A Bacterial Microcompartment Is Used for Choline Fermentation by Escherichia coli 536

Bacterial choline degradation in the human gut has been associated with cancer and heart disease. In addition, recent studies found that a bacterial microcompartment is involved in choline utilization byProteus andDesulfovibrio species. However, many aspects of this process have not been fully defined. Here, we investigate choline degradation by the uropathogenEscherichia coli 536. Growth studies indicatedE. coli 536 degrades choline primarily by fermentation. Electron microscopy indicated that a bacterial microcompartment was used for this process. Bioinformatic analyses suggested that the choline utilization (cut ) gene cluster ofE. coli 536 includes two operons, one containing three genes and a main operon of 13 genes. Regulatory studies indicate that thecutX gene encodes a positive transcriptional regulator required for induction of the maincut operon in response to choline supplementation. Each of the 16 genes in thecut cluster was individually deleted, and phenotypes were examined. ThecutX ,cutY ,cutF ,cutO ,cutC ,cutD ,cutU , andcutV genes were required for choline degradation, but the remaining genes of thecut cluster were not essential under the conditions used. The reasons for these varied phenotypes are discussed.IMPORTANCE Here, we investigate choline degradation inE. coli 536. These studies provide a basis for understanding a new type of bacterial microcompartment and may provide deeper insight into the link between choline degradation in the human gut and cancer and heart disease. These are also the first studies of choline degradation inE. coli 536, an organism for which sophisticated genetic analysis methods are available. In addition, thecut gene cluster ofE. coli 536 is located in pathogenicity island II (PAI-II536 ) and hence might contribute to pathogenesis.