Specific RubisCO activities of yet uncultured Proteobacteria depending on flanking genes

Here we used the first solely activity-based approach for identifying RubisCO active fosmid clones from a metagenomic library. Hydrothermal vent fluids derived from the interface zone between hot fluids emanating from Drachenschlund and ambient cold seawater at 8°18'S/13°30'W served as initial sample for library construction. Among 1056 screened fosmid clones 12 exhibited RubisCO activity. The metagenomic fragments of all twelve clones resembled genes from Hydrogenovibrio crunogenus. One of these clones was further analyzed. It contained a 35.2 kb metagenomic insert carrying the RubisCO gene cluster and flanking DNA regions. Knockouts of 12 genes and 2 intergenic regions on this metagenomic fragment demonstrated that the RubisCO activity was significantly impaired and was attributed to deletions in genes encoding putative transcriptional regulators and those believed to be vital for RubisCO activation. Our new technique revealed a novel link between a poorly-characterized gene and RubisCO activity.