Abstract
L-forms are cell wall-deficient bacteria that divide through unusual mechanisms, involving dynamic perturbations of the cellular shape and generation of vesicles, independently of the cell-division protein FtsZ. Here we describe FtsZ-independent mechanisms, involving internal and external vesicles, by which Listeria monocytogenes L-forms proliferate. Using micromanipulation of single cells and vesicles, we show that small vesicles are formed by invagination within larger intracellular vesicles, receive cytoplasmic content, and represent viable progeny. In addition, the L-forms can reproduce by pearling, that is, generation of extracellular vesicles that remain transiently linked to their mother cell via elastic membranous tubes. Using photobleaching and fluorescence recovery, we demonstrate cytoplasmic continuity and transfer through these membranous tubes. Our findings indicate that L-forms' polyploidy and extended interconnectivity through membranous tubes contribute to the generation of viable progeny independently of dedicated division machinery, and further support L-forms as models for studies of potential multiplication mechanisms of hypothetical primitive cells.
Highlights
L-forms are cell wall-deficient bacteria that divide through unusual mechanisms, involving dynamic perturbations of the cellular shape and generation of vesicles, independently of the cell-division protein FtsZ
We employed a stable L-form derivative of L. monocytogenes strain EGDe able to grow in various media, including liquid culture, soft agar and agar plates[17]
L-forms grown in liquid culture were transferred into multi-well glass bottom dishes, carefully centrifuged and spun onto the glass layer, and overlaid with Listeria L-form medium (LLM) soft agar to minimize passive motility, that is, Brownian motion of the cells
Summary
L-forms are cell wall-deficient bacteria that divide through unusual mechanisms, involving dynamic perturbations of the cellular shape and generation of vesicles, independently of the cell-division protein FtsZ. Our findings indicate that L-forms’ polyploidy and extended interconnectivity through membranous tubes contribute to the generation of viable progeny independently of dedicated division machinery, and further support L-forms as models for studies of potential multiplication mechanisms of hypothetical primitive cells. Formed L-forms in liquid culture remain transiently linked to each other, via filament-like tubular strands of lipid material These strands show a high degree of mechanical flexibility and stability, mediate cytoplasmic continuity and allow transfer of cytoplasmic material between cells. The highly polyploid nature of L-forms, and the transfer of essential molecules through membranous tubes, contribute to the generation of viable progeny in the absence of dedicated division machinery
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