Factors which Affect the Size of the Organisms and the Optical Density of Suspensions of Pseudomonas aeruginosa and Escherichia coli

Abstract

SUMMARYWhen water-washed organisms of a strain of Pseudomonas aeruginosa were exposed to solutions of NaCl or sucrose, they shrank in size and became more dense. The optical density of suspensions increased rapidly. Pre-treatment of the organisms with various cations, surface-active agents and heat and cold, affected the reaction, and the organisms then behaved differently toward NaCl and sucrose. Some but not all of the effects observed with P. aeruginosa were also observed with a strain of Escherichia coli.

Influence of Suspending Media upon the Susceptibility of Pseudomonas aeruginosa NCTC 6750 and Its Spheroplasts to Polymyxin B

“…Optical density changes indicated that P. aeruginosa cells are almost impermeable to sodium chloride (Table 1). Similar results were obtained by Bernheim (1) for both sodium chloride and sucrose.…”

Increased cell size and shortened peptidoglycan interpeptide bridge of NaCl-stressed Staphylococcus aureus and their reversal by glycine betaine

“…During an investigation of the effects of growth in the presence of NaCl on the production of penicillin-binding protein 2a and autolytic activity (20), it was observed that cells grown in complex medium containing 0.85 M NaCl were larger than cells grown in complex medium alone (21). Similar observations of larger cells in complex medium containing NaCl than in complex medium alone have also been reported by others (13,17).When bacterial cells such as Escherichia coli are exposed to a sudden increase in external osmotic pressure, there is initially a fast efflux of water, resulting in decreased turgor pressure, plasmolysis, and cell shrinkage (1,5,18). Mitchell and Moyle (25) have shown a similar response for S. aureus cells transferred from dilute to concentrated NaCl solutions.…”

“…When bacterial cells such as Escherichia coli are exposed to a sudden increase in external osmotic pressure, there is initially a fast efflux of water, resulting in decreased turgor pressure, plasmolysis, and cell shrinkage (1,5,18). Mitchell and Moyle (25) have shown a similar response for S. aureus cells transferred from dilute to concentrated NaCl solutions.…”

The Effect of Pyruvate and Acetate on the Rate of Decrease in Optical Density of Suspensions of Pseudomonas aeruginosa in Sodium, Potassium or Sodium-Potassium Phosphate Buffers

“…Ions, however, accelerate the swelling. As shown previously (Bernheim, 1963) osmolar sucrose shrinks the organisms to the same extent as inorganic salts, but the subsequent swelling is a t a much slower rate unless a salt is added. A potassium salt increases the rate more than sodium which in turn is more effective than lithium, caesium, or rubidium.…”

“…The organisms were centrifuged down and washed twice with distilled water; in this process they lost potassium (Bernheim, 1963). They were finally suspended in distilled water and the concentration adjusted for estimation of light absorption in a Coleman junior spectrophotometer at 490 m p so that the initial optical density varied no more than 10 yo between experiments.…”