PHENOTYPIC, GENOTYPIC, AND CHEMICAL CHANGES IN STARVING POPULATIONS OF AEROBACTER AEROGENES

Harrison, Arthur P., Jr. (Vanderbilt University, Nashville, Tenn.) and Felix R. Lawrence. Phenotypic, genotypic, and chemical changes in starving populations of Aerobacter aerogenes. J. Bacteriol. 85:742-750. 1963.-Cells harvested from postlogarithmic (maximal stationary phase) Aerobacter aerogenes cultures and starved in dilute sodium phosphate at 40 C remained viable for many hours. On the other hand, most cells from logarithmic-phase cultures succumbed, although a relatively small number remained viable. This viable segment of the original population thus responded like cells from postlog-phase cultures and, in fact, had properties in common with them. The residual segment was comprised of cells of two kinds. The first were mutants; when cultivated, harvested during log-phase growth, and again starved, they were resistant. The second were wild-type; they responded exactly as before. During starvation, the mutant is at an advantage because it has the ability to convert from susceptible log-phase physiology to resistant postlog-phase physiology more rapidly than can wild-type. The mutant differs from wild-type in yet other ways. It is smaller in size, slower in growth rate, lower in ribonucleic acid (RNA)-deoxyribonucleic acid ratio, greater in light-scattering ability, and, during the first 4 hr of starvation, it loses a higher proportion of its RNA. Selection of mutants of low growth rate between periods of active clonal growth indicates that evolutionary advantage may not necessarily be with the fast-growing members of the clone.