The analysis of cell division and cell wall synthesis genes reveals mutationally inactivatedftsQandmraYin a protoplast-type L-form ofEscherichia coli

Abstract

Cell division and cell wall synthesis are tightly linked cellular processes for bacterial growth. A protoplast-type L-form Escherichia coli, strain LW1655F+, indicated that bacteria can divide without assembling a cell wall. However, the molecular basis of its phenotype remained unknown. To establish a first phenotype-genotype correlation, we analyzed its dcw locus, and other genes involved in division of E. coli. The analysis revealed defective ftsQ and mraY genes, truncated by a nonsense and a frame-shift mutation, respectively. Missense mutations were determined in the ftsA and ftsW products yielding amino-acid replacements at conserved positions. FtsQ and MraY, obviously nonfunctional in the L-form, are essential for cell division and cell wall synthesis, respectively, in all bacteria with a peptidoglycan-based cell wall. LW1655F+ is able to survive their loss-of-functions. This points to compensatory mechanisms for cell division in the absence of murein sacculus formation. Hence, this L-form represents an interesting model to investigate the plasticity of cell division in E. coli, and to demonstrate how concepts fundamental for bacterial life can be bypassed.

The membrane: transertion as an organizing principle in membrane heterogeneity

“…In bacterial L-forms, which lack a cell wall, it might be supposed that the requirement for many of the dcw genes would be reduced and less transertion would occur. This would be consistent with the findings that, in L-forms of E. coli , some of the genes were mutated (Siddiqui et al, 2006) and the levels of FtsZ were fivefold lower (Onoda et al, 2000) whilst in an L-form of B. subtilis FtsZ could be eliminated altogether (Leaver et al, 2009). …”

Glycerol Uptake Is Important for L-Form Formation and Persistence in Staphylococcus aureus

“…Despite numerous studies, little is known about the mechanisms of L-form formation. Previous studies have mainly identified mutations in genes involved in cell wall synthesis or cell division in stable L-form bacteria being important for L-form formation [6], [9], [10], [11]. Using E. coli unstable L-form bacteria as a model, we recently systematically examined the molecular basis of L-form formation by microarray analysis and mutant screens and identified a network of genes and pathways involved in L-form formation or survival [7].…”

Proliferation of Listeria monocytogenes L-form cells by formation of internal and external vesicles

“…The L -forms may assume a transient state (that is, reversion to the walled form is possible), or a stable state, in which they can be cultivated in absence of the inducing agent (without reversion). Several mutations were reported to support L -form conversion345, and it was also shown that deleterious mutations may accumulate during the L -form state, possibly preventing subsequent regeneration of a mature cell wall6.…”