MASS-BALANCE METHOD FOR DETERMINATION OF THE INTRACELLULAR POOL OF RESPIRATORY SUBSTRATES

A mass-balance method for determining the size of the intracellular po ol of respiratory metabolism substrates is suggested. It involves regi stration of the response of starving microorganisms to microamendment by a limiting substrate (glucose). In a continuous Pseudomonas fluores cense culture, the relationship between the intensity of respiration q (resp) and the pool of intracellular compounds L obeyed the Michaelis - Menten equation: q(resp) = Q(resp) L / (K-L + L), where Q(resp) = 29 .1 mmole O-2/h/gC biomass and K-L = 12.14 mg C/gC biomass. The pool va lues determined by the mass balance method (1.5-3.5 mg C/gC biomass) w ere close to the ''mobile'' part of the intracellular compounds extrac ted by cold TCA and to the content of free intracellular amino acids. It was concluded from the study of respiration sensitivity to cyanide that the intracellular pool of oxidizable compounds was common for sub strate and endogenous respiration. The suggested method may be used fo r determining the size of the pool of actively growing and that of sta rving microorganisms.