UNUSUAL RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE GENES FROM A MARINE MANGANESE-OXIDIZING BACTERIUM/

The Gram-negative bacterium strain S185-9A1 is a novel marine alpha-pr oteobacterium that oxidizes manganese(II) to manganese(IV). Initial DN A hybridization screening showed that S185-9A1 possesses a gene simila r to cbbL, the gene coding for the large subunit of ribulose-1,5-bisph osphate carboxylase/oxygenase (RubisCO; EC 4.1.1.39). However, no Rubi sCO enzyme activity was found in cultures of S185-9A1, Genes coding fo r both large (cbbL) and small (cbbS) subunits of a RubisCO enzyme were identified, isolated and sequenced. When these genes were introduced into an Escherichia coli host strain, ribulose-1,5-bisphosphate-depend ent CO2 fixation occurred under control of a lac promoter, indicating that the protein is functional in E. coli. Although their function is unknown, this is the first direct evidence for the presence of RubisCO genes in a manganese-oxidizing bacterium. Phylogenetic analysis of th e RubisCO genes of strain S185-9A1 showed that they are divergent, but are more related to those from non-chlorophyte algal chloroplasts tha n are those from other bacteria. The fact that the RubisCO sequence of strain S185-9A1 is not closely related to any other published RubisCO sequence suggests that the protein may be valuable for studies of the function and evolution of the RubisCO enzyme as well as its activity in the environment.