Analysis of an L-Histidinol-utilizing Mutant of Pseudomonas aeruginosa

Abstract

S U M M A R YTransductional analysis was applied to the Pseudomonas aeruginosa mutant P A O I~ (hnc-I). This mutant can utilize L-histidinol as sole source of carbon and nitrogen and has a 60-fold increased histidinol dehydrogenase (HDH) content (Dhawale, Creaser & Loper, 1972). Transductional analysis was carried out using I 8 histidine-requiring mutants to see where the hnc-I locus maps in relation to the structural genes of histidine biosynthesis. The hnc-I marker cotransduced with group IV genes at 97 to IOO % and not at all with group I, which is known to be the structural gene for HDH.The data obtained in the studies of K , (histidinol) and K, (NAD), and the effect of pH and temperature on the HDH activity from PAOI and P A O I~ are in full agreement with the genetic data that the hnc-I mutation is not in the structural gene for HDH. It is suggested that hnc-I may be a mutation in a regulatory gene affecting HDH synthesis in P A O I~ and may map close to his-ZV whose function in histidine biosynthesis is not known. I N T R O D U C T I O NPrevious work on the evolution of mechanisms for utilization of histidinol as sole source of carbon and nitrogen (Dhawale, Creaser & Loper, 1 9 7 2 ) showed that whereas Arthrobacter histidinolovorans produced a second, inducible enzyme system for the conversion of histidinol to histidine, Pseudomonas aeruginosa appeared to have developed a new control system for the increased formation of histidinol dehydrogenase (HDH).We isolated a mutant of P . aeruginosa which can utilize histidinol (hnc-I: P A O I~) as the sole source of nitrogen and carbon, and gives a 60-fold increase in total HDH activity. However, polyacrylamide gel electrophoresis was unable to separate the enzyme activity of the mutant from that obtained from the parent strain PAOI grown on glucose plus minimal medium. The 'mutant' enzyme is inducible by histidinol and its synthesis is repressed by the catabolites of histidinol and histidine. It has been suggested that HDH produced by the mutant strain P A O I~ is the same as that synthesized by the wild-type strain (PAOI) grown on mineral salts, glucose and NH,NO,. To test this hypothesis further, two approaches were used. Firstly, a genetic analysis was carried out using histidine-requiring mutants in order to relate the hnc-I mutation to other genes of histidine biosynthesis in this bacterium. Secondly, the kinetic properties of the enzymes, which included K , (histidinol), K , (NAD), optimum pH and optimum temperature of the enzyme reaction were studied.There appear to be at least five groups of genes involved in histidine biosynthesis in P.

Study of the Correlation Between Severity of Endophthalmitis and Posterior Vitreous Detachment Using a Rabbit Endophthalmitis Model

“…The bacterial strain used was Pseudomonas aeruginosa strain PAO-1. 14 , 15 Culture was performed in NAC medium (Eiken Chemical Co. Ltd., Tokyo, Japan), which is a selective medium for P. aeruginosa , at 37°C for 24 hours, and adjusted to 1.0 × 10 8 CFU/mL.…”