Lee Ken-Ichi, Kobayashi Naoki, Watanabe Maiko, Sugita-Konishi Yoshiko, Tsubone Hirokazu, Kumagai Susumu, Hara-Kudo Yukiko
Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
Microb Biotechnol. 2014 Nov;7(6):621-9. doi: 10.1111/1751-7915.12071. Epub 2013 Aug 6.
To elucidate the effect of fungal hyphae on the behaviour of Shiga toxin-producing Escherichia coli (STEC) O157, the spread and change in stress resistance of the bacterium were evaluated after coculture with 11 species of food-related fungi including fermentation starters. Spread distances of STEC O157 varied depending on the co-cultured fungal species, and the motile bacterial strain spread for longer distances than the non-motile strain. The population of STEC O157 increased when co-cultured on colonies of nine fungal species but decreased on colonies of Emericella nidulans and Aspergillus ochraceus. Confocal scanning microscopy visualization of green fluorescent protein-tagged STEC O157 on fungal hyphae revealed that the bacterium colonized in the water film that existed on and between hyphae. To investigate the physiological changes in STEC O157 caused by co-culturing with fungi, the bacterium was harvested after 7 days of co-culturing and tested for acid resistance. After co-culture with eight fungal species, STEC O157 showed greater acid resistance compared to those cultured without fungi. Our results indicate that fungal hyphae can spread the contamination of STEC O157 and can also enhance the stress resistance of the bacteria.
为阐明真菌菌丝对产志贺毒素大肠杆菌（STEC）O157行为的影响，在与包括发酵剂在内的11种与食品相关的真菌共培养后，评估了该细菌的传播情况及抗逆性变化。STEC O157的传播距离因共培养的真菌种类而异，运动型菌株比非运动型菌株传播得更远。当与9种真菌的菌落共培养时，STEC O157的数量增加，但在构巢曲霉和赭曲霉的菌落上数量减少。对真菌菌丝上绿色荧光蛋白标记的STEC O157进行共聚焦扫描显微镜观察发现，该细菌定殖于菌丝上及菌丝间存在的水膜中。为研究与真菌共培养引起的STEC O157生理变化，共培养7天后收获该细菌并检测其耐酸性。与8种真菌共培养后，STEC O157比未与真菌共培养的细菌表现出更强的耐酸性。我们的结果表明，真菌菌丝可传播STEC O157污染，还能增强细菌的抗逆性。
