Microbial Ecology

, Volume 60, Issue 4, pp 873–884 | Cite as

Determining the Effects of a Spatially Heterogeneous Selection Pressure on Bacterial Population Structure at the Sub-millimetre Scale

  • Frances R. Slater
  • Kenneth D. Bruce
  • Richard J. Ellis
  • Andrew K. Lilley
  • Sarah L. Turner


A key interest of microbial ecology is to understand the role of environmental heterogeneity in shaping bacterial diversity and fitness. However, quantifying relevant selection pressures and their effects is challenging due to the number of parameters that must be considered and the multiple scales over which they act. In the current study, a model system was employed to investigate the effects of a spatially heterogeneous mercuric ion (Hg2+) selection pressure on a population comprising Hg-sensitive and Hg-resistant pseudomonads. The Hg-sensitive bacteria were Pseudomonas fluorescens SBW25::rfp and Hg-resistant bacteria were P. fluorescens SBW25 carrying a gfp-labelled, Hg resistance plasmid. In the absence of Hg, the plasmid confers a considerable fitness cost on the host, with µmax for plasmid-carrying cells relative to plasmid-free cells of only 0.66. Two image analysis techniques were developed to investigate the structure that developed in biofilms about foci of Hg (cellulose fibres imbued with HgCl2). Both techniques indicated selection for the resistant phenotype occurred only in small areas of approximately 178–353 μm (manually defined contour region analysis) or 275–350 μm (daime analysis) from foci. Hg also elicited toxic effects that reduced the growth of both Hg-sensitive and Hg-resistant bacteria up to 250 μm from foci. Selection for the Hg resistance phenotype was therefore highly localised when Hg was spatially heterogeneous. As such, for this model system, we define here the spatial scale over which selection operates. The ability to quantify changes in the strength of selection for particular phenotypes over sub-millimetre scales is useful for understanding the scale over which environmental variables affect bacterial populations.



F.R.S. was funded by a Natural Environment Research Council Algorithm studentship. We are grateful to Holger Daims for useful advice in the early stages of the study, Stewart Houten for useful discussions in the later stages of the study and six anonymous reviewers for constructive comments on the manuscript.

Supplementary material

248_2010_9687_MOESM1_ESM.doc (7 mb)
ESM Figures S1 (DOC 7140 kb)


  1. 1.
    Young IM, Crawford JW (2004) Interactions and self-organization in the soil–microbe complex. Science 304:1634–1637CrossRefPubMedGoogle Scholar
  2. 2.
    Gans J, Wolinsky M, Dunbar J (2005) Computational improvements reveal great bacterial diversity and high metal toxicity in soil. Science 309:1387–1390CrossRefPubMedGoogle Scholar
  3. 3.
    Schloss PD, Handelsman J (2006) Toward a census of bacteria in soil. PLoS Comput Biol 2:786–793CrossRefGoogle Scholar
  4. 4.
    Ramette A, Tiedje JM (2007) Multiscale responses of microbial life to spatial distance and environmental heterogeneity in a patchy ecosystem. Proc Natl Acad Sci U S A 104:2761–2766CrossRefPubMedGoogle Scholar
  5. 5.
    Jessup CM, Kassen R, Forde SE, Kerr B, Buckling A, Rainey PB, Bohannan BJM (2004) Big questions, small worlds: microbial model systems in ecology. Trends Ecol Evol 19:189–197CrossRefPubMedGoogle Scholar
  6. 6.
    Ranjard L, Nazaret S, Gourbiere F, Thioulouse J, Linet P, Richaume A (2000) A soil microscale study to reveal the heterogeneity of Hg(II) impact on indigenous bacteria by quantification of adapted phenotypes and analysis of community DNA fingerprints. FEMS Microbiol Ecol 31:107–115CrossRefPubMedGoogle Scholar
  7. 7.
    Muller AK, Rasmussen LD, Sorensen SJ (2001) Adaptation of the bacterial community to mercury contamination. FEMS Microbiol Lett 204:49–53CrossRefPubMedGoogle Scholar
  8. 8.
    Muller AK, Westergaard K, Christensen S, Sorensen SJ (2001) The effect of long-term mercury pollution on the soil microbial community. FEMS Microbiol Ecol 36:11–19PubMedGoogle Scholar
  9. 9.
    Rasmussen LD, Sorensen SJ (2001) Effects of mercury contamination on the culturable heterotrophic, functional and genetic diversity of the bacterial community in soil. FEMS Microbiol Ecol 36:1–9CrossRefPubMedGoogle Scholar
  10. 10.
    Lilley AK, Bailey MJ (1997) The acquisition of indigenous plasmids by a genetically marked pseudomonad population colonizing the sugar beet phytosphere is related to local environmental conditions. Appl Environ Microbiol 63:1577–1583PubMedGoogle Scholar
  11. 11.
    Tett A, Spiers AJ, Crossman LC, Ager D, Ciric L, Dow JM, Fry JC, Harris D, Lilley AK, Oliver A, Parkhill J, Quail MA, Rainey PB, Saunders NJ, Seeger K, Snyder LAS, Squares R, Thomas CM, Turner SL, Zhang XX, Field D, Bailey M (2007) Sequence-based analysis of pQBR103: a representative of a unique, transfer-proficient megaplasmid resident in the microbial community of sugar beet. ISME J 1:331–340PubMedGoogle Scholar
  12. 12.
    Ellis RJ, Lilley AK, Lacey SJ, Murrell D, Godfray HCJ (2007) Frequency-dependent advantages of plasmid carriage by Pseudomonas in homogeneous and spatially structured environments. ISME J 1:92–95CrossRefPubMedGoogle Scholar
  13. 13.
    Slater FR, Bruce KD, Ellis RJ, Lilley AK, Turner SL (2008) Heterogeneous selection in a spatially structured environment affects fitness tradeoffs of plasmid carriage in pseudomonads. Appl Environ Microbiol 74:3189–3197CrossRefPubMedGoogle Scholar
  14. 14.
    Liu J, Dazzo FB, Glagoleva O, Yu B, Jain AK (2001) CMEIAS: a computer-aided system for the image analysis of bacterial morphotypes in microbial communities. Microb Ecol 41:173–194PubMedGoogle Scholar
  15. 15.
    Heydorn A, Nielsen AT, Hentzer M, Sternberg C, Givskov M, Ersboll BK, Molin S (2000) Quantification of biofilm structures by the novel computer program COMSTAT. Microbiology-SGM 146:2395–2407Google Scholar
  16. 16.
    Daims H, Lucker S, Wagner M (2006) daime, a novel image analysis program for microbial ecology and biofilm research. Environ Microbiol 8:200–213CrossRefPubMedGoogle Scholar
  17. 17.
    Maixner F, Noguera DR, Anneser B, Stoecker K, Wegl G, Wagner M, Daims H (2006) Nitrite concentration influences the population structure of Nitrospira-like bacteria. Environ Microbiol 8:1487–1495CrossRefPubMedGoogle Scholar
  18. 18.
    Kara D, Luppens SBI, van Marle J, Ozok R, ten Cate JM (2007) Microstructural differences between single-species and dual-species biofilms of Streptococcus mutans and Veillonella parvula, before and after exposure to chlorhexidine. FEMS Microbiol Lett 271:90–97CrossRefPubMedGoogle Scholar
  19. 19.
    Reed MG, Howard CV (1999) Stereological estimation of covariance using linear dipole probes. J Microsc 195:96–103CrossRefPubMedGoogle Scholar
  20. 20.
    Bellmann C, Caspari A, Albrecht V, Doan TTL, Mader E, Luxbacher T, Kohl R (2005) Electrokinetic properties of natural fibres. Colloid Surface A 267:19–23CrossRefGoogle Scholar
  21. 21.
    Yang XM, Beyenal H, Harkin G, Lewandowski Z (2001) Evaluation of biofilm image thresholding methods. Water Res 35:1149–1158CrossRefPubMedGoogle Scholar
  22. 22.
    Barkay T, Miller SM, Summers AO (2003) Bacterial mercury resistance from atoms to ecosystems. FEMS Microbiol Rev 27:355–384CrossRefPubMedGoogle Scholar
  23. 23.
    Slater FR, Bailey M, Tett A, Turner SL (2008) Progress towards understanding the fate of plasmids in bacterial communities. FEMS Microbiol Ecol 66:3–13CrossRefPubMedGoogle Scholar
  24. 24.
    Slater FR (2008) The Impact of spatially heterogeneous selection on bacterial plasmid ecology. Ph.D. Thesis, King's College LondonGoogle Scholar
  25. 25.
    Yin YJ, Allen HE, Huang CP, Sparks DL, Sanders PF (1997) Kinetics of mercury(II) adsorption and desorption on soil. Environ Sci Technol 31:496–503CrossRefGoogle Scholar
  26. 26.
    Blackburn N, Fenchel T, Mitchell J (1998) Microscale nutrient patches in planktonic habitats shown by chemotactic bacteria. Science 282:2254–2256CrossRefPubMedGoogle Scholar
  27. 27.
    Schafer H, Abbas B, Witte H, Muyzer G (2002) Genetic diversity of ‘satellite’ bacteria present in cultures of marine diatoms. FEMS Microbiol Ecol 42:25–35PubMedGoogle Scholar
  28. 28.
    Jasti S, Sieracki ME, Poulton NJ, Giewat MW, Rooney-Varga JN (2005) Phylogenetic diversity and specificity of bacteria closely associated with Alexandrium spp. and other phytoplankton. Appl Environ Microbiol 71:3483–3494CrossRefPubMedGoogle Scholar
  29. 29.
    Rodriguez-Navarro DN, Dardanelli MS, Ruiz-Sainz JE (2007) Attachment of bacteria to the roots of higher plants. FEMS Microbiol Lett 272:127–136CrossRefPubMedGoogle Scholar
  30. 30.
    Bianciotto V, Andreotti S, Balestrini R, Bonfante P, Perotto S (2001) Mucoid mutants of the biocontrol strain Pseudomonas fluorescens CHA0 show increased ability in biofilm formation on mycorrhizal and nonmycorrhizal carrot roots. Mol Plant Microbe Interact 14:255–260CrossRefPubMedGoogle Scholar
  31. 31.
    Lugtenberg BJJ, Dekkers LC (1999) What makes Pseudomonas bacteria rhizosphere competent? Environ Microbiol 1:9–13CrossRefPubMedGoogle Scholar
  32. 32.
    Gantner S, Schmid M, Durr C, Schuhegger R, Steidle A, Hutzler P, Langebartels C, Eberl L, Hartmann A, Dazzo FB (2006) In situ quantitation of the spatial scale of calling distances and population density-independent N-acyl homoserine lactone-mediated communication by rhizobacteria colonized on plant roots. FEMS Microbiol Ecol 56:188–194CrossRefPubMedGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Frances R. Slater
    • 1
    • 2
    • 4
  • Kenneth D. Bruce
    • 2
  • Richard J. Ellis
    • 3
    • 5
  • Andrew K. Lilley
    • 1
    • 2
  • Sarah L. Turner
    • 1
    • 6
  1. 1.The Centre for Ecology and HydrologyOxfordUK
  2. 2.Pharmaceutical Sciences DivisionKing’s College LondonLondonUK
  3. 3.NERC Centre for Population Biology, Division of BiologyImperial College LondonBerkshireUK
  4. 4.The University of Queensland, Advanced Water Management Centre (AWMC)BrisbaneAustralia
  5. 5.Molecular Pathogenesis and GeneticsVeterinary Laboratories AgencySurreyUK
  6. 6.CEH WallingfordOxfordshireUK

Personalised recommendations