Figure 1.1
8
Bacterial Cellulose
with. an. insertion. in. the. acsAB. gene. (Saxena. and. Brown. 1995).. The. role. of.
the.acsAB,.acsC,.and.acsD.genes.in.in.vivo.and.in.vitro.cellulose.synthesis.in.
G. xylinus.ATCC.23769.was.analyzed.by.mutant.and.biochemical.analyses.and.
it.was.found.that.while.both.acsAB.and.acsC.are.essential.for.cellulose.production.in.vivo,.mutation.of.the.acsD.gene.affects.both.the.amount.and.crystalline.
form.of.cellulose.produced.(Saxena.et.al..1994).
Two.additional.genes.(ORF1.and.ORF2).present.upstream.of.the.cellulosesynthesizing.operon.in.G. xylinus.were.identified.during.characterization.of.
Cel − .mutants.(Standal.et.al..1994),.and.both.these.genes.have.been.suggested.
to.have.a.role.in.cellulose.biosynthesis..ORF1.codes.for.a.CMCase.(an.endoglucanase).and.the.gene.is.also.referred.to.as.cmcax,.while.ORF2.codes.for.a.
protein.that.is.suggested.to.play.a.role.in.both.the.production.and.crystallization.of.cellulose.I.(Nakai.et.al..2002),.and.this.gene.is.designated.as.ccp.
An. organization. of. cellulose. synthesis. genes. similar. to. those. identified. in. G. xylinus. strains. ATCC. 53582,. ATCC. 23769,. and. 1306-3. have. been.
identified. in. a. few. other. strains. of. this. bacterium. (Umeda. et. al.. 1999).. A.
representative. . organization. of. these. genes. from. two. different. strains. of.
G. xylinus.is.shown.in.Figure 1.1..After.the.identification.of.genes.for.cellulose.
synthesis.in.G. xylinus,. homologous.sequences.and.a.similar.organization.of.
cellulose-synthesizing. genes. have. been. observed. in. a. number. of. bacterial.
species.(Nobles.and.Brown.2007;.Römling.2007;.Valla.et.al..2009);.the.organization.of.genes.from.E. coli.is.shown.in.Figure 1.1..This.bacterium.has.no.
homolog.to.the.G. xylinus bcsD.gene,.and.the.endoglucanase.gene.(bcsZ).is.
present.between.bcsB.and.bcsC..In.addition,.a.yhjQ.gene.is.present.upstream.
of.bcsA.in.E. coli..For.the.sake.of.uniformity,.we.suggest.that.the.organization.
of.genes.containing.the.gene.for.cellulose.synthase.in.bacteria.be.referred.to.
as.the.bacterial.cellulose.synthesis.operon.(bcs.operon).and.the.genes.in.this.
operon.be.labeled.as.bcsA,.bcsB.(or.bcsAB,.where.bcsA.and.bcsB.are.fused.into.
a.single.gene),.bcsC,.and.bcsD.(Figure 1.1).
G. xylinus
cmcax ccp
bcsAB
bcsC bcsD
bglx
Strain ATCC 23769
cmcax ccp bcsA
bcsB
bcsC
bcsD
bglx
Strain JCM 7664
yhjR yhjQ bcsA
bcsB bcsZ bcsC
E. coli
Figure 1.1
Organization. of. genes. for. cellulose. synthase. (bcsA/bcsAB). and. other. proteins. involved. in.
. cellulose.biosynthesis.in.the.bacterial.cellulose.synthesis.(bcs).operon.in.G. xylinus.and.E. coli.
8
Bacterial Cellulose
with. an. insertion. in. the. acsAB. gene. (Saxena. and. Brown. 1995).. The. role. of.
the.acsAB,.acsC,.and.acsD.genes.in.in.vivo.and.in.vitro.cellulose.synthesis.in.
G. xylinus.ATCC.23769.was.analyzed.by.mutant.and.biochemical.analyses.and.
it.was.found.that.while.both.acsAB.and.acsC.are.essential.for.cellulose.production.in.vivo,.mutation.of.the.acsD.gene.affects.both.the.amount.and.crystalline.
form.of.cellulose.produced.(Saxena.et.al..1994).
Two.additional.genes.(ORF1.and.ORF2).present.upstream.of.the.cellulosesynthesizing.operon.in.G. xylinus.were.identified.during.characterization.of.
Cel − .mutants.(Standal.et.al..1994),.and.both.these.genes.have.been.suggested.
to.have.a.role.in.cellulose.biosynthesis..ORF1.codes.for.a.CMCase.(an.endoglucanase).and.the.gene.is.also.referred.to.as.cmcax,.while.ORF2.codes.for.a.
protein.that.is.suggested.to.play.a.role.in.both.the.production.and.crystallization.of.cellulose.I.(Nakai.et.al..2002),.and.this.gene.is.designated.as.ccp.
An. organization. of. cellulose. synthesis. genes. similar. to. those. identified. in. G. xylinus. strains. ATCC. 53582,. ATCC. 23769,. and. 1306-3. have. been.
identified. in. a. few. other. strains. of. this. bacterium. (Umeda. et. al.. 1999).. A.
representative. . organization. of. these. genes. from. two. different. strains. of.
G. xylinus.is.shown.in.Figure 1.1..After.the.identification.of.genes.for.cellulose.
synthesis.in.G. xylinus,. homologous.sequences.and.a.similar.organization.of.
cellulose-synthesizing. genes. have. been. observed. in. a. number. of. bacterial.
species.(Nobles.and.Brown.2007;.Römling.2007;.Valla.et.al..2009);.the.organization.of.genes.from.E. coli.is.shown.in.Figure 1.1..This.bacterium.has.no.
homolog.to.the.G. xylinus bcsD.gene,.and.the.endoglucanase.gene.(bcsZ).is.
present.between.bcsB.and.bcsC..In.addition,.a.yhjQ.gene.is.present.upstream.
of.bcsA.in.E. coli..For.the.sake.of.uniformity,.we.suggest.that.the.organization.
of.genes.containing.the.gene.for.cellulose.synthase.in.bacteria.be.referred.to.
as.the.bacterial.cellulose.synthesis.operon.(bcs.operon).and.the.genes.in.this.
operon.be.labeled.as.bcsA,.bcsB.(or.bcsAB,.where.bcsA.and.bcsB.are.fused.into.
a.single.gene),.bcsC,.and.bcsD.(Figure 1.1).
G. xylinus
cmcax ccp
bcsAB
bcsC bcsD
bglx
Strain ATCC 23769
cmcax ccp bcsA
bcsB
bcsC
bcsD
bglx
Strain JCM 7664
yhjR yhjQ bcsA
bcsB bcsZ bcsC
E. coli
Figure 1.1
Organization. of. genes. for. cellulose. synthase. (bcsA/bcsAB). and. other. proteins. involved. in.
. cellulose.biosynthesis.in.the.bacterial.cellulose.synthesis.(bcs).operon.in.G. xylinus.and.E. coli.