Growth of cell wall-defective variants of Escherichia coli: comparison of aerobic and anaerobic induction frequencies

Abstract

A method for quantitating the conversion of Escherichia coli to colony-forming, cell wall-defective (CWD) bacteria has been developed. The induction frequency, i.e., the percentage of the population recovered as CWD colonies was determined for 20 randomly selected clinical isolates of E. coli under aerobic and anaerobic incubation conditions. Penicillin (1,000 U/ML) was the inducing agent. The 20 strains segregated into three groups. Group I organisms produced CWD colonies with high frequency both aerobically and anaerobically. Grout II organisms showed a much higher induction frequency anaerobically than aerobically. Group III organisms were poor inducers. Thirty percent of the strains were group I, 50% were group II, and 20% were group III organisms. These data indicate that anaerobic conditions enhance the induction and growth of CWD E. coli in the research laboratory and suggest that anaerobic incubation may be important in recovery of medically significant CWD bacteria.

Characterization of the L-form switch in the Gram-negative pathogen Streptobacillus moniliformis

“… 2015 , 2019 ). Thus, reduction of RC activity or depletion of oxygen can promote robust L-form growth (Dienes and Weinberger 1951 ; Huber and Brinkley 1977 ; Kawai et al . 2015 , 2019 ; Chikada et al .…”

“…Instead, it seems to involve a simple biophysical effect based on an increased rate of cell surface growth relative to volume, driving cell shape deformations that lead to spontaneous scission (Mercier, Kawai and Errington 2013 ). However, because reactive oxygen species originating from the respiratory chain (RC) pathway are abnormally increased in cell wall-deficient cells, the reduction of RC activity, high levels of ROS scavengers or depletion of oxygen is normally required to support robust L-form growth in a Gram-positive Bacillus subtilis or a Gram-negative Escherichia coli (Dienes and Weinberger 1951 ; Huber and Brinkley 1977 ; Kawai et al . 2015 , 2019 ; Chikada et al .…”

Cell wall deficiency – an alternate bacterial lifestyle?

“…This could indicate that these strains have alternative mechanisms to cope with oxidative stress and the loss of cell wall can be accommodated by species-specific and strain-specific stress responses. The requirement for protection from oxidative stress is also supported by several older studies on unstable CWD bacteria that showed anaerobic growth conditions supported CWD transition and growth [61, 118, 119]. Therefore, as with stable CWD variants, oxidative stress also affects survival of unstable CWD bacteria.…”

On the mechanisms of lysis triggered by perturbations of bacterial cell wall biosynthesis

“…ROS-dependent cell death in L-forms is also evident in E . coli and Streptobacillus moniliformis 25 , 37 – 39 . These results highlight that dysregulation of cell wall metabolism in the target-proximal triggers toxic consequences from downstream metabolic pathways that contribute to bacterial cell death.…”