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Open Access Highly Accessed Research article

Quorum sensing influences growth and photosynthetic membrane production in high-cell-density cultivations of Rhodospirillum rubrum

Lisa Carius1*, Anke B Carius1, Matthew McIntosh2 and Hartmut Grammel13

Author Affiliations

1 Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106, Magdeburg, Germany

2 Loewe Center for Synthetic Microbiology, Philipps-University Marburg, Hans-Meerwein-Str. 6, 35043, Marburg, Germany

3 Biberach Universtiy of Applied Science, Karlsstr 11, 88400, Biberach, Germany

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BMC Microbiology 2013, 13:189  doi:10.1186/1471-2180-13-189

Published: 8 August 2013

Abstract

Background

The facultative anoxygenic photosynthetic bacterium Rhodospirillum rubrum exhibits versatile metabolic activity allowing the adaptation to rapidly changing growth conditions in its natural habitat, the microaerobic and anoxic zones of stagnant waters. The microaerobic growth mode is of special interest as it allows the high-level expression of photosynthetic membranes when grown on succinate and fructose in the dark, which could significantly simplify the industrial production of compounds associated with PM formation. However, recently we showed that PM synthesis is no longer inducible when R. rubrum cultures are grown to high cell densities under aerobic conditions. In addition a reduction of the growth rate and the continued accumulation of precursor molecules for bacteriochlorophyll synthesis were observed under high cell densities conditions.

Results

In the present work, we demonstrate that the cell density-dependent effects are reversible if the culture supernatant is replaced by fresh medium. We identified six N-acylhomoserine lactones and show that four of them are produced in varying amounts according to the growth phase and the applied growth conditions. Further, we demonstrate that N-acylhomoserine lactones and tetrapyrrole compounds released into the growth medium affect the growth rate and PM expression in high cell density cultures.

Conclusions

In summary, we provide evidence that R. rubrum possesses a Lux-type quorum sensing system which influences the biosynthesis of PM and the growth rate and is thus likely to be involved in the phenotypes of high cell density cultures and the rapid adaptation to changing environmental conditions.

Keywords:
Rhodospirillum rubrum; Quorum sensing; Acylhomoserine lactones; High cell density cultivation; Lux genes