Horizontal transfer of bacteriocin biosynthesis genes requires metabolic adaptation to improve compound production and cellular fitness

Biosynthetic gene clusters (BGCs) encoding the production of bacteriocins are widespread amongst bacterial isolates and are important genetic determinants of competitive fitness among bacterial lineages within a given habitat. Staphylococci produce a tremendous diversity of compounds and the corresponding gene clusters (Staphylococcal Antibiosis Islands - SAbIs) are frequently associated with mobile genetic elements, suggesting acquisition and loss of biosynthetic capacity. Pharmaceutical biology has shown that compound production in heterologous hosts is often challenged by the lack of optimal precursor supplies. Accordingly, many recipients produce low compound amounts or show reduced growth rates. To assess whether transfer of SAbIs between closely related S. aureus strains has similar effects, we used as model the SAbI encoding the ribosomally synthesized and post-translationally modified peptide (RiPP) Micrococcin P1 (MP1). We found that acquisition of the SAbI by S. aureus RN4220 did allow immediate MP1 production but also imposed a metabolic burden. Adaptive evolution selected for strains with increased TCA-cycle activity, which enhanced metabolic fitness and levels of compound production. Metabolome analysis showed that the adaptive mutation increased the levels of central metabolites including citrate and a-ketoglutarate, and the increased availability of citrate turned out to be essential to overcome SAbI associated growth defects. Our results indicate that acquisition of SAbIs represents a blessing for the recipient strain as long as its genetic and metabolic predispositions allow integration of bacteriocin production into the cellular metabolism. This in turn may be crucial to ensure the competitive fitness of SAbI recipients within natural bacterial communities. Overall design: Differential expression analysis between a wild type strain of RN4220 and two strains with plasmid pD4-19 of which one was altered using an adaptive evolution experiment.