Thermophilic bacterial communities in hot composts as revealed by most probable number counts and molecular (16S rDNA) methods

Thermogenic composts are known to host a variety of thermophilic micro-organisms that were recently investigated by cultural means and identified as Thermus thermophilus, Bacillus spp., and Hydrogenobacter spp. In this paper, we present a classical, cultural enumeration of thermophilic populations on the one hand, and a molecular investigation of the bacterial community by restriction enzyme analyses of a clone library of bacterial 16S rRNA genes on the other hand. Bacterial diversity, revealed by the clone analyses of four samples, was shown to undergo a dramatic change between the young (13-18-day) and the old (39-41-day) samples, possibly linked to the general decrease in temperature and the physicochemical evolution of organic matter during the composting process. Among the 200 clones investigated, 69 clones could be identified as Thermus thermophilus and thermophilic Bacillus spp. These results proved both taxa to be among the dominant bacterial populations at the highest temperatures reached by thermogenic compost

The rhizosphere: Molecular interactions between microorganisms and roots.

The rhizosphere has a large impact on plant performance in several ways. A stand-specific, more or less high diversity of microorganisms not only supports the plant in the acquisition of water and nutrients, but also modulates its ability to cope with pathogens. This diversity, however, has to be maintained and thus causes a considerable drain of photoassimilates, which are then not available for shoot development. In this chapter, we try to explain why the considerable allocation of carbon to the root system is a “wise” decision by the plant. We thus focus on the function of root-associated bacteria and their relevance for plant growth and development of disease resistance, and deliver data on the molecular basis of the root–fungus symbiosis (mycorrhiza)