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Infection and Immunity, November 1999, p. 6026-6033, Vol. 67, No. 11
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Differential Expression of Translational Elements by Life Cycle Variants of Coxiella burnetii

Rekha Seshadri, Laura R. Hendrix, and James E. Samuel*

Department of Medical Microbiology and Immunology, Texas A & M University System Health Science Center, College Station, Texas 77843-1114

Received 1 June 1999/Returned for modification 23 July 1999/Accepted 31 August 1999

Coxiella burnetii replicates as distinct morphological forms, which may allow potential life cycle variants to survive the harsh environment of the phagolysosome. Monoclonal antibodies (MAbs) were compared by Western blotting for reactivity with large cell variant (LCV) and small cell variant (SCV) antigens to characterize proteins differentially expressed by C. burnetii. MAb NM7.3 reacted with a ~32-kDa LCV-upregulated antigen, and MAb NM183 reacted with a ~45-kDa LCV-specific antigen. MAb NM7.3 was used to screen a lambda ZapII C. burnetii DNA expression library, and an immunoreactive clone was identified with sequence similarity to the Escherichia coli tsf gene, which encodes elongation factor Ts (EF-Ts). Since a similar screen with MAb NM183 did not identify immunoreactive clones, an alternate strategy was devised to clone the reactive antigen based on observations of cross-reactivity with the 45-kDa elongation factor Tu (EF-Tu) protein from Chlamydia trachomatis. The highly conserved nature of EF-Tu among eubacteria allowed PCR amplification of a tuf gene fragment (encoding ~95% of the predicted EF-Tu open reading frame) from C. burnetii using degenerate primers. The product of the cloned tuf gene fragment reacted with MAb NM183 in Western blot analysis, confirming the identity of the 45-kDa LCV-specific antigen. Identification of two proteins differentially expressed by C. burnetii, EF-Tu and EF-Ts, both essential components of the translational machinery of the cell, supports the hypothesis that LCVs are metabolically more active than SCVs.

* Corresponding author. Mailing address: Department of Medical Microbiology and Immunology, 407 Reynolds Medical Building, Texas A & M University System Health Sciences Center, College Station, TX 77843-1114. Phone: (409) 862-1684. Fax: (409) 845-3479. E-mail: jsamuel{at}tamu.edu.

Infection and Immunity, November 1999, p. 6026-6033, Vol. 67, No. 11
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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