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The adnA transcriptional factor affects persistence and spread of Pseudomonas fluorescens under natural field conditions

Marshall, B., Robleto, E.A., Wetzler, R., Kulle, P., Casaz, P., Levy, S.B.
Applied and environmental microbiology 2001 v.67 no.2 pp. 852-857
Pseudomonas fluorescens, transcription factors, mutants, transposons, agricultural soils, colonizing ability, population density, mortality
A soil plot was inoculated with a mixture of Pseudomonas fluorescens PF0-2, the wild type, and Pf0-5a, a Tn5 insertion mutant in adnA, at 7.84 log CFU/g of soil. Over a period of 231 days, culturable populations of both strains were measured at selected times below and away from the point of inoculation. Pf0-5a did not spread as fast and attained significantly lower populations than Pf0-2. At sample depths below the inoculation site, the adnA mutant showed a significant decrease in CFU/g of soil as compared to Pf0-2. Pf0-2 was first detected at the 1.5-cm annular site at 3 days after inoculation, whereas Pf0-5a required 7 days to travel the same distance. At this distance, the wild-type strain could be detected at a 21.5- to 25-cm depth, whereas Pf0-5a could be detected only as deep as 15.5 to 18 cm. At 4.5 cm from the site of inoculation and in soil fractions corresponding to 13 to 18 cm, Pf0-2 was the only strain detected. These results suggest that the transcription factor AdnA provides a fitness advantage in P. fluorescens, allowing it to spread and survive in soil under field conditions.