Abstract
Induction of high-affinity iron transport during root colonization by Pseudomonas fluorescens Pf-5 (pvd-inaZ) was examined in lupine and barley growing in microcosms. P. fluorescens Pf-5 (pvd-inaZ) contains a plasmid carrying pvd-inaZ; thus, in this strain, ice nucleation activity is regulated by pyoverdin production. Lupine or barley plants were grown for 18 or 8 days, respectively, in soil amended with 2% calcium carbonate and inoculated with P. fluorescens Pf-5 (pvd-inaZ) at a density of 4 x 10(sup8) CFU g (dry weight) of soil(sup-1). A filter paper blotting technique was used to sample cells from the rhizosphere in different root zones, and then the cells were resuspended for enumeration and measurement of ice nucleation activity. The population density of P. fluorescens Pf-5 (pvd-inaZ) in the rhizosphere decreased by one order of magnitude in both lupine and barley over time. The ice nucleation activity ranged from -3.4 to -3.0 log ice nuclei CFU(sup-1) for lupine and -3.0 to -2.8 log ice nuclei CFU(sup-1) for barley, was similar in all root zones, and did not change over time. An in vitro experiment was conducted to determine the relationship between ice nucleation activity and pyoverdin production in P. fluorescens Pf-5 (pvd-inaZ). An ice nucleation activity of approximately -3.0 log ice nuclei CFU(sup-1) was measured in the in vitro experiment at 25 to 50 (mu)M FeCl(inf3). By using the regression between ice nucleation activity and pyoverdin production determined in vitro and assuming a P. fluorescens Pf-5 (pvd-inaZ) population density of 10(sup8) CFU g of root(sup-1), the maximum possible pyoverdin accumulation by P. fluorescens Pf-5 (pvd-inaZ) in the rhizosphere was estimated to be 0.5 and 0.8 nmol g of root(sup-1) for lupine and barley, respectively. The low ice nucleation activity measured in the rhizosphere suggests that nutritional competition for iron in the rhizosphere may not be a major factor influencing root colonization by P. fluorescens Pf-5 (pvd-inaZ).
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- Akers H. A. Isolation of the siderophore schizokinen from soil of rice fields. Appl Environ Microbiol. 1983 May;45(5):1704–1706. doi: 10.1128/aem.45.5.1704-1706.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Buyer J. S., Kratzke M. G., Sikora L. J. A method for detection of pseudobactin, the siderophore produced by a plant-growth-promoting pseudomonas strain, in the barley rhizosphere. Appl Environ Microbiol. 1993 Mar;59(3):677–681. doi: 10.1128/aem.59.3.677-681.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hamdan H., Weller D. M., Thomashow L. S. Relative importance of fluorescent siderophores and other factors in biological control of Gaeumannomyces graminis var. tritici by Pseudomonas fluorescens 2-79 and M4-80R. Appl Environ Microbiol. 1991 Nov;57(11):3270–3277. doi: 10.1128/aem.57.11.3270-3277.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jurkevitch E., Hadar Y., Chen Y., Chino M., Mori S. Indirect utilization of the phytosiderophore mugineic acid as an iron source to rhizosphere fluorescent Pseudomonas. Biometals. 1993 Summer;6(2):119–123. doi: 10.1007/BF00140113. [DOI] [PubMed] [Google Scholar]
- KING E. O., WARD M. K., RANEY D. E. Two simple media for the demonstration of pyocyanin and fluorescin. J Lab Clin Med. 1954 Aug;44(2):301–307. [PubMed] [Google Scholar]
- Loper J. E., Lindow S. E. A biological sensor for iron available to bacteria in their habitats on plant surfaces. Appl Environ Microbiol. 1994 Jun;60(6):1934–1941. doi: 10.1128/aem.60.6.1934-1941.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- O'Sullivan D. J., O'Gara F. Traits of fluorescent Pseudomonas spp. involved in suppression of plant root pathogens. Microbiol Rev. 1992 Dec;56(4):662–676. doi: 10.1128/mr.56.4.662-676.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Poole K., Young L., Neshat S. Enterobactin-mediated iron transport in Pseudomonas aeruginosa. J Bacteriol. 1990 Dec;172(12):6991–6996. doi: 10.1128/jb.172.12.6991-6996.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]