High hydrostatic pressure harnesses the biosynthesis of secondary metabolites via the regulation of polyketide synthesis genes of hadal sediment-derived fungi

Abstract

Deep-sea fungi have evolved extreme environmental adaptation and possess huge biosynthetic potential of bioactive compounds. However, not much is known about the biosynthesis and regulation of secondary metabolites of deep-sea fungi under extreme environments. Here, we presented the isolation of 15 individual fungal strains from the sediments of the Mariana Trench, which were identified by internal transcribed spacer (ITS) sequence analysis as belonging to 8 different fungal species. High hydrostatic pressure (HHP) assays were performed to identify the piezo-tolerance of the hadal fungi. Among these fungi, Aspergillus sydowii SYX6 was selected as the representative due to the excellent tolerance of HHP and biosynthetic potential of antimicrobial compounds. Vegetative growth and sporulation of A. sydowii SYX6 were affected by HHP. Natural product analysis with different pressure conditions was also performed. Based on bioactivity-guided fractionation, diorcinol was purified and characterized as the bioactive compound, showing significant antimicrobial and antitumor activity. The core functional gene associated with the biosynthetic gene cluster (BGC) of diorcinol was identified in A. sydowii SYX6, named as AspksD. The expression of AspksD was apparently regulated by the HHP treatment, correlated with the regulation of diorcinol production. Based on the effect of the HHP tested here, high pressure affected the fungal development and metabolite production, as well as the expression level of biosynthetic genes which revealed the adaptive relationship between the metabolic pathway and the high-pressure environment at the molecular level.

Insight into the adaptation mechanisms of high hydrostatic pressure in physiology and metabolism of hadal fungi from the deepest ocean sediment

“…Early studies on culturable filamentous fungi, to our knowledge, were mostly under mild HHP ( 17 , 60 ), and very few of them exceed 30 MPa ( 9 , 18 , 32 ). Considering the truth that conidia and hyphae showed serious growth defects under 60 MPa in our preliminary experiment, a compromised pressure of up to 40 MPa was ultimately employed in our study.…”

“…Besides, we also collected the sediment samples and stored them in sterile plastic bags from the terrestrial area at Luchaogang Beach in Shanghai, China. The method of isolating and culturing fungi was followed as the method described in our previous study ( 18 ). For fungal isolation, 100 µL diluted sediments were spread plated on potato dextrose agar (PDA: 200 g/L potato, 20 g/L dextrose, 28 g/L sodium chloride, and 15 g/L agar; 100 µg/mL ampicillin), and the plates were incubated at 28°C for 3–7 days until fungal mycelium was present.…”

“…have demonstrated good secondary metabolic activity and potential to degrade the xenobiotic compounds under elevated HHP ( 3 , 17 ). Deng et al have reported that HHP regulated the production of fungal secondary metabolites ( 18 ). These studies suggest that deep-sea fungi possess distinctive metabolic pathways and adaptive mechanisms under HHP.…”

Penicillium janthinellum: A Potential Producer of Natural Products

“…Compound 47 exhibited significant antiproliferative activity against U87MG and U251 with IC 50 values of 4.4 and 6.2 µM, respectively [79], and inhibited the growth of K562 at 30 µM [80]. Compound 47 separated from Aspergillus sydowii showed significant cytotoxicity against NCI-H460, HepG2, MCF-7 and MDA-MB-231 with inhibition rates of 90%, 55%, 57%, and 78% at a concentration of 200 µM, respectively, and the results had no statistically significant difference with the positive control, Adriamycin [81]. Compound 47 showed cytotoxicity against mouse splenic cells with a minimum inhibiting concentration of 110 µM [82].…”

“…Compound 47 showed antipathogen activity against a fungus, C. albicans, and six bacteria, Chromobacterium violaceum, S. aureus, Enterococcus faecalis, Salmonella choleraesuis, M. smegmatis and E. coli, with inhibition rates ranging from 45% to 64% at the condition of 10 mg/mL. Then, the MIC values of five sensitive pathogens, namely C. violaceum, C. albican, S. aureus, E. faecalis and S. choleraesuis, were determined to be 12.50, 6.25, 12.50, 6.25 (comparable to the positive control gentamicin) and 25.00 µg/mL [81]. Compound 47 showed weak antibacterial activity against Acidovorax avenae subsp.…”