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microbiology 2007,Chapter 13(Unit13C):12. 42. van Winkelhoff AJ, Kippuw N, de Graaff J: Serological characterization of black-pigmented Bacteroides endodontalis . Infect Immun 1986,51(3):972–974.PubMed Authors’ contributions JB performed the cloning work, mutant construction, hydrophobicity test, density gradient centrifugation, negative staining, serotyping and drafted the manuscript. NBEI made see more the growth curves and did the sedimentation assay. NS and NBEI together performed the fibroblast infection experiments, the transcription analyses and statistical analyses. DMD analyzed the strains using Real-Time PCR and performed part of the statistical analysis. ML, AJvW and WC were involved in the study design, supervision and helped to draft the manuscript. All authors read and approved the

final manuscript.”
“Background Humans can be considered as “”superorganisms”" with an internal ecosystem of diverse symbiotic microorganisms and parasites that have interactive metabolic processes. Their homeostatic balance is dependent upon the interactions between the host and PTK6 its microbial components [1]. The human intestine is home to some 100 trillion microorganisms of at least 1000 species. The density of bacterial cells in the colon has been estimated at 1011 to 1012 per ml, which makes it one of the most densely populated microbial habitats known [2, 3]. This microbial ecosystem serves numerous important functions for the human host, including protection against pathogens, nutrient processing, stimulation of angiogenesis, modulation of intestinal immune response and regulation of host fat storage [4, 5]. The composition of the adult gastrointestinal microbiota has been intensely studied, using both cultivation and, more recently, culture-independent, small subunit (SSU) ribosomal DNA (rDNA) sequence-based methods [6–8].