Insulin‐related material in prokaryotes

We have reported previously on the presence of vertebrate‐type peptide hormones in Tetrahymena pyriformis and Escherichia coli . We now have examined other prokaryotes for immunologically detectable insulin‐like material. The bacteria studied were E. coli, Acinetobacter calcoaceticus RAG‐1, Bordetella pertussis and Halobacteria solinarium; they were grown in defined minimal salt media under varying growth conditions. All these bacteria contain insulin‐related material (1–12 pg per g cell wet wt). No insulin immunoactivity was detected in the media prior to inoculation. The content of insulin‐related material was not affected by the carbon source used for cell growth. These data are in good agreement with data published previously, and suggest that prokaryotes and unicellular eukaryotes are capable of producing hormone‐like material; the function of these peptides, if any, is as yet unknown.