The amino acids required for growth and as energy sources by 10 strains of Legionella pneumophila were determined by using a chemically defined medium. All strains required arginine, cysteine, isoleucine, leucine, threonine, valine, methionine, and phenylalanine or tyrosine. Most strains (7 of 10) required serine, and two strains had to be supplied proline before growth could be established. All 10 strains used serine and, to a lesser extent, threonine as the sole sources of
Serial passage of six strains of Legionella pneumophila and one strain of Pseudomonas aeruginosa in a liquid chemically defined medium deficient in trace metals resulted in the death of five L. pneumophila strains and very limited growth in the remaining strain and the P. aeruginosa strain. Addition of either iron or magnesium restored growth to almost normal levels in ail of the strains when early-passage inocula were used. A low concentration of magnesium stimulated growth with cobalt, copper, iron, manganese, molybdenum, vanadium, or zinc. When a complete defined medium containing trace metals was used, growth was inhibited by adding the chelators ethylenediaminetetraacetic acid, citrate, or 2,2'-bipyridyl. Chelator inhibition was partly or fully relieved with either calcium, cobalt, copper, iron, magnesium, manganese, molybdenum, nickel, vanadium, or zinc. P. aeruginosa differed from L. pneumophila in that it required higher concentrations of each chelator to inhibit growth and that its growth was stimulated by only four metals: calcium, iron, magnesium, and zinc. A trace-metal supplement for L. pneumophila was designed which included all metals stimulating growth in these experiments and which proved to be sufficient for optimal growth of all the strains.
In the past few years several investigators have demonstrated the importance of the role of L-alanine for the germination of spores from aerobic bacilli. Hills (1949) found that the germination of Bacillus anthracis spores was greatly stimulated by L-alamine, L-tyrosine, and adenosine. The requirement for L-alanine could not be replaced by related compounds, and in addition its activity was strongly inhibited by D-alanine. The germination of spores of B. subtilis suspended in a buffered medium containing only L-alanine has also been described (Hills, 1950; Powell, 1950). Stewart and Halvorson (1953) reported the germination of B. terminali8 in the presence of L-alanine and adenosine. Recently Church, Halvorson, and Halvorson (1954) have shown that L-alamnie is stimulatory for the germination of B. terminali8, B. cereu8, B. polymyxa, B. subtilis, and B. globigii.
Reciprocal cross-protective antigens have been demonstrated between types 3 and 31 cocci, and one-way cross-protective antigens have been demonstrated between types 46 and 51 cocci. The reciprocal cross-protective antigen of types 3 and 31 is distinct from the specific M protein of either type. In the one-way cross relationship, type 46 cocci contain both type 46 and type 51 M proteins and therefore stimulate protective antibodies against both types. Type 51 cultures contain only the homologous M antigen. These relationships were demonstrated by capillary precipitin tests, indirect bactericidal tests, and in agar-gel diffusion patterns. The practical significance of these relationships in the serological typing of group A streptococci is discussed along with their possible role in immunity to streptococcal infections in man.
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