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Biotechnol Lett (2009) 31:265–270
DOI 10.1007/s10529-008-9858-3

ORIGINAL RESEARCH PAPER

Mutational analysis of the gum gene cluster required
for xanthan biosynthesis in Xanthomonas oryzae pv oryzae
Sang-Yoon Kim Æ Jeong-Gu Kim Æ
Byoung-Moo Lee Æ Jae-Yong Cho

Received: 15 August 2008 / Revised: 22 September 2008 / Accepted: 23 September 2008 / Published online: 15 October 2008
Ó Springer Science+Business Media B.V. 2008

Abstract Genome sequence analysis of Xanthomonas oryzae pv. oryzae has revealed a cluster of 12
ORFs that are closely related to the gum gene cluster
of Xanthomonas campestris pv. campestris. The gum
gene cluster of X. oryzae encodes proteins involved in
xanthan production; however, there is little experimental evidence supporting this. In this study,
biochemical analyses of xanthan produced by a
defined set of X. oryzae gum mutant strains allowed
us to preliminarily assign functions to most of the

gum gene products: biosynthesis of the pentasaccharide repeating unit for GumD, GumM, GumH,
GumK, and GumI, xanthan polymerization and
transport for GumB, GumC, GumE, and GumJ, and
modification of the pentasaccharide repeating unit for
GumF, GumG, and GumL. In addition, we found that
the exopolysaccharides are essential but not specific
for the virulence of X. oryzae.

Sang-Yoon Kim and Jeong-Gu Kim contributed equally to this
work.

Introduction

Electronic supplementary material The online version of
this article (doi:10.1007/s10529-008-9858-3) contains
supplementary material, which is available to authorized users.
S.-Y. Kim Á J.-Y. Cho (&)
Division of Animal Science and Biotechnology,
Sangji University, 660 Woosan-dong, Wonju-si,
Gangwon-do 220-702, Korea
e-mail: jycho@sangji.ac.kr
J.-G. Kim Á B.-M. Lee
Microbial Genetics Division, National Institute
of Agricultural Biotechnology, 225 Seodun-dong,
Suwon 441-707, Korea
J.-Y. Cho
LabGene Inc., Sangji University, 660 Woosan-dong,
Wonju-si, Gangwon-do 220-702, Korea

Keywords Gum gene cluster Á Gum mutants Á
Virulence Á Xanthan Á Xanthomona oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae is a Gram-negative
bacterium that causes bacterial blight on rice. One of
the most important virulence factors of this species is
the production of large amounts of an exopolysaccharide called xanthan. Xanthan is a polymer that is
comprised of repeating pentasaccharide units with the
structure of a b-1,4-linked D-glucose backbone with
trisaccharide side chains composed of mannose(b-1,4)-glucuronic acid-(b-1,...
ORIGINAL RESEARCH PAPER
Mutational analysis of the gum gene cluster required
for xanthan biosynthesis in Xanthomonas oryzae pv oryzae
Sang-Yoon Kim Æ Jeong-Gu Kim Æ
Byoung-Moo Lee Æ Jae-Yong Cho
Received: 15 August 2008 / Revised: 22 September 2008 / Accepted: 23 September 2008 / Published online: 15 October 2008
Ó Springer Science+Business Media B.V. 2008
Abstract Genome sequence analysis of Xanthomo-
nas oryzae pv. oryzae has revealed a cluster of 12
ORFs that are closely related to the gum gene cluster
of Xanthomonas campestris pv. campestris.Thegum
gene cluster of X. oryzae encodes proteins involved in
xanthan production; however, there is little experi-
mental evidence supporting this. In this study,
biochemical analyses of xanthan produced by a
defined set of X. oryzae gum mutant strains allowed
us to preliminarily assign functions to most of the
gum gene products: biosynthesis of the pentasaccha-
ride repeating unit for GumD, GumM, GumH,
GumK, and GumI, xanthan polymerization and
transport for GumB, GumC, GumE, and GumJ, and
modification of the pentasaccharide repeating unit for
GumF, GumG, and GumL. In addition, we found that
the exopolysaccharides are essential but not specific
for the virulence of X. oryzae.
Keywords Gum gene cluster Á Gum mutants Á
Virulence Á Xanthan Á Xanthomona oryzae pv. oryzae
Introduction
Xanthomonas oryzae pv. oryzae is a Gram-negative
bacterium that causes bacterial blight on rice. One of
the most important virulence factors of this species is
the production of large amounts of an exopolysac-
charide called xanthan. Xanthan is a polymer that is
comprised of repeating pentasaccharide units with the
structure of a b-1,4-linked
D-glucose backbone with
trisaccharide side chains composed of mannose-
(b-1,4)-glucuronic acid-(b-1,2)-mannose attached to
alternate glucose residues in the backbone by a-1,3
linkages (Jansson et al. 1975). The mannose residues
are acetylated and pyruvylated at specific sites, but to
varying degrees (Stankowski et al. 1993). The
biosynthetic pathway by which xanthan is produced
involves three steps: (1) conversion of simple
Sang-Yoon Kim and Jeong-Gu Kim contributed equally to this
work.
Electronic supplementary material The online version of
this article (doi:10.1007/s10529-008-9858-3) contains
supplementary material, which is available to authorized users.
S.-Y. Kim Á J.-Y. Cho (&)
Division of Animal Science and Biotechnology,
Sangji University, 660 Woosan-dong, Wonju-si,
Gangwon-do 220-702, Korea
e-mail: jycho@sangji.ac.kr
J.-G. Kim Á B.-M. Lee
Microbial Genetics Division, National Institute
of Agricultural Biotechnology, 225 Seodun-dong,
Suwon 441-707, Korea
J.-Y. Cho
LabGene Inc., Sangji University, 660 Woosan-dong,
Wonju-si, Gangwon-do 220-702, Korea
123
Biotechnol Lett (2009) 31:265–270
DOI 10.1007/s10529-008-9858-3
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