Bp. Mcnamara et Ms. Donnenberg, Evidence for specificity in type 4 pilus biogenesis by enteropathogenic Escherichia coli, MICROBIO-UK, 146, 2000, pp. 719-729
Type 4 fimbriae (pili) are surface appendages that are expressed by many sp
ecies of Gram-negative bacteria. Previous studies have demonstrated that Ps
eudomonas aeruginosa can express and assemble pilin subunits from several u
nrelated species, indicating a common mechanism for biogenesis of type 4 pi
ll whereby structural subunits from one system may be interchanged with tho
se of another. In this study, an isogenic mutant of enteropathogenic Escher
ichia coli (EPEC) was constructed containing the entire tcpA gene from Vibr
io cholerae O395, which encodes the major structural subunit of the toxin-c
oregulated pilus (TCP). in place of bfpA, which encodes the major structura
l subunit of the bundle-forming pilus (BFP), Surprisingly. expression of ty
pe 4 pilin structures and the associated phenotype of bacterial autoaggrega
tion in culture media were not observed for cells of the EPEC strain contai
ning tcpA nor for those containing an additional mutation in bfpF. which ot
herwise is associated with a hyperfimbriate phenotype, In addition. cells o
f a bfpA mutant EPEC strain containing plasmids designed to express either
of two different chimeric type 4 pilin subunits containing segments of BfpA
and TcpA also failed to form bacterial aggregates and express type 4 pilin
structures. Collectively. these results indicate that the type 4 pilin ass
embly system of SPEC exhibits specificity with regard to pilin subunit reco
gnition and assembly.