Effect of starvation upon the constitution of bacteria.

Abstract

WHEN bacteria, which have grown in a mineral salts medium, are transferred to fresh medium of the same composition a lag period may develop before growth is resumed1. Lag is reduced by addition of sterile culture filtrates or by certain compounds shown to be present in such filtrates2. We have recently observed changes within the cells themselves when they are transferred to phosphate buffer. Esch. coli was harvested from a growth medium containing 0.5 per cent peptone, 0.2 per cent glucose and mineral salts and the crop was divided into two equal parts. One half was disrupted immediately in the Hughes bacterial press3 without abrasive and the crushed cells extracted with phosphate buffer. The other half of the crop was suspended in the same volume of phosphate buffer as that of the medium in which the cells had grown. After incubation at 30° C. for 2 hr. the bacteria were harvested, crushed under the same conditions as those used for the first half of the original crop and the two extracts were adjusted to the same protein content by addition of buffer. The ultracentrifuge pattern for the extract from the cells crushed immediately after harvesting from their growth medium is shown in Fig. 1a. It agrees closely with patterns reported by previous authors4–6. When the cells are incubated in the absence of compounds necessary for growth, however, a dramatic modification occurred in the distribution of macromolecules in the extract. The leading boundary, which has an uncorrected sedimentation coefficient of 40S, was largely abolished while that sedimenting at 20S was somewhat augmented (Fig. 1b).