Stability of β-Galactosidase in Starved Escherichia coli

Abstract

THE endogenous metabolism of micro-organisms in aqueous suspension in the absence of added nutrients may involve the utilization of endogenous protein and RNA¹, as well as amino-acid pool constituents and reserve substances such as glycogen and polyhydroxybutyric acid (see reviews by Dawes and Ribbons²). Investigations with Aerobacter aerogenes¹, Escherichia coli and Pseudomonas fluorescens have shown that starvation in aerated saline buffer at 37° results in a considerable loss of protein during a period when viability of the populations remains at 95–100 per cent. Since analyses of ultracentrifugal fractions separated from A. aerogenes after various periods of starvation showed decreases in the protein content of the insoluble, ribosomal and soluble fractions³, the loss apparently represents a depletion of various cell proteins. It is interesting, therefore, that induced β-galactosidase in Escherichia coli was found to be relatively stable while other proteins were being rapidly degraded during turnover⁴. The relative stability of induced β-galactosidase in a wild-type strain of E. coli during starvation has been investigated and this communication records the relevant data.