ENERGY-METABOLISM AND ALGINATE BIOSYNTHESIS IN PSEUDOMONAS-AERUGINOSA- ROLE OF THE TRICARBOXYLIC-ACID CYCLE

Infection,vith mucoid, alginate-producing strains of Pseudomonas aerug inosa is the leading cause of mortality among patients with cystic fib rosis. Alginate production by P. aeruginosa is not constitutive but is triggered by stresses such as starvation. The algR2 (also termed algQ ) gene has been previously identified as being necessary for mucoidy; an algR2 mutant strain is unable to produce alginate when grown at 37 degrees C. We show here that the levels of phosphorylated succinyl coe nzyme A synthetase (Scs) and nucleoside diphosphate kinase (Ndk), whic h form a complex in P. aeruginosa, are reduced in the algR2 mutant. We were able to correlate the lower level of phosphorylated Scs with a d ecrease in Scs activity. Western blots (immunoblots) also showed a dec reased level of Ndk in the algR2 mutant, but the presence of another k inase activity sensitive to Tween 20 provides the missing Ndk function . The effect of AlgR2 on tricarboxylic acid (TCA) cycle enzymes appear s to be specific for Scs, since none of the other TCA cycle enzymes me asured showed a significant decrease in activity. Furthermore, the abi lity of the algR2 mutant to grow on TCA cycle intermediates, but not g lucose, is impaired. These data indicate that AlgR2 is responsible for maintaining proper operation of the TCA cycle and energy metabolism.