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RECORD NUMBER: 33 OF 39

Main Title Relationship of Total Viable and Culturable Cells in Epiphytic Populations of 'Pseudomonas syringae'.
Author Wilson, M. ; Lindow, S. E. ;
CORP Author California Univ., Berkeley. Dept. of Plant Pathology.;Corvallis Environmental Research Lab., OR.
Publisher c1992
Year Published 1992
Report Number EPA-R-815305; EPA/600/J-93/291;
Stock Number PB93-222826
Additional Subjects Microbial colony count ; Phaseolus ; Culture media ; Nalidixic acid ; Genetic engineering ; Reprints ; Pseudomonas syringae
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NTIS  PB93-222826 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 8p
Abstract
The direct viable count method, used to detect viable but nonculturable bacteria in aquatic systems, was modified to examine epiphytic populations of Pseudomonas syringae. Viable-population sizes determined from the number of cells that elongated when incubated with yeast extract and nalidixic acid were compared with those determined by the conventional plate count method. The plate count method accurately determined the number of viable cells in epiphytic P. syringae populations in a state of active growth under conditions of high relative humidity. The plate count method also accurately determined the number of viable cells in P. syringae inoculum, or a growing P. syringae population, subject to desiccation stress under conditions of low relative humidity. In epiphytic populations of P. syringae older than 80 h, however, the plate count underestimated the viable-population size by about two- to fourfold, suggesting that up to 75% of the P. syringae population was nonculturable. These nonculturable cells may have entered a starvation-survival state, induced by low nutrient availability in the phyllosphere environment. Epiphytic P. syringae populations undergoing rapid size changes due to growth and death under fluctuating environmental conditions in the field should be accurately enumerated by the plate count method. However, the possible underestimation of viable-population size under some circumstances should be considered in epidemiological studies of phytopathogenic bacteria and when genetically engineered microorganisms in terrestrial ecosystems are monitored. (Copyright (c) 1992, American Society for Microbiology.)