TABLE 4.

Competitiveness of the mutants in the acpXL-lpxXL cluster

S. meliloti mutant strain used in the competition assaya	Amount of each mutant strain within the nodules (percentage of total bacteria within the nodules)b
	Class I nodules	Class II nodules
	%	%
acpXL	3.3 ± 8.5 (n = 16)	53.3 (n = 1)
fabZXL	5.9 ± 9.6 (n = 22)	92.9 ± 10.1 (n = 2)
fabF2XL	3.9 ± 9.0 (n = 18)	85.2 ± 15.5 (n = 6)
fabF1XL	6.1 ± 11.4 (n = 21)	94.1 ± 10.3 (n = 3)
adhA2XL	3.1 ± 9.1 (n = 21)	90.3 ± 13.1 (n = 3)

^a The mutant and parent strains were inoculated onto alfalfa seedlings in a 1:1 ratio.

^b The nodules analyzed fell into two classes, Class I and Class II nodules, which were infected primarily by either the parent or mutant strains, respectively. The data sets shown are average values from the defined number of nodules (n).