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Plasmid genes increase membrane permeability in Escherichia coli
Abstract:
The membrane permeability to o-nitrophenyl beta-D-galactoside is increased in the presence of rifampicin in Escherichia coli cells carrying srnB+ or pnd+ plasmids, but not in the cells carrying srnB- or pnd- mutant plasmids. The same permeability alteration was also observed at 42 degrees C when a rpoC4- mutant strain was used as a host strain in the absence of rifampicin. These results and the blockage of the effects by action of chloramphenicol suggest that the increase of permeability to o-nitrophenyl galactoside was caused by the expression of srnB+ or pnd+ gene, respectively. srnB+ gene expression leads to massive RNA degradation, probably through the activation of the rna+ gene product. In an rna- strain carrying the srnB+ plasmid, the extent of RNA degradation was reduced, whereas the permeability to o-nitrophenyl galactoside was increased to the same level as in the rna+ strain. Also, the increase in permeability to o-nitrophenyl galactoside was observed at 30 degrees C, although high-temperature incubation (42 degrees C) was necessary for the induction of RNA degradation. These results suggest that the alteration in permeability is a more direct effect of the expression of srnB+ or pnd+ gene and that the RNA degradation is a secondary phenomenon caused by the alteration in the membrane.
Insights
The expression of srnB+ or pnd+ genes in Escherichia coli increases membrane permeability. This alteration is a direct effect, with RNA degradation being a secondary phenomenon.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli membrane permeability is crucial for cellular functions.
- The roles of srnB+ and pnd+ genes in regulating membrane properties are not fully understood.
Purpose of the Study:
- To investigate the effect of srnB+ and pnd+ gene expression on Escherichia coli membrane permeability.
- To determine the relationship between gene expression, RNA degradation, and membrane alterations.
Main Methods:
- Utilized Escherichia coli strains with srnB+ and pnd+ plasmids.
- Assessed membrane permeability using o-nitrophenyl beta-D-galactoside.
- Investigated the impact of rifampicin, temperature shifts, and chloramphenicol treatment.
Main Results:
- Increased membrane permeability to o-nitrophenyl beta-D-galactoside was observed with srnB+ or pnd+ expression.
- The permeability alteration occurred independently of massive RNA degradation, suggesting a direct effect.
- RNA degradation was identified as a secondary consequence of the membrane alteration.
Conclusions:
- Expression of srnB+ or pnd+ directly alters Escherichia coli membrane permeability.
- RNA degradation is a downstream effect, not the primary cause, of the observed permeability changes.