Synthesis, Microbiology, and Biophysical Characterization of Mutanofactins from the Human Oral Microbiome

Mutanofactins are a family of natural products produced by Streptococcus mutans from the human oral microbiome. We report a unified approach to all mutanofactins by developing a total synthesis amenable to diversification. The key to success for the most complex members, mutanofactins 607 and 697, was an acyl ketene based strategy. Access to the family enabled comprehensive biological profiling, where we demonstrate that all mutanofactins are biofilm promoting in Streptococcus mutans. Experiments were extended to other inhabitants of the oral microbiome for the first time: Streptococcus gordonii and Streptococcus oralis, two early colonizers, were similarly affected with mutanofactins being biofilm promoting. Conversely, Veillonella dispar and Fusobacterium nucleatum showed little to no reaction to mutanofactins. Biophysical investigations based on quartz crystal microbalance with dissipation monitoring and atomic force microscopy reveal a previously unknown mucin-mutanofactin 697 interaction. Incubation of a mucin layer with mutanofactin 697 induces a morphology change within the mucin layer, which promotes bacterial adhesion and biofilm formation. This unique property of mutanofactin 697 might be key to early stages of biofilm formation in the human oral microbiome. Combined, an interdisciplinary approach consisting of total synthesis, microbiology and biophysical characterization provides insight into the roles of mutanofactins in the oral microbiome.