See Mridha & Kümmerli, J Evol Biol.
An open question in microbiology is whether natural selection can favour division of labour where subpopulations or species specialise in the production of a single public good, whilst sharing the complementary goods at the group level. In this work, the Kümmerli group explored the conditions under which specialisation can lead to division of labour. By growing engineered specialists of the bacterium P. aeruginosa, each of which which only produce one of two siderophores, at different mixing ratios under varying levels of iron limitation, they could show that enforcing specialisation with regard to siderophore production does not lead to beneficial division of labour in P. aeruginosa. Rather, this enforced specialisation leads to the stable co-existence of the two specialists through mutual cheating. Mridha and Kümmerli propose that in generalists, natural selection might favour fine-tuned regulatory mechanisms over division of labour, because in fluctuating environments, this fine-tuning allows generalists to maintain the flexibility to adequately adjust public good investments.