DISTINCT RESPONSES TO DIFFERENT MANNERS OF CELL WALL SYNTHESIS DISRUPTION IN ESCHERICHIA COLI

Abstract

Cell shape is a defining and important feature of many bacteria, and one that is regulated by explicit mechanisms that are just now being understood. The cell wall is known to play a significant role in the maintenance of cell shape. In this study we examine the manner in which cell wall synthesis is controlled in the rod-shaped bacteria Escherichia coli both at the transcriptional level and in terms of a macroscopic phenotype. Using a library of E. coli strains with 1,830 unique E. coli promoters fused to GFP, we assay for promoters that were significantly repressed or induced by one or more of three antibiotics—fosfomycin, mecillinam, and A22—all of which disrupt cell wall synthesis in different ways. We find that in minimal media, 314 promoters are significantly induced and 205 are repressed by one of more of the three antibiotics. Hierarchical clustering of these promoters revealed substantial differences between the pattern of promoter induction and repression caused by A22 and those caused by fosfomycin or mecillinam. Ontological analysis of the promoters induced and repressed by each antibiotic yielded genes of interest; among these were spr, one of two genes induced by all three antibiotics, as well as oppA, secE, tolB, and tatE. Additionally, we observed that unlike in minimal media or in LB with mecillinam, cultures grown in LB with fosfomycin undergo cell death, though they can be rescued by the addition of glucose. We find that disruptions of cell wall synthesis induce transcriptional responses that are different for different manners of disruption. Furthermore, cells with differently disrupted cell wall synthesis display distinct sensitivities to extracellular conditions, suggesting that there are significant dissimilarities in the biology of cells that have been disrupted differently.