A Genealogical Study of Clonal Development of Escherichia coli

Abstract

The generation times of individual Escherichia coli cells inoculated on to a cellophane membrane surrounded by liquid synthetic medium in a continuous flow system were determined by direct observation for up to seven generations. The presence and production of nonviable cells was also recorded. A wide variety of developmental patterns was found among the developing clones; increased viability and a decrease in generation times with increasing age of the population were .observed. The phenomenon of alternation of generations is described and discussed. Five factors contributory to the lag phase were distinguished, and their relative effect may be deduced from the results. I 28

Stress resistance and recovery potential of culturable and viable but nonculturable cells of Vibrio vulnificus

“…The microcolony assays performed in our study showed, however, that VBNC cells of V. vulnificus are not capable of any, even limited, divisions under conditions conducive for growth of the organism. Incubation of microcolony and MPN assays for at least 10 d revealed no delayed recovery and outgrowth, as reported for Escherichia coli for example (Quesnel, 1963), under the conditions applied. Taken together, the results presented here rule out the possibility that resuscitation of VBNC cells of V. vulnificus could be triggered by either temperature shifts alone, as described earlier (Nilsson et al ., 1991), or by the addition of standard nutrients or growth factors, or by the addition of culture supernatants, as was shown for M. luteus (Kaprelyants et al ., 1994).…”

“…vulnzjczts are not capable of any, even limited, divisions under conditions conducive for growth of the organism. Incubation of microcolony and MPN assays for at least 10 d revealed n o delayed recovery and outgrowth, as reported for Escbericbia coli for example (Quesnel, 1963), under the conditions applied. Taken together, the results presented here rule out the possibility that resuscitation of VBNC cells of I/.…”

Hard Surface Disinfection and its Evaluation

“…Li & Umbreit (1966) have agreed that the highest sensitivity to harmful effects occurs during the late-lag-early-log phase of growth. These findings appear to fit exactly with the theory on which my models are based, and other work in this field is explained in more detail elsewhere especially by Bisset (1955) and Quesnel (1963). Such specific information is of the greatest practical value to those concerned with hard surface disinfection evaluation.…”

Comparison of MacConkey broth, Teepol broth and glutamic acid media for the enumeration of coliform organisms in water

“…It follows, therefore, that marginal chlorination may merely be selecting the older cells. Some of these older cells may also be in a resting stage or at least have a prolonged generation time (Quesnel, 1963). This would account for the slow growth obtained in the trials.…”