Get access

Cultivation of globally distributed soil bacteria from phylogenetic lineages previously only detected in cultivation-independent surveys

Authors

  • Michelle Sait,

    1. Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.
    Search for more papers by this author
  • Philip Hugenholtz,

    1. ComBinE Group, Advanced Computational Modelling Centre, The University of Queensland, Brisbane 4072, Australia.
    Search for more papers by this author
    • Present address: Environmental Science, Policy and Management, Division of Ecosystem Sciences, 151 Hilgard Hall, University of California Berkeley, Berkeley, CA 94720–3110, USA.

  • Peter H. Janssen

    Corresponding author
    1. Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.
    Search for more papers by this author

For correspondence. E-mail pjanssen@unimelb.edu.au; Tel. (+61) 38344 5706; Fax (+61) 39347 1540.

Summary

The culturability of microorganisms in a 10 cm core of an Australian pasture soil was investigated using a minimal agar medium with xylan as the growth substrate. Culturability decreased with increasing depth, from a maximum of 19% of the total microscopically countable cells in the 0–2 cm section to 2.4% in the 8–10 cm section. Seventy-one isolates from the core were identified by comparative 16S rRNA gene sequence analysis. Many of these isolates belong to groups of globally distributed soil bacteria, including well-characterized families of the classes Alphaproteobacteria and Betaproteobacteria, and of the subclass Actinobacteridae. Other isolates belong to groups with few or no cultivated representatives: 10 isolates in two subdivisions of the phylum Acidobacteria, five isolates in a new order and nine isolates in a new family of the class Alphaproteobacteria, two isolates in a new order of the class Gammaproteobacteria, three isolates in two new families of the subclass Actinobacteridae, and two isolates in the subclass Rubrobacteridae. These new isolates represent the first laboratory cultures able to be assigned to some of these groups and greatly increase the number of cultivated strains known for others. This demonstrates that a minimal change in cultivation strategy (using a polymeric growth substrate and longer incubation times) can result in the isolation of globally distributed but previously uncultured phylogenetically novel soil bacteria.

Ancillary