THE EFFECT OF AMINO ACIDS AND RELATED COMPOUNDS UPON THE GROWTH, VIRULENCE, AND ENZYME ACTIVITY OF CROWN GALL BACTERIA

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Abstract
The influence of amino acids and related compounds upon the growth and virulence of Agrobacterium tumefaciens has been investigated. Compounds which inhibited growth and produced complete attenuation are, in decreasing order of their activity: alpha-amino-n-butyric acid, threonine, norvaline, valine, norleucine, isoleucine, glycine, serine, alanine, leucine, lysine, and diglycine. With leucine isomers, it was noted that D(+) leucine, the unnatural isomer, was more inhibitory than the L(-) isomer. Dicarboxylic amino acids stimulated growth but had no effect on virulence even at higher concns. After 17 transfers in glycine media, 70% of the cultures on stock media regained virulence. But after 25 transfers, only 2% regained virulence. Inhibition of growth by amino acids was not reversed by other amino acids, vitamins, or growth factors. Liver extract induced slight reversal. Virulent and attenuated cultures were not differentiated by cultivation in various media, serological reactions, or enzyme activities. Glycine-attenuated strains grew better and were enzymatically more active in the presence of glycine than were unacclimatized strains.