Research: Determination of the Proteins of Salmonella Enteritidis Involved in Colonization of the Chicken Ceca Using Protein Analysis
The results of this investigation revealed that the whole-cell protein profile of S. Enteritidis harvested from the chicken intestine was very different to that of bacteria cultured in vitro in nutrient broth. As visualised on SDS-PAGE, the in vivo protein extract had a lower protein content and a reduced number of visible protein bands; after protein extraction by sonication, and despite the fact that the amount of protein loaded was the same for both in vivo and in vitro extracts, very few protein bands from the in vivo bacteria were detectable on SDS-PAGE. The two ceca are the main site of the colonization of Salmonella in chickens, and the bacteria can be easily harvested from the ceca for analysis; therefore this study aimed to identify protein(s) associated with colonization using protein technology.
In this study newly-hatched chickens (within 10 hours of their hatching) were infected with S. Enteritidis, the bacteria were harvested from the ceca 18 hours post infection and bacterial proteins were extracted by sonication and analysed utilizing SDS-PAGE electrophoresis, and compared with that obtained from broth culture. This comparison showed differences between the two profiles and indicated that it is difficult to make a reasonable comparison as out of about 40 protein bands of in vitro preparation only a few 3-4 bands could be visualized from in vivo preparation, the reason behind that was thought to be the degradation of in vivo protein which was investigated in another study and the result revealed that some avian proteases might be responsible. Subsequently, some individual proteins from both preparations were identified by Mass spectrometry.