Turbidity Changes in Bacterial Suspensions: Kinetics and Relation to Metabolic State

Abstract

SUMMARY: The kinetics of the turbidity changes in bacterial suspensions due to variations in the osmotic pressure of the medium were investigated. The time curve of the turbidity changes followed a monomolecular course, but the velocity constant was strongly dependent on the osmotic pressure. The value of the temperature coefficient (&)of the reactionwas close to two. The rapid adjustment of the turbidity (increase or decrease) to the changes in osmotic pressure of the medium was followed by a phase of slow decline in light extinction. In this slow phase the rate of turbidity decrease was independent of the prevailing osmotic pressure, but varied with the nature of the solute used ; it was markedly accelerated by KCN or HgCl, . The effect of HgCl, was annulled by thiol compounds. Certain substances affected the optical effect and the respiration in a parallel manner. The similarity between these observations and the findings of several authors with regard to turbidity changes in mitochondrial suspensions is discussed.It has been shown in the preceding communication (Mager, Kuczynski, Schatzberg & Avi-Dor, 1956) that changes in the osmotic pressure of the medium elicited corresponding changes in the turbidity of suspensions of Gram-negative micro-organisms. This optical effect ( o.E.) was tentatively attributed to changes in the state of swelling of the bacterial cytoplasm. The present study presents some further observations, which have a bearing on the nature of this phenomenon. METHODSThe chemicals, micro-organisms and the experimental procedures employed were the same as described before (Mager et al. 1956). The conditions of ultraviolet irradiation are indicated in the text. For dry weight determination, the centrifuged bacterial mass was dried in a vacuum oven a t 60" to constant weight. For kinetic studies, the Beckman spectrophotometer model D.U.equipped with a thermospacer for temperature control, was used.

Effect of R Plasmid RP1 on the Nutritional Requirements of Escherichia coli in Batch Culture

“…Absorbance, as a measure of growth, varies with the environment (Avi-dor et al, 1956). However, growth was assessed for cells growing exponentially with medium components in Table I .…”

Osmotically Induced Volume and Turbidity Changes of Escherichia coli due to Salts, Sucrose and Glycerol, with Particular Reference to the Rapid Permeation of Glycerol into the Cell

“…This method has been utilized to study substrate transport in cells (Sen & Widdas, 1962) and organelles (Chappell & Haarhoff, 1967) but has been little used in bacterial systems (Avi-dor, Kuczynski, Schatzberg & Mager, 1956 ;Mitchell & Moyle, 1956;Bovell, Packer & Helgerson, 1963).…”

Transport and Retention of K + and Other Metabolites in a Marine Pseudomonad and Their Relation to the Mechanism of Optical Effects

“…An optical density (OD) increase occurs in suspensions of many species of gram-negative bacteria when the solute concentration of the suspending medium is increased. This increase is often followed by a slow decrease to values approaching those prevailing initially (1,3,9,11,14). The first phase of this phenomenon, the increase in OD, has most often been ascribed either to plasmolysis of or to a decrease in the size of the cells caused by the osmotic action of a nonpenetrating or slowly penetrating solute.…”