What are Endophytes? -- What are Endophytes? -- Endophytic Bacteria -- Spectrum and Population Dynamics of Bacterial Root Endophytes -- Bacterial Endophytes as Elicitors of Induced Systemic Resistance -- Control of Plant Pathogenic Fungi with Bacterial Endophytes -- Role of Proteins Secreted by Rhizobia in Symbiotic Interactions with Leguminous Roots -- Research on Endophytic Bacteria: Recent Advances with Forest Trees -- Endophytic Fungi -- Biodiversity of Fungal Root-Endophyte Communities and Populations, in Particular of the Dark Septate Endophyte Phialocephala fortinii s. l. -- Endophytic Root Colonization by Fusarium Species: Histology, Plant Interactions, and Toxicity -- Microbial Endophytes of Orchid Roots -- Fungal Endophytes in Submerged Roots -- Nematophagous Fungi as Root Endophytes -- Molecular Diversity and Ecological Roles of Mycorrhiza-Associated Sterile Fungal Endophytes in Mediterranean Ecosystems -- Oidiodendron maius: Saprobe in Sphagnum Peat, Mutualist in Ericaceous Roots? -- Mycorrhizal and Endophytic Fungi of Epacrids (Ericaceae) -- Mutualistic Interactions with Fungal Root Endophytes -- Understanding the Roles of Multifunctional Mycorrhizal and Endophytic Fungi -- Methods -- Isolation Procedures for Endophytic Microorganisms -- Microbial Interactions with Plants: a Hidden World? -- Application of Molecular Fingerprinting Techniques to Explore the Diversity of Bacterial Endophytic Communities. Plant roots may not only be colonized by mycorrhizal fungi, but also by a myriad of bacterial and fungal root endophytes that are usually not considered by the investigators of classic symbioses. This is the first book dedicated to the interactions of non-mycorrhizal microbial endophytes with plant roots. The phenotypes of these interactions can be extremely plastic, depending on environmental factors, nutritional status, genetic disposition and developmental stages of the two partners. The book deals with diversity, life history strategies, interactions, applications in agriculture and forestry, methods for isolation, cultivation, and both conventional and molecular methods for identification and detection of these endophytes. The comprehensive reviews demonstrate the high diversity of interactions and will provoke further studies to better understand the mechanisms which determine whether a plant-microbial interaction remains asymptomatic, leads to disease or to a mutualistic interaction.