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J. Bacteriol., 08 1995, 4279-4288, Vol 177, No. 15
M Bayer, R Eferl, G Zellnig, K Teferle, A Dijkstra, G Koraimann and G Hogenauer
F-like plasmids require a number of genes for conjugation, including tra
operon genes and genes traM and traJ, which lie outside the tra operon. We
now establish that a gene in the "leading region," gene 19, provides an
important function during conjugation and RNA phage infection. Mutational
inactivation of gene 19 on plasmid R1-16 by introduction of two nonpolar
stop codons results in a 10-fold decrease in the conjugation frequency.
Furthermore, infection studies with the male-specific bacteriophage R17
revealed that the phage is not able to form clear plaques in Escherichia
coli cells carrying an R1-16 plasmid with the defective copy of gene 19.
The total number of cells infected by phage R17 is reduced by a factor of
10. Both the conjugation- and infection-attenuated phenotypes caused by the
defective gene 19 can be complemented in trans by introducing gene 19
alleles encoding the wild- type protein. Restoration of the normal
phenotypes is also possible by introduction of the pilT gene encoded by the
unrelated IncI plasmid R64. Our functional studies and similarities of
protein 19 to proteins encoded by other DNA transfer systems, as well as
the presence of a conserved motif in all of these proteins (indicative for
a putative muramidase activity) suggest that protein 19 of plasmid R1
facilitates the passage of DNA during conjugation and entry of RNA during
phage infection.
Copyright © 1995, American Society for Microbiology
Gene 19 of plasmid R1 is required for both efficient conjugative DNA transfer and bacteriophage R17 infection
Institut fur Mikrobiologie, Karl-Franzens-Universitat Graz, Austria.
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