RESUMO
A development mutant, named V103, was obtained spontaneously from the A strain of A. nidulans. The A strain contains a duplicated segment of chromosome I that has undergone translocation to chromosome II (I ¨ II). It is mitotically unstable and generates phenotypically deteriorated types, some with enhanced stability. The deteriorated variants of A. nidulans show abnormal development, exhibiting slower colony growth, variations in colony pigmentation and changes in conidiophore structure. The alterations observed in the conidiophore include fewer metulae and phialides, further elongation and ramification of these structures, delayed nuclear migration and the presence of secondary conidiophores.
Assuntos
Aspergillus nidulans/crescimento & desenvolvimento , Aspergillus nidulans/isolamento & purificação , Movimento Celular , Cromossomos Fúngicos , Esporos Fúngicos/genética , Fenótipo , Supressão Genética , Métodos , Microscopia Eletrônica , Métodos , VirulênciaRESUMO
The secretion of proteinaceous toxins is a widespread characteristic in environmental and laboratory yeast isolates, a phenomenon called "killer system". The killer phenotype (K+) can be encoded by extrachromosomal genetic elements (EGEs) as double stranded DNA or RNA molecules (dsDNA, dsRNA) or in nuclear genes. The spectrum of action and the activity of killer toxins are influenced by temperature, salinity and pH of media. In the present work we determined the existence of K+ in a collection of S. cerevisiae and P. anómala yeasts isolated from environmental, industrial and clinical sources. The assays were performed in strains belonging to three yeast genera used as sensitive cells and under a wide range of pH and temperatures. Approximately 51 percent of isolates tested showed toxicity against at least one sensitive yeast strain under the conditions tested. The K+ P. anómala isolates showed a wide spectrum of action and two of them had toxic activity against strains of the three yeast genera assayed, including C. albicans strains. In all S. cerevisiae K+ isolates an extrachromosomal dsRNA molecule (4.2 Kb) was observed, contrary to P. anómala K+ isolates, which do not possess any EGEs. The K+ phenotype is produced by an exported protein factor and the kinetics of killer activity production was similar in all isolates with high activity in the log phase of growth, decaying in the stationary phase.
Assuntos
Humanos , Fatores Matadores de Levedura/biossíntese , Pichia/metabolismo , Saccharomyces cerevisiae/metabolismo , Cromossomos Fúngicos/genética , DNA Fúngico/genética , DNA Mitocondrial/genética , Eletroforese em Gel de Ágar , Meio Ambiente , Concentração de Íons de Hidrogênio , Fenótipo , Reação em Cadeia da Polimerase , Pichia/genética , Saccharomyces cerevisiae/genética , TemperaturaRESUMO
Industrial ethanol fermentation is a complex microbiological process to which yeast cells must adapt for survival. One of the mechanisms for adaptation is thought to involve chromosome rearrangements. We found that changes in chromosome banding patterns measured by pulsed-field gel electrophoresis can also be produced in laboratory media under simulated industrial conditions. Based on analysis of their generational variation, we found that these chromosome changes were specific to the genetic backgrounds of the initial strains. We conclude that chromosome rearrangements could be one of the factors involved in yeast cell adaptation to the industrial environment.
Assuntos
Instabilidade Cromossômica , Cromossomos Fúngicos/genética , DNA Fúngico/genética , Etanol/metabolismo , Saccharomyces cerevisiae/genética , Adaptação Fisiológica , Biotecnologia , Impressões Digitais de DNA , DNA Fúngico/isolamento & purificação , Fermentação , Cariotipagem , Reatores Biológicos/microbiologia , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/fisiologiaRESUMO
The mutants of Saccharomyces cerevisiae assigned to complementation group G199 are deficient in mitochondrial respiration and lack a functional cytochrome oxidase complex. Recombinant plasmids capable of restoring respiration were cloned by transformation of mutants of this group with a yeast genomic library. Sequencing indicated that a 2.1-kb subclone encompasses the very end (last 11 amino acids) of the PET111 gene, the COX7 gene and a new gene (YMR255W) of unknown function that potentially codes for a polypeptide of 188 amino acids (about 21.5 kDa) without significant homology to any known protein. We have shown that the respiratory defect corresponding to group G199 is complemented by plasmids carrying only the COX7 gene. The gene YMR255W was inactivated by one-step gene replacement and the disrupted strain was viable and unaffected in its ability to grow in a variety of different test media such as minimal or complete media using eight distinct carbon sources at three pH values and temperatures. Inactivation of this gene also did not affect mating or sporulation.
Assuntos
Cromossomos Fúngicos/genética , DNA Fúngico/genética , Saccharomyces cerevisiae/genética , Sequência de Aminoácidos/genética , Sequência de Bases/genética , Clonagem Molecular , Complexo IV da Cadeia de Transporte de Elétrons/genética , Genótipo , Mutação/genética , FenótipoRESUMO
Resumo: O objetivo desse estudo foi descrever aspectos do comportamento nuclear durante a divisäo miótica em conídios e células miceliais do fungo celulolítico Humicola so. A sequência dos eventos mitóticos foi similar aquela observada em outros fungos filamentosos. O número de cromossomos observados no final da metáfase näo pode ser determinado com segurança, mas pareceu estar entre 6 e 8. As culturas de Humicola sp frequentemente mostraram anastomose de hifas e a presença de núcleos na ponte hifal, o que permitiria a ocorrência de heterocariose,e indica que o ciclo parasexual pode ocorrer nessa espécie (au)
