Heterogeneity in the secondary metabolism of Photorhabdus and Xenorhabdus

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Although natural products (NP) like antibiotics play an important role in our daily life we hardly know anything about the regulation of their production. Bacterial NP producers usually have the capacity to produce several different NP and often can produce even several different derivatives thereof at a given time. As this requires a large proportion of the cells energy and resources due to the often huge enzymatic complexes involved, a system in which a small fraction of cells produce only a fraction of compounds (division of labor) might be advantageous for the bacterial colony as by that all cells can make and use all compounds made by the community. First experiments with NP gene promoters fused to genes encoding fluorescence proteins showed that for some NP gene promoters only a small fraction of cells show the expected fluorescence, making a division of work model very likely. The underlying mechanisms will be investigated in Photorhabdus and Xenorhabdus bacteria, which are known producers of several bioactive natural products. Two NP biosynthesis gene promoters will be analyzed in parallel (and with a constitutive promoter as control) with different fluorescence reporters using fluorescence microscopy or flow cytometry. The different populations will be sorted by fluorescence activated cell sorting (FACS) to study the population stability. Transcription factors acting as global regulators have been shown to influence not only NP production but also promoter heterogeneity and additional regulator proteins will be invested in detail. Finally, the biochemical principles underlying the regulation of anthraquinone (AQ) biosynthesis will be studied in detail. Here, a novel class of transcription factor has already been identified and how it regulates AQ biosynthesis and how itself is regulated will be analyzed including NPs that might act as ligands for this and other transcription actors already shown to bind to the respective AQ promoter. The resulting data will be used to model the underlying regulatory mechanisms in collaboration with other groups and this knowledge in turn will be used to increase the production of bioactive natural products and to increase our knowledge of bacterial heterogeneity in general.