Morphological and physical characterization of the capsular layer of Vibrio cholerae O139 |
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Authors: | Y Meno Matthew K Waldor John J Mekalanos Kazunobu Amako |
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Institution: | (1) Department of Health and Welfare, Seinan Jogakuin University, 1–3–5 Ibori, Kokura Kita-ku, Kitakyushu, Fukuoka, 803–0835, Japan e-mail: k01030@simail.ne.jp Tel. +81-93-583-0046; Fax +81-93-592-4287, JP;(2) Department of Bacteriology, Faculty of Medicine, Kyushu University, Fukuoka 812–8235 Japan, JP;(3) Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA, US |
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Abstract: | The morphological and physical characteristics of the capsule of Vibrio cholerae O139 were examined. An electron microscopic study using the freeze-substitution technique showed that all of the V. cholerae strains of the O139 serogroup examined have a very thin fibrous layer on the outside of the outer membrane. In contrast,
the mutants of strain O139, strain MO10T4 (which lacks capsule synthesis), and strain Bengal-2R1 (which fails to synthesize
both the capsule and the O-antigen of lipopolysaccharide) were all found to have lost the surface layer. In addition, the
capsule layer could also not be observed on the surface of V. cholerae strain O1. To determine the biological characteristics of the capsule of strains of the O139 serogroup, we investigated the
serum killing activity and bacterial phagocytosis by polymorphonuclear leukocytes. The O139 strains were more resistant to
the serum killing activity than were the V. cholerae O1 strain and the O139 mutant strains, thus suggesting that the existence of the capsule gave a serum-resistant character
to the O139 strains. The surface character of the O139 strains had the same hydrophobic character as did that of the O139
mutant strains and the O1 strain. In addition, all the V. cholerae O1 and O139 strains examined, including the mutant strains, were effectively ingested by the human polymorphonuclear leukocytes.
The number of ingested bacteria was not significantly different among the strains, and the ingestion of the acapsular O139
mutants thus showed that the capsule does not play an antiphagocytic role. These data suggest that the capsule of V. cholerae O139 has a physiological function different from that of the ordinal hydrophilic capsule that is found in invasive bacteria
such as Klebsiella pneumoniae.
Received: 23 March 1998 / Accepted: 28 July 1998 |
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Keywords: | V cholerae O139 Lipopolysaccharide Electron microscopy Freeze-substitution technique Capsule |
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