MFAP9: Characterization of an extracellular thermostable antibacterial peptide from marine fungus with biofilm eradication potential.

An extracellular thermostable antibacterial peptide designated as MFAP9 was purified from marine Aspergillus fumigatus BTMF9 by ammonium sulfate precipitation followed by ion exchange chromatography on a DEAE-sepharose column. The molecular weight of MFAP9 was found to be∼3 kDa in SDS-PAGE gel corresponding a single intensity peak in MALDI-TOF. The distinct peak with a retention time of 32.5 min appeared in high performance liquid chromatography (HPLC), further confirming the purity. Isoelectric focusing, two-dimensional gel electrophoresis and peptide mass fingerprinting were performed for the characterization of MFAP9. Functional analysis of purified MFAP9 exhibited strong antibacterial activity against Bacillus circulans (NCIM 2107) with MIC and MBC values of 0.525 μg/mL and 4.2 μg/mL, respectively. The in vitro antibiofilm effect of MFAP9 was analyzed against bacteria which have strong biofilm forming potential. The antibiofilm effect of MFAP9 treatment on Bacillus pumilus was examined using scanning electron microscopy. MFAP9 was found to be active at high temperatures and a wide range of pH (28). In addition, it showed varied sensitivity towards proteolytic enzymes. The peptide was nontoxic to human RBCs at higher concentrations. These results indicate that MFAP9 is an antibacterial peptide, suitable for the development of novel anti-infective agent with strong antibiofilm potential.