Diversidade e bioprospecção de enzimas, surfactantes e herbicidas de fungos presentes em sedimentos marinhos do Oceano Austral ao longo da Antártica Marítima

Abstract

The diversity of fungal communities present in Antarctic marine sediments is still little known and information about their real richness, ecology and biotechnological potential is scarce. In this sense, this dissertation aimed to identify fungi present in marine sediments of the Southern Ocean through independent (DNA metabarcoding) and culture-dependent (obtaining cultures) techniques, as well as prospecting exoenzymes, biosurfactants and herbicidal metabolites produced by cultivable fungi. The marine sediment samples used were collected from different depths (Walker Bay: 52m, Whalers Bay: 151m and English Strait: 404m) along the Southern Ocean in Maritime Antarctica. For the characterization of non-cultivable fungi, total DNA extraction, amplification and sequencing of the ITS2 ribosomal region were performed from the sediment samples and the assigned taxa after bioinformatic analysis of the sequences obtained in comparison with the UNITE and GenBank curated databases . The cultivable fungi were obtained from the inoculation of sediment samples in the culture media glucose marine agar (MAG), sabouraud agar (SAB), malt extract agar (MEA), dicloran rose bengal agar (DRBC) and dichloran glycerol agar 18 (DG18) and incubated at 15 °C for 60 days. Cultivable fungi were identified using polyphasic taxonomy and screened to determine their ability to produce enzymes, biosurfactants and herbicidal metabolites. For non-cultivable fungi, a total of 193.436 DNA reads were detected in sediments at 52 m (48.112), 151 m (104.704) and 404 m (40.620) depths and identified 133 taxa, 88 detected at 52 m, 32 at 151 m and 59 to 404 m deep. The non-cultivable fungal community was dominated by taxa of the phyla Ascomycota and Basidiomycota, as well as those belonging to the kingdom Straminopila (phylogenetically close to fungi), which in terms of functional ecology were characterized as saprotrophic, pathogenic and symbiotic. The dominant non-cultivable taxa were Thelebolus balaustiformis, Ciliophora sp., Pseudogymnoascus sp., Fungi sp. 1, Agaricomycetes sp. (Fungi) and Chaetoceros sp. 1 (Straminopile). Among the cultivable fungal community, the predominant genera were Meyerozyma, Penicillium, Antarctomyces, Thelebolus, Pseudeurotium and Cladosporium. The dominant cultivable species were Meyerozyma guilliermondii, Penicillium chrysogenum, Penicillium cf. palitans, Pseudeurotium cf. bakeri and Thelebolus balaustiformis. Most cultivable fungi exhibited positive activity for more than one evaluated enzyme, mainly for proteases (63 isolates - 92%), invertases (58 - 85%), cellulases (37 - 54%), lipases (36 - 52%), carrageenans (35 - 51%), agarases (32 - 47%), pectinases (30 - 44%) and esterases (11 - 16%), with emphasis on Penicillium sp. Furthermore, the M. guilliermondii UFMGCB 19667 and 19651 isolates exhibited the best Enzyme Indexes for invertase and protease (3,05 and 2,76, respectively). Four isolates showed significant biosurfactant activity, especially Antarctomyces sp. UFMGCB 19617, with a higher IE24 value (81,38%), compared to the positive control (84,56%) in 1% SDS. All extracts obtained from P. cf. palitans (24) exhibited herbicidal effect against Lactuca sativa (curly lettuce) and Allium schoenoprasum (onion), highlighting the UFMGCB 19623 and 19625 isolates that exhibited phytotoxicity for both targets at a concentration of 1 mg mL-1; the other isolates of this species had selective activity only against A. schoenoprasum seeds at concentrations of 1 to 0,5 mg mL-1. The results found indicate that marine sediments from the Antarctic region are capable of harboring a significant taxonomic group of cultivable and non-cultivable fungi, revealed by cultivation-independent and cultivation-dependent techniques, which may have different ecological roles in Southern Ocean sediments. In addition, taxa of cultivables were able to produce active exoenzymes, biossurfactants and herbicidal metabolites that may represent interesting resources in industrial and agricultural biotechnological applications