Specific RubisCO activity of currently uncultured microorganisms inhabiting hydrothermal deep sea vents

In 2014 we described a new activity-based screen suited to seek active recombinant RubisCOs from the environment - independent of the native host's culturability. Within this study we aimed at seeking novel RubisCO active enzymes from the environment. For this purpose we screened six metagenomic fosmid libraries from hydrothermal vent environments, differing with respect to their (i) geographic origin (north or south Mid Atlantic Ridge) and their (ii) environmental characteristics (basalt vs. ultramafic hosted, temperature, and pH). Overall we screened roughly 12500 metagenomic fosmid clones and identified forty active RubisCOs. Additional sequence-based screening uncovered eight further RubisCOs, which could then also be detected by a modified version of the screen. Seven were active form III RubisCOs from yet uncultured Archaea. This indicates the potential of the activity-based screen to detect RubisCO enzymes even from organisms that would not be expected to be targeted.