Diversidade de leveduras associadas ao sedimento de manguezal da Barra de Santo Antônio, Alagoas, Brasil

Abstract

Mangroves are transitional ecosystems between marine and terrestrial environments present in tropical and subtropical regions. It is considered the most important ecosystem. Due to the fact that the high organic content of soils and rhizosphere enables it to encompass a diversity of microorganisms interacting with each other, with other organisms and also with environmental factors. Several studies have demonstrated associations between bacteria and some species of mangrove plants. However, yeast communities associated with mangrove species receive much less attention. Thus, our objective was to verify the diversity and composition of yeasts associated with sediments adjacent to the rhizosphere of the L. racemosa species and to assess whether biotic and abiotic factors in the environment can influence diversity. Therefore the physical-chemical parameters were measured and sediment samples were collected at three different points in the mangrove swamp of the Santo Antônio river. Samples were diluted and seeded on modified YM Agar, followed by incubation at 25-28 ºC for 5-7 days. To perform molecular identification the D1/D2 LSU rDNA region of the isolates was amplified and sequenced. The physical-chemical parameters of the environment did not show significant variation statistically between the points. A total of 132 isolated were obtained belonging to 32 species distributed in 18 genera. Most species had a single occurrence in the samples and a possible new species belonging to the genus Barnettozyma was isolated. Furthermore, we verified that the yeast community of the sampled points is compositionally stable, but the taxonomic and phylogenetic diversities between the sampled points had significant differences increasing as the sampling sites were farther from the sea. These results indicate that, despite the daily fluctuations of environmental factors, there is stability in the composition of the community of yeasts which live in association with the species L. racemosa. The extrapolation curve did not reach the asymptote, indicating that there are still yeast species in association with the L. racemosa species which we were unable to sample. Through the analysis of the data obtained, it was concluded that the physicalchemical parameters measured did not influence the diversity of sampled yeasts. The taxonomic diversity of yeasts in the same plant species can vary throughout the mangrove and probably due to the tidal regime there will be a cycle of entry and exit of species. Therefore, new collections must be made to better elucidate the dynamics of yeast species present in mangroves.