Characterization of <Emphasis Type="Italic">chsA,</Emphasis> a new gene controlling the chemotactic response in <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> Sp7

We report, here, the characterization of a mutant strain of Azospirillum brasilense Sp7 impaired in surface motility and chemotactic response. Presence of flagella in the mutant strain was confirmed by western blot analysis, using antisera raised against the polar and lateral flagellins, and by electron microscopy. Genetic complementation and nucleotide sequencing led to the identification of a new gene, named chsA. The deduced translation product, ChsA protein, contained a PAS sensory domain and an EAL domain. As ChsA displayed characteristic signaling protein architecture, it is thought that this protein is a component of the signaling pathway controlling chemotaxis in Azospirillum.     

Pectinolytic enzyme production by Colletotrichum truncatum,causal agent of soybean anthracnose

BackgroundColletotrichum truncatum is the most common pathogenic fungus associated with soybean anthracnose, a prevalent disease in Argentina. Pectinolytic enzymes are involved in the pathogenicity of a wide range of plant pathogenic fungi.ObjectivesTo explore pectinolytic enzyme production in Argentinian Colletotrichum strains isolated from diseased soybean plants from different geographic locations, as a preliminary step to establish the biological role of the pectinolytic enzymes in the Colletotrichum spp.–soybean system, yet unknown.MethodsTen strains were screened for in vitro pectinolytic enzyme production on a defined medium based on pectin as carbon source.ResultsAll isolates were able to grow in this medium and polymethylgalacturonase (PMG), polygalacturonase (PG) and pectin lyase (PL) activities were detected. On the whole, the peak of polygalacturonases activities preceded the day of maximum growth, while PL activity reached its highest level afterwards. Strain BAFC 3097 (from Santa Fe province) yielded high titles of the three enzymes (1.08 U/ml PG, 1.05 U/ml PMG, 156 U/ml PL), after a short incubation period (7–10 days). Low synthesis of polygalacturonases in cultures containing glucose as unique carbon source suggests that these enzymes are constitutive in contrast with PL, which was not detected.ConclusionsThe disparity observed in enzyme production among strains cannot be related to fungal growth, since no major differences in mycelial yield were found; it was not connected with their geographic origin, but might be associated with differences in virulence among strains not yet evaluated.     

Synchronicity of pollination and inoculation with Claviceps africana and its effects on pollen-pistil compatibility and seed production in sorghum

Sorghum ergot (caused by Claviceps africana) is a disease that affects sorghum seed development and yield. The interaction between pollen tube growth and hyphal development determines whether ovaries will be fertilized or colonized. Thus their respective deposition times on the stigma are critical. The effect of the time interval between pollination and inoculation on stigma receptivity and seed production was measured under field conditions in the male-sterile line A9 at Montecillo, State of México (2240m altitude). Pollination and inoculation treatments, from simultaneous application to 2 and 4h difference, were imposed when all stigmas on the panicle had emerged. Control panicles were either only pollinated or only inoculated. Eighteen hours later, pollen grains that adhered to, and germinated within the stigma, pollen tubes in the style and ovary, and fertilized pistils were counted. Pistils showing some disease expression (germinated spores, mycelium growth, or tissue necrosis) at 18, 48, and 72h were recorded. The number of diseased florets was registered at the dough growth stage, while number of seeds, grain yield and 100-seeds weight was measured at the physiological maturity. The pathogen applied in a water suspension of macro and secondary conidia caused a decrease in stigma receptivity; the greatest decrease (40-60%) occurred when the pollen and the inoculum were deposited almost simultaneously, regardless of which was deposited first. The route of the pollen tube was also the route for fungal infection. On average, treatments first inoculated had 60% more diseased florets and 36% less grain yield, 30% fewer seeds and seed size decreased 8%, than those first pollinated.     

Human activity recognition based on Evolving Fuzzy Systems

Environments equipped with intelligent sensors can be of much help if they can recognize the actions or activities of their users. If this activity recognition is done automatically, it can be very useful for different tasks such as future action prediction, remote health monitoring, or interventions. Although there are several approaches for recognizing activities, most of them do not consider the changes in how a human performs a specific activity. We present an automated approach to recognize daily activities from the sensor readings of an intelligent home environment. However, as the way to perform an activity is usually not fixed but it changes and evolves, we propose an activity recognition method based on Evolving Fuzzy Systems.     

Association of CTLA-4 variation with type I diabetes in Filipinos

The role of non-HLA single nucleotide polymorphisms from a panel of candidate genes in genetic susceptibility to type I diabetes (TID) among Filipinos was examined by PCR/SSOP typing of 90 patients and 94 controls, previously typed for the HLA class I and class II loci. We report the association of CTLA-4 A49G variation (cytotoxic T-lymphocyte associated-4) to TID among Filipinos, consistent with some but not all previous reports in other ethnic groups. The G allele frequency (0.61 versus 0.45, P=0.003) and GG genotype frequency (0.42 versus 0.22, P=0.004) were each increased in patients compared to controls, respectively. Among Filipinos, the CTLA-4 genotypes are associated with disease only in the presence of the predisposing DR3, 4, and 9 haplotypes (P=0.012). Compared to the AA genotype, the increased risk of diabetes predisposition is greatest in genotype GG bearing the DR susceptible alleles (DR3, 4, and 9) (odds ratio=4.6, P=0.001), demonstrating that non- HLA loci, acting in concert with HLA, can play potent roles in modifying susceptibility to TID.     

An isolate of Rhizopus nigricans capable of tolerating and removing pentachlorophenol

Rhizopus nigricans, isolated from an industrial effluent (paper mill), was resistant to pentachlorophenol (PCP) in Petri dishes and in submerged cultures (100 and 25 mg l^–1 respectively). It was shown that this strain of R. nigricans can remove PCP in submerged culture. When 12.5 mg of PCPl^–1 were added at 48 h, this compound had been completely removed by 144h. Results indicated that the fungus did not produce extracellular lignin peroxidase (LiP) and laccase, but extracellular phenoloxidase production was observed. The synthesis of the latter enzyme was stimulated by the presence of PCP and/or tyrosine. These results indicate that this fungus, and probably other filamentous fungi, have an interesting potential to be used in processes for chlorophenol biodegradation.