup. A set of 23 polymorphic simple sequence repeat (SSR) markers was identified, and polymorphism in the various accessions was scored by determining amplicon variability. Allele frequency, genetic diversity, and polymorphism information content (PIC) were determined for each SSR marker, and a neighbor joining dendrogram was generated to show the genetic relationship among the individual accessions. A total of 75 allelic variants was defined, with the average number of alleles per locus calculated to be three. The average genetic diversity (D) was 0.47, and PIC was 0.4. Three main clusters were identified by phylogenetic analysis, and the clusters and sub-grouping were supported by STRUCTURE and principal component analysis. This grouping had a moderate fixation index value of 0.075 and gene flow (Nm) of 3.176, indicating that the accessions possess wide diversity within individuals and populations. The accessions showed no clustering by geographical origins. Three well-characterized molecular markers (SSR1, C42-2B, and 61RM2) for race specific resistance to Striga gesnerioides in the cowpea cultivar B301 were used to evaluate the accessions for their potential for use in genetic improvement against this pest. Based on this analysis, only two accessions, 222890–2 from Gambela and 286–2 from the Southern Nations, Nationalities, and Peoples (SNNP) region, were found to cluster with B301 and contain the SSR1 resistance allele. These findings will assist in germplasm conservation efforts by the Institute of Biodiversity and Conservation of Ethiopia, and contribute to future studies aimed at the genetic improvement of local germplasm for improved overall agronomic performance as well as Striga resistance in particular.     

Genetic mapping of the stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn) resistance gene Sr13 in wheat (Triticum aestivum L.)

Puccinia graminis f. sp. tritici, the causative agent of stem rust in wheat, is known for its high virulence variability and ability to evolve new virulence to resistance genes. Thus, pyramiding of several resistance genes in a single line is the best strategy for a sustainable control of wheat stem rust. Sr13 is one of the few resistance genes that are effective against wide ranging P. graminis f. sp. tritici races, including the pestilent race Ug99. Its effectiveness to Ug99 makes it a valuable source for resistance to stem rust. Molecular markers play a pivotal role in the genetic characterization of the new sources of resistance as well as in stacking two or more resistance genes in a single line. Therefore, the aim of this study was to develop molecular markers for Sr13 facilitating efficient pyramiding of Sr genes. Based on the 158 F₂ individuals derived from a cross of Khapstein/9*LMPG × Morocco and SSR analyses, the Sr13 locus was mapped on chromosome 6A of wheat, and a genetic map comprising about 90 cM was constructed with the closest marker barc37 being located 4.0 cM distally of Sr13. Of the nine mapped markers, barc37 amplified an allele specific for the presence of Sr13 as shown by testing different cultivars and breeding lines. These newly developed markers will increase the efficiency of incorporating Sr13 into cultivars that are widely adopted, but susceptible to hazardous Ug99 and/or assist for the development of new elite lines that are resistant to Ug99.     

Most germ-line mutations in the nevoid basal cell carcinoma syndrome lead to a premature termination of the PATCHED protein, and no genotype-phenotype correlations are evident.

The human homologue of the Drosophila segment polarity gene patched is implicated in the development of nevoid basal cell carcinoma syndrome (NBCCS) and in the genesis of sporadic basal cell carcinomas. In order to examine the phenotypic variability in NBCCS and to highlight functionally important domains of the PTCH protein, we have now screened 71 unrelated NBCCS individuals for mutations in the PTCH exons. We identified 28 mutations that are distributed throughout the entire gene, and most (86%) cause protein truncation. As part of this analysis, we demonstrate that failure of one NBCCS family to show clear linkage to chromosome 9q22.3-31 is most likely due to germinal mosaicism. We have identified three families bearing identical mutations with variable phenotypes, suggesting phenotypic variability in NBCCS is a complex genetic event. No phenotype genotype correlation between the position of truncation mutations and major clinical features was evident. Two missense mutations have been identified, and their location within transmembrane domains supports the notion that PTCH may have a transport function. The preponderance of truncation mutants in the germ line of NBCCS patients suggests that the developmental defects associated with the disorder are most likely due to haploinsufficiency.     

Development of Microsatellite Markers and Analysis of Genetic Diversity and Population Structure of Colletotrichum gloeosporioides from Ethiopia

Twenty three polymorphic microsatellite markers were developed for citrus plant pathogenic fungus, Colletotrichum gloeosporioides, and were used to analyze genetic diversity and population structure of 163 isolates from four different geographical regions of Ethiopia. These loci produced a total of 118 alleles with an average of 5.13 alleles per microsatellite marker. The polymorphic information content values ranged from 0.104 to 0.597 with an average of 0.371. The average observed heterozygosity across all loci varied from 0.046 to 0.058. The gene diversity among the loci ranged from 0.106 to 0.664. Unweighted Neighbor-joining and population structure analysis grouped these 163 isolates into three major groups. The clusters were not according to the geographic origin of the isolates. Analysis of molecular variance showed 85% of the total variation within populations and only 5% among populations. There was low genetic differentiation in the total populations (F_ST = 0.049) as evidenced by high level of gene flow estimate (N_m = 4.8 per generation) among populations. The results show that Ethiopian C. gloeosporioides populations are generally characterized by a low level of genetic diversity. The newly developed microsatellite markers were useful in analyzing the genetic diversity and population structure of the C. gloeosporioides populations. Information obtained from this study could be useful as a base to design strategies for better management of leaf and fruit spot disease of citrus in Ethiopia.