Figure 5

Mixed nodules. (a) Microscopic image of a mixed nodule on a pea root, which seems to have been infected by more than two rhizobia. The nitrogen-fixing strain is celB (blue) marked (3841 celB), and the non-fixing mutant strain is gusA (magenta) marked (OPS0365). (b) Microscopic image of a mixed nodule on a pea root infected by two rhizobia. The gusA marked nitrogen-fixing strain (3841 gusA) is magenta, and the celB marked non-fixing mutant strain (OPS0366) is blue. (c) Nodules, including mixed nodules, on a pea root. The gusA marked nitrogen-fixing strain (3841 gusA) is magenta, and the celB marked non-fixing mutant strain (OPS0366) is blue. (d) Mixed nodules occur more often when the probability that different strains encounter each other during nodule formation is higher (t ₃₉  = 4.913, p = 1.65 × 10⁻⁵). Generalized linear model with quasibinomial distribution and logit link function shown with 95% confidence interval.