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

• Published in: FEMS microbiology letters 2021-11, Vol.368 (21-24), p.1
• Main Authors: Roberts, David M, Errington, Jeff, Kawai, Yoshikazu
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antibiotics; Bacteria; Bacterial Outer Membrane - drug effects; Bacterial Outer Membrane - metabolism; Cell Proliferation - physiology; Cell Wall - drug effects; Cell Wall - metabolism; Chemical properties; Cytoplasm - metabolism; Dosage and administration; L Forms - physiology; Mechanical properties; Microbiological research; Physiological aspects; Plant cell walls; Research Letter; Streptobacillus - drug effects; Streptobacillus - growth & development
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1093/femsle/fnab156

ABSTRACT Almost all major classes of bacteria are surrounded by a peptidoglycan cell wall, which is a crucial target for antibiotics. It is now understood that many bacteria can tolerate loss of the cell wall provided that they are in an isotonic environment. Furthermore, in some cases the cells can continue to proliferate in a state known as the L-form. L-form proliferation occurs by an unusual blebbing or tubulation mechanism that is completely independent of the normally essential division machine or cell wall synthetic enzymes, and is resistant to cell wall-active antibiotics. However, the growth is limited by reactive oxygen species generated by the respiratory chain pathway. In this work, we examined the walled to L-form transition in a pathogenic Gram-negative bacterium, Streptobacillus moniliformis, which naturally lacks the respiratory chain pathway, under aerobic conditions. L-form-like cells often emerged spontaneously, but proliferation was not observed unless the cells were treated with cell wall-active antibiotics. Time-lapse imaging revealed that cell division of S. moniliformis L-forms involves unusual membrane dynamics with an apparent imbalance between outer membrane and cytoplasmic volume growth. The results suggest that outer membrane expansion may be an important general factor for L-form proliferation of diderm bacteria. This work investigates general factors involved in a process of the walled to L-form switching using a Gram-negative bacterium, Streptobacillus moniliformis, which was the first organism in which the L-form state was reported.