The R1 Conjugative Plasmid Increases Escherichia coli Biofilm Formation Through Envelope Stress Response

Artie McFerrin Department of Chemical Engineering, the Department of Biology, and the Zachry Department of Civil Engineering

^* To whom correspondence should be addressed. Email: Thomas.Wood{at}chemail.tamu.edu.

	Abstract

Differential gene expression in biofilm cells suggests that adding the derepressed conjugative plasmid R1drd19 increases biofilm formation by affecting envelope stress (rseA, cpxAR), biofilm-related genes (bssR, cstA), energy production (glpDFK), acid resistance (gadABCEX, hdeABD), cell motility (csgBEFG, yehCD, yadC, yfcV), outer membrane proteins (ompACF), phage shock proteins (pspABCDE), cold shock proteins (cspACDEG), and phage-related genes. To investigate the link between the identified genes and biofilm formation upon adding R1drd19, 40 isogenic mutants were classified according to their different biofilm formation phenotypes. Cells with Class I mutations (rseA, bssR, cpxA, and ompA) exhibited no difference in biofilm formation compared to the wild-type strain and no increase upon adding R1drd19. Class II mutations (gatC, yagI, ompC, cspA, pspD, pspB, ymgB, gadC, pspC, ymgA, slp, cpxP, cpxR, cstA, rseC, ompF, and yqjD) increased biofilm formation compared to the wild-type strain but decreased biofilm formation upon adding R1drd19. Class III mutations increased biofilm formation compared to the wild-type strain and increased biofilm upon adding R1drd19. Class IV mutations increased biofilm formation compared to the wild-type strain but had little difference upon adding R1drd19, and Class V mutations had no difference compared to the wild-type strain but increased biofilm formation upon adding R1drd19. Therefore, proteins encoded by the genes of Class I are involved in R1drd19-promoted biofilm formation, primarily through their impact on cell motility. We hypothesize that the pili formed upon adding the conjugative plasmid disrupt the membrane (induce ompA) and activate the two-component system CpxAR as well as the other envelope stress response system, RseA-^E, both of which, along with BssR, play a key role in bacterial biofilm formation.