A Rapid Method for Determining the Proportion of Viable Bacteria in a Culture

Powell, E. O.

doi:10.1099/00221287-14-1-153

Cited by 17 publications

(7 citation statements)

References 10 publications

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“…Frazier and Boyer, 1934 (94) Hanging blocks of agar inoculated with bacterial suspension and observed micro- Kelly and Rahn, 1932 (87) scopically for multiplication for four generations Individual cell multiplication on solid medium followed by photocinematography Bayne-Jones and Adolph, 1932 (87) Growing microorganisms examined microscopically by oblique incident illumination Pearce and Powell, 1951 in a moist chamber on solid nutrient surface (128) Culture chamber containing cellophane membrane inoculated with individual micro-Harris and Powell, 1951 (63) organisms observed for multiplication Graticulated cellophane membrane inoculated with bacterial culture; microscopic Powell, 1956 (139) counting of organisms before and after a short incubation period For orientation, Formvar grid replicas inoculated with bacteria and periodically ob -Taubeneck, 1958 (164) served microscopically for multiplication Microcolony formation on membrane filters of small cells observed microscopically Jannasch, 1958 (73) Organisms dispersed in thin agar films suspended in wire loops immersed in liquid Jebb and Tomlinson, 1960 medium; after various incubation periods films are stained and observed micro-(79) scopically on slides for number of bacteria per colony Short-term incubation of bacteria on agar films followed by differentation by micro-Postgate et al, 1961 (136) scopic counting of number of microcolonies per number of total bacteria Agar films on blotting paper in chambers inoculated with bacterial suspensions and Bretz, 1962 (14) incubated 1 to 6 h; phase-contrast microscopic observation of growth of viable and moribund cells Cellophane membrane inoculated with bacteria in a continuous flow through cham- Quesnell, 1963 (140) ber containing liquid synthetic medium observed microscopically for seven gener- Optical density of a suspension of live bacteria is greater in a saline solution than in distilled water; dead bacteria show no change Barer et al, 1953 (8) Mager et al, 1956 105Optical density is 25% greater for live organisms in saline than in distilled water, whereas killed organisms show no effect; mixtures show optical effect in proportion to % live organisms from + 25% to -10% of optical density in water; used as a measure of intact osmotic barrier required for living organisms Postgate and Hunter, 1962…”

Section: Detectionmentioning

confidence: 99%

Survival strategies of bacteria in the natural environment.

Roszak¹,

Colwell²

1987

Microbiological Reviews

1,092

581

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Section: Detectionmentioning

confidence: 99%

Survival strategies of bacteria in the natural environment.

Roszak¹,

Colwell²

1987

Microbiological Reviews

1,092

581

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“…The generation times of individual organisms are far from uniform; the scatter appears to depend on the growth medium, and is on the whole greater in multicellular than in unicellular species (Powell, 1955(Powell, , 1956 Some care is needed in defining the distribution of generation time, especially when actual measurements are envisaged (Powell, 1955). The frequency function of generation time, f(7) d7, is the probability that a newly formed organism will have a generation time in the range 7 , 7+d7.…”

Section: The Distribution Of Generation Timesmentioning

confidence: 99%

Growth Rate and Generation Time of Bacteria, with Special Reference to Continuous Culture

Powell¹

1956

Journal of General Microbiology

Self Cite

408

302

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SUMMARY:The relations between growth rate, generation time distribution and age distribution in growing bacterial cultures are derived. The effect of inheritance on generation time is probably negligible. Some applications to experimental data exemplif'y the mathematical results. The validity of the principal assumptions is discussed.It appears to be tacitly assumed by many bacteriologists, in particular by some who are concerned with the study of continuous cultures, that there is a simple relationship between growth rate and generation time. It is sometimes stated that during the phase of steady expohential growth of a batch culture the following equation holds :where N (supposed very large) is the number of organisms in the culture, v is the number growth rate constant, and 7 is the mean generation time (in a sense not clearly defined). Equation (1) is false except in special cases that are apparently never realized in practice. Similarly, in the steady state of a continuous culture running at dilution rate D it is usually false that log 2 D = -. 7The true relationships, though more subtle, differ quantitatively from ('I) and (2) by very little, but so far as (2) is concerned, that little is an expression of the selective power which is so important a feature of continuous culture.In this paper I describe some simple quantitative features of bacterial populations which result from the dispersion of the individual generation times. I assume (i) that the populations under discussion are homogeneous, i.e. that they consist of organisms of only one type, and that the cultures have continued in steady growth long enough for the age distribution to have become constant; fii) that the numbers of organisms present are so large that variations can be regarded as continuous, and statistical fluctuation as negligible. Some of the mathematical results are not new, but they are somewhat inaccessible to bacteriologists, and I have given simple derivations, glossing over many difficulties which the pure mathematician must attend to, but which are resolved by observation for the bacteriologist.To avoid the use of inappropriate or ambiguous phrases, I adopt the following terminology : the ' inception ' and ' termination ' of an organism are t N 8 t d logarithms are used throughout.

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“…An adopted criterion must depend on reproductive power, since neither growth nor any chemical activity is uniquely a property of living organisms ; furthermore, viability itself is not absolute, but only has a meaning in an environment which can be specified (Powell, 1956b). I submit the following remarks to provide a definite context for the few data I have to present, and so to avoid misunderstanding.…”

Section: T H E Incidence Of Non-viable# Organismsmentioning

confidence: 99%

An Outline of the Pattern of Bacterial Generation Times

Powell¹

1958

Journal of General Microbiology

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145

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SUMMARY: The generation times of four species of organisms have been measured, each under several sets of conditions : Aerobacter cloacae, Serratia marcescens, Streptococcus f aecalis and Pseudomonas aeruginosa. Minor variations in the experimental conditions appear to affect the mean generation time less in large samples than in small. This can be explained as a result of association between the generation times of closely related organisms. Positive correlation between the generation times of sisters, cousins and perhaps second cousins shows that the influence of an ancestor is felt through two or three generations. The observed correlation between mothers and daughters is usually small, probably because of bias due to the interval between fission of cytoplasm and fission of cell wall. The coefficient of variation of generation time is not a constant for the species but it is stable under given circumstances. It is possibly related systematically to the chemical complexity of the growth medium. In unhampered growth, less than 1% of the organisms produced are non-viable. There is positive association between the viabilities of sisters, and between the viability of an organism and the generation time of its mother. The distribution of generation times can be represented by a Pearson Type I11 or else a Pearson Type V distribution ; both are convenient in applications.The generation time of an individual is considered to be determined partly by molecular accidents, partly by heredity.In a previous paper on this subject (Powell, 1955), I gave an account of some preliminary work designed to test and compare the hypotheses of Rahn (1932) and Kendall (1948, 1952) about the causes of variability in the generation times ( 7 ) of individual bacteria. It turned out that a comparison of the observed distributions of 7 with those predicted by the hypotheses was not altogether satisfactory, and I suggested that a further test might be made by determining the effect of alterations in temperature and growth medium on the coefficient of variation of 7. At the same time I concluded that such experiments should await improvements in observational technique. There appeared to be a possibility that the relevance of the observations was altogether vitiated by ' delayed fission ', that is, by the lapse of an appreciable and variable interval between the termination of the processes considered by Rahn and Kendall, and the overt occurrence of fission.The results which I now present consist of generation time measurements on unicellular organisms of four species-Aerobacter cloacae, Serratia marcescens, Streptococcus faeculis and Pseudomonas aeruginosa-each under several different growth conditions. The undertaking was originally encouraged by the development of an improved culture chamber (Powell, 1956a), which would permit much greater accuracy in the determination of times of fission. At first, I hoped that the results would be of enhanced diacritical value, but it soon became clear that the generation times of bacteria do not depend ...

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A Rapid Method for Determining the Proportion of Viable Bacteria in a Culture

Abstract: SUMMARY: A method of making graticules on the surface of Cellophane is described. The proportion of viable bacteria in a culture can be estimated by inoculating a sample on to such a graticule, and counting the organisms before and after a short period of growth.

Cited by 17 publications

References 10 publications

Survival strategies of bacteria in the natural environment.

Survival strategies of bacteria in the natural environment.

Growth Rate and Generation Time of Bacteria, with Special Reference to Continuous Culture

An Outline of the Pattern of Bacterial Generation Times

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