Efeito de herbicidas sintéticos sobre leveduras da microbiota de insetos polinizadores

Abstract

Food production is based worldwide on conventional agriculture and uses increasingly exorbitant amounts of synthetic products to control pests in the field, which leads to food contamination, farmer exposure to toxic products, and impact on the microbiota present in agricultural areas. Besides being useful for various biotechnological applications, these microorganisms (including yeasts, which are unicellular fungi) perform several ecosystem services, promoting the growth and defense of plant organisms and contributing to the ecological balance of the environment. This work was developed in two parts: Chapter 1 contains a review article highlighting the importance of yeasts in the environment, the impact synthetic products have on them, and the resistance mechanisms developed by these microorganisms. Chapter 2 presents data from laboratory tests performed with seven wild yeast strains from the collection of the Laboratory of Yeast Biochemistry of the Campus Chapecó of UFFS, previously isolated from the insects Astylus variegatus, Tetragonisca angustula, and Scaptotrigona postica. The yeast strains were inoculated in liquid YPD medium containing synthetic herbicides with the active ingredients glyphosate (at concentrations of 3.255 g/L, 6.51 g/L, 13.02 g/L, and 26.04 g/L) and 2,4-D (at concentrations of 1.51 g/L, 3.02 g/L, 6.045 g/L, and 12.09 g/L) and maintained for 48 h at 30 °C in an orbital shaker at 145 rpm. Samples were taken at time zero and 14, 24, 38, and 48 h of culture to determine cell growth. In parallel, the potential of yeasts was also investigated for the degradation of the auxinic herbicide 2,4-D, by high-performance liquid chromatography, and for the production of indoleacetic acid (IAA), by a colorimetric method with the Salkowski reagent in a spectrophotometer at 530 nm. The results demonstrate that the herbicide glyphosate prevented the growth of yeasts at all concentrations tested within 48 hours of cultivation. In contrast, yeasts showed enhanced tolerance to the herbicide 2,4-D. In this case, cell growths decreased and latency phases increased proportionally with the increase in pesticide concentration in the culture medium. Among the tolerant strains, CHAP-237 stood out for its ability to reduce the amount of 2,4-D in the medium, both at low and high concentrations of the herbicide, which suggests a possible use of this yeast as a bioremediation tool. In the production of IAA, the strain CHAP-239 stood out, producing over 3.7 mg/L of the auxin, indicating the potential use of this strain in inducing plant growth and seed germination. Therefore, our results highlight different possibilities for biotechnological applications of wild yeasts. These microorganisms can be explored by science in order to develop alternatives to agriculture and promote growth in plant productivity with less impact on the environment.