GROWTH, DEVELOPMENT, AND DIFFERENTIATION 195 



Multiplication of Bacteria, Fungi, and Other Microorganisms 



Bacterial growth is apparently fairly resistant to malonate, despite the 

 many observations of enzyme and metabolic inhibitions in these organisms. 

 The absence of any effect on E. coli at malonate concentrations up to 100 mM 

 reported by Czekalowski was mentioned above, but Loveless et al. (1954) 

 found 50% inhibition of growth at 19.2 ml/ malonate, with no effect on cell 

 size. Malonate at 300 roM produces somewhat elongated E. coli cells and 

 at 800 mM they are markedly lengthened and often U-shaped: division is 

 abolished but the cells continue to elongate slowly (Schweisfurth and 

 Schwartz, 1959). The effects of malonate must depend on many factors, 

 including the nutrient medium, the duration of the growth phase studied, 

 and the pH. Although Rosenberg (1948) found the growth of Clostridium 

 saccharobutyricum to be inhibited by malonate, a concentration of 100 mM 

 was used, so that the mechanism of the effect is not clear. His observation 

 that the inhibition is overcome by meso-inositol and borate must be inter- 

 preted as indicating a unique approach to the study of malonate inhibition. 

 Malonate at 10 mM has a slightly depressant action on rate of germination 

 of Bacillus subtilis spores but does not affect growth in culture (Hachisuka 

 et al., 1955). The bacteriostatic concentrations of malonate were given as 

 3.2 mM for Pseudomonas fluorescens and 7.7 mM for B. aerogenes (Cooper 

 and Goddard, 1957) but the acid was used, the pH being 2.5 and 1.5, re- 

 spectively, so that a nonspecific acid effect is the most likely explanation, 

 especially as succinic acid is as inhibitory. It is clear that the investigations 

 of the effects of malonate on bacterial growth leave everything to be desired. 



The sporulation and growth of yeast are inhibited by malonate quite 

 potently and in parallel fashion, 50% depression of each occurring at 5 mM 

 (Miller and Halpern, 1956). On the other hand, Hensenula ellipsoidospora, 

 a vellum-forming yeast, grows more rapidly in the presence of malonate 

 (Luteraan, 1953). It would certainly not be too surprising to find certain 

 microorganisms stimulated by malonate inasmuch as many can oxidize 

 malonate readily (page 228). Malonate arrests sporulation of Aspergillus 

 niger without suppressing growth (Behal, 1959) but germination of Neuro- 

 spora ascospores is not blocked by 10 mM malonate even at pH 2.3 and 

 after 24 hr (Sussman et al., 1958), nor is the germination of Puccinia uredo- 

 spores affected significantly by 20 mM malonate at pH 4.8, although the 

 respiration is inhibited around 37% (Farkas and Ledingham, 1959). The 

 formation of conidia is often essential for the spread of the scab disease 

 of apple caused by Venturia inaequalis and so Kirkham and Flood (1963) 

 investigated the effects of various respiratory inhibitors on ascosporulation. 

 Malonate was found to inhibit at high concentrations, the inhibition sur- 

 prisingly increasing with increase in the pH (see accompanying tabulation). 

 This might imply an action on or within the membrane; this is supported 

 by the relative lack of effect on the respiration and the rather potent inhi- 



