Limits...
Intracellular vesicles as reproduction elements in cell wall-deficient L-form bacteria.

Briers Y, Staubli T, Schmid MC, Wagner M, Schuppler M, Loessner MJ - PLoS ONE (2012)

Bottom Line: Premature depolarization of the surrounding membrane promotes activation of daughter cell metabolism prior to release.Based on genome resequencing of L-forms and comparison to the parental strain, we found no evidence for predisposing mutations that might be required for L-form transition.Further investigations revealed that propagation by intracellular budding not only occurs in Listeria species, but also in L-form cells generated from different Enterococcus species.

View Article: PubMed Central - PubMed

Affiliation: Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.

ABSTRACT
Cell wall-deficient bacteria, or L-forms, represent an extreme example of bacterial plasticity. Stable L-forms can multiply and propagate indefinitely in the absence of a cell wall. Data presented here are consistent with the model that intracellular vesicles in Listeria monocytogenes L-form cells represent the actual viable reproductive elements. First, small intracellular vesicles are formed along the mother cell cytoplasmic membrane, originating from local phospholipid accumulation. During growth, daughter vesicles incorporate a small volume of the cellular cytoplasm, and accumulate within volume-expanding mother cells. Confocal Raman microspectroscopy demonstrated the presence of nucleic acids and proteins in all intracellular vesicles, but only a fraction of which reveals metabolic activity. Following collapse of the mother cell and release of the daughter vesicles, they can establish their own membrane potential required for respiratory and metabolic processes. Premature depolarization of the surrounding membrane promotes activation of daughter cell metabolism prior to release. Based on genome resequencing of L-forms and comparison to the parental strain, we found no evidence for predisposing mutations that might be required for L-form transition. Further investigations revealed that propagation by intracellular budding not only occurs in Listeria species, but also in L-form cells generated from different Enterococcus species. From a more general viewpoint, this type of multiplication mechanism seems reminiscent of the physicochemical self-reproducing properties of abiotic lipid vesicles used to study the primordial reproduction pathways of putative prokaryotic precursor cells.

Show MeSH

Related in: MedlinePlus

Membrane disruption triggers release and activation of daughter cells.Panel A: Brief exposure of large, vesiculated L-form cells to nisin induces membrane permeability. The subsequent occurrence of green fluorescent signals from intracellular vesicles indicates preliminary activation of daughter cells. Panels B, C: Nisin also promotes disintegration of mother cell membranes, followed by release of the vesicles (compare Movie S1).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368840&req=5

pone-0038514-g006: Membrane disruption triggers release and activation of daughter cells.Panel A: Brief exposure of large, vesiculated L-form cells to nisin induces membrane permeability. The subsequent occurrence of green fluorescent signals from intracellular vesicles indicates preliminary activation of daughter cells. Panels B, C: Nisin also promotes disintegration of mother cell membranes, followed by release of the vesicles (compare Movie S1).

Mentions: An explanation for the fact that most of the daughter cells remain silent until their release is that creation of charge and polarity across the daughter cell membrane is counteracted as long as the surrounding mother cell maintains its own respiratory activity and membrane potential. However, a fraction of the internal vesicles can overcome this barrier and show activity while still being enclosed within the maternal cytoplasm and charged membrane. We tested this hypothesis using the pore-forming lantibiotic nisin to trigger depolarization and subsequent destruction of the maternal cytoplasmic membrane. Nisin is a small (34 aa) peptide which binds to lipid II molecules [14], abundant in L-form membranes [8]. It inserts into the membranes, oligomerizes, and forms pores, resulting in an unspecific efflux of ions and small molecules including ATP [15]. Pulse-challenge of L-form mother cells using low nisin concentrations (185 nM) strongly increased the frequency of green fluorescent intracellular vesicles, indicating a role of membrane charge for viability of daughter vesicles (Figure 6A). Simultaneously, nisin exposure also triggered collapse of large mother cells and release of progeny vesicles, at a much higher rate than in the absence of nisin (Figure 6B-C, Movie S1). These findings indicate that charged mother cell membranes directly influence respiratory processes of the intracellular progeny, i.e., the energized membrane of the mother cells prevent establishment of charge and polarity among the internal vesicle membranes.


Intracellular vesicles as reproduction elements in cell wall-deficient L-form bacteria.

Briers Y, Staubli T, Schmid MC, Wagner M, Schuppler M, Loessner MJ - PLoS ONE (2012)

Membrane disruption triggers release and activation of daughter cells.Panel A: Brief exposure of large, vesiculated L-form cells to nisin induces membrane permeability. The subsequent occurrence of green fluorescent signals from intracellular vesicles indicates preliminary activation of daughter cells. Panels B, C: Nisin also promotes disintegration of mother cell membranes, followed by release of the vesicles (compare Movie S1).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368840&req=5

pone-0038514-g006: Membrane disruption triggers release and activation of daughter cells.Panel A: Brief exposure of large, vesiculated L-form cells to nisin induces membrane permeability. The subsequent occurrence of green fluorescent signals from intracellular vesicles indicates preliminary activation of daughter cells. Panels B, C: Nisin also promotes disintegration of mother cell membranes, followed by release of the vesicles (compare Movie S1).
Mentions: An explanation for the fact that most of the daughter cells remain silent until their release is that creation of charge and polarity across the daughter cell membrane is counteracted as long as the surrounding mother cell maintains its own respiratory activity and membrane potential. However, a fraction of the internal vesicles can overcome this barrier and show activity while still being enclosed within the maternal cytoplasm and charged membrane. We tested this hypothesis using the pore-forming lantibiotic nisin to trigger depolarization and subsequent destruction of the maternal cytoplasmic membrane. Nisin is a small (34 aa) peptide which binds to lipid II molecules [14], abundant in L-form membranes [8]. It inserts into the membranes, oligomerizes, and forms pores, resulting in an unspecific efflux of ions and small molecules including ATP [15]. Pulse-challenge of L-form mother cells using low nisin concentrations (185 nM) strongly increased the frequency of green fluorescent intracellular vesicles, indicating a role of membrane charge for viability of daughter vesicles (Figure 6A). Simultaneously, nisin exposure also triggered collapse of large mother cells and release of progeny vesicles, at a much higher rate than in the absence of nisin (Figure 6B-C, Movie S1). These findings indicate that charged mother cell membranes directly influence respiratory processes of the intracellular progeny, i.e., the energized membrane of the mother cells prevent establishment of charge and polarity among the internal vesicle membranes.

Bottom Line: Premature depolarization of the surrounding membrane promotes activation of daughter cell metabolism prior to release.Based on genome resequencing of L-forms and comparison to the parental strain, we found no evidence for predisposing mutations that might be required for L-form transition.Further investigations revealed that propagation by intracellular budding not only occurs in Listeria species, but also in L-form cells generated from different Enterococcus species.

View Article: PubMed Central - PubMed

Affiliation: Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.

ABSTRACT
Cell wall-deficient bacteria, or L-forms, represent an extreme example of bacterial plasticity. Stable L-forms can multiply and propagate indefinitely in the absence of a cell wall. Data presented here are consistent with the model that intracellular vesicles in Listeria monocytogenes L-form cells represent the actual viable reproductive elements. First, small intracellular vesicles are formed along the mother cell cytoplasmic membrane, originating from local phospholipid accumulation. During growth, daughter vesicles incorporate a small volume of the cellular cytoplasm, and accumulate within volume-expanding mother cells. Confocal Raman microspectroscopy demonstrated the presence of nucleic acids and proteins in all intracellular vesicles, but only a fraction of which reveals metabolic activity. Following collapse of the mother cell and release of the daughter vesicles, they can establish their own membrane potential required for respiratory and metabolic processes. Premature depolarization of the surrounding membrane promotes activation of daughter cell metabolism prior to release. Based on genome resequencing of L-forms and comparison to the parental strain, we found no evidence for predisposing mutations that might be required for L-form transition. Further investigations revealed that propagation by intracellular budding not only occurs in Listeria species, but also in L-form cells generated from different Enterococcus species. From a more general viewpoint, this type of multiplication mechanism seems reminiscent of the physicochemical self-reproducing properties of abiotic lipid vesicles used to study the primordial reproduction pathways of putative prokaryotic precursor cells.

Show MeSH
Related in: MedlinePlus