Polysaccharide breakdown by anaerobic microorganisms inhabiting the mammalian gut

This chapter reviews the state of knowledge with particular emphasis on the utilization of dietary polysaccharides by anaerobic gut bacteria, drawing information from the rumen and large intestinal systems. The rumen and large intestine are the most densely colonized regions of the mammalian gut. The chapter discusses the main steps involved in the utilization of polysaccharides by individual micro-organisms. These steps include attachment to the substrate; disruption and enzymatic degradation of the substrate; transport of breakdown products into the cell—accompanied by further degradation, metabolism, and energy generation. Furthermore, the wealth of available ribosomal sequence data has allowed the development of techniques for microbial detection independent of cultivation that are based on oligonucleotide probes, quantitative polymerase chain reaction (QPCR), and molecular profiling. Finally, genome sequencing of further representative polysaccharide-degrading microorganisms—allied to gene expression studies—helps to reveal the transport systems, enzyme systems, and regulatory circuits that allow them to utilize polysaccharides.