Biotype 1 and 2 strains of Agrobacterium tumefaciens were isolated from crown gall tumors of Lippia canescens plants growing as ground cover in Arizona. The isolates were agrocin 84 sensitive, did not catabolize octopine, nopaline, agropine, or mannopine, and were limited in their tumorigenic host range. One biotype 2 strain, AB2/73, showed the most limited host range; it incited tumors only on Lippia strains, the cucurbit family of plants, and Nicotiana glauca. Megaplasmids were detected in the isolates by vertical agarose gel electrophoresis. The unusual host range, as well as sensitivity to agrocin 84, were plasmid specified since they were conjugally cotransferred with plasmids from donor strain AB2/73.

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Two types of Pseudomonas putida PpG2 mutants which were unable to degrade branched-chain amino acids were isolated after mutagenesis and selection for ability to grow on succinate, but not valine, as a sole source of carbon. These isolates were characterized by growth on the three branched-chain amino acids (valine, isoleucine, and leucine), on the corresponding branchedchain keto acids (2-ketoisovalerate, 2-keto-3-methylvalerate, and 2-ketoisocaproate), and on other selected intermediates as carbon sources, and by their enzymatic composition. One group of mutants lost 2-ketoisovalerate-inducible branched-chain keto acid dehydrogenase that was active on all three keto acids. There was also a concomitant loss of ability to grow on all three branched-chain amino acids as well as on all three corresponding keto acids, but there was retention of ability to use subsequent intermediates in the catabolism of branched-chain amino acids. Another type of mutant showed a marked reduction in branched-chain amino acid transaminase activity and grew poorly at the expense of all three amino acids, but it utilized subsequent intermediates as carbon sources. Both the transaminase and branched-chain keto acid dehydrogenase mutants retained the ability to degrade camphor. These findings are consistent with the view that branched-chain amino acid transaminase and branched-chain keto acid dehydrogenase are common enzymes in the catabolism of valine, isoleucine, and leucine.

The effect of the proline analogue, L-thiazolidine-4-carboxylic acid (thioproline), on growth, and its relation to the metabolic function of proline in protein synthesis in Escherichia coli K-12, has been studied. Thioproline causes linear growth in E. coli within one generation. The inhibition is specifically reversed by the simultaneous addition of L-proline. Thioproline, or a closely related metabolic derivative, is incorporated into bacterial proteins. Proline antagonizes the incorporation of "thioproline" into protein. The analogue specifically inhibits the rate and extent of prolyl-ribonucleic acid formation. The effectiveness of thioproline as a proline analogue is attributed to its ability to interfere with the utilization of proline for protein synthesis and to mimic proline in its function of being incorporated into proteins. The effect of the incorporation of thioproline on protein structure and enzyme activity is discussed. ' This paper was taken from a thesis submitted by L. Unger to the faculty of the University of Illinois Graduate College in partial fulfillment of the requirements for the Ph.D. degree.