Expanding the physical niche available for colonisation increases Wrinkly Spreader fitness. Differently shaped containers were used to produce microcosms with a range of surface areas but with constant volumes (shown here as the SA/V ratio). Microcosms were incubated for 3 days before assay and the competitive fitness (W) of the Wrinkly Spreader was determined compared to the non-biofilm-forming P. fluorescens SBW25. Here, the relative fitness () is provided where the reference microcosms with a SA/V ratio of 0.45 have a relative fitness of one (marked by the horizontal dashed line); the curve indicated here is illustrative only. Means ± SE are shown (), and means not linked by the same letter are significantly different (TK-HSD, ).