Distribution of RuBisCO Genotypes along a Redox Gradient in Mono Lake, California

Partial sequences of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) (EC 4.1.1.39) genes were retrieved from samples taken along a redox gradient in alkaline, hypersaline Mono Lake, Calif. The form I gene (cbbL) was found in all samples, whereas form II (cbbM) was not retrieved from any of the samples. None of the RuBisCO sequences we obtained were closely related (nucleotide similarity, <90%) to sequences in the database. Some could be attributed to organisms isolated from the lake (Cyanobium) or appearing in enrichment cultures. Most (52%) of the sequences fell into in one clade, containing sequences that were identical to sequences retrieved from an enrichment culture grown with nitrate and sulfide, and another clade contained sequences identical to those retrieved from an arsenate-reducing, sulfide-oxidizing enrichment.