Adsorption of Methylene Blue as a Means of Determining Cell Concentration of Dead Bacteria in Suspensions

Abstract

The uptake of methylene blue by dead bacterial cells follows physicochemical adsoprtion laws, whether the microorganism is Gram-positive or Gram-negative. This fact was observed with Sarcina lutea, Bacillus subtilis, Micrococcus flavus, Serratia marcescens, Eschericiha coli, Proteus vulgaris and Pseudomonas aeruginosa. The initial dye concentration was about 100 mg/lit, and the maximum dry cell concentration varied from 0.3 to 2.2 gm/lit. A new method is described for determining colorimetrically the total bacterial cell concentration, analogous to our published method for yeasts (J. Bact., 76, 251-5 1958).