Efeito de indutores abióticos no volatiloma de Penicillium citrinum coletado em solo de manguezal

Abstract

Microorganisms play an essential role in the dynamics of ecosystems, including through the emission of volatile organic compounds (VOCs) molecules of low molecular weight, low water solubility, and high vapor pressure, often associated with distinct odors. These compounds function as chemical mediators between microorganisms and the environment. Among the main producers of VOCs are filamentous fungi, such as those of the Penicillium genus, found in diverse habitats like soils, decomposing organic matter, and humid environments. The VOCs synthesized by these organisms comprise a broad spectrum of molecules belonging to different chemical classes, such as alcohols, fatty acids, aldehydes, terpenes, and aromatic compounds. The production of these metabolites can be modulated by changes in environmental conditions or culture medium. Among the abiotic factors that directly affect microbial metabolism, metal ions and light intensity are prominent. Redox-active metals, such as Fe, Mn, and Co, act as cofactors in enzymes of biosynthetic pathways. Light, especially UV-A radiation, influences processes such as germination, growth, and fungal sporulation, triggering significant metabolic alterations. In this context, the present study aimed to investigate, through gas chromatography-mass spectrometry (GC-MS), molecular networking tools, and statistical analyses, the alterations in the volatilome of the fungus Penicillium citrinum, isolated from mangrove soil in Maranhão, under stress induced by high concentrations of Mn²⁺ and Co²⁺ ions, as well as by different intensities of UV-A radiation. The cultures were grown in 2 L round-bottom flasks using a liquid medium composed of glucose, yeast extract, mineral salts, and FeSO₄·4H₂O. For the solid medium, hydrated parboiled rice was used. Sterilization was performed by autoclaving (15 min at 120°C and 1 atm). Metal induction consisted of replacing Fe²⁺ with 19.8 g/L of MnCl₂·4H₂O and 2.38 g/L of CoCl₂·6H₂O in the liquid medium, and by adding 7.13 g/L of MnCl₂·4H₂O and 0.86 g/L of CoCl₂·6H₂O to the solid medium. The UV-A experiment was conducted only in liquid medium under two regimes: a 12/12 h photoperiod and continuous exposure. All cultures had a duration of 14 days. The extraction of VOCs was performed by hydrodistillation with diethyl ether, using a modified Clevenger apparatus under reflux for 2 hours. After extraction, the hydrosol was discarded, and the organic fraction containing the volatile compounds was collected for analysis. The results showed that the abiotic stresses induced significant alterations in the metabolic pathways of the P. citrinum strain, with emphasis on enzymes such as lipoxygenases, sesquiterpene synthases, and O-methyltransferases. There were significant changes in the production of several volatile metabolites.