The Relationship Between Segmented Filamentous Bacterias (SFB) And Host Immunity System And Preliminary Culture

Segmented filamentous bacteria as an indigenous bacteria is widely distribute in human and animal gut. As early as 1849, Leidy found a "like plant" bacteria in termite gut. But until now, we can not culture this bacterium in vitro. However, some researches shown that SFB can promote the maturation of gut immune system in animal model, especially affect the secretion of SIgA. These results showed that the SFB is related to the maturation of the innate immune system. Now, so many scientists interested in this bacterium. So, it is very important to find some methods to culture this bacterium in vitro and understand the relationship between SFB and host.Due to the drawbacks of traditional culture methods, we can not get the pure culture bacterium of SFB. The aim of this research are construct the molecular biology methods including FISH and Real-time PCR to detect this bacterium in broker chickens, and understand the relationship between SFB and host immunity using different intervene methods. Also, we try to culture this bacterium using the in vitro model. The results are showed below:1. We constructed the method of FISH and Real-time PCR to detect the SFB in chicken gut, and used this method to investigate the distribution in different gut site and the dynamic changes due to age. The results showed that the concentration of SFB in the end of ileum mucosa is higher than other site and with the increase of age, the dynamic change of SFB have a pattern.2. Detected the concentration of SIgA and dynamic changes of SFB in chickens. In this experiment, AA broker chickens were randomly allotted into three groups:CL group (control), CTX group(immune suppressive) and LAC group(Lactobacillus). In order to determine the intervene effects, we detected the height and the number of white blood cells. We detected the concentration of SIgA at the end of ileum mucosa. The results show that the concentration of SIgA increased with age, but in the CL and LAC groups, it is up to the highest between day 9-13, and then decrease to a lower level. At the same time, we used FISH and Real-time PCR to detect the number of SFB, we found that the highest ratio of SFB is appeared more early in LAC group than CL and CTX groups. We also found that the number of SFB decreased with the increase of age in LAC and CL groups, but in CTX group, the concentration of SIgA and the number of SFB is increased with the increase of age.3. Tried to culture the SFB in vitro model, including optimize the culture media and grope the culture conditions. We used the in vitro model to investigate the effects of different irons and antibiotics on the growth of SFB. The results showed that the SFB can growth after adding the iron of K into the basic media (HBCT) and can not growth after adding the iron of Co or Cu into the basic media (HBCT). And in the media of IL, we can detect SFB after adding Cyclophosphamide, kanamycini and Ampicillin, and we can not detect the SFB after adding glucose and starch. This work will direct the next experiment for SFB culture in vitro.