Figure 2.

Cells harbouring the Ti plasmid have a lower fitness than pTi⁻ cells when competing in low-carbon and low-nitrogen environments for approximately 35 generations. In contrast, neither strain has a competitive advantage in environments with high carbon and nitrogen. ‘High C, high N and pH 7’ media is standard ATGN, and ‘high C, high N and low pH’ media is ATGN modified to be buffered by 20 mM MES to pH 5.6. ‘Low C’ media is AT minimal media supplemented with 1 mM glucose and 15 mM (NH₄)₂SO₄, while ‘low N’ media is AT minimal media supplemented with 27.5 mM glucose and 0.6 mM (NH₄)₂SO₄. Values represent LS means ± s.e. of 10 replicates. Means marked with different letters are significantly different (p < 0.05). The low C and low N treatment means are significantly lower than one (p < 0.0001), whereas the other two treatment means are not significantly different from one (p > 0.05).