RESUMEN
Fusarium proliferatum is a member of the Fusarium fujikuroi species complex (FFSC) involved in the maize ear rot together with Fusarium verticillioides, which is a very closely related species. Recently, different studies have detected natural fumonisin contamination in wheat kernels and most of them have shown that the main species isolated was F. proliferatum. Fusarium strains obtained from freshly harvested durum wheat samples (2008 to 2011 harvest seasons) from Argentina were characterized through a phylogenetic analysis based on translation elongation factor-1 alpha (EF-1α) and calmodulin (CaM) genes, determination of mating type alleles, and evaluation of fumonisin production capability. The strains were identified as F. proliferatum (72%), F. verticillioides (24%) and other Fusarium species. The ratio of mating type alleles (MAT-1 and MAT-2) obtained for both main populations suggests possible occurrence of sexual reproduction in the wheat fields, although this seems more frequent in F. proliferatum. Phylogenetic analysis revealed greater nucleotide variability in F. proliferatum strains than in F. verticillioides, however this was not related to origin, host or harvest year. The fumonisin-producing ability was detected in 92% of the strains isolated from durum wheat grains. These results indicate that F. proliferatum and F. verticillioides, among the fumonisin producing species, frequently contaminate durum wheat grains in Argentina, presenting a high risk for human and animal health.
Asunto(s)
Fumonisinas/metabolismo , Fusarium/genética , Genes Fúngicos/genética , Variación Genética , Triticum/microbiología , Argentina , Calmodulina/genética , Fumonisinas/análisis , Fusarium/química , Fusarium/clasificación , Fusarium/aislamiento & purificación , Genes del Tipo Sexual de los Hongos/genética , Factor 1 de Elongación Peptídica/genética , FilogeniaRESUMEN
Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight of wheat. The authors used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of two G. zeae populations from commercial wheat fields. The working hypothesis was that sufficient genetic exchange occurs between local populations to prevent significant partitioning of allelic variation. We analysed 216 AFLP loci for 113 isolates collected during the 2002 harvest season. All strains had AFLP profiles typical of G. zeae lineage 7. Both populations were genotypically diverse but genetically similar and potentially part of a larger, randomly mating population, with significant genetic exchange probably occurring between the two subpopulations. Linkage disequilibrium was low, but higher than reported for many other populations of G. zeae, and about 20% of the alleles detected were specific to one of the two subpopulations - results consistent with limited gene exchange between the two subpopulations. This study extends previous work with populations of G. zeae to include those found in Argentina, one of the world's largest wheat growing countries.
Asunto(s)
Análisis del Polimorfismo de Longitud de Fragmentos Amplificados/métodos , Fusarium/genética , Genes Fúngicos/genética , Gibberella/genética , Polimorfismo de Longitud del Fragmento de Restricción/genética , Triticum/microbiología , Argentina , Contaminación de Alimentos , Fusarium/aislamiento & purificación , Frecuencia de los Genes/genética , Variación Genética/genética , Gibberella/aislamiento & purificación , Estadística como AsuntoRESUMEN
An investigation of Klebsiella pneumoniae hemolytic activity was carried out. Strains isolated from different infected specimens were hemolytic in tryptic soy agar with rabbit blood; incubation at 4 degrees C enhanced the hemolysis. There was no evident red blood cell lysis in plates with human, sheep, mouse, and chicken erythrocytes. The culture in tryptic soy broth, its supernatant and bacterial lysate did produce evident hemolysis of rabbit red blood cells when they were preincubated with 2-mercaptoethanol. Klebsiella pneumoniae hemolysin showed the Arrhenius effect, while temperatures over 60 degrees C for 10 min reduced the activity of crude hemolysin to zero; purified hemolysin, however, was heat stable. Two hemolysins active on rabbit red blood cells were purified and both shared several properties. This work represents the initial description of a thiol-activated hemolysin in Gram-negative bacteria.