Abstract

The 16S rRNA gene sequences of Rickettsia tsutsugamushi and Rickettsia sibirica were determined by PCR and DNA sequencing. Phylogenetic analysis revealed that R. sibirica is positioned in a cluster of the genus Rickettsia with a similarity value of 98.1–99.6%, whereas R. tsutsugamushi is located apart from the cluster with a similarity value of 90.2–90.6%. This evidence suggests that R. tsutsugamushi should be excluded taxonomically from the genus Rickettsia. The phylogenetic classification of six antigenic variants in R. tsutsugamushi moderately reflected their antigenic relationship known in closely and distantly related strains.

References

[1]
Weiss
E.
Moulder
J.W.
(
1984
) In
Bergey's Manual of Systematic Bacteriology
 
Krieg
N.R.
Holt
J.G.
, Eds) Vol.
1
, pp
687
688
Williams and Wilkins
,
Baltimore.
[2]
Weisburg
W.G.
Dobson
M.E.
Samuel
J.E.
Dasch
G.A.
Mallavia
L.P.
Baca
O.
Mandelco
L.
Sechrest
J.E.
Weiss
E.
Woese
C.R.
(
1989
)
Phylogenetic diversity of the rickettsiae
J. Bacteriol.
 ,
171
,
4202
4206
.
[3]
Anderson
B.E.
Dawson
J.E.
Jones
D.D.
Wilson
K.H.
(
1991
)
Ehrlichia chaffeensis, a new species associated with human ehrlichiosis
J. Clin. Microbiol.
 ,
29
,
2838
2842
.
[4]
Brenner
D.J.
O'connor
S.P.
Winkler
H.H.
Steigerwalt
A.G.
(
1993
)
Proposals to unify the genera Bartonella and Rochalimaea, with descriptions of Bartonella quintana comb, nov., Bartonella vinsonii comb, nov., Bartonella henselae comb, nov., and Bartonella elizabethae comb, nov., and to remove the family Bartonellaceae from the order Rickettsiales
Int. J. Syst. Bacteriol.
 ,
43
,
777
786
.
[5]
O'Neill
S.L.
Giordano
R.
Colbert
A.M.E.
Karr
T.L.
Robertson
H.M.
(
1992
)
16S rRNA phylogenetic analysis of the bacterial endosymbionts associated with cytoplasmic incompatibility in insects
.
89
, In
Proc. Natl. Acad. Sci. USA
, pp
2699
2702
.
[6]
Amano
K.
Tamura
A.
Ohashi
N.
Urakami
H.
Kaya
S.
Fukushi
K.
(
1987
)
Deficiency of peptidoglycan and lipopolysaccharide components in Rickettsia tsutsugamushi
Infect. Immun.
 ,
55
,
2290
2292
.
[7]
Tamura
A.
Ohashi
N.
Urakami
H.
Takahashi
K.
Oyanagi
M.
(
1985
)
Analysis of polypeptide composition and antigenic components of Rickettsia tsutsugamushi by polyacrylamide gel electrophresis and immunoblotting
Infect. Immun.
 ,
48
,
671
675
.
[8]
Tamura
A.
Urakami
H.
Ohashi
N.
(
1991
)
A comparative view of Rickettsia tsutsugamushi and the other groups of rickettsiae
Eur. J. Epidemiol.
 ,
7
,
259
269
.
[9]
Tamura
A.
Takahashi
K.
Tsuruhara
T.
Urakami
H.
Miyamura
S.
Sekikawa
H.
Kenmotsu
M.
Shibata
M.
Abe
S.
Nezu
H.
(
1984
)
Isolation of Rickettsia tsutsugamushi antigenically different from Kato, Karp, and Gilliam strains from patients
Microbiol. Immunol.
 ,
28
,
873
882
.
[10]
Yamamoto
S.
Kawabata
Tamura
A.
Urakami
H.
Ohashi
N.
Murata
M.
Yoshida
Y.
Kawamura
A.
Jr.
(
1986
)
Immunological properties of Rickettsia tsutsugamushi, Kawasaki strain, isolated from a patient in Kyushu
Microbiol. Immunol.
 ,
30
,
611
620
.
[11]
Yamamoto
S.
Kawabata
N.
Oura
K.
Murata
M.
Minamishima
Y.
(
1989
)
Antigenic types of Rickettsia tsutsugamushi isolated from patients with tsutsugamushi fever anf their distribution in Miyazaki Prefecture
J. Jpn. Assoc. Infect. Dis.
 ,
63
,
109
117
.
[12]
Ohashi
N.
Tamura
A.
Sakurai
H.
Yamamoto
S.
(
1990
)
Characterization of a new antigenic type, Kuroki, of Rickettsia tsutsugamushi isolated from a patient in Japan
J. Clin. Microbiol.
 ,
28
,
2111
2113
.
[13]
Tamura
A.
Urakami
H.
Tsuruhara
T.
(
1982
)
Purification of Rickettsia tsutsugamushi by Percoll density gradient centrifugation
Microbiol. Immunol.
 ,
26
,
321
328
.
[14]
Weiss
E.
Coolbaugh
J.C.
Williams
J.C.
(
1975
)
Separation of viable Rickettsia typhi from yolk sac and L cell host components by Renografin density gradient centrifugation
Appl. Microbiol.
 ,
30
,
456
463
.
[15]
Ohashi
N.
Nashimoto
H.
Ikeda
H.
Tamura
A.
(
1992
)
Diversity of immunodominant 56-kDa type-specific antigen (TSA) of Rickettsia tsutsugamushi: Sequence and comparative analyses of the genes encoding TSA homologues from four antigenic variants
J. Biol. Chem.
 ,
267
,
12728
12735
.
[16]
Weisburg
W.G.
Barns
S.M.
Pelletier
D.A.
Lane
D.J.
(
1991
)
16S ribosomal DNA amplification for phylogenetic study
J. Bacteriol.
 ,
173
,
697
703
.
[17]
Kawamori
F.
Akiyama
M.
Sugieda
M.
Kanda
T.
Akahane
S.
Yamamoto
S.
Ohashi
N.
Tamura
A.
(
1993
)
Two-step polymerase chain reaction for diagnosis of scrub typhus and identification of antigenic variants of Rickettsia tsutsugamushi
J. Vet. Med. Sci.
 ,
55
,
749
755
.
[18]
Hwang
C.B.-C.
(
1991
)
Current Protocols in Molecular Biology
Ausubel
F.M.
Brent
R.
Kingston
R.E.
Moore
D.D.
Seidman
J.G.
Smith
J.A.
Strahl
K.
, Eds)
Greene Publishing Associates and Wiley Interscience
, New York Supplement 16, 15.2.4.
[19]
Gojobori
T.
Ishii
K.
Nei
M.
(
1982
)
Estimation of average number of nucleotide substitutions when the rate of subustitution varies with nucleotide
J. Mol. Evol.
 ,
18
,
414
423
.
[20]
Saitou
N.
Nei
M.
(
1987
)
The neighbor-joining method: a new method for reconstructing phylogenetic trees
Mol. Biol. Evol.
 ,
4
,
406
425
.
[21]
Woese
C.R.
(
1987
)
Bacterial evolution
Microbiol. Rev.
 ,
51
,
221
271
.