Factors Limiting Bacterial Growth

Abstract

In earlier papers of this series (Hershey, 1939b) it has been shown that growth during the latent period is continuous with the subsequent growth accompanied by cell division, the two phases being described by a single law. The observations were made with Escherichia coli and Shigella dysenteriae. Further test of the general validity of the conclusions reached with these organisms seemed desirable. This could be done by applying similar methods at random to the study of various species. We have attempted to proceed more purposefully. One could, a prior, anticipate several causes of lag (Penfold, 1914) which would be different from what we shall call the normal latency exhibited by the organisms mentioned. For example, growth on transplant should occur at increasing rate if bacteria in an aging culture sustain injury to labile constituents of catalytic mechanisms which are not essential to viability, but on which the rate of growth under favorable conditions depends. No authenticated instance of this is known. Recovery from injury has been suggested as a possible explanation of lag in pneumococcus cultures (Chesney, 1916), which are known to accumulate hydrogen peroxide in toxic concentrations; a similar explanation might be put forward to account for dormancy (Burke, Sprague and Barnes, 1925) of spores or of vegetative cells, whether the injury is of unknown cause or wilfully inflicted (Hollaender and Duggar, 1938; earlier work discussed by Buchanan and Fulmer, 1928). It is evident that this mechanism is