Induction of Hemagglutinating Activity of Edwardsiella tarda by Sodium Chloride.
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Edwardsiella tarda の赤血球凝集活性に及ぼす培地塩分濃度の影響
Mahmoud Mostafa Mahmoud
モルモット赤血球を用いてE. tarda の血球凝集活性を調べた。供試した55株中52株で, NaClを添加しない培地での培養 (0% NaCl培養) に比べ, NaClを3%添加した場合 (3% NaCl培養) にその凝集活性が上昇した。この血球凝集活性とE. tarda の線毛タンパク質 (19.3kDa) の発現との間には相関性が認められた。ヒラメに対する経口感染実験において, 3% NaCl培養菌の方が0% NaCl培養に比べ比較的強い病原性を示した。
The hemagglutinating activity (HA) of Edwardsiella tarda, which had been isolated from cultured fish and culture environments, was investigated in relation to NaCl concentration of the growth medium. E. tarda cells were cultured in a peptone-yeast extract broth supplemented with 3% NaCl (3%-NaCl culture) and without NaCl (0%-NaCl culture). Hemagglutination assays with guinea pig erythrocytes classified the strains into three HA patterns. Seventeen strains exhibited HA only with the 3%-NaCl culture (type A). A more frequent type (35 strains) displayed HA in both 0%- and 3%- NaCl cultures but the 3%-NaCl culture showed higher HA activity than the 0%-NaCl culture (type B). No HA was detected in both cultures of the other three strains (type C). The NaCl-induced HA was well correlated with the expression of a 19.3 kDa protein, a fimbrial major subunit (FimA). Infection experiments with a selected strain (type A) of E. tarda revealed that the 3%-NaCl culture was more virulent to Japanese flounder Paralichthys olivaceus than the 0%-NaCl culture, when fish were challenged by an oral route. This induction of the fimbrial protein under higher NaCl concentration may play an important role in the virulence of E. tarda in marine environments.
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