Antimicrobial screening of tropical microfungi isolated from sinkholes located in the Yucatan peninsula, Mexico

Fungal explorations of two freshwater sinkholes led to isolate 96 strains which were identified to species or genus level (54%). All isolates were cultured on fermented rice, and their respective ethyl acetate extracts that were tested against Alternaria tagetica, Bacillus subtilis, Candida albicans, Colletotrichum gloeosporioides, Erwinia carotovora, Fusarium oxysporum, Staphylococcus aureus, and Xanthomonas campestris. Antimicrobial effect was displayed by 78 fungal extracts against at least one target strain and a broad activity spectrum that was detected in 53% of them. A total of 19 extracts showed the greatest diameter of inhibition halo (> 15 mm) against bacteria and target yeast. In this way, the extracts yielded by isolates Acremonium pseudozeylanicum, Gliocladium penicilloides, Gliocladium sp. TH16, Penicillium citrinum and six unidentifed isolates (TA11, TA13, TA41, 2TA2, 2TA7, 2TS4, 2XA7) displayed significant activity against target bacteria and yeast target (MIC = 50 to 200 mu g/ml). Promissory antifungal action was presented by Beltrania rhombica, Fusarium sp. XH1Ga, and six unidentified strains (TA53, TH34, 2TA2, 2TA6, 2TS6, 2XA7). This is the first report on the isolation and biological evaluation of microfungi isolated from sinkholes. The results obtained suggest that the mycobiota of this unique habitat could be a promising biotechnology resource.