Variabilidade no perfil enzimático das assembléias de actinobactérias em gradiente de desertificação

Abstract

Deserts are characterized by adverse conditions, such as aridity, intense ultraviolet solar radiation and sudden changes in temperature, where the availability of water directly affects organisms. The diversity of actinobacteria niches is reflected in their physiological ability to grow under multiple conditions and this characteristic justifies the range of ecosystem services that this group provides. Some strains of actinobacteria form complex structures such as spore, spore chain, sporangium and sporangiospore, such attributes associated with the growth and rupture of the reverse mycelium, are important morphological characteristics for the classification of actinobacteria equally, microscopy is considered an important tool for the taxonomic classification of these microorganisms. This group of bacteria also produces secondary metabolites of economic importance and a wide range of bioactive molecules, such as cellulases. Among these metabolites, xylanase production stands out. Amylase, on the other hand, is an enzyme that hydrolyzes starch molecules into polymers that are made up of glucose units, being extracted from various microorganisms, including actinobacteria. Cellulase, in turn, also produced by this bacterial group produces energy compounds, through its degradation, playing an important role in the carbon cycle. Pectinases, excreted by organisms such as bacteria, help to maintain ecological balance. Thus, the existence of actinobacteria with the ability to cleave plant polysaccharides such as xylan, starch, cellulose and pectin that favor the cycling of nutrients, through the degradation of complex molecules, is essential for the maintenance of the living components of this environment. In this research, we used soil samples from areas susceptible to desertification as a study model to understand how the structuring of populations of actinobacteria in the soil of this region can contribute to strategies for the conservation of microbial components in terrestrial ecosystems. In the first chapter, our objective was to measure population density and evaluate, by comparing cultural and morphological characteristics, the main genera of 46 strains of actinobacterials in three levels of vegetation cover. In addition, it was also studied how this bacterial group responds to environmental stresses: temperature, pH and salinity. We found that the lack of vegetation cover did not influence the density of populations of actinobacteria and the three areas studied showed heterogeneity under thechromatic aspect of the colonies, as well as varied morphology, with predominanceof the genus Streptomyces. The open area, in turn, showed the greatest diversity ofgenera and most isolates were able to develop under different levels of temperature,pH and salinity. In the second chapter, we determine the enzymatic profile forxylanase, amylase, cellulase and pectinase in areas with different levels ofdesertification, in order to investigate how this process influences the enzymaticvariation of actinobiota. We detected that there was a significant difference in theenzymatic activity due to the gradient of desertification, since the enzyme xylanaseexhibited the highest values, followed by pectinase, amylase and cellulase. Inaddition, the best performance for the degradation of xylan compounds was revealedin the open area. This result suggests that the lack of vegetation cover and the lowavailability of soil nutrients influenced this enzymatic activity.