Monitoring of Biodegradative Pseudomonas putida Strains in Aquatic Environments Using Molecular Techniques

Abstract Monitoring strategies were developed to track non–genetically engineered Pseudomonas putida strains in the open environment. The strain E1 was used for four years for the biodegradation of phenolic compounds in industrial wastewater in P?lva, Estonia. In this study we used the strain E2 which is a non-carbenicillin-resistant variant of the strain E1. Both strains have a deletion of approximately 34 kb in the TOL plasmid pWW0 which served as a basis for discrimination from indigenous bacteria by molecular analyses. Other targets used for PCR and DNA hybridization were the xylE gene and a sequence located in the left-handed region of to the transposon Tn4652. In laboratory tests we demonstrated that two cells inoculated into 20 ml of river water could be detected against a background of more than 10⁷ colony forming units (CFUs) by a combination of growth on selective media and molecular analysis. Using the same combination of methods in a deliberate release experiment, detection of the released strain was possible only to 32 h after release. It is assumed that the released strains did not survive in the aquatic ecosystem, mainly due to the high dilution rate. The combination of cultivation on selective media and molecular analyses proved useful for tracking Pseudomonas putida strain E2 in an aquatic environment. Received: 29 March 1996; Accepted: 1 April 1996     

Effects of chorda tympani nerve anesthesia on taste responses in the NST

Human clinical and psychophysical observations suggest that the taste system is able to compensate for losses in peripheral nerve input, since patients do not commonly report decrements in whole mouth taste following chorda tympani nerve damage or anesthesia. Indeed, neurophysiological data from the rat nucleus of the solitary tract (NST) suggests that a release of inhibition (disinhibition) may occur centrally following chorda tympani nerve anesthesia. Our purpose was to study this possibility further. We recorded from 59 multi- and single- unit taste-responsive sites in the rat NST before, during and after recovery from chorda tympani nerve anesthesia. During anesthesia, average anterior tongue responses were eliminated but no compensatory increases in palatal or posterior tongue responses were observed. However, six individual sites displayed increased taste responsiveness during anesthesia. The average increase was 32.9%. Therefore, disinhibition of taste responses was observed, but infrequently and to a small degree in the NST At a subset of sites, chorda tympani-mediated responses decreased while greater superficial petrosal-mediated responses remained the same during anesthesia. Since this effect was accompanied by a decrease in spontaneous activity, we propose that taste compensation may result in part by a change in signal-to-noise ratio at a subset of sites.