Figure 6.11
130
Bacterial Cellulose
the.surface.of.the.NOC.is.strong.enough,.the.bacterium.follows.the.track.of.
the.molecular.template..As.the.polymer.orientation.of.the.NOC.is.not.necessarily.perfect,.the.. bacterium.may.jump.off.the.track.at.a.structural.defect.
(Figure 6.10-3)..After.the.. bacterium.leaves.the.track.(Figures 6.10-3–10-6),.two.
forces,.the.inverse.force.of.the.secretion.and.the.close.interaction.of.adjacent.
microfibrils,. affect. the. bacterium,. possibly. resulting. in. the. synthesis. of. a.
. spiral.ribbon.of.micro. fibrils..In.addition,.the.bacterium.begins.to.rotate.on.its.
own.axis..This.rotation.is.the.. visible.result.of.ribbon.twisting,.which.occurs.
to. relieve. strain. induced. by. the. absence. of. interaction. with. the. substrate..
When.the.ribbon.is.assembled.in.direct.contact.with.the.oriented.molecular.
NOC.substrate,.ribbon.twisting.is.prevented,.thus.suggesting.a.control.of.this.
oriented. solid. surface. over. the. final. physical. interaction. of. polymer. chains.
immediately.after.synthesis.and.during.the.early.stages.of.crystallization.
Ribbon.interaction.is.more.clearly.shown.by.field.emission.scanning.electron. microscopy. (FE-SEM). in. Figures 6.11A. and. 6.11B.. In. this. experiment,.
the.motion.of.the.same.sample.is.observed.using.light.microscopy.and.then.
the.sample.is.prepared.for.FE-SEM.observations..In.Figures 6.10a.and.6.10b.
the.time.course.sequence.demonstrates.an.intense,.directed.nanodeposition.
that.is.exclusively.linear.and.without.cell.rotation.as.the.bacterium.follows.
the.track..This.is.confirmed.by.the.ribbon.structure.shown.by.the.FE-SEM.
images.in.Figures 6.11A.and.6.11B,.which.reveal.no.twisting.and.a.more.perfect.alignment.with.the.substrate..Likewise,.when.the.bacterium.“jumps.off”.
the.track,.the.cellulose.ribbon.is.twisted.(data.not.shown)..Figures 6.11c–6.11f.
indicate. the. active. Gluconacetobacter cells. cultured. on. the. oriented. surface.
A
B
1 µm
1 µm
25 µm
25 µm
25 µm
25 µm
1
3
2
4
Figure 6.11
FE-SEM.images.of.the.cellulose.nanofiber.deposition.process..(A,.B).Examples.of.bacteria.synthesizing.cellulose.fibers.on.the.oriented.molecular.track.of.NOC..(A).Demonstrates.the.tight.
association.between.the.molecular.track.and.the.cellulose.fiber..In.(B),.a.bacterium.shows.a.flat.
fiber.immediately.behind.its.site.of.synthesis..(1–4).Successive.images.showing.the.motion.of.
a.bacterium.on.a.nematic.ordered.blended.film.of.cellulose.and.cellulose.acetate.that.has.been.
unixially.stretched.in.the.same.manner.as.NOC.
130
Bacterial Cellulose
the.surface.of.the.NOC.is.strong.enough,.the.bacterium.follows.the.track.of.
the.molecular.template..As.the.polymer.orientation.of.the.NOC.is.not.necessarily.perfect,.the.. bacterium.may.jump.off.the.track.at.a.structural.defect.
(Figure 6.10-3)..After.the.. bacterium.leaves.the.track.(Figures 6.10-3–10-6),.two.
forces,.the.inverse.force.of.the.secretion.and.the.close.interaction.of.adjacent.
microfibrils,. affect. the. bacterium,. possibly. resulting. in. the. synthesis. of. a.
. spiral.ribbon.of.micro. fibrils..In.addition,.the.bacterium.begins.to.rotate.on.its.
own.axis..This.rotation.is.the.. visible.result.of.ribbon.twisting,.which.occurs.
to. relieve. strain. induced. by. the. absence. of. interaction. with. the. substrate..
When.the.ribbon.is.assembled.in.direct.contact.with.the.oriented.molecular.
NOC.substrate,.ribbon.twisting.is.prevented,.thus.suggesting.a.control.of.this.
oriented. solid. surface. over. the. final. physical. interaction. of. polymer. chains.
immediately.after.synthesis.and.during.the.early.stages.of.crystallization.
Ribbon.interaction.is.more.clearly.shown.by.field.emission.scanning.electron. microscopy. (FE-SEM). in. Figures 6.11A. and. 6.11B.. In. this. experiment,.
the.motion.of.the.same.sample.is.observed.using.light.microscopy.and.then.
the.sample.is.prepared.for.FE-SEM.observations..In.Figures 6.10a.and.6.10b.
the.time.course.sequence.demonstrates.an.intense,.directed.nanodeposition.
that.is.exclusively.linear.and.without.cell.rotation.as.the.bacterium.follows.
the.track..This.is.confirmed.by.the.ribbon.structure.shown.by.the.FE-SEM.
images.in.Figures 6.11A.and.6.11B,.which.reveal.no.twisting.and.a.more.perfect.alignment.with.the.substrate..Likewise,.when.the.bacterium.“jumps.off”.
the.track,.the.cellulose.ribbon.is.twisted.(data.not.shown)..Figures 6.11c–6.11f.
indicate. the. active. Gluconacetobacter cells. cultured. on. the. oriented. surface.
A
B
1 µm
1 µm
25 µm
25 µm
25 µm
25 µm
1
3
2
4
Figure 6.11
FE-SEM.images.of.the.cellulose.nanofiber.deposition.process..(A,.B).Examples.of.bacteria.synthesizing.cellulose.fibers.on.the.oriented.molecular.track.of.NOC..(A).Demonstrates.the.tight.
association.between.the.molecular.track.and.the.cellulose.fiber..In.(B),.a.bacterium.shows.a.flat.
fiber.immediately.behind.its.site.of.synthesis..(1–4).Successive.images.showing.the.motion.of.
a.bacterium.on.a.nematic.ordered.blended.film.of.cellulose.and.cellulose.acetate.that.has.been.
unixially.stretched.in.the.same.manner.as.NOC.