title: Altered Gene Expression and Intracellular Changes of the Viable But Nonculturable State in Ralstonia solanacearum by Copper Treatment.
abstract: Environmental stresses induce several plant pathogenic bacteria into a viable but nonculturable (VBNC) state, but the basis for VBNC is largely uncharacterized. We investigated the physiology and morphology ofthe copper-induced VBNC state in the plant pathogen Ralstonia solanacearum in liquid microcosm. Supplementation of 200 μM copper sulfate to the liquid microcosm completely suppressed bacterial colony formation on culture media; however, LIVE/DEAD BacLight bacterial viability staining showed that the bacterial cells maintained viability, and that the viable cells contain higher level of DNA. Based on electron microscopic observations, the bacterial cells in the VBNC state were unchanged in size, but heavily aggregated and surrounded by an unknown extracellular material. Cellular ribosome contents, however, were less, resulting in a reduction of the total RNA in VBNC cells. Proteome comparison and reverse transcription PCR analysis showed that the Dps protein production was up-regulated at the transcriptional level and that 2 catalases/peroxidases were present at lower level in VBNC cells. Cell aggregation and elevated levels of Dps protein are typical oxidative stress responses. H2O2 levels also increased in VBNC cells, which could result if catalase/peroxidase levels are reduced. Some of phenotypic changes in VBNC cells of R. solanacearum could be an oxidative stress response due to H2O2 accumulation. This report is the first of the distinct phenotypic changes in cells of R. solanacearum in the VBNC state.
authors.affiliation: Department of Medical Bioscience, Dong-A University, Busan 604-714, Korea.
authors.forename: Hae Young
authors.initials: HY
authors.lastname: Um
authors.affiliation: Department of Applied Biology, Dong-A University, Busan 604-714, Korea.
authors.forename: Hyun Gi
authors.initials: HG
authors.lastname: Kong
authors.affiliation: Department of Applied Biology, Dong-A University, Busan 604-714, Korea.
authors.forename: Hyoung Ju
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Medical Bioscience, Dong-A University, Busan 604-714, Korea.
authors.forename: Hye Kyung
authors.initials: HK
authors.lastname: Choi
authors.affiliation: Department of Applied Biology, Dong-A University, Busan 604-714, Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Park
authors.affiliation: Department of Plant Bioscience, Pusan National University, Miryang 627-706, Korea.
authors.forename: Sun Tae
authors.initials: ST
authors.lastname: Kim
authors.affiliation: Department of Applied Biology, Dong-A University, Busan 604-714, Korea.
authors.forename: Senthilkumar
authors.initials: S
authors.lastname: Murugiyan
authors.affiliation: Department of Medical Bioscience, Dong-A University, Busan 604-714, Korea.
authors.forename: Eunsook
authors.initials: E
authors.lastname: Chung
authors.affiliation: Division of Applied Life Science, Gyeongsang National University, Jinju 660-701, Korea.
authors.forename: Kyu Young
authors.initials: KY
authors.lastname: Kang
authors.affiliation: Department of Medical Bioscience, Dong-A University, Busan 604-714, Korea ; Department of Applied Biology, Dong-A University, Busan 604-714, Korea.
authors.forename: Seon-Woo
authors.initials: SW
authors.lastname: Lee
keywords: Ralstonia solanacearum; copper; dps; oxidative stress; viable but nonculturable (VBNC) state