Asaia bogorensis, a member of acetic acid bacteria (AAB), is an aerobic bacterium isolated from flowers and fruits, as well as an opportunistic pathogen that causes human peritonitis and bacteraemia. Here, we determined the complete genomic sequence of the As. bogorensis type strain NBRC 16594, and conducted comparative analyses of gene expression under different conditions of co-culture with mammalian cells and standard AAB culture. The genome of As. bogorensis contained 2,758 protein-coding genes within a circular chromosome of 3,198,265 bp. There were two complete operons encoding cytochrome bo3-type ubiquinol terminal oxidases: cyoABCD-1 and cyoABCD-2. The cyoABCD-1 operon was phylogenetically common to AAB genomes, whereas the cyoABCD-2 operon belonged to a lineage distinctive from the cyoABCD-1 operon. Interestingly, cyoABCD-1 was less expressed under co-culture conditions than under the AAB culture conditions, whereas the converse was true for cyoABCD-2. Asaia bogorensis shared pathogenesis-related genes with another pathogenic AAB, Granulibacter bethesdensis, including a gene coding pathogen-specific large bacterial adhesin and additional genes for the inhibition of oxidation and antibiotic resistance. Expression alteration of the respiratory chain and unique hypothetical genes may be key traits that enable the bacterium to survive under the co-culture conditions.

The carbonic anhydrase nacrein participates in the formation of the nacreous or prismatic layer of Pinctada fucata. We isolated a genomic clone containing the nacrein gene and cloned the 5 0 -flanking region. Within the 1336 bp 5 0 flanking region, we identified putative cis-acting elements, including the TATA box (TATAAAA) at -82 bp, and AP1 (-819 bp) and Oct-1 (-1244 bp) binding sites. In addition to the mantle, the nacrein gene is also expressed in the adductor muscle, liver, and foot. These results showed that nacrein not only takes part in the formation of the hard tissue but also might be involved in acid-base balance, ion transport, and maintenance of ionic concentration. In vitro transcription experiments showed that the addition of human c-jun activates transcription from the nacrein promoter. This is the first report of a promoter from a gene that controls the formation of the hard tissue of mollusk shells.

Bone morphogenetic protein (BMP)-2 plays an important role in morphogenesis in both vertebrates and invertebrates. BMP-2 is one of the most powerful bioactive substances known to induce the osteogenic differentiation of mesenchymal cells. We examined the structural and functional conservation of Pinctada fucata BMP-2 in inducing osteogenesis in the murine mesenchymal stem cells, C3H10T1/2. Exposure of C3H10T1/2 cells to the recombinant mature fragment of Pinctada fucata BMP-2 resulted in osteoblastic differentiation. The sequence, SVPKPCCVPTELSSL, within the C-terminal portion of Pinctada fucata BMP-2, is homologous to the knuckle epitope of human BMP-2. This synthetic polypeptide was able to induce differentiation of C3H10T1/2 along the osteoblastic lineage, as confirmed by an increase in alkaline phosphatase activity, and the accumulation of calcium, as determined by von Kossa staining. Furthermore, using immunohistochemical staining, we observed an increased expression of collagen type I, osteopontin, and osteocalcin, which are known markers of osteogenesis. These results show that BMP-2 is conserved, not only in terms of its homology at the amino acid sequence, but also in terms of driving the formation of hard tissues in vertebrates and invertebrates.