Synchronous Growth of Enteric Bacteria

Shehata, T. E.; Marr, Allen G.

doi:10.1128/jb.103.3.789-792.1970

Cited by 36 publications

(12 citation statements)

References 20 publications

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“…The Coulter counter may be used to estimate cell multiplication in cultures of M. avium if certain problems are recognized. When the counter is calibrated to count the smallest cells of M. avium, which may be one-fifth the volume of cells of Escherichia coli (14), particulate material that sloughs off the cells during growth will also be counted. Most of this material passes an 0.8-,um filter and few viable cells do.…”

Section: Discussionmentioning

confidence: 99%

Electronic Counting in Growth Studies of Mycobacterium avium

McCarthy

1971

Applied Microbiology

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Metabolically uniform cells of Mycobacterium avium were obtained by selective filtration. The life cycle of these cells was followed by photomicrographs, electronic enumeration, and sizing and by viability and protein determinations. The cells elongate to form filaments several times their initial length; the increase in mass is reflected by a fiveto sixfold increase of total protein in the culture. The filaments then fragment causing the production of viable coccobacilli. The techniques employed to obtain this form of growth are described and comparisons with nocardial growth are noted. Brieger and Fell (4), 26 years ago, described for Mycobacterium avium three forms of slow growth and a "standard" life cycle. Their description of the standard life cycle of M. avium growing on chicken embryo extract was as follows: ".... the bacillus elongates during the first 24 hr. to form a filament several times its original length; this divides repeatedly to form a bunch of 20-30 filaments which on the 2nd or 3rd day break down into short rods, which continue to multiply slowly by ordinary binary fission. If the bacilli are subcultivated in fresh embryo extract the cycle is repeated but not otherwise." With the introduction of 7H10 agar (11), it was possible to detect stable colony variants of M. avium (15) which Brieger and Fell were unable to distinguish on their more complex media. Two colony variants, opaque and transparent, differ in that the transparent variant is more pathogenic for chickens and mice (12, 13), is more drug-resistant (8), and forms less cell mass (10) than the opaque variant. Because of the existence of two physiologically distinct variants and the possibility of a life cycle in M. avium, an attempt was made to define the temporal sequence of events in cell growth and division in this organism. In addition to the measurement of culture density, viability, and protein increases during growth, a Coulter counter was used to determine, electronically, numbers and sizes of the cells at different stages of growth. This method proved useful in delineating events in the "standard" life cycle of M. avium that was described by Brieger and Fell (4). MATERIALS AND METHODS Organism and medium. An isolate from a patient

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Section: Discussionmentioning

confidence: 99%

Electronic Counting in Growth Studies of Mycobacterium avium

McCarthy

1971

Applied Microbiology

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“…Experiments for determining specific growth rates were conducted in a G76 gyratory water-bath shaker (New Brunswick Scientific Co., New Brunswick, N.J.) adjusted to predetermined temperatures (5 to 35 C) and an agitation rate of 120 rev/min. A 250-ml Erlenmeyer flask containing 50 ml of TSB was inoculated with 0.2 ml of culture (grown at 10 C for 2 to 3 days in TSB), and the culture was transferred periodically (inoculum, 0.1 ml) until it reached the steadystate of growth (13,14). Growth was determined by periodically measuring optical density at 600 nm with a Beckman spectrophotometer (model DB) with 5-cm cuvettes.…”

Section: Materuils and Methodsmentioning

confidence: 99%

Isolation and Identification of Psychrophilic Species of Bacillus from Milk

Shehata

Collins

1971

Applied Microbiology

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Forty isolates from 97 raw milk samples (heated to 80 C for 10 min and stored at 4 to 7 C for 3 to 4 weeks) were sporeforming, aerobic, gram-positive or gramvariable, rod-shaped bacteria. Fifteen isolates that were identified had characteristics similar to species of Bacillus, except that they had lower growth temperature ranges, were gram-variable, and were somewhat different in sugar fermentations. Four isolates grew well within 2 weeks at 0 C, but they grew faster at 20 to 25 C. These psychrophilic sporeforming bacteria, the importance of which is discussed, are considered to be variant strains of mesophilic bacilli adapted to low temperatures. Most psychrophilic bacteria isolated from natural sources are heat-sensitive, gram-negative, nonsporeforming rods (3, 5, 10, 19, 22). However, Larkin and Stokes (11) and Sinclair and Stokes (15) isolated psychrophilic species of Bacillus and Clostridium from soil, mud, and water, and Marshall and Ohye (12) isolated a gram-negative psychrophilic Bacillus from sub

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“…This strain was cultivated for 2 months in continuous exponential growth at low density by periodic transfer in glucose minimal medium, after which cultivation a clone was isolated as a colony on a plate of eosinmethylene blue-lactose agar. The isolate (29) which has been designated strain ML30G ("G" denoting long cultivation in glucose minimal medium), was kept on slants of the same medium.…”

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confidence: 99%

Effect of Nutrient Concentration on the Growth of Escherichia coli

1971

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The relationship between specific growth rate of Escherichia coli and the concentration of limiting nutrient (glucose or phosphate or tryptophan) has been determined for populations in a steady state. At high concentrations the specific growth rate is independent of the concentration of nutrient, but at low concentrations the specific growth rate is a strong function of the nutrient concentration. Such a relationship was predicted by Monod; however, Monod's equation does not predict the relationship over the entire range of nutrient concentration. If parameters of the equation are estimated from the results obtained at low concentrations, then at high concentrations of nutrient, the specific growth rate is significantly higher than that predicted by Monod's equation. These results were interpreted on the basis that the rate of growth is controlled by at least two parallel reactions and that the affinities of the enzymes catalyzing these reactions are different. The relationship between specific growth rate and mean cell volume was also measured, and the results indicate that mean cell volume depends not only on the specific growth rate but also on the nature of the limiting nutrient. There are different mean cell volumes at the same specific growth rate established by different limiting nutrients. Therefore, the mean cell volume is not uniquely determined by the specific growth rate. vide a test of the relationship inferred by Monod 210 on July 4, 2020 by guest

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Synchronous Growth of Enteric Bacteria

Cited by 36 publications

References 20 publications

Electronic Counting in Growth Studies of Mycobacterium avium

Electronic Counting in Growth Studies of Mycobacterium avium

Isolation and Identification of Psychrophilic Species of Bacillus from Milk

Effect of Nutrient Concentration on the Growth of Escherichia coli

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