Abstract
Owing to the prominent capabilities of bioconversion and biosynthesis, A. terreus has become attractive in biotechnical and pharmaceutical industry. In this work, an Aspergillus strain with potential antibacterial activities, was isolated from sponge in South China Sea. Based on the morphological and phylogenetic analysis, the strain was identified as A. terreus B12. Via the Illumina MiSeq sequencing platform, the complete genome was obtained, showing a genetic richness of biosynthetic gene clusters (BGCs), which might underpin the metabolic plasticity and adaptive resilience for the strain. Genome mining identified 67 BGCs, among which, 6 gene clusters could allocate to known BGCs (100% identity), corresponding to diverse metabolites like clavaric acid, dihydroisoflavipucine/isoflavipucine, dimethylcoprogen, alternariol, aspterric acid, and pyranonigrin E. Moreover, a range of compounds was isolated from B12 fermentation, e.g., terrein, butyrolactone I, terretonin A&E, acoapetaline B, and epi-aszonalenins A. Of note, acoapetaline B and epi-aszonalenins A, which had been respectively reported in plants and A. novofumigatus but with scarce information, was unexpectedly obtained from this species for the first time. The genomic and metabolic heterogeneity observed in strain B12, should be at least partially attributed to the genetic variability and biochemical diversity of A. terreus, which could be an interesting issue open to future efforts.
Highlights
We present the draft genome of B12, an A. terreus strain with broad antibacterial activities in preliminary screening
Escherichia coli ATCC 25922, Klebsiella aerogenes ATCC 700603, Pseudomonas aeruginosa PA101, methicillin-resistant Staphylococcus aureus (MRSA) USA300, methicillin-resistant Staphylococcus epidermidis (MRSE) ATCC 35984, Micrococcus luteus ACCC11001, and Acinetobacter baumannii ATCC 19606 were utilized as control strains
Antibacterial activities screening A range of pathogenic bacteria were hired to assess the antimicrobial property of B12 (Fig.1)
Summary
Materials and methods conditions of fermentation TheB12 was activated in the PDB liquid medium, and inoculated onto corn medium (corn 100g, MgSO4 0.2g, sea salt 1.5g, malt sugar 2g, sorbitol 2g; yeast extract 0.3g, tryptophane 0.05g, sodium glutamate 1g, K2HPO4 0.05g,water 1L) to culture at 28 °C for 15 days. The fermented products were extracted by methanol (MeOH) followed by decompressing distillation to acquire a crude extract. The crude extract was dissolved in 2 mL MeOH and test for antibacterial activity by the agar diffusion method. Single colonies of indicator bacteria was inoculated into Mueller-Hinton (MH,Solarbio, China) broth and cultured to logarithmic phase. The bacterial inoculum(OD600nn≈0.1 ) was spread onto MH agar (Solarbio, China). Wells measuring 6 mm in diameter were punched onto the surface of the agar using a sterile hole puncher. 30 μL crude extract was added to the wells and incubated for 24 h at 28 °C. The diameters (in mm) of the inhibition zone were recorded to estimate antimicrobial activities, which were expressed by the ratio of the inhibition zone relative to that of the positive control. The bacteriostatic activities were considered strong if the ratio was greater than 1.0, moderate when the scale was between 0.5 and 1, and weak if it was less than 0.5
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