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Infect. Immun., Apr 1996, 1208-1214, Vol 64, No. 4
N Schramm, CR Bagnell and PB Wyrick
Chlamydia trachomatis serovar L2 is an obligate intracellular bacterium
which is internalized in target epithelial cells by endocytosis and resides
within a membrane-bound vesicle. Over the next several hours following
entry, individual serovar L2-containing vesicles fuse with one another to
form a single membrane-bound vesicle (or inclusion) within which the
microcolony develops. The experiments reported here directly examined the
pH of vesicles containing chlamydiae. The pH was determined by measuring
emission ratios of the fluorescent, pH- sensitive probe SNAFL (5-[and
6-]-carboxyseminaphthofluorescein-1, succinimidyl ester) conjugated to
chlamydiae. The pH remained above 6.0 at 2, 4, and 12 h after infection,
while the pH of vesicles contained heat-killed organisms fell 5.3. In the
presence of amines, which raise the pH of acidic compartments, C.
trachomatis inclusion formation was unaffected. Inactivation of Na+,K+
-ATPases, the ion pumps responsible for maintaining a pH above 6 within
early endocytic vesicles, inhibited the growth of C. trachomatis within
epithelial cells. Preventing vesicular acidification by inhibiting the
vacuolar proton ATPase did not affect chlamydial growth. Thus, chlamydiae
do not reside within highly acidic vesicles and avoid the pathway leading
to lysosomes.
Copyright © 1996, American Society for Microbiology
Vesicles containing Chlamydia trachomatis serovar L2 remain above pH 6 within HEC-1B cells
Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27599-7290, USA.
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