Different procedures for yeast stock collection; phenotype and genotype diversity study / Diferentes processos de armazenamento de leveduras: estudos sobre a variabilidade fenotipica e genotipica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The maintenance of microorganisms is useful to preserve microbial species in clinical, technical and research laboratories. Different methods to yeast stocking are available in order to obtain long time viability and stability of cell properties. The best methods to store microorganisms need to provide the cell survival as well as purity and stability of their properties. Some researches, however, have mentioned phenotypic and/or genotytpic changes in laboratorial samples, which may influence yeast typing, studies and the applications of those organisms in different areas. Therefore, additional studies are needed to evaluate the yeast samples properties stability after stocking through different methods. The aim of this study was to evaluate the influence of the yeast storage methods in terms of their morphological and biochemistry characteristics. Candida spp. standard strains, four of medical importance and two industrial species were evaluated. Those strains were submitted to five storage methods: serial transferences in agar medium, mineral oil, distilled water, freeze with glycerol at -70ºC and freeze-drying. The samples were characterized with phenotypic techniques before being stocked, and after that in different periods of time up to 18 months. It was tested the characteristics of the colonies in CHROMagar Candida® medium, micromorphology in corn meal agar, carbohydrates assimilation and fermentation, phospholipases and proteinases production in solid medium, growth test in 45ºC and growth test in hypertonic medium. In addition, the DNA extraction of all samples was carried out in time zero, 6, 12 and 18 months, in order to posterior genotypic analyses by Randomly Amplified Polymorphic DNA (RAPD) using two different primers for each strain. The results showed that all yeast preservation methods tested were able to maintain the viability of the samples during the period of the study, except the strain Candida dubliniensis stocked in mineral oil, which not survived after 12 months in these conditions. It was not observed phenotypic alterations in the results of morphological and biochemistry tests after laboratorial preservation with all used methods. However, some non stable variations were observed in phospholipase and proteinase production and in the hypertonic growth for some samples. Such variations were not related to one specific maintenance method and the altered result could be reversible in subsequent tests. Changes in the RAPD pattern were not detected in, at least, two independent reactions for both tested primers. The results showed that the maintenance methods applied in this study were able to preserve the stability of the phenotypic and genotypic characteristics, in all yeast samples stocked during the analyzed period of time. Therefore, the technical and research applicability of the samples are not unfeasible when they are preserved with those methods. Strains designated to use for specific purposes must be tested individually, in order to select the best preservation method

ASSUNTO(S)

yeast fungi criopresevação genotype fenotipo leveduras (fungos) phenotype cryopresevation genotipo

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