<em>Aspergillus</em>: interactions among biofilms, oxygen, antifungal drugs, and melanin

Abstract

Pathogenesis often involves the formation of biofilms and adaptation to low oxygen environments to survive in the human body. <em>Aspergillus</em> fungi are opportunistic pathogens that can form biofilms and adapt to microenvironments that vary in oxygen. However, interactions between biofilms and low oxygen environments are not well understood, The first chapter, we studied biofilm formation <em>in vitro</em> by <em>A. fumigatus</em>, <em>A. niger, A. flavus</em>, and<em> A. terreus</em> in microaerophilic conditions. All species formed biofilms in microaerophilic conditions. In the second chapter, we compared biofilm formation vs. planktonic cells of <em>Aspergillus spp</em>. in microaerophilic vs. aerobic conditions and compared resistance to Amphotericin B in different conditions. <em>A. flavus</em> was more resistant to AMB than <em>A. fumigatus</em> in microaerophilic conditions. In the third chapter, we studied the roles of melanin in biofilm formation and virulence. We evaluate biofilms formation in microaerophilic vs. aerobic conditions in <em>A. fumigatus</em> mutants deficient in pyomelanin (<em>hppd</em>) and DHN-melanin (<em>alb1</em>). Melanin was not crucial for biofilm formation. The <em>alb1</em> mutants showed increased metabolic activity in a microaerophilic environment. Also, the <em>alb1</em>-mutant was more virulent in<em> Drosophila melanogaster</em> than several wild type strains of <em>A. fumigatus</em>. These data support why aspergillosis infections are challenging to eradicate.