Abstract
BackgroundBacterial gas vesicles, composed of two major gas vesicle proteins and filled with gas, are a unique class of intracellular bubble-like nanostructures. They provide buoyancy for cells, and thus play an essential role in the growth and survival of aquatic and soil microbes. Moreover, the gas vesicle could be applied to multimodal and noninvasive biological imaging as a potential nanoscale contrast agent. To date, cylinder-shaped gas vesicles have been found in several strains of cyanobacteria. However, whether the functional gas vesicles could be produced in the model filamentous cyanobacteria Anabaena sp. PCC 7120 remains controversial.ResultsIn this study, we found that an intact gvp gene cluster indeed exists in the model filamentous cyanobacteria Anabaena sp. PCC 7120. Real-time PCR assays showed that the gvpA gene is constitutively transcribed in vivo, and its expression level is upregulated at low light intensity and/or high growth temperature. Functional expression of this intact gvp gene cluster enables the recombinant Escherichia coli to gain the capability of floatation in the liquid medium, thanks to the assembly of irregular gas vesicles. Furthermore, crystal structure of GvpF in combination with enzymatic activity assays of GvpN suggested that these two auxiliary proteins of gas vesicle are structurally and enzymatically conserved, respectively.ConclusionsOur findings show that the laboratory strain of model filamentous cyanobacteria Anabaena sp. PCC 7120 possesses an intact but partially degenerated gas vesicle gene cluster, indicating that the natural isolate might be able to produce gas vesicles under some given environmental stimuli for better floatation.
Highlights
Bacterial gas vesicles, composed of two major gas vesicle proteins and filled with gas, are a unique class of intracellular bubble-like nanostructures
Formation of Gas vesicle (GV) is related to a conserved cluster of 8 ~ 14 genes, encoding two major structural proteins and several essential minor components that might putatively function as chaperones, nucleators and regulators [2, 5, 7]
Eight out of the 5368 putative open reading frames in the genome were annotated as gvp genes: gvpA, gvpB, gvpC, gvpN, gvpJ, gvpK, gvpF and gvpG, without annotations of gvpV and gvpW compared to some other gvp gene clusters
Summary
Bacterial gas vesicles, composed of two major gas vesicle proteins and filled with gas, are a unique class of intracellular bubble-like nanostructures. They provide buoyancy for cells, and play an essential role in the growth and survival of aquatic and soil microbes. Formation of GVs is related to a conserved cluster of 8 ~ 14 genes (termed gas vesicle protein gene cluster, or gvp gene cluster for short), encoding two major structural proteins and several essential minor components that might putatively function as chaperones, nucleators and regulators [2, 5, 7]. GvpF is reported to be a structural protein localized at the inner surface of GVs [18]
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