THE ESCHERICHIA-COLI GENES SSPA AND RNK CAN FUNCTIONALLY REPLACE THE PSEUDOMONAS-AERUGINOSA ALGINATE REGULATORY GENE ALGR2

The algR2 (also known as algQ) gene of Pseudomonas aeruginosa has prev iously been identified as being necessary for alginate production at 3 7 degrees C. We have cloned two genes, from a cosmid library of Escher ichia coli, which can restore mucoidy to an algR2 mutant of P. aerugin osa. The complementing regions of both cosmids were localized by subcl oning restriction fragments. One of the E. coli genes identified here has not previously been described; we have named this gene rnk (regula tor of nucleoside diphosphate kinase). It encodes a 14.9 kDa protein w ith no homology to any other protein. The other gene, sspA, is a regul ator involved in stationary-phase regulation in E. coli. Either gene w ill restore mucoidy to an algR2-deficient strain of P. aeruginosa. Alg R2 has been shown to regulate at least two enzymes, succinyl-CoA synth etase (Scs) and nucleoside diphosphate kinase (Ndk), which form a comp lex in P. aeruginosa. When we examined the ability of the E. coil anal ogues to regulate Ndk, we found that rnk but not sspA was able to rest ore Ndk activity to the P. aeruginosa algR2 mutant. Furthermore, rnk w as able to restore growth of the algR2 mutant in the presence of Tween 20, which inhibits other Ndk-like activities.