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第61号(2006-12-10) >

Please use this identifier to cite or link to this item: http://hdl.handle.net/11173/1429

Title: ストレス環境下における細菌の増殖と形態変化
Other Titles: Bacterial Growth and Morphological Changes under Stressful Environmental Conditions
Authors: 横山, 佳子
Yokoyama, Keiko
松田, 葵
Matsuda, Aoi
Issue Date: 10-Dec-2006
Publisher: 京都女子大学食物学会
Abstract: 食品の製造過程では,食品の品質低下防止および品質保持のために食品への様々な処理が行なわれる。これらの処理が不十分な場合,食品中の細菌は生残し,生残した菌体は,より厳しい処理条件に対しても適応できるようになる。本研究では加熱,塩分および三杯酢について,細菌の生存に不利であるが生残する程度のストレスを非芽胞形成細菌に負荷し,その生育状況や形態変化を検討した。走査型電子顕微鏡による観察結果から,大腸菌MC4100株では,50℃および三杯酢処理により細菌細胞が桿状から球状化する傾向が認められた。黄色ブドウ球菌NCTC8325株では,10%NaCl存在下ではコントロールと比較してやや細胞が大きくなり,また5%NaCl存在下では細胞間隙が分泌物のようなもので満たされている顕微鏡像が得られた。三杯酢で処理をすると,細胞が単独化する傾向が認められた。2種類の供試菌は,三杯酢中では1時間後にLB寒天培地上でのコロニー形成能を失うが,回復培地で培養すると再び寒天培地上でコロニーを形成した。三杯酢処理下では「生きているが通常の培地では培養できない」状態,すなわちVBNCの状態で存在していることが示唆された。
In food processing environment, several treatments are given to the food to preserve its quality as well as shelf-life. If these treatments are not severe enough, the bacteria survive and are able to adapt to even harsher treatments. The purpose of this investigation was to examine the bacterial growth and morphological changes with respect to non spore-forming bacteria under adverse conditions, namely mild heat treatment, salinity or acid treatment with sanbaisu (mixture of vinegar, sugar and soy sauce). From the results of observation with scanning electron microscopy, Escherichia coli MC4100 showed that the cells tended to convert from a bacillary to a coccobacillary shape under each condition of heat treatment at 50°C for 24h, treatment with 10% NaCl for 24h or with sanbaisu for 10 min. The cells of Staphylococcus aureus NCTC 8325 grown in the presence of NaCl were appeared to be somewhat larger than control cells. Furthermore, the gaps between NaCl-grown cells were filled in something like secretion. The cells treated with sanbaisu tended to be individual cells. E. coli MC4100 and S.aureus NCTC8325 treated with sanbaisu for 1h were lost capability of the colony formation on Luria-Bertani (LB) agar plate. However, sanbaisu-treated cells cultured with recovery medium (LB broth) for 24h were restored to colony formation again. These results raised the possibility that the both organisms became transiently viable but nonculturable (VBNC) state by acid stress (sanbaisu treatment).
URI: http://hdl.handle.net/11173/1429
Appears in Collections:第61号(2006-12-10)

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