Listeria monocytogenes L-forms respond to cell wall deficiency by modifying gene expression and the mode of division.
Cell wall-deficient bacteria referred to as L-forms have lost the ability to maintain or build a rigid peptidoglycan envelope. We have generated stable, non-reverting L-form variants of the Gram-positive pathogen Listeria monocytogenes, and studied the cellular and molecular changes associated with this transition. Stable L-form cells can occur as small protoplast-like vesicles and as multinucleated, large bodies. They have lost the thick, multilayered murein sacculus and are surrounded by a cytoplasmic membrane only, although peptidoglycan precursors are still produced. While they lack murein-associated molecules including Internalin A, membrane-anchored proteins such as Internalin B are retained. Surprisingly, L-forms were found to be able to divide and propagate indefinitely without a wall. Time-lapse microscopy of fluorescently labelled L-forms indicated a switch to a novel form of cell division, where genome-containing membrane vesicles are first formed within enlarged L-forms, and subsequently released by collapse of the mother cell. Array-based transcriptomics of parent and L-form cells revealed manifold differences in expression of genes associated with morphological and physiological functions. The L-forms feature downregulated metabolic functions correlating with the dramatic shift in surface to volume ratio, whereas upregulation of stress genes reflects the difficulties in adapting to this unusual, cell wall-deficient lifestyle.
Dell'Era
Simone
S
Institute of Food Science and Nutrition, ETH Zurich, CH-8092 Zurich, Switzerland.
Buchrieser
Carmen
C
Couvé
Elisabeth
E
Schnell
Barbara
B
Briers
Yves
Y
Schuppler
Markus
M
Loessner
Martin J
MJ
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000648:ultrastructure*; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D007740:L Forms / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D008089:Listeria monocytogenes / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D046529:Microscopy, Electron, Transmission; D020411:Oligonucleotide Array Sequence Analysis; D012329:RNA, Bacterial / Q000235:genetics; D017422:Sequence Analysis, DNA
D001425:Bacterial Outer Membrane Proteins; D012329:RNA, Bacterial