The genome of the African trypanosome Trypanosoma brucei

African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.     

Cotyledon thermal behavior and pectic solubility as related to cooking quality in common beans

The characteristic of proteins, starch and pectic substances in cotyledons of two bean cultivars varying in cooking time were determined to investigate their possible contribution to bean cooking quality. Both cultivars showed the same enthalpies of starch gelatinization but different protein denaturation enthalpies. The proportion of hot water soluble pectins was higher in Michigan, the cultivar with the lower cooking time, than in Ojo de Cabra, the cultivar with the higher cooking time. These results were not due to differences in pectin methylation or in the ratio of monovalent to divalent cations in the tissue, suggesting that in fresh beans the β-elimination reaction is not the sole or predominant route of thermal pectin degradation. Overall, this study indicates that varietal differences in bean cooking quality may be reflections of the rate of pectin loss during soaking/heating and that the thermal properties of starch and protein fractions seem to have a minor contribution. Researchers involved in this study propose that in fresh beans, the thermal pectin loss results from a two step mechanism: pectin enzymic breakdown during the bean soaking followed by thermal solubilization rather than β-elimination during the bean heating.     

Population responses of oribatids and enchytraeids to ectomycorrhizal and saprotrophic fungi in plant-soil microcosms

The oribatid mites Oppiella nova, Tectocepheus velatus and Nothrus silvestris and the enchytraeid worm Cognettia sphagnetorum are four common animal species in boreal forest soils. According to the literature, they respond differently to clear-cutting of forest stands. O. nova responds with population decreases, T. velatus and N. silvestris with small changes and C. sphagnetorum with population increases. We hypothesised that the presence/absence of ectomycorrhizal (EM) fungi is a major factor in explaining these reactions. The population responses of these soil animals to inoculation of five species of EM fungi growing in symbiosis with their host tree (Pinus sylvestris L.) and one saprotrophic fungus, Hypholoma capnoides, growing on wood were tested in pot microcosms with artificial soil (peat and vermiculite) for 70-84 days. Additionally, plants without inoculation of EM fungi, plants growing in forest soil (FS) and plant-free peat and vermiculite (PV) were included. O. nova increased significantly in abundance in the treatments with the EM fungi Suillus variegatus and Paxillus involutus, but not in the other treatments. T. velatus increased significantly in abundance in FS, but declined in most of the other treatments, and N. silvestris showed a similar, albeit not significant, response. C. sphagnetorum did not increase in abundance in any of the treatments with EM fungi but increased its abundance four times in both FS and PV. The results show that the fungivore O. nova preferentially feeds on certain EM fungi, especially S. variegatus, whereas the EM fungus Piloderma fallax and the saprotrophic H. capnoides are not preferred. In contrast, C. sphagnetorum is restricted in its population growth by the EM fungi studied, and this dominant microbi-detritivore is clearly favoured by the absence of EM fungi.     

Distribution center and retail conditions affect the sensory and compositional quality of bulk and packaged slicing cucumbers

During distribution and retail display, fruits and vegetables are often exposed to undesirable temperature and humidity conditions which often result in increased waste due to weight loss and objectionable appearance. Unwaxed fresh-market slicing cucumbers (cv. Calypso) were harvested from a commercial operation and shipped to a distribution center (DC) in Florida. At the DC, 2 d after harvest, cucumbers were sorted and either commercially machine packaged in expanded polystyrene trays covered with a polyvinylchloride film or remained unpackaged for bulk retail display. Cucumbers were transported the next day by truck to a retail store in Gainesville, collected from the store, and stored under optimum (10 °C and 90% RH) or simulated retail display conditions (4 °C or 14 °C and 90–92% RH). Sensory (visual and instrumental color, firmness, shriveling, chilling injury and decay) and compositional quality (pH, titratable acidity, soluble solids and chlorophyll contents) were evaluated initially at the DC and after a 4-d simulated retail display period. Overall, bulk cucumbers were softer, appeared more shriveled, and were more affected by pitting and decay than packaged cucumbers. Bulk cucumbers also appeared lighter green and more yellowish than packaged fruit. Hue angle was less in bulk than in packaged cucumbers, but no consistent differences were observed in the L*, chroma, and hue values between the different temperatures. Small variations in the L*, hue, and chroma values compared to significant losses in chlorophyll content suggest that insufficient chlorophyll degradation occurred to cause major visual color changes. The greater weight loss in bulk cucumbers compared to packaged fruit was associated with accelerated chlorophyll degradation, lower acidity, and lower soluble solids content. Although packaged cucumbers had better visual quality than bulk cucumbers, there was higher RH inside the packages and greater development of decay on packaged fruit. Overall, after the 4-d simulated retail display, the appearance of the cucumbers used in this study was considered to be objectionable due to either yellowing, loss of firmness, shriveling or decay, regardless of the treatment. Results from this study demonstrate the importance of using an appropriate protective package in addition to maintaining the optimum temperature during distribution and retail display. Moreover, initial quality evaluation should be performed upon reception at the DC, and before cucumbers are displayed at the retail store, in order to estimate the remaining shelf life before this product becomes unacceptable for sale.     

Draft genome sequence of the sexually transmitted pathogen Trichomonas vaginalis

We describe the genome sequence of the protist Trichomonas vaginalis, a sexually transmitted human pathogen. Repeats and transposable elements comprise about two-thirds of the approximately 160-megabase genome, reflecting a recent massive expansion of genetic material. This expansion, in conjunction with the shaping of metabolic pathways that likely transpired through lateral gene transfer from bacteria, and amplification of specific gene families implicated in pathogenesis and phagocytosis of host proteins may exemplify adaptations of the parasite during its transition to a urogenital environment. The genome sequence predicts previously unknown functions for the hydrogenosome, which support a common evolutionary origin of this unusual organelle with mitochondria.     

Relation of peel damage in citrus fruit to wind climate in orchard and its control

Peel damage originated by wind is the main abiotic cause of citrus fruit discards for export in Uruguay. Natural windbreaks such as Eucalyptus and Casuarinas have not been effective in reducing it. This research was carried out during three years in a citrus orchard situated in the coastal plain of Uruguay (35° SL). The purpose of this work was to study wind climate inside the orchard, fruit seasonal sensitivity, basal leaf effect on the onset and evolution of peel damage, and the efficiency of artificial windbreaks to reduce fruit discard of ‘Ellendale’ tangor. Average wind velocity in the orchard did not exceed 5 m s⁻¹. First peel scars were evident two weeks after petal fall and damaged fruit percentage importantly increased during the first stage of fruit growth. Low energy vortexes caused almost permanent friction between basal leaves and the developing fruitlets growing in their axil. Removal of the basal leaf decreased significantly wind damaged fruit. Natural wind flow modification through the use of semi-porous artificial windbreak nets (5 cm by 10 cm mesh) modified low energy vortexes and increased significantly the percentage of export quality fruit. We conclude that this type of net is more efficient than natural windbreaks or classical nets to reduce wind damage in citrus fruit.     

Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts

The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SS_SPI-6 and T6SS_SPI-19. This study has determined the contribution of T6SS_SPI-6 and T6SS_SPI-19 to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SS_SPI-6/∆T6SS_SPI-19) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SS_SPI-6 mutant, suggesting that this serotype requires a functional T6SS_SPI-6 for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SS_SPI-19 was not necessary for colonization of either chickens or mice. Transfer of T6SS_SPI-6, but not T6SS_SPI-19, restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SS_SPI-6 for efficient colonization of mice and chickens, and that the T6SS_SPI-6 and T6SS_SPI-19 are not functionally redundant.     

Spatiotemporal interactions between wild boar and cattle: implications for cross-species disease transmission

Controlling infectious diseases at the wildlife/livestock interface is often difficult because the ecological processes driving transmission between wildlife reservoirs and sympatric livestock populations are poorly understood. Thus, assessing how animals use their environment and how this affects interspecific interactions is an important factor in determining the local risk for disease transmission and maintenance. We used data from concurrently monitored GPS-collared domestic cattle and wild boar (Sus scrofa) to assess spatiotemporal interactions and associated implications for bovine tuberculosis (TB) transmission in a complex ecological and epidemiological system, Doñana National Park (DNP, South Spain). We found that fine-scale spatial overlap of cattle and wild boar was seasonally high in some habitats. In general, spatial interactions between the two species were highest in the marsh-shrub ecotone and at permanent water sources, whereas shrub-woodlands and seasonal grass-marshlands were areas with lower predicted relative interactions. Wild boar and cattle generally used different resources during winter and spring in DNP. Conversely, limited differences in resource selection during summer and autumn, when food and water availability were limiting, resulted in negligible spatial segregation and thus probably high encounter rates. The spatial gradient in potential overlap between the two species across DNP corresponded well with the spatial variation in the observed incidence of TB in cattle and prevalence of TB in wild boar. We suggest that the marsh-shrub ecotone and permanent water sources act as important points of TB transmission in our system, particularly during summer and autumn. Targeted management actions are suggested to reduce potential interactions between cattle and wild boar in order to prevent disease transmission and design effective control strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-014-0122-7) contains supplementary material, which is available to authorized users.