Team:Groningen/Brainstorm/Buoyant Bacteria


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About 150 species of prokaryotes in aquatic habitats have been shown to contain gas vesicles. These gas vesicles provide cells with bouyancy. Gas vesicles are made exclusively of proteins and contain gas. When gas vesicles are present in a cell, the overall density of that cell is lowered and the cell becomes bouyant.

We want to utilize this bouyancy for an application like for example separation of specific molecules or specific cells.

Gas vesicles in iGEM

In iGEM 2007, Melbourne created a biobrick for gas vesicle formation. In iGEM 2008 Kyoto had the idea to lift the titanic from the bottom of the sea with the help of bouyant bacteria.

[wiki website | Melbourne iGEM 2007 team] constructed a bouyant E. coli and also they added a [Partsregistry | BioBrick] of the short version of the gvp-cluster (without gvpA,P,Q, ORF-1 and AraC). This BioBrick is available and also in the microtiter plate send by HQ to us, so we can use this. Melbourne changed the gvp-cluster by cleaning it from 3 EcoRI sites and 1 PstI site, this leaded to a accidental addition of a 10x repeat of "TCTGCAAATTA". They mention that they added the BioBrick prefix and suffix to the BioBrick, though the restriction sites of these additions cannot be found by CloneManager in the sequence available on the Partregistry. Hopefully the part is available on a standard vector, which has the pre- and suffix for BioBricks. For cloning this part we can use the [wiki Melbourne | optimized protocol ] (restriction on part with XbaI and SpeI, on the vector with SpeI) for ldigation of the gvp-cluster and a vector, this unluckaly leads to ligation of the gvp-cluster in an unspecific direction. This can of course be tested by restriction, PCR or sequencing, but it takes more time as another step will be introduced.

Alternative cloning strategy

Another possibility is to use eg. EcoRI and SpeI and also cut the vector with these enzymes, this would lead to ligation of the gvp-cluster in one direction. Possible vectors on the partsregistry are: [partsregistry | BBa_J610035 or BBa_23018] (2298 bp), this is a high copy number vector this may influence the bouyancy fenotype. By Melbourne a somewhat larger vector was used [BBa_23018??] (32??bp) --> ?? copy number??, with this vector it is not possible to clone the insert directional. But it has two selection markers: Ampicillin and Gentamycin.

Missing information

  • Used promotor for expression of the gvp-cluster:
    • Inducible (may be used for proof-of-principle)
    • Constituative (may be used for proof-of-principle)
    • Metal sensitive
  • What kind of vector was used by Li and Cannon (1995) or Melbourne (2007)? Is there a negative effect of high copy number?
  • What is the maximum amount of pressure gas vesicles can handle? At which depth would this be, how can one put this kind of pressure on a water column?
  • What is the density of gas vesicles in cells (normally or in case of over-expression)
  • Modelling parameters:

-Cyanobacteria (Bowen and Jensen, 1965): gas vacuoles made up of gas vesicles (75 nm in diameter and up to 1.0 ,um in length, single wall layer only 2 nm thick) 0,7MPa gives irreversible loss of buoyancy fenotype, but found in next generation.


Walsby, A.E. 1994. Gas Vesicles. Microbiological reviews. Vol. 58, No. 1, p. 94-144.

Li, N., Cannon, M.C. 1998. Gas Vesicle Genes Identified in Bacillus megaterium and Functional Expression in Escherichia coli. Journal of Bacteriology. Vol. 180, No. 9, p. 2450–2458.

Astrid C. Sivertsen et al. 2009 Solid-State NMR Evidence for Inequivalent GvpA Subunits in Gas Vesicles. Journal of Molecular Biology 387, p1032–1039.

Lewinson O., Lee A.T., Rees D.C. 2009. A P-type ATPase importer that discriminates between essential and toxic transition metals. PNAS. vol. 106, no. 12, p. 4677-4682.