Zhang Hongyu, Mu Xiyan, Wang Hongwei, Wang Haibo, Wang Hui, Li Yingren, Mu Yingchun, Song Jinlong, Xia Lei
Fishery Resource and Environment Research Center, Chinese Academy of Fishery Sciences, Beijing 100141, China.
Chinese Academy of Fishery Sciences, Beijing 100141, China.
Microorganisms. 2021 Dec 9;9(12):2547. doi: 10.3390/microorganisms9122547.
Lactic acid bacteria (LAB) are commonly applied to fish as a means of growth promotion and disease prevention. However, evidence regarding whether LAB colonize the gastrointestinal (GI) tract of fish remains sparse and controversial. Here, we investigated whether ATCC 393 (Lc) can colonize the GI tract of crucian carp. Sterile feed irradiated with Co was used to eliminate the influence of microbes, and 100% rearing water was renewed at 5-day intervals to reduce the fecal-oral circulation of microbes. The experiment lasted 47 days and was divided into three stages: the baseline period (21 days), the administration period (7 days: day -6 to 0) and the post-administration period (day 1 to 19). Control groups were fed a sterile basal diet during the whole experimental period, whereas treatment groups were fed with a mixed diet containing Lc (1 × 10 cfu/g) and spore of (Gs, 1 × 10 cfu/g) during the administration period and a sterile basal diet during the baseline and post-administration periods. An improved and highly sensitive selective culture method (SCM) was employed in combination with a transit marker (a Gs spore) to monitor the elimination of Lc in the GI tract. The results showed that Lc (<2 cfu/gastrointestine) could not be detected in any of the fish sampled from the treatment group 7 days after the cessation of the mixed diet, whereas Gs could still be detected in seven out of nine fish at day 11 and could not be detected at all at day 15. Therefore, the elimination speed of Lc was faster than that of the transit marker. Furthermore, high-throughput sequencing analysis combined with SCM was used to reconfirm the elimination kinetics of Lc in the GI tract. The results show that the Lc in the crucian carp GI tract, despite being retained at low relative abundance from day 7 (0.11% ± 0.03%) to 21, was not viable. The experiments indicate that Lc ATCC 393 cannot colonize the GI tract of crucian carp, and the improved selective culture in combination with a transit marker represents a good method for studying LAB colonization of fish.
乳酸菌（LAB）通常被应用于鱼类，作为促进生长和预防疾病的一种手段。然而，关于乳酸菌是否能在鱼类胃肠道（GI）中定殖的证据仍然稀少且存在争议。在此，我们研究了ATCC 393（Lc）是否能在鲫鱼的胃肠道中定殖。用钴辐照的无菌饲料来消除微生物的影响，并且每隔5天更换100%的养殖用水，以减少微生物的粪口循环。实验持续47天，分为三个阶段：基线期（21天）、给药期（7天：第-6天至第0天）和给药后期（第1天至第19天）。对照组在整个实验期间喂食无菌基础饲料，而处理组在给药期喂食含有Lc（1×10 cfu/g）和枯草芽孢杆菌（Gs，1×10 cfu/g）孢子的混合饲料，在基线期和给药后期喂食无菌基础饲料。采用一种改进的、高度灵敏的选择性培养方法（SCM）并结合一个转运标记物（Gs孢子）来监测Lc在胃肠道中的清除情况。结果显示，在停止混合饲料投喂7天后，从处理组取样的任何鱼类中均未检测到Lc（<2 cfu/胃肠道），而在第11天，9条鱼中有7条仍能检测到Gs，在第15天则完全检测不到。因此，Lc的清除速度比转运标记物的清除速度更快。此外，高通量测序分析结合SCM被用于再次确认Lc在胃肠道中的清除动力学。结果表明，鲫鱼胃肠道中的Lc，尽管从第7天（0.11%±0.03%）到第21天以低相对丰度保留，但已无活力。这些实验表明，Lc ATCC 393不能在鲫鱼的胃肠道中定殖，并且改进的选择性培养结合转运标记物是研究鱼类乳酸菌定殖的一种好方法。
