A simple bacterial colony counting device

Sims, A L; Jordan, R.C.

doi:10.1088/0950-7671/18/12/407

Cited by 5 publications

(3 citation statements)

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“…This procedure was found to give more evenly spaced colonies with a minimum of spreading ones. Eight plates were made from each sample, and after incubation at 35 C for 48 hours the colonies were counted, using the automatic counting device of Sims and Jordan (1941). Statistical analysis (Fisher, 1938) of the data from numerous plate counts showed the methods employed to be satisfactory.…”

Section: Apparatus and Methodsmentioning

confidence: 99%

The Growth of Bacteria with a Constant Food Supply

1944

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Section: Apparatus and Methodsmentioning

confidence: 99%

The Growth of Bacteria with a Constant Food Supply

1944

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“…This mean was then multiplied by the number of sub-samples to give an estimate of the total Aphid population of the sample. As an aid to counting, a modification of an apparatus described by Sims & Jordan (1941) was made; it consisted of an electro-magnetic counter operated by a microswitch from the A.C. main supply. .…”

Section: Methods Of Counting the Aphidsmentioning

confidence: 99%

A Method for estimating Populations and counting large Numbers of Aphis fabae Scop

Banks

1954

Bull. Entomol. Res.

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It is often necessary to estimate the numbers of Aphids in the field over a period of time, a problem which is accentuated when the species concerned is very numerous. This paper describes a method for estimating population changes of the Black Bean Aphid, Aphis fabae Scop., on beans, and a simple volumetric method for counting large numbers of the Aphid in the laboratory. The method, which might be applied for other small arthropods, is illustrated by the results obtained from a study of three bean plots during the summer of 1952.The essentials of the method are as follows: in the field, a large number of bean stems was examined and each placed in one of five arbitrary classes of Aphid nfestation. Sample stems of each of these classes were removed from the plot bo the laboratory and the Aphids on each stem counted. The mean numbers of Aphids for each of the classes, estimated from the sample results, were multiplied by the appropriate number of stems of each class and the products, when added, gave an estimate of the Aphid population of all the stems examined in the field.The adoption of a system of classification of stems in the field not only allows a large number of stems to be examined but also eliminates the necessity of removing a large number of samples. Similar systems were used by Gorham in surveys of potato Aphids (see Broadbent, 1948) and by Ripper (1944) for Aphids on brussels sprouts. The present classification is developed from a method used by C. G. Johnson and J. A. Nelder (unpublished work) for Aphid populations of beans.

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“…This is usually six or eight and these are incubated at 350 C. for 48 hr. before the colonies are counted, using the automatic counting device of Sims & Jordan (1941).…”

Section: Introductionmentioning

confidence: 99%

Studies in the dynamics of disinfection: I. New data on the reaction between phenol andBact. coliusing an improved technique, together with an analysis of the distribution of resistance amongst the cells of the bacterial populations studied

Jordan

Jacobs

1944

Epidemiol. Infect.

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1. The action of phenol onBact. colihas been studied quantitatively in detail under such conditions that unfavourable circumstances other than the presence of the germicide were as far as possible eliminated. Briefly, this involved the addition of phenol solution directly to a large volume of culture developed under rigidly standardized conditions.2. When the mortality exceeded 95% the variation between the numbers of colonies on replicate plates, when determining the numbers of survivors, was often excessive.3. Under the conditions used the death-rate was not constant. First, there was a phase (1) of slow but increasing death-rate which merged gradually into a phase (2) of approximately constant rate which was also the maximum for a given phenol concentration. There are indications that the death-rate may decline towards the extreme end of the disinfection process.4. The virtual extinction time (the time taken for the survivors to fall to 1 per ml. as determined by extrapolation of the log survivors-time curve) increased as the phenol concentration decreased, as also did the duration of phase 1. The latter occupied about 60% of the virtual extinction time when the concentration was 3·48 g. phenol per 1., but with rising concentration its duration decreased at a greater rate than the virtual extinction time so that at about 7 g. per 1. phase 1 was very short though still detectable. The standard errors of the virtual extinction times varied between ± 1·5% and ± 5·43%.5. Using the probit method it has been shown that at low concentrations of phenol the distribution of resistance ofBact. coliis approximately normal when the resistance is measured in terms of the survival times.6. The distribution of resistance was found to be normal at all concentrations of phenol used, when that resistance was measured in units of the logarithms of the survival times, with the exception that at the lower concentrations there was a sudden change in the slope of the probit-log survival-time line at about 20% mortality. This change became less marked with rising concentration and was probably absent at 8·00 g. phenol per 1.7. After conversion into the dosage-mortality form, the data reveal that about 70% of the cells show an approximately normal distribution of resistance when the latter is expressed in terms of the dosage survived for a fixed time, provided that the exposure time is less than 50 min.8. The distribution tends to be normal for longer exposure times when the resistance is measured in terms of the logarithms of the dosages survived. On this basis a change of slope of the probit-log dosage line is observed as in the case when resistance is measured in terms of the logarithms of survival times.

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A simple bacterial colony counting device

Cited by 5 publications

References 0 publications

The Growth of Bacteria with a Constant Food Supply

The Growth of Bacteria with a Constant Food Supply

A Method for estimating Populations and counting large Numbers of Aphis fabae Scop

Studies in the dynamics of disinfection: I. New data on the reaction between phenol andBact. coliusing an improved technique, together with an analysis of the distribution of resistance amongst the cells of the bacterial populations studied

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