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One size doesn't fit all

¹ Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Science, Foresterhill, Aberdeen AB25 2ZD, UK
² School of Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK

Correspondence
G. Hobbs
(g.hobbs{at}livjm.ac.uk)

In his Comment article in the May issue of Microbiology (Ferenci, 2006), Dr Ferenci provides a very timely ‘pull on the reigns’ and reminds us that what we all have been taught classically about continuous cultures is a gross oversimplification. Pragmatically, or by necessity if you like, the theory of the continuous culture is based upon a simple mathematical model. If we look at the constants in that model, µ_max and K_s, we really should stop to think. These are not invariable within a population of cells and, as such, mutations will sweep through a population due to selective pressures (as indicated by Dr Ferenci). These mutant ‘take-overs’ have been described in several studies, and have been shown to be strain-dependent. Indeed, our laboratories work mainly with Streptomyces coelicolor, where visually obvious mutants (asporulent and pigmented antibiotic variants) occur frequently upon prolonged continuous culture. These strain variabilities and mutational effects are approached in our laboratories by restricting prolonged studies (reduction in generation times) when the mutational aspect is not the reason for study, thus material required for analysis is harvested on or at the establishment of (quasi-) steady-state, especially for global studies. With respect to our previous article (Hoskisson & Hobbs, 2005), we failed to indicate that the establishment of (quasi-) steady-state under empirically established conditions may be problematic in the initiation of studies, and a careful experimental design strategy is required.

It is not doubted that continuous culture systems are of huge benefit to a multitude of studies, and the study of bacterial evolution and selection processes are a major beneficiary of the versatility of continuous culture. However, I feel that, providing the pitfalls outlined by Dr Ferenci are appreciated, the initiation of global studies of transcription, proteomics and metabolomics in continuous culture systems will provide useful insights into the biology of bacterial physiology.

REFERENCES

Ferenci, T. (2006). A cultural divide on the use of chemostats. Microbiology 152, 1247–1248.[Free Full Text]

Hoskisson, P. A. & Hobbs, G. (2005). Continuous culture – making a comeback? Microbiology 151, 3153–3159.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Hoskisson, P. A. Articles by Hobbs, G. Search for Related Content PubMed PubMed Citation Articles by Hoskisson, P. A. Articles by Hobbs, G. Agricola Articles by Hoskisson, P. A. Articles by Hobbs, G.