Molecular characterization of a chemotaxis operon in the oral spirochete, Treponema denticola

• Published in: Gene Vol. 232; no. 1; pp. 59 - 68
• Main Authors: Greene, S.R., Stamm, L.V.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 17-05-1999
• Subjects: Amino Acid Sequence; Base Sequence; Blotting, Southern; cheA gene; Chemotaxis - genetics; cheW gene; cheX gene; cheY gene; Genes, Bacterial; Humans; Molecular Sequence Data; Motility; Multigene Family; Operon - genetics; Periodontal disease; Periodontal Diseases - microbiology; Phylogenetic analysis; Phylogeny; Reverse Transcriptase Polymerase Chain Reaction; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Signal Transduction; Signal transduction system; Transcription, Genetic; Treponema - genetics; Treponema - physiology; Treponema denticola; Treponemal Infections - microbiology; aa, amino acid(s); Hs, Halobacterium salinarium; oligo, oligodeoxyribonucleotide; Motility; GCG, Wisconsin Genetics Computer Group; UNC-CH, University of North Carolina at Chapel Hill; bp, base pair(s); LB, Luria–Bertani medium; Rm, Rhizobium meliloti; Phylogenetic analysis; Lm, Listeria monocytogenes; St, Salmonella typhimurium; kb, kilobase(s); Tm, Thermatoga maritima; RT, reverse transcriptase; Bs, Bacillus subtilis; BLAST, Basic Local Alignment Search Tool; RT–PCR, reverse transcriptase–PCR; Tp, Treponema pallidum subspecies pallidum; Ec, Escherichia coli; tsp, transcriptional start point; ORF, open reading frame; Signal transduction system; Rc, Rhodospirillum centenum; Td, Treponema denticola; Periodontal disease; RBS, ribosome binding site; Bb, Borrelia burgdorferi; nt, nucleotide(s); che, chemotaxis; Pp, Pseudomonas putida; Tpp, Treponema pallidum subspecies pertenue; Rs, Rhodobacter sphaeroides; PCR, polymerase chain reaction; P, promoter
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/S0378-1119(99)00115-8

A chemotaxis gene cluster from
Treponema
denticola (
Td), a pathogenic spirochete associated with human periodontal diseases, was cloned, sequenced, and analyzed. The gene cluster contained three chemotaxis (
che) genes (
cheA,
cheW, and
cheY) and an open reading frame (
cheX) that is homologous with
Treponema pallidum (
Tp) and
Borrelia burgdorferi (
Bb)
cheX. The
Td
che genes have the same transcriptional orientation with a sigma 70-like promoter located upstream of
cheA and a stem–loop structure characteristic of a Rho-independent transcriptional terminator downstream of
cheY. Primer extension analysis identified a transcriptional start point six nucleotides (nt) downstream of the −10 (TAAAAA) promoter sequence. Reverse-transcriptase–polymerase chain reaction (RT–PCR) data indicated that
cheA through
cheY are co-transcribed and suggested that transcription is terminated after
cheY. The gene organization of the
Td che operon is identical to that of the
Tp
che operon. Southern blot analysis indicated the presence of one copy of each
che gene on the
Td genome. The
cheA,
cheW,
cheX, and
cheY genes are 2403, 1332, 462, and 438
nt long, respectively, and encode proteins with predicted molecular masses of 88.2, 49.7, 16.8, and 16.0
kDa, respectively. Functional domains of the
T.
denticola CheA and CheY proteins are highly conserved with those of the
Escherichia coli (
Ec) CheA and CheY proteins. Phylogenetic analysis of
Td CheY indicated that it is closely related to
Tp CheY and
Bb CheY3.