METABOLISM OF PATHOGENIC BACTERIA I

Abstract

A procedure is outlined for safely conducting metabolic expts. with pathogenic microorganisms. Accurately measured volumes of the medium are pipetted into small containers, preferably bottles, and inoculated with a measured quantity of a culture or suspension of the organism. The culture is then incubated, preferably in a water bath, and acidified at any desired time to stop growth and metabolic activities. The acidified culture is tightly stoppered and kept in the refrigerator until ready for analysis. Analytical procedures are described in detail for reducing substances (glucose), hydrolyzable sugar, alcohols, volatile acids, lactic acid, CO2 and total titratable acids. These were applied to carbohydrate-rich meat infusion or meat extract media which contained from 0.3 to 0.75% of phosphate buffer, and which were enriched with 1% of peptone. Of the alcohols, only ethyl alcohol was produced. The volatile acids consisted of formic and acetic acids only. Metabolic data are presented which show that lactic acid, alcohol, and volatile acids account for 90-95% of the sugar metabolized by staphylococci and streptococci. These 3 products accounted for 85-90% of the metabolized sugar in 5 cultures of the pneumococcus and 1 culture each of Shigella dysenteriae Flexner, Eberthella typhosa, and Salmonella suipestijer. About 75% was similarly accounted for in single cultures of Escherichia coli, Friedlander''s bacillus, Salmonella typhi murium, S. enteritidis, S. schottmuelleri paratyphosus B, Escherichia acidi lactici and Vibrio cholerae. The yield of metabolic products is great enough so that a complete analysis by all of the methods descr. can be made on a minimum of 25 cc. of the culture. The metabolic data demonstrate the effectiveness of acid, both for stopping metabolic activities and for preserving the culture. Consistency as a whole of the data from bacteria differing widely in their cultural and morphological characters is evidence of the reliability of the analytical procedures. Where the inoculum is small, with the present methods it is impossible to obtain reliable complete metabolic data from the young culture representing the first third or half of the rapid growth phase.