The genome of the obligately intracellular bacterium Ehrlichia canis reveals themes of complex membrane structure and immune evasion strategies.
Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, alpha-proteobacterium, is the primary etiologic agent of globally distributed canine monocytic ehrlichiosis. Complete genome sequencing revealed that the E. canis genome consists of a single circular chromosome of 1,315,030 bp predicted to encode 925 proteins, 40 stable RNA species, 17 putative pseudogenes, and a substantial proportion of noncoding sequence (27%). Interesting genome features include a large set of proteins with transmembrane helices and/or signal sequences and a unique serine-threonine bias associated with the potential for O glycosylation that was prominent in proteins associated with pathogen-host interactions. Furthermore, two paralogous protein families associated with immune evasion were identified, one of which contains poly(G-C) tracts, suggesting that they may play a role in phase variation and facilitation of persistent infections. Genes associated with pathogen-host interactions were identified, including a small group encoding proteins (n = 12) with tandem repeats and another group encoding proteins with eukaryote-like ankyrin domains (n = 7).
Mavromatis
K
K
Department of Energy, Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598, USA. Kmavrommatis@lbl.gov
Doyle
C Kuyler
CK
Lykidis
A
A
Ivanova
N
N
Francino
M P
MP
Chain
P
P
Shin
M
M
Malfatti
S
S
Larimer
F
F
Copeland
A
A
Detter
J C
JC
Land
M
M
Richardson
P M
PM
Yu
X J
XJ
Walker
D H
DH
McBride
J W
JW
Kyrpides
N C
NC
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D004283:Dog Diseases / Q000382:microbiology; D004285:Dogs; D041061:Ehrlichia canis / Q000145:classification / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D016873:Ehrlichiosis / Q000662:veterinary; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D006023:Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D011544:Pseudogenes; D012329:RNA, Bacterial / Q000235:genetics; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D006023:Glycoproteins; D012329:RNA, Bacterial