REGULATION OF NUCLEOSIDE DIPHOSPHATE KINASE AND SECRETABLE VIRULENCE FACTORS IN PSEUDOMONAS-AERUGINOSA - ROLES OF ALGR2 AND ALGH

Alginate is an important virulence factor for Pseudomonas aeruginosa d uring infection of the Lungs of cystic fibrosis patients, The genes en coding enzymes for alginate production by P. aeruginosa are normally s ilent. They are activated in response to several environmental conditi ons, including high osmolarity, exposure to ethanol, or long-term grow th under conditions of nutrient deprivation, Several genes which parti cipate in the activation of alginate gene promoters have been identifi ed; among these is the algR2 (algQ) gene. AlgR2 is an 18-kDa protein w hich has been shown to regulate the critical algD gene encoding GDP-ma nnose dehydrogenase as well as to regulate the levels of a tricarboxyl ic acid cycle enzyme, i,e,, succinyl coenzyme A synthetase, and nucleo side diphosphate kinase (Ndk), an enzyme involved in nucleoside tripho sphate synthesis. Succinyl coenzyme A synthetase and Ndk form a comple x in P. aeruginosa. While algR2 is required for alginate synthesis at 37 degrees C, an algR2 insertion mutant was still able to make alginat e slowly at 37 or at 30 degrees C. We used this observation to identif y and clone a gene, termed algH, A strain with mutations in both algR2 and algH is unable to produce alginate at either 37 or 30 degrees C, and it is fully defective in Ndk production.