Mechanistic Origin of Cell-size Control and Homeostasis in Bacteria

Abstract

Multicomponent efflux complexes remove antibiotics and other toxins from Gram-negative bacteria and thereby contribute to antibiotic resistance. Multicomponent efflux complexes can shift dynamically between an assembled functional state and a disassembled non-functional state. We have previously shown that mechanical stress promotes disassembly of CusCBA, an RND family efflux complex that is responsible for removing toxic Cu þ and Ag þ from Escherichia coli. It is unclear if mechanical stress also influences other efflux complexes. Here, we examine the effect of mechanical stress on the disassembly of MacAB-TolC, an efflux complex from the ABC family that contributes to resistance to macrolide antibiotics. Mechanical stress was applied to Escherichia coli using a microfluidic device that uses fluid pressure to force bacteria into narrow tapered channels where they experience mechanical stress and deformation. The assembly of the MacAB-TolC efflux complex was examined by measuring the motion of the inner membrane pump protein MacB (fast moving MacB was not assembled) in more than 600 cells at fluid pressure levels ranging from 0 to 30 kPa. At greater magnitudes of mechanical stress, the proportion of disassembled MacAB-TolC complexes increased (p=1.7*10 À5 ). MacB diffusivity decreased at greater levels of mechanical stress (p=1.9*10 À14 ). Our findings show that mechanical stress not only influences RND family efflux complexes but also ABC family efflux complexes that enable resistance to clinically relevant antibiotics.

Mother machine image analysis with MM3

“…MM3 indeed includes methods for fluorescence analysis, from simple quantification of the fluorescence signal to foci tracking 14 .…”

“…It includes support for phase contrast and fluorescence images, and has been tested with different species (bacteria and yeast), mother machine designs, and optical configurations. We refer potential users to our recent publications for examples of the use of MM3 14,15 .…”

Stochasticity in bacterial division control: Preliminary consequences for protein concentration

“…Current models describing division propose two mechanisms acting independently: the division and the chromosome replication (Si, et al 2019). Some efforts understanding division mechanisms have been done both theoretically (Amir 2014, Ghusinga, Vargas-Garcia and Singh 2016) and experimentally (Taheri-Araghi, et al 2015, Campos, et al 2014).…”

“…In E. coli underlying mechanism seems to be related to the formation of the FtsZ ring which triggers division (Si, et al 2019).…”

Spatio-temporal control of DNA replication by the pneumococcal cell cycle regulator CcrZ

“…Different models emerged from the mid-1900's to explain how bacterial cells handle DNA replication together with cell division in Escherichia coli or Bacillus subtilis [4][5][6][7] . The current cellsize control model suggests that cells initiate DNA replication independently from their original size, and grow to a constant size independently from their size at birth (adder model) [8][9][10][11][12] . How cells sense changes in cell size and convert it to trigger replication initiation is not known, but these models imply the existence of regulatory controls 3,[13][14][15] .…”