## 4 Discussion  
Following the 2010 Deepwater Horizon oil spill, fungal strains from oil-soaked sand patties collected from beaches [41] and bacteria from oiled beach sands at Pensacola Beach, FL, USA [42], both sites located in the American EEZ, were identified as potential bioremediation microorganisms. Fungi synthesize a battery of enzymes, including lacases, peroxididases, lytic polysaccharide monooxygenases, and monooxygenase cytochrome P450 that degrade different and complex substrates, including PAHs [43; 44]. In addition, isolates from extreme environments have been proven to produce extracellular extremophilic ligninolytic enzymes, which can perform catalytic activities under adverse environments without being denatured [45]. These metabolic capacities and rapid mycelial propagation pose fungi as attractive prospects for bioremediation applications [46]. Notably, marine-derived fungi have been recognized as promising bioremediation agents due to their metabolic adaptations to naturally occurring oil sources [47; 48]. Yet, they have been scarcely studied for their ability to use recalcitrant elements of HCO and EHCO. In this study, we showed the ability of _Alternaria_ sp., _Penicillium_ spp., and _Stemplybium_ sp., isolates recovered from deep-sea sediments of the Mexican EEZ of the Gulf of Mexico to grow using HCO and, most importantly, the ability of _Alternaria_ sp. to grow using EHCO as sole carbon source. Unfortunately, given the nature of the EHCO and the strong attachment of _Alternaria_ sp. mycelium to the EHCO in the glass rod, the quantification of the biomass was not successfully attained. However, at the visible level, one could observe the mycelium of _Alternaria_ sp. only in the cultures supplemented with EHCO (Figure S3). We concluded that the toluene added for protein quantification to get an indirect measurement of the fungal biomass probably interfered with the complete recovery of the mycelium, and the protein content obtained was not an accurate estimate of the actual amount of protein. Although the fungal taxa identified in this study have been previously reported as light and medium crude oil degraders, there are no previous reports of HCO or EHCO degradation by any of them. _Penicillium_ spp. isolated from diverse polluted environments have been extensively reported as capable of removing a wide array of contaminants, including heavy metals and petroleum hydrocarbons [49; 50]. _Penicillium_ spp. can efficiently degrade polycyclic aromatic hydrocarbons such as fluorene [51], pyrene [52], and phenanthrene [53]. The _Stemplybium_ sp. has been isolated from petroleum-contaminated soils in Iran [54] and from a Mediterranean marine site after an oil spill, where _C. halotolerans_ was recovered as well [55]. _P. corylophilum_ was isolated from ship-breaking yards of Bangladesh and was able to degrade petroleum hydrocarbon [56]. _Alternaria_ spp. have been isolated from terrestrial contaminated zones with evidence of PAH degradation [57], from tar balls with a very limited ability to degrade crude oil [49], and from noncontaminated gardens showing the ability to degrade octane and decane [58]. _A. alternata_ has the capacity to synthesize enzymes related to hydrocarbon degradation, such as manganese peroxidase and lignin peroxidase [59; 60]. There is a comparative analysis of the secretome profile of Manganese (II)-Oxidizing [61], as well as a report of lignin peroxidase production [62], and this sets a precedent for the potential degradation capacity of _Alternaria_ sp. Heavy crude oils contain a high proportion of high molecular weight hydrocarbons and elevated levels of hetero compounds, including sulfur, nitrogen, oxygen, and heavy metals [63]. The typical SARA composition of heavy oils is 4-23% saturates, 14-32% aromatics, 27-46% resins, and 15-43% asphaltenes [64]. The high concentration of resins and asphaltenes, together with the high concentration of high molecular weight PAHs in EHCO, poses a challenge for biodegradation and bioremediation processes.