Microbiologia da filosfera: explorando a biodiversidade, ecologia e taxonomia no sistema leveduras-bromélias em escala global e no semiárido brasileiro

Abstract

Drylands are areas characterized by aridity indexes ≤0.65. In this type of environment, rainfall is decisive for biological dynamics and occurs in pulses (rare events of overavailability of resources). During drought, nutritional and metabolic demand is decreased. Thus, the longer the dry period, the greater the nutritional reservoir accumulated in the environment. Reservoir size influences the strength of the response to the water pulse. That is, there is an environmental 'memory' of the previous rainfall event. Another example of an ecosystem with a frequent water deficit is the phyllosphere (the aerial part of plants). This environment is one of the largest sources of microorganisms on the planet. The phyllosphere of bromeliads, typically neotropical plants, harbor several microbial groups, including yeasts. However, knowledge about yeasts in bromeliads is scattered and still incipient. In this study our objectives were: 1) Compile, synthesize and understand the extent of knowledge about yeasts from the bromeliad phyllosphere. 2) To verify the effect of rain and environmental memory on the diversity and taxonomic, phylogenetic and functional structure of yeasts from the phyllosphere of bromeliads in the Caatinga. 3) Propose the description of the new species Carlosrosaea xxxxxxx sp. nov. To this end, the literature on yeasts in bromeliads was systematically reviewed. Furthermore, yeasts were regularly isolated for two years from bromeliads in the Private Natural Heritage Reserve (RPPN) Tocaia, in the municipality of Santana do Ipanema, Alagoas. In the academic production of the last three decades, records of more than 180 species of yeasts were found in the phyllosphere of bromeliads, distributed in four compartments: flowers, fruits, leaves and tanks. About 70% of the species occurred exclusively in a single compartment and only 2% were common to all. More than 20 new yeast species were described in bromeliads during this period and at least 50 species showed some biotechnological potential. As for the effect of rainfall, alpha-diversity did not differ significantly between seasonal periods. However, the taxonomic composition differed by more than 70%, although it was functionally stable. Rain, drought and environmental memory had little influence on diversity metrics. However, they showed a relationship with the structure of the community. The analysis of the ITS and D1/D2 regions of the 26S rRNA gene of eight Caatinga isolates indicated a possible new yeast species with affinity to the genus Carlosrosaea. Therefore, a new species of Carlosrosaea is proposed to group the cited isolates. Our results bring information about the diversity and dynamics of yeasts in the bromeliad phyllosphere and how it relates to rainfall pulses, drought, seasonality and memory effect. Furthermore, we aggregate information about the tolerance of the phyllosphere yeast community to seasonal changes, from a taxonomic, phylogenetic and functional point of view. By understanding the effect of rain and drought on the phyllosphere microbiota, especially in dry regions, we can think about how the microbial community of the leaves will be affected by climate changes that alter the dry-wet cycles and, consequently, how this relates to the host.