Open reading frames and nucleotide sequence homologies in the recA-amplicons from Calyptogena clam symbionts. A, Open reading frames (ORFs) of the recA-amplicons. Filled column, intact gene. Open columns, pseudogene or remnant gene. Gray column, part of the gene for RibD (bifunctional riboflavin biosynthesis protein). Blue column, recA. Light gray column, recX. Brown column, part of the gene for the ABC transporter ATP-binding protein (ABC-t). *, mutated stop codon. B, Aligned recA-amplicons showing their nucleotide sequence identities and deletion profiles with that of the C. phaseoliformis symbiont.