Bacterial Invasion Into Eukaryotic Cells : Springer : 9780306462900 : 0306462907 : 31 Jan 2000 : Strategies of Bacterial Interaction with Eukaryotic Cells *Tobias A. Oelschlaeger and Jorg Hacker 1. BENEFICIAL BACTERIAL-HOST INTERACTIONS Already during birth and soon thereafter mammals are colonized by bacte­ ria belonging to the resident microbial flora. Cutaneous and mucosal sur­ faces and the gastrointestinal tract are the areas which become colonized. These indigenous or autochthonous bacteria have a variety of beneficial effects on their hosts. They play a protective role by bacterial antagonism in fighting infections (Hoszowski and Truszczynski, 1997; Hentges, 1979). Pro­ duction of vitamin K is another essential contribution of the resident microbial flora to the health of the host (Hill, 1997). Even more important, studies with germ-free animals demonstrated the involvement of the microbial flora on the development of the immune system. Such animals have underdeveloped and relat