Table 2.

	Recombination events in Gc grown in vitro after T84 cell infection			Recombination events in pilE genes amplified from T84 cell lysates
Monolayer	# pilE Clones	# Recomb. Events	Frequency of pilin Av	# pilE Clones	# Recomb. Events	Frequency of pilin Av
A	37	19	0.51	37	12	0.32
B	45	27	0.60	36	10	0.27
C	47	31	0.66	37	15	0.41
Average	43	26	0.59	37	12	0.33

T84 cells were infected in triplicate with 1−81-S2 as described in Fig. 1. 24 h post-infection, CFU were enumerated from cell lysates (left columns). Chromosomal DNA was used as the template in pilE-specific PCR reactions and cloned into E. coli (right columns). In each population, the number of pilE sequences analyzed, the number of pilE recombination events, and the resulting frequency of pilin Av per monolayer are presented. The difference in the frequency of pilin Av measured in the two populations was statistically significant (P < 0.01 by Student's t-test).