Latest revision as of 19:01, 27 October 2010

BCCS-Bristol
iGEM 2010

• Overview • Bead Materials • Making Beads • Beads in Solution • Beads in Soil • Image Gallery •

Beads

One of the factors that differentiate us from other teams is our use of technology to facilitate using our bacteria safely and more effectively in real life situations. More specifically; we encapsulated our bacteria in a non-toxic gel substances, forming beads of highly concentrated bacteria.

Why did we do this?

Our new beads

Initial soil visibility experiments (see here) raised the major problem that high levels of cell death when E. coli were spread freely in the soil resulted in very low signals. This isn't surprising, given lab-grade E. coli are deliberately synthesised such that they can't survive outside of very specific conditions, and are easily out competed by naturally occurring soil bacteria.

Whilst developed to solve this problem, our beads have a number of beneficial features:

Beads provide a protective environment, reducing cell death.
Large concentrations of cells in a small area ensure high, easily detectable signals.
Nutrients can be added to beads, further improving bacteria survival.
Bacteria are kept separate from the environment, reducing public safety fears.
Increased access to Nitrate.

More Information

We hope our work on bacterial encapsulation will prove useful to teams in the future - as encapsulation has a number of applications beyond our soil sensor (and has considerable safety benefits) - so have provided below information on the material we chose to use, and the exact procedure for making beads. Above you can find links materials and procedures, as well as experiments analysing the performance of beads containing our new BioBrick, and a gallery of bead images.

@@ Line 1: / Line 1: @@
 {{:Team:BCCS-Bristol/Header}}
-==Beads==
+<center> • [[:Team:BCCS-Bristol/Wetlab/Beads|Overview]] • [[:Team:BCCS-Bristol/Wetlab/Beads/Gellan |Bead Materials]] • [[:Team:BCCS-Bristol/Wetlab/making_beads|Making Beads]]
+• [[:Team:BCCS-Bristol/Wetlab/difference_solution|Beads in Solution]] • [[:Team:BCCS-Bristol/Wetlab/difference_soil|Beads in Soil]] • [[:Team:BCCS-Bristol/Wetlab/Beads/ImageGallery|Image Gallery]] • </center>
-Why beads? make the case for encapsulation, subpages for specifics:
-[[:Team:BCCS-Bristol/Wetlab/Beads/Gellan]]
+=Beads=
-[[:Team:BCCS-Bristol/Wetlab/Beads/Safety_Benefits]]
+One of the factors that differentiate us from other teams is our use of technology to facilitate using our bacteria safely and more effectively in real life situations. More specifically; we encapsulated our bacteria in a non-toxic gel substances, forming beads of highly concentrated bacteria.
-[[:Team:BCCS-Bristol/Wetlab/Beads/Procedure]]
+==Why did we do this?==
-[[:Team:BCCS-Bristol/Wetlab/Beads/Improvements]]
+[[Image:Beads.png|thumbnail|400px|right|Our new beads]]
-[[:Team:BCCS-Bristol/Wetlab/Beads/Encapsulation_Applications]]
+Initial soil visibility experiments (see [https://2010.igem.org/Team:BCCS-Bristol/Wetlab/signal_soil here]) raised the major problem that high levels of cell death when ''E. coli'' were spread freely in the soil resulted in very low signals. This isn't surprising, given lab-grade ''E. coli'' are deliberately synthesised such that they can't survive outside of very specific conditions, and are easily out competed by naturally occurring soil bacteria.
+Whilst developed to solve this problem, our beads have a number of beneficial features:
-There are several reasons why the E. coli cells are encapsulated in a gel bead. The primary
+* Beads provide a protective environment, reducing cell death.
-concerns were visibility of the ﬂuorescent signal and being able to keep the cells separated from the
+* Large concentrations of cells in a small area ensure high, easily detectable signals.
-environment. There are secondary beneﬁts too, it is possible to include nutrients in the gels for the
+* Nutrients can be added to beads, further improving bacteria survival.
-bacteria to consume and the beads can help to absorb nitrates from the soil.
+* Bacteria are kept separate from the environment, reducing public safety fears.
+* Increased access to Nitrate.
-Initial experiments looking at the visibility of E. coli constitutively expressing GFP on soil, e.g.
+==More Information==
-ﬁg. 2, showed that it would be diﬃcult to observe ﬂuorescence from E. coli simply sprayed onto soil
-in solution. The lab-grade E. coli are designed to be out-competed by naturally occurring bacteria
-and they are unable to synthesise certain amino acids. This is designed as a safety feature, it ensures
-that they will not survive for long outside of a lab environment. This means that when sprayed
-directly onto unsterilised soil the E. coli will die relatively quickly, so only those that survive will
-be able to sense nitrate and produce a signal. The bead provides a protective environment for the
-E. coli and packages a large amount of them together to produce a large signal. The bead can also
-be infused with a nutrient broth to provide the cells with an adequate supply of energy and amino
-acids to ensure survival and continued production of GFP and RFP.
-Initial experiments using beads that had just the PyeaR+GFP BioBrick showed that the in-
+We hope our work on bacterial encapsulation will prove useful to teams in the future - as encapsulation has a number of applications beyond our soil sensor (and has considerable safety benefits) - so have provided below information on the material we chose to use, and the exact procedure for making beads. Above you can find links materials and procedures, as well as experiments analysing the performance of beads containing our new BioBrick, and a gallery of bead images.
-crease in ﬂuorescence is easily detectable, before and after images can be seen in ﬁg. 4. The beads
-were placed on wet unsterilised soil that had been saturated with a 20nM potassium nitrate solu-
-tion. There is some ﬂuorescence in the ’before’ picture, this is due to ’leakage’ expression of GFP,
-i.e. the residual expression in the absence of nitrate due to the repressor not repressing every singleP
-yeaR site.
-It is expected that the beads will limit the spread of E. coli into the ﬁeld. Since the E. coli
-are dependant upon amino acids in their nutrient broth they should not last too long outside of
-the bead environment, and when they have exhausted their supply internally they should die oﬀ
-too. This factor of the bead design has not been rigorously experimentally tested though. It is
-unclear exactly how densely packed the E. coli are in the bead, and how much movement they
-have, preliminary data from high magniﬁcation confocal microscopy that those at the edge of the
-bead can move out of it quite freely.