title: Involvement of nitric oxide synthase in sucrose-enhanced hydrogen peroxide tolerance of Rhodococcus sp. strain APG1, a plant-colonizing bacterium.
abstract: Hydrogen peroxide (H2O2) tolerance of Rhodococcus sp. strain APG1, previously isolated from the aquatic fern Azolla pinnata, was examined in relation to nitric oxide (NO) production by cells cultured on a variety of C sources. Cells inoculated onto A. pinnata fronds established a surface-sterilant resistant density of 2-4x10(7) cells g(-1) without causing disease. Compared to cultures containing glucose, fructose, mannitol, or glycerol, those provided only with sucrose displayed, on a per C basis, substantially lower (<10%) growth yields and higher resistance to H2O2. NO, a positive regulator of catalase synthesis in bacteria, was produced in larger amounts in sucrose-grown cells as evidence by eightfold greater per cell accumulations in the medium of nitrite (NO2-), a stable oxidation product of NO. Addition to cells of L-arginine, the substrate for nitric oxide synthase (NOS), stimulated production of NO, detected both by fluorometric reaction with diaminofluorescein-FM diacetate (DAF-FM DA) and by increased levels of NO2- in the culture medium. These results suggest that sucrose may enhance H2O2 tolerance of Rhodococcus APG1 by increasing cellular NO producing capacity. We propose a regulatory role for NOS in promoting tolerance of Rhodococcus APG1 to oxidative stress in the phyllosphere.
authors.affiliation: Division of Functional Genomics, Center of Molecular Biosciences, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Cohen
authors.forename: Hideo
authors.initials: H
authors.lastname: Yamasaki
mesh_terms: D002374:Catalase / Q000378:metabolism; D005456:Fluorescent Dyes; D006861:Hydrogen Peroxide / Q000378:metabolism*; D009569:Nitric Oxide / Q000032:analysis / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009573:Nitrites / Q000032:analysis / Q000378:metabolism; D063245:Plant Development; D010944:Plants / Q000382:microbiology*; D012240:Rhodococcus / Q000254:growth & development / Q000378:metabolism*; D013395:Sucrose / Q000494:pharmacology
chemical_list: D005456:Fluorescent Dyes; D009573:Nitrites; D009569:Nitric Oxide; D013395:Sucrose; D006861:Hydrogen Peroxide; D002374:Catalase; D019001:Nitric Oxide Synthase