Abstract
Serratia marcescens SM-6 when starved for a required amino acid stops synthesizing protein and RNA and accumulates two nucleotides which cochromatograph with ppGpp and pppGpp. These features are characteristic of bacterial strains with stringent RNA control (rel +). Two independent mutants were isolated which resemble relaxed (relA) mutants ofEscherichia coli; they continue to synthesize RNA and accumulate neither ppGpp nor pppGpp when deprived of the required amino acid. The extracellular enzyme activities (nuclease, protease, lipase) of the relaxed mutants are about the same as those of the parental stringent strain when studied under standard growth conditions. Exoenzyme-deficient (nuc; prt) and exoenzyme-hyperproducing (nuc su) mutants were isolated from both stringent and relaxed strains ofS. marcences SM-6 and no change of the cellular ability to form ppGpp and pppGpp could be observed. From these results it appears that the formation of exoenzymes ofS. marcescens SM-6 is independent of stringent/relaxed RNA control.
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Abbreviations
- cpd :
-
cyclic nucleotide phosphodiesterase deficient
- nuc :
-
nuclease deficient
- nuc su :
-
nuclease hyperproducing
- prt :
-
protease deficient
- rel :
-
relaxed control
- spo :
-
ppGpp deficient (spot less)
- ppGpp:
-
guanosine tetraphosphate
- pppGpp:
-
guanosine pentaphosphate
- TCA:
-
trichloroacetic acid
- OD:
-
optical density
- EU:
-
enzyme units
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Bohne, L., Winkler, U. Relaxed mutants ofSerratia marcescens SM-6. Biochemical traits and relevance of therel + allele for the formation of exoenzymes. Arch. Microbiol. 121, 181–186 (1979). https://doi.org/10.1007/BF00689984
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DOI: https://doi.org/10.1007/BF00689984