The rhizosphere as a reservoir for opportunistic human pathogenic bacteria

The interface between soil and plant roots—the rhizosphere—is, because of root exudates and the resulting high nutrient content, a unique microenvironment in terrestrial ecosystems (Sørensen, 1997; Raaijmakers et al., 2009). Cultivation-independent methods on the basis of DNA/RNA, such as microbial fingerprinting techniques, fluorescence in situ hybridization, and pyrosequencing, have given interesting insights into the structure of rhizosphere-associated bacterial communities (reviewed in Smalla 2004; Hartmann et al., 2009; Mendes et al., 2011). But what do we know about the functions of plant-associated bacteria? Firstly, bacteria play a role in plant growth. They can support nutrient uptake, enhance the availability of phosphorous, and produce a broad range of phytohormones (Costacurta and Vanderleyden, 1995). An interesting phenomenon is the enhancement of stress tolerance by lowering the …