Studies on Bacterial Nutrition

Abstract

In previous papers it has been shown that unheated plant tissue, in the form of potato, contains the two factors necessary for the growth of organisms of the hemoglobinophilic group. Further studies (5) confirmed these findings and showed that yellow and white turnip, carrot, beet, parsnip, and sweet potato can replace blood in the cultivation of Bacillus influenzæ. In the present paper it has been shown that vegetable tissues also greatly facilitate and stimulate the growth of other organisms entirely unrelated to Bacillus influenzæ. Three varieties of Gram-positive cocci have been used in the present study, pneumococcus, Streptococcus hamolyticus, and Streptococcus viridans. With pneumococcus it has been previously shown that prompt and luxuriant growth will occur in broth containing unheated potato even though the seeding be so small that no growth whatever will occur with the same seeding in plain broth (5). In the present study it has been shown that even in dextrose broth this minimal inoculation is followed by a prolonged period of lag, whereas in potato broth this same inoculum serves to initiate immediate and rapid growth. When pneumococci are grown in potato broth not only is the period of lag abolished, but the stationary period of growth is extended and cell death is delayed. Moreover, in plant tissue medium the zone of hydrogen ion concentration within which growth of pneumococcus can be initiated is considerably extended beyond the acid and alkaline limits of the optimal range in ordinary bouillon. It has been found also that the presence of unheated plant tissue in the media likewise stimulates growth of hemolytic and non-hemolytic streptococci. In this investigation no attempt has been made to determine the exact nature of the substances in plant tissue upon which these properties depend. That they are not of the nature of readily fermentable carbohydrates, however, is made evident by the fact that no increased production of acid occurs in the pneumococcus culture when potato is present.

The Effects of Acidity Upon the Growth of Pneumococcus in Culture Media Containing Proteins

“…That acidity in vitro exerts a bacteriostatic effect upon the pneumococcus was proven by the studies of Demby and Avery (2), and Lord and Nye (3,4), which showed that in broth, hydrogen ion concentrations greater than pH 6.80 not only inhibit growth but within a short time produce death of this bacterium. However, Morgan and Avery (5) have shown that the range of hydrogen ion concentrations at which pneumococcus growth can be initiated may be extended to a degree of acidity as great as pH 6.2 in broth by the addition of fresh unheated plant tissues. Possible evidence that acidity may be less active in inhibiting the growth of pneumococcus in animal tissue fluids is afforded by the observations of Felton and Dougherty (6) who were able to maintain growth of this microorganism in milk at pH 5.00, when adjusted with hydrochloric acid.…”

An Unknown Factor Stimulating the Formation of Butyl Alcohol by Certain Butyric Acid Bacteria

“…The organisms affected by some of these factors include yeasts (Robertson and Davis (1923)) and bacteria. Among the latter are butyric acid bacteria (Ruschmann and Harder (1931)), hemolytic organisms (Morgan and Avery (1923)), staphylococci (Leichtentritt and Zielaskowski (1922)), streptococci (Thompson (1929)), the pneumococci (Thjotta and Avery (1921), Kollath (1926, Kopp, (1927)), and the tubercle organisms (Uyei (1930)). Little is known about the role played by the stimulating factors or about their actual chemical nature.…”

Growth-Inhibitory Substances in Pneumococcus Cultures

“…In the case of pneumococcus it is known that the reaction of the medium is of great importance (1,2). It has been shown that growth cannot be initiated in plain broth more acid than pH 7, or more alkaline than pH 8.3, and that the optimum reaction for growth is pH 7.8.…”