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J Bacteriol, April 1998, p. 2110-2117, Vol. 180, No. 8
Department of Genetics, Trinity College,
Dublin 2, Ireland,1 and
Novo Nordisk
A/S, Bagsværd, Denmark2
Received 1 December 1997/Accepted 12 February 1998
Four genes identified within the late operon of PBSX show
characteristics expected of a host cell lysis system; they are
xepA, encoding an exported protein; xhlA,
encoding a putative membrane-associated protein; xhlB,
encoding a putative holin; and xlyA, encoding a putative
endolysin. In this work, we have assessed the contribution of each gene
to host cell lysis by expressing the four genes in different
combinations under the control of their natural promoter located on the
chromosome of Bacillus subtilis 168. The results show that
xepA is unlikely to be involved in host cell lysis. Expression of both xhlA and xhlB is necessary
to effect host cell lysis of B. subtilis. Expression of
xhlB (encoding the putative holin) together with
xlyA (encoding the endolysin) cannot effect cell lysis,
indicating that the PBSX lysis system differs from those identified in
the phages of gram-negative bacteria. Since host cell lysis can be
achieved when xlyA is inactivated, it is probable that PBSX
encodes a second endolysin activity which also uses XhlA and XhlB for
export from the cell. The chromosome-based expression system developed
in this study to investigate the functions of the PBSX lysis genes
should be a valuable tool for the analysis of other host cell lysis
systems and for expression and functional analysis of other lethal gene
products in gram-positive bacteria.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Lysis Genes of the Bacillus subtilis
Defective Prophage PBSX
*
Corresponding author. Mailing address: Department of
Genetics, Trinity College, Lincoln Place Gate, Dublin 2, Ireland.
Phone: (353)-1-6081872. Fax: (353)-1-6798558. E-mail:
kdevine{at}tcd.ie.
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