Turbidity Changes in Bacterial Suspensions in relation to Osmotic Pressure

Mager, J.; Kuczynski, Miriam; Schatzberg, Gisela; Avi‐Dor, Y.

doi:10.1099/00221287-14-1-69

Cited by 79 publications

(33 citation statements)

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“…In a previous communication, Mager et al (1956) reported an increase in the light extinction of Gram-negative bacterial suspensions in isotonic saline or glucose as compared with suspensions in water (optical effect: o.E.). Under these conditions of assay no appreciable change could be demonstrated with Gram-positive bacteria.…”

Section: Resultsmentioning

confidence: 91%

Turbidity Changes in Suspensions of Gram-Positive Bacteria in Relation to Osmotic Pressure

Kuczynski-Halmann

Avi‐Dor

Mager³

1958

Journal of General Microbiology

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The turbidity of suspensions of Gram-negative micro-organisms is known to be influenced by the tonicity of the suspending medium. In contrast to this, suspensions of Gram-positive micro-organisms have the same optical density in 0.2 M-NaC1 as in distilled water. At higher salt concentrations, however, occasionally some batches were found to display changes in turbidity. Correlation was shown between the concentration of the amino acid pool of the organisms and their response to changes in osmotic pressure of the suspending medium. Depletion of the amino acid pool resulted in an increase in the changes in turbidity, with the simultaneous suceptibility of Gram-positive bacteria to plasmolysis. A possible correlation between this optical effect and the separation of cytoplasmic membrane from the bacterial cell wall is discussed.It was reported in preceding communications (Mager, Kuczynski, Schatzberg & Avi-Dory 1956; , that variations in the osmotic pressure of the suspending medium elicited corresponding changes in turbidity of Gram-negative bacteria. The light-scattering ability of suspensions of Gram-positive micro-organisms was found, however, to be independent of the prevailing tonicity. The object of the present study was to investigate the cause of the different response of these two classes of micro-organisms to changes in the osmotic pressure. METHODSCulture media. Escherichia coli was grown on nutrient agar (Difco) at 37".Bacillus megaterium was cultivated in a 2 yo (w/v) solution of an enzymic casein hydrolysate (N.B.C.), fortified with 0-1 yo (w/v) Marmite and incubated at 30' with shaking. Staphylococcus aureus was grown under the same conditions as B. meguterium with the addition of 1% (w/v) glucose to the culture medium.Inoculum. A volume of 0.1 ml. of 24 hr. slope culture of bacteria suspended in 5 ml. saline was used for inoculation of 100 ml. medium.Duration of incubation: 18 hr. Chemicals. All chemicals used were of reagent grade. Determination of ninhydrin-reacting substances released by boiling. A 2 ml. Procedure for measuring the optical eflect. The optical effect (o.E.) was measured as described before (Mager et al. 1956). The magnitude of the effect (E') was expressed as a percentage where E , is the light extinction of the suspension in water, and E , the extinction in the solute. RESULTSIn a previous communication, Mager et al. (1956) reported an increase in the light extinction of Gram-negative bacterial suspensions in isotonic saline or glucose as compared with suspensions in water (optical effect: o.E.). Under these conditions of assay no appreciable change could be demonstrated with Gram-positive bacteria. In further studies, however, when an increased concentration of NaCl was used ( 0 . 5~) occasionally batches of Gram-positive The amount of ninhydrin-reacting substances released by boiling of the organism was determined as described in 'Methods' and is calculated as 'glutamate'. micro-organisms were encountered which showed the optical effect in varying degree. It was also observed...

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Section: Resultsmentioning

confidence: 91%

Turbidity Changes in Suspensions of Gram-Positive Bacteria in Relation to Osmotic Pressure

Kuczynski-Halmann

Avi‐Dor

Mager³

1958

Journal of General Microbiology

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“…It is of interest that the concentration of exogenous potassium ( 0 . 0 5~) in which A. wogenes was most stable a t 47' was also the minimum concentration in which a measurable 'optical effect' (change in turbidity of a suspension as compared with a similar suspension in water ; Mager, Kuczynski, Schatzberg & Avi-Dor, 1956) occurred.…”

Section: Discussionmentioning

confidence: 99%

Effects of Thermal Stress on Viability and Ribonucleic Acid of Aerobacter aerogenes in Aqueous Suspension

Strange¹,

Shon²

1964

Journal of General Microbiology

105

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SUMMARYThe death-rate of washed Aerobucter aerogernes in aqueous suspension at 47" depended on the nature of the growth medium, the composition of the liquid used to wash and resuspend the bacteria, the bacterial growth phase, the bacterial concentration in heated suspensions, the pH value, the oxygen tension and the composition of the diluent in which bacteria were heated. The relative resistance of bacteria in different growth phases differed according to the growth medium and the washing fluid; stationary phase bacteria were not more resistant than exponential phase organisms under all conditions. Starvation increased the thermal resistance of exponential and stationary phase bacteria. High bacterial concentration favoured survival a t 47" under most conditions; cell-free filtrate from a heated dense suspension (1010 bacteria/ml.) protected a sparser population of fresh bacteria ( 107-10g/ml.) heated in it. Protective material in filtrate was heat-stable ( 100°/15 min.) and diffused through cellophan. The optimum pH value for survival at 47" was near pH 6-5. Aerobic conditions favoured survival in distilled water but not in salt solutions or phosphate saline (pH 6-5). The effects of various concentrations of NaCl and KC1 on the survival of bacteria at 47' under aerobic conditions were different, K+ concentrations above 0.1 M being more lethal than equivalent concentrations of Na+; the lethal effect of heating in mixtures of these salts (total M > 0.1) increased with K+ concentration. Growth medium, Mg2+ (0-01-5 mM) and, to a lesser extent, Mn*+ (0.5 mM) or Co2+ ( 5 mM) decreased the death-rate, whereas ethylenediamine tetraacetic acid (mM), or various sugars, increased it. Mga+ but not M n 2 + reversed the lethal effect of sugars.Generally, conditions which accelerated the death-rate of Aerobucter wogem?s at 47" also increased the rate of degradation of endogenous RNA. This was accompanied by an increase in the ultraviolet absorption of cold acid-extracts of bacteria and of the suspending fluid. Bacterial protein was degraded to a smaller extent. Depletion of RNA is probably not the primary cause of death a t 47" but the effect on bacterial metabolism of a rapid increase in endogenous pool constituents resulting from RNA degradation may contribute to the lethal effect.

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“…Osmotic response was estimated by measuring the ability of Salmonella exposed to a given treatment to respond to PBS ϩ 0.75 M NaCl relative to PBS alone. In hypertonic solutions (i.e., PBS ϩ 0.75 M NaCl), cells will plasmolyze, resulting in an increase in optical density (OD) relative to the OD of the control (i.e., PBS) (32); this change in OD will here be referred to as the osmotic response. Osmotic response assays were performed essentially as described previously (52).…”

Section: Methodsmentioning

confidence: 99%

Immediate Reduction of Salmonella enterica Serotype Typhimurium Viability via Membrane Destabilization following Exposure to Multiple-Hurdle Treatments with Heated, Acidified Organic Acid Salt Solutions

Milillo

Martin

Muthaiyan

et al. 2011

Appl Environ Microbiol

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The antimicrobial activity of organic acids in combination with nonchemical treatments was evaluated for inactivation of Salmonella enterica serotype Typhimurium within 1 min. It was observed that the effectiveness of the multiple-hurdle treatments was temperature (P < 0.05) and pH (P < 0.05) dependent and corresponded to the degree of organic acid lipophilicity (sodium acetate being least effective and sodium propionate being the most effective). This led to the hypothesis that the loss in viability was due at least in part to cell membrane disruption. Evaluation of osmotic response, potassium ion leakage, and transmission electron micrographs confirmed treatment effects on the cell membrane. Interestingly, all treatments, even those with no effect on viability, such as with sodium acetate, resulted in measurable cellular stress. Microarray experiments explored the specific response of S. Typhimurium to sodium acetate and sodium propionate, the most similar of the tested treatments in terms of pK a and ionic strength, and found little difference in the changes in gene expression following exposure to either, despite their very different effects on viability. Taken together, the results reported support our hypothesis that treatment with heated, acidified, organic acid salt solutions for 1 min causes loss of S. Typhimurium viability at least in part by membrane damage and that the degree of effectiveness can be correlated with lipophilicity of the organic acid. Overall, the data presented here indicate that a combined thermal, acidified sodium propionate treatment can provide an effective antimicrobial treatment against Salmonella.

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Turbidity Changes in Bacterial Suspensions in relation to Osmotic Pressure

Cited by 79 publications

References 7 publications

Turbidity Changes in Suspensions of Gram-Positive Bacteria in Relation to Osmotic Pressure

Turbidity Changes in Suspensions of Gram-Positive Bacteria in Relation to Osmotic Pressure

Effects of Thermal Stress on Viability and Ribonucleic Acid of Aerobacter aerogenes in Aqueous Suspension

Immediate Reduction of Salmonella enterica Serotype Typhimurium Viability via Membrane Destabilization following Exposure to Multiple-Hurdle Treatments with Heated, Acidified Organic Acid Salt Solutions

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