1887

Abstract

Ferric iron is an essential element for microbial growth but its water solubility in aerobic environments is considered to be low. Thus it is a limiting resource for which microbes must compete in natural habitats. Since competition for iron occurs at the level of individual cells, knowledge of the variability in iron bioavailability to such individuals is required to assess the nature of the competition in these habitats. Ferric iron availability to cells of was assessed by quantifying the fluorescence intensity of single cells harbouring a plasmid-borne transcriptional fusion of an iron-regulated promoter from a locus encoding a membrane receptor for a pyoverdine siderophore with a reporter gene encoding green fluorescent protein (GFP) following fluorescence microscopy. Cells of this iron biosensor exhibited iron-dependent GFP fluorescence that was inversely proportional to the amount of iron added to the media, and which differed by over 20-fold in iron-replete compared to iron-deplete culture media. Cells cultured in a medium of a given iron content exhibited a very narrow range of fluorescence intensities. In contrast, the fluorescence intensity of cells of the biosensor strain recovered from the rhizosphere or phylloplane of inoculated bean plants varied greatly. The distribution of fluorescence intensities was strongly right-hand skewed, with about 10% of the cells exhibiting substantially higher GFP fluorescence than that of the median cell. Cells of a positive control strain, harbouring a fusion of the constitutive II promoter with the reporter gene, exhibited uniform GFP fluorescence both in culture media and on plants. These results indicate that there is substantial heterogeneity of iron biovailability to cells of on plants, with only a small subset of cells experiencing low iron availability. Such heterogeneity places constraints on models of interactions of bacteria in natural habitats that are based on competition for limited iron.

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2000-10-01
2024-11-03
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References

  1. Amann R. I., Krumholz L., Stahl D. A. 1990; Fluorescent-oligonucleotide probing of whole cells for determinative, phylogenetic, and environmental studies in microbiology. J Bacteriol 172:762–770
    [Google Scholar]
  2. Beattie G. A., Lindow S. E. 1994; Comparison of the behavior of epiphytic fitness mutants of Pseudomonas syringae under controlled and field condition. Appl Environ Microbiol 60:3799–3808
    [Google Scholar]
  3. Buyer J. S., Sikora L. J. 1991; Rhizosphere interactions and siderophores. In The Rhizosphere and Plant Growth pp. 263–369Edited by Keister D. L., Cregan P. B. Dordrecht: Kluwer;
    [Google Scholar]
  4. Christensen B. B., Sternberg C., Andersen J. B., Eberl L., Moller S., Givskov M., Molin S. 1998; Establishment of new genetic traits in a microbial biofilm community. Appl Environ Microbiol 64:2247–2255
    [Google Scholar]
  5. Dowling D. N., Sexton R., Fenton A., Delany I., Fedi S., McHugh B., Callanan M., Moenne-Loccoz Y., O’Gara F. 1996; Iron regulation in plant associated Pseudomonas fluorescens M114: implications for biological control. In Molecular Biology of Pseudomonads pp. 502–511Edited by Nakazawa T.others Washington, DC: American Society for Microbiology;
    [Google Scholar]
  6. Eberl L., Schulze R., Ammendola A., Geisenberger O., Erhart R., Sternberg C., Molin S., Amann R. 1997; Use of green fluorescent protein as a marker for ecological studies of activated sludge communities. FEMS Microbiol Lett 149:77–83 [CrossRef]
    [Google Scholar]
  7. Ehrlich H. L. 1990; Geomicrobiology of iron. In Geomicrobiology pp. 283–346 New York: Marcel Dekker;
    [Google Scholar]
  8. Gill P. R., Warren G. J. 1988; An iron-antagonized fungistatic agent that is not required for assimilation from a fluorescent rhizosphere pseudomonad. J Bacteriol 170:163–170
    [Google Scholar]
  9. Guerinot M. L. 1994; Microbial iron transport. Annu Rev Microbiol 48:743–772 [CrossRef]
    [Google Scholar]
  10. Hojberg O., Sorensen J. 1993; Microgradients of microbial oxygen consumption in a barley rhizosphere model system. Appl Environ Microbiol 59:431–437
    [Google Scholar]
  11. Jacobi C. A., Roggenkamp A., Rakin A., Zumbihl R., Leitritz L., Heesemann J. 1998; In-vitro and in-vivo expression studies of yopE from Yersinia enterocolitica using the gfp reporter gene. Mol Microbiol 30:865–882 [CrossRef]
    [Google Scholar]
  12. Jaeger C. H. III, Lindow S. E., Miller W., Clark E., Firestone M. K. 1999; Mapping of sugar and amino acid availability in soil around roots with bacterial sensors of sucrose and tryptophan. Appl Environ Microbiol 65:2685–2690
    [Google Scholar]
  13. Kinkel L. L. 1997; Microbial population dynamics on leaves. Annu Rev Phytopathol 35:327–347 [CrossRef]
    [Google Scholar]
  14. Kragelund L., Hosbond C., Nybroe O. 1997; Distribution of metabolic activity and phosphate starvation response of lux-tagged Pseudomonas fluorescens reporter bacteria in the barley rhizosphere. Appl Environ Microbiol 63:4920–4928
    [Google Scholar]
  15. Leeman M., den Ouden F. M., van Pelt J. A., Dirkx F. P. M., Steijl H., Bakker P. A. H. M., Schippers B. 1996; Iron availability affects induction of systemic resistance to Fusarium wilt of raddish by Pseudomonas fluorescens. Phytopathology 86:149–155 [CrossRef]
    [Google Scholar]
  16. Li S., Spear R. N., Andrews J. H. 1997; Quantitative fluorescence in situ hybridization of Aureobasidium pullulans on microscope slides and leaf surfaces. Appl Environ Microbiol 63:3261–3267
    [Google Scholar]
  17. Lindow S. E. 1995; The use of reporter genes in the study of microbial ecology. Mol Ecol 4:555–566 [CrossRef]
    [Google Scholar]
  18. Lindsay W. L., Schwab A. P. 1982; The chemistry of iron in soils and its availability to plants. J Plant Nutr 5:821–840 [CrossRef]
    [Google Scholar]
  19. Loeppert R. H., Wei L.-C., Ocumpaugh W. R. 1994; Soil factors influencing the mobilization of iron in calcareous soils. In Biochemistry of Metal Micronutrients in the Rhizosphere pp. 343–357Edited by Manthey J. A., Crowley D. E., Luster D. G. Boca Raton, FL: CRC Press;
    [Google Scholar]
  20. Loper J. E., Buyer J. S. 1991; Siderophores in microbial interactions on plant surfaces. Mol Plant–Microbe Interact 4:5–13 [CrossRef]
    [Google Scholar]
  21. Loper J. E., Henkels M. D. 1997; Availability of iron to Pseudomonas fluorescens in rhizosphere and bulk soil evaluated with an ice nucleation reporter gene. Appl Environ Microbiol 63:99–105
    [Google Scholar]
  22. Loper J. E., Henkels M. D. 1999; Utilization of heterologous siderophores enhances levels of iron available to Pseudomonas putida in the rhizosphere. Appl Environ Microbiol 65:5357–5363
    [Google Scholar]
  23. Loper J. E., Ishimaru C. A. 1991; Factors influencing siderophore-mediated biocontrol activity of rhizosphere Pseudomonas spp. In The Rhizosphere and Plant Growth pp. 253–261Edited by Keister D. L., Cregan P. B. Dordrecht: Kluwer;
    [Google Scholar]
  24. Loper J. E., Lindow S. E. 1987; Lack of evidence for in situ fluorescent pigment production by Pseudomonas syringae pv. syringae on bean leaf surfaces. Phytopathology 77:1449–1454 [CrossRef]
    [Google Scholar]
  25. Loper J. E., Lindow S. E. 1994; A biological sensor for iron available to bacteria in their habitats on plant surfaces. Appl Environ Microbiol 60:1934–1941
    [Google Scholar]
  26. Marschner H. 1995editor Mineral Nutrition of Higher Plants New York: Harcourt Brace;
    [Google Scholar]
  27. Marschner P., Crowley D. E. 1997; Iron stress and pyoverdine production by a fluorescent pseudomonad in the rhizosphere of white lupin (Lupinus albus L.) and barley (Hordeum vulgare L.). Appl Environ Microbiol 63:227–281
    [Google Scholar]
  28. Miller W. G., Lindow S. E. 1997; An improved GFP cloning cassette designed for prokaryotic transcriptional fusions. Gene 191:149–153 [CrossRef]
    [Google Scholar]
  29. Moller S., Sternberg C., Ansersen J. B., Christensen B. B., Ramos J. L., Givskov M., Molin S. 1998; In situ gene expression in mixed-culture biofilms: evidence of metabolic interactions between community members. Appl Environ Microbiol 64:721–732
    [Google Scholar]
  30. O’Sullivan D. J., O’Gara F. 1992; Traits of fluorescent Pseudomonas spp. involved in suppression of plant root pathogens. . Microbiol Rev 56:662–676
    [Google Scholar]
  31. Poole K., Dean C., Heinrichs D., Neshat S., Krebes K., Young L., Kilburn L. 1996; Siderophore-mediated iron transport in Pseudomonas aeruginosa. In Molecular Biology of Pseudomonads pp. 371–383Edited by Nakaazawa T.others Washington, DC: American Society for Microbiology;
    [Google Scholar]
  32. Raaijmakers J. M., Leeman M., van Oorschot M. M. P., van der Sluis I., Schippers B., Bakker P. A. H. M. 1995a; Dose-response relationships in biological control of Fusarium wilt of radish by Pseudomonas ssp. Phytopathology 85:1075–1081 [CrossRef]
    [Google Scholar]
  33. Raaijmakers J. M., van der Sluis L., Koster M., Bakker P. A. H. M., Weisbeek P. J., Schippers B. 1995b; Utilization of heterologous siderophores and rhizosphere competence of fluorescent Pseudomonas spp. Can J Microbiol 41:126–135 [CrossRef]
    [Google Scholar]
  34. Shapiro S. S., Wilk M. B. 1965; An analysis of variance test for normality (complete samples). Biometrika 52:591–611 [CrossRef]
    [Google Scholar]
  35. Stephens M. A. 1974; EDF statistics for goodness of fit and some comparisons. J Am Stat Assoc 69:730–737 [CrossRef]
    [Google Scholar]
  36. Sugita H., Hinrose Y., Matsuo N., Deguchi Y. 1998; Production of the antibacterial substance by Bacillus sp. strain NM 12, an intestinal bacterium of Japanese coastal fish. Aquaculture 165:269–280 [CrossRef]
    [Google Scholar]
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