This course is designed to cover the influence of the soil environment on the microbial occurrence and the activity of the microbial cenosis (microbiome) in the pedological context. After the completion of this course, students should have acquired a comprehensive overview of both the major phyla of microorganisms found in soil and the methods (including the new molecular high-throughput sequencing technologies) for their quantitative estimation as well as for the characterization of the microbial biodiversity either in bulk soil or in the rhizosphere. Particular emphasis will be given to plant-microbe interactions, with a special attention to the multiple cross signaling mechanisms among plants and PGPR (Plant Growth Promoting Rhizobacteria) at the rhizosphere level. Symbiotic nitrogen fixation and different mycorrhizal associations will be discussed in deep details. Transformations mediated by soil microorganisms will be treated. Ultimately, the understanding of soil microbial ecology principles will allow the students to correctly interpret environment-friendly strategies for improvement of crop productivity, biological control of plant pathogens and biodegradation/bioremediation of polluted sites.
Part I – The soil medium
Inert component: Solid mineral fraction, Organic matter, Liquid phase, Gaseous phase, Soil structure. Living components: microbiota and macrobiota with particular emphasis to bacteria and fungi. The Rhizosphere concept. Root exudates.
Part II – The soil microbiome
Microbial biodiversity in bulk soil and rhizosphere: copiotrophs and oligotrophs. Methods for quantitative and qualitative (taxonomical) estimation of soil microbial populations. Measurement of biological activity in the soil: Microbial biomass, Metabolic reactions. Effects of physico-chemical and edaphic factors on soil microbial cenoses: Water content and availability, Soil pH, Oxygen concentration in soil atmosphere and redox potential, Concentration of nutrients, Xenobiotic compounds and heavy metals. Significance of soil microbial biodiversity to biogeochemical cycling.
Part III – Microbial interactions
Microbe-microbe interactions. Effects of microorganisms on plants. Effects of plants on microorganisms. Plant Growth Promoting Rhizobacteria (PGPR). Symbiotic diazotrophs: Rhizobia and association with legumes. Mycorrhizal associations: Ectomycorrhizae, Endomycorrhizae with particular emphasis to AM fungi, Ectendomycorrhizae.
Part IV – Managing rhizosphere microbiome
Perspectives for the development of novel strategies for sustainable crop production, biological control of plant pathogens and environmental bioremediation through rhizosphere microbiome exploitation.
Oral presentation consisting in an in-depth discussion of a particular topic among the themes treated during the Course + Final written examination.