Novel fimbrial subunit genes of Dichelobacter nodosus: recombination in vivo or in vitro?
Polymerase chain reaction (PCR) was used to amplify the variable region of the fimbrial subunit encoding gene (fimA) of Dichelobacter nodosus from sheep and goats infected with footrot. Two amplimers (designated X and Y) generated single-strand conformation polymorphism (SSCP) patterns different to those of previously identified serogroups and serotypes. DNA sequencing revealed that these two fragments were novel. The upstream of X (nt 1-183) was identical to serotype M1 while its downstream (nt 223-414) was identical to serotype F1; the upstream of Y (nt 1-116) was identical to serotype E1, whereas its downstream (nt 148-423) was identical to serotype F1. A 14-mer sequence consisting of two partially overlapping Chi-like sequences, 5'-GCTGGTGCTGGTGA-3', was also found in these fragments. Two primer sets with the downstream primer specific for serotype F1 and the upstream primer specific for serotype M or E1, generated PCR products of the expected sizes from the footrot samples from which fragments X and Y were isolated, respectively. These primer sets did not appear to amplify artificially mixed genomic DNA from serotypes M and F1 or E1 and F1. However, when the reactions were re-amplified, PCR recombination artifacts were observed, suggesting that PCR recombination does occur, but at a low frequency. It, therefore, seems more likely that fragments X and Y reflect genuine fimA genes of D. nodosus which have resulted from in vivo DNA recombination rather than from a PCR recombination artifact.
Zhou
H
H
Animal & Food Sciences Division, P.O. Box 84, Lincoln University, Canterbury, Lincoln, New Zealand.
Hickford
J G
JG
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D020376:Dichelobacter nodosus / Q000235:genetics*; D036781:Fimbriae Proteins; D005535:Foot Rot / Q000382:microbiology; D006041:Goats; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011995:Recombination, Genetic; D012756:Sheep
D001426:Bacterial Proteins; C063055:fimbrillin; D036781:Fimbriae Proteins