Caracterização da diversidade morfológica, estrutural e funcional de liquens da Amazônia maranhense

Abstract

Introduction: Lichens are perennial species widely distributed on various substrates, such as rocks, tree trunks, and soil. Their morphology varies depending on the environment, with crusty, squamous, dimorphic, gelatinous, and foliose thalli. In addition to their ecological relevance, they are known as bioindicators of environmental quality and producers of various secondary metabolites. Objective: This study aims to analyze the morphostructural and functional diversity of lichens in municipalities in the Amazon region of Maranhão.Methodology: The research was conducted in the municipalities of Anajatuba and Morros, Maranhão, with collections in areas with varying levels of environmental conservation. Sixty-eight lichen samples were collected, 48 in Morros and 18 in Anajatuba, from different substrates. The samples were properly stored and identified using an integrative taxonomy approach, utilizing morphological and chemical evaluation. A cyanolichen of the genus Leptogium (ANA13) had its metagenome sequenced on the AVITI platform. Sequence quality was assessed with FastQC and Trimmomatic, and read assembly was performed with metaSPAdes, followed by assembly quality analysis. Biosynthetic gene clusters were identified using antiSMASH. Binning was performed using MetaBAT2 and MaxBin2 CONCOCT programs and analyzed using the DAS Tool. Taxonomic analysis was performed with Kaiju and GOTTCHA2. Finally, taxonomic and functional analyses were conducted with MAG01.Results: Taxonomic analysis of the samples revealed significant lichen diversity in the municipalities of Anajatuba and Morros, with a predominance of crustose, foliose, and filamentous forms. In Anajatuba, the genera Cryptothecia, Coenogonium, Leptogium, Phyciella, and Heterodermia stood out, in addition to representatives of the Graphidaceae family. In Morros, an even more diverse lichen community was observed, with the genera Cryptothecia, Coenogonium, Cladonia, Coccocarpia, Lepraria, Leptogium, and Parmotrema, as well as representatives of the families Physciaceae, Parmeliaceae, and Caliciaceae. Metagenomic analysis of sample ANA13 revealed a functionally diverse microbial community, with an abundance of genes related to secondary metabolite biosynthesis, totaling 218 biosynthetic gene clusters, of which 102 were bacterial and 116 were fungal, primarily of the NRPS, T1PKS, and terpene types. Taxonomic analyses of the metagenome confirmed the symbiotic association between Leptogium and Nostoc. Binning allowed the recovery of a nearly complete genome (99.56%) with 3.59% contamination, later identified as belonging to the Nostoc genus, containing 8,649 coding sequences associated with multiple metabolic pathways.Conclusion: The results obtained demonstrate the significant lichen diversity present in the Maranhão Amazon, reinforcing the importance of these environments for biodiversity conservation and their enormous biotechnological potential. This study represents an unprecedented contribution to knowledge of the region's lichens, recording for the first time the occurrence of the genus Leptogium in the state, in addition to the recovery of a genome of symbiotic Nostoc. The metagenomic analysis revealed a rich metabolic diversity, highlighting the relevance of these organisms both for Maranhão and for understanding the microbial diversity of the Brazilian Amazon.