Bacterial metabolism has been studied primarily in liquid cultures, and exploration of other natural growth conditions may reveal new aspects of bacterial biology. Here, we investigate metabolic changes occurring when Escherichia coli grows as surface-attached biofilms, a common but still poorly characterized bacterial lifestyle. We show that E . coli adapts to hypoxic conditions prevailing within biofilms by reducing the amino acid threonine into 1-propanol, an important industrial commodity not known to be naturally produced by Enterobacteriaceae . We demonstrate that threonine degradation corresponds to a fermentation process maintaining cellular redox balance, which confers a strong fitness advantage during anaerobic and biofilm growth but not in aerobic conditions. Whereas our study identifies a fermentation pathway known in Clostridia but previously undocumented in Enterobacteriaceae , it also provides novel insight into how growth in anaerobic biofilm microenvironments can trigger adaptive metabolic pathways edging out competition with in mixed bacterial communities. Author summary Whereas Escherichia coli does not naturally produce the 1-propanol unless subjected to extensive genetic modifications, we show that this important industrial commodity is produced in hypoxic conditions inside biofilms. 1-propanol production corresponds to a native threonine fermentation pathway previously undocumented in E . coli and other Enterobacteriaceae . This widespread adaptive response contributes to maintain cellular redox balance and bacterial fitness in biofilms and other amino acid-rich hypoxic environments. This study therefore shows that mining complex lifestyles such as biofilm microenvironments provides new insight into the extent of bacterial metabolic potential and adaptive bacterial physiological responses.
【초록키워드】 adaptive, metabolism, pathway, Degradation, change, Bacterial, Amino acid, cellular, metabolic pathways, Trigger, Escherichia coli, balance, 1-propanol, threonine, Enterobacteriaceae, metabolic pathway, growth, complex, hypoxic conditions, exploration, competition, Clostridia, liquid cultures, propanol, microenvironment, Genetic modifications, widespread, aerobic, physiological responses, hypoxic, bacterial communities, produced, identify, characterized, provide, condition, contribute, reducing, maintain, conditions, E . coli, hypoxic condition, 【제목키워드】 adaptive, biofilm, pathway, amino-acid, microenvironment, widespread, induce,