Abstract
E.Coli STs are small peptides encoded on plasmids, detectable by the suckling mouse assay (SMA). We have previously reported the production of an enterotoxin produced by Citrobacter freundii (Cf), whose physico-chemical and biological characteristics are similar to E.Coli STa. In order to investigate whether this toxin might be structurally related to E.Coli STa we developed a rapid, small scale purification scheme and determined the primary sequence of the purified toxin. This procedure is a sequential chromatography on XAD resin followed by reverse phase separation on C-18 silica cartridges and a C-18 silica analytical HPLC column using a methanolic buffer system and a final run in acetonitrile. The recovery of the toxin was monitored at each step by an Elisa method. HPLC-purified Cf toxin: 1) was active in the SMA; 2) competed with pure 18 aminoacid E.Coli STa in the Elisa and 3) comigrated with this in analytical reverse phase chromatography. Sequence analysis of the toxin revealed that Cf ST is an octadecapeptide consisting of the identical aminoacid sequence of the 18 aminoacid STa produced by E.Coli. These data raised the possibility that the organisms may trade plasmids. To ascertain if plasmids encoding ST could be transferred between different bacterial species, ST positive Cf culture was incubated with ST negative, Rifamplein resistant E.Coli. After 24 hours culture was plated onto XLD + Rifampicin. E.Coli strains grown had acquired the ability to produce ST. In conclusion: Cf ST is identical to E.Coli 18 aminoacld STa. The ability of producing STa may be transferred from a species to another through conjugation.
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Guarino, A., Alessio, M., Tarallo, L. et al. 12 HEAT-STABLE ENTEROTOXIN (ST) ENCODED ON TRANSMISSABLE PLASMID. Pediatr Res 24, 407 (1988). https://doi.org/10.1203/00006450-198809000-00035
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DOI: https://doi.org/10.1203/00006450-198809000-00035