[Cloning and sequence analysis of a sialidase gene (siaHI) from Bacteroides forsythus ATCC 43037].

Bacteroides forsythus is known as a periodontopathogen associated with periodontitis, and it produces a tripsin-like protease, cell-death inducing factor, and sialidase (neuraminidase), as putative virulence factors. The purpose of this study was to clone the sialidase gene from B. forsythus ATCC 43037, and to analyze the biological characteristics. A positive clone (pHI-1) was successfully isolated, among a total of 455 recombinant clones, using a filter paper sialidase assay with the fluorogenic sialidase substrate 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid (MUNeuNAc). Sequencing of the inserted DNA of pHI-1(3.2 kbp) was carried out, and analysis of the sequence with DNASIS software revealed that the ORF (designated siaHI: 1.4 kbp) would code for the protein with a deduced molecular mass of 52 kDa and a pI of 6.60. Furthermore, we confirmed that siaHI gene was contained in chromosomal DNA from B. forsythus ATCC 43037 and the 3 clinical isolates of B. forsythus. The highest amino acid sequence homology was observed between siaHI gene and a part of sialidase gene from Streptococcus pnumoniae. This is the first report on the cloning and expression of the B. forsythus sialidase gene.