13th International Conference on Microbial Interactions & Microbial Ecology July 19-20, 2018 Rome, Italy

Biography:

Dr. Elisa Bona. Researcher in Microbiology at the Università del Piemonte Orientale. She holds a Specialization degree in Microbiology and Virology (2010) at the Università di Genoa and a Ph.D. (2006) in Environmental Science at the Università del Piemonte Orientale. She is teacher in different courses at UPO University: since 2015, Professor of General Microbiology, Professor of Applied Bacteriology and Professor Diagnostic in Microbiology. (AA 2013-2014) Professor of Environmental Microbiology and Professor of Agri-Environmental Microbiology.

Abstract:

Vitis vinifera is a Mediterranean crop with relevant impact on the Italian landscape, culture and economy. The rhizosphere is a hotspot where the release of root exudates modulates bacterial density and diversity. Despite the high bacterial number found in rhizosphere, only 1-10% of the soil bacteria are able to grow on laboratory media, so that the majority of the bacterial cells in soil results to be viable, unculturable, but active; even more, this percentage change according to the host plant. Thanks to culture-independent methods (metagenomics) the complexity of the soil/rhizosphere microbial community has been explored. However, metagenomics doesn’t provide information regarding the activity and the molecular interactions between the bacterial communities and roots. Proteins are the drivers of cellular activities encoded by the genome. Therefore, proteomic tools could be useful to gain information about microbial community activity and to better understand the real interactions pathways between roots and soil. A comparison between the microbial community structure in rhizosphere and bulk soil using metagenomics (pyrosequencing of 16S rDNA) and proteomics (MS/MS analysis of the total protein occurring in soil samples) was performed.

Actinobacteria were the dominant class in all the soil samples, followed by Proteobacteria, Gemmatimonadetes and Bacteroidetes. While Actinobacteria and Proteobacteria are well known as dominant in soil, for the first time, members belonging to Gemmatimonadetes have been observed in vineyard soils.  Bacteria belonging to Streptomyces, Bacillus, Bradyrhizobium, Burkholderia and Pseudomonas genera were the most active. Concerning the biological activity of these genera, in the rhizosphere (Figure 1), we observed the exclusive presence of phosphorus metabolic process and the regulation of: biosynthetic, cellular, macromolecule, nitrogen compound and primary metabolic process.

Our results underlined the difference between the metagenomic and metaproteomic approaches and the potentiality of proteomics in describing the environmental bacterial communities and their activity.

 

Biography:

Dr Verena Hauke-Poinsot is a Research Director of the CNRS (National Scientific Research Center). She published over 60 rank-A papers, based on separation techniques hyphenated with mass spectrometry for the structural elucidation of biological active compounds. Recruted in 1997 by the CNRS in Toulouse, she became within ten years a world expert of the LCO analyses. From 2012-2017, she was involved in a big project financed by the Bill and Melinda Gates foundation (ENSA: Engineering the Sym pathway of cereals for recognition of nitrogen fixing bacteria). She is one of the discoverers of the Myc factors keys for the mycorrhization (Nature paper in 2011).

Abstract:

Nitrogen fixation results from a successful and complex interaction between bacteria (rhizobia) and a family of crops (legumes). This process is an endosymbiosis as the bacteria invade the root hairs and dedicated root organs: the nodules. One crucial signal to start this interaction is a family of lipochito oligosaccharides (LCO) called Nod factors (1). The variety of the backbone decorations and the length of the fatty chain are keys to the specific recognition of the host. The plant recognizes one precise design, allowing protecting itself from the invasion of pathogens. Their structure has been studied in detail in recent decades and encoding genes (almost located on a plasmid (pSym)) have been determined (2). However, the time-course of their biosynthesis is a recent discovery (2016). This could only be achieved by combining site-directed mutagenesis on a rhizobium model (here Sinorhizobium sp. IRBG) with highly specific and sensitive LC/MSMS analyses (MRM, EPI and EMS) of LCOs and COs. The last are chitooligomers without lipid chain, which are synthesis intermediates that could be analyzed in parallel to the Nod factors (3). These advances in analytical techniques provided a new point of view on the biosynthesis of LCOs. Actually, even if some decoration genes are in the same locus than the one encoding the skeleton and even some other genes encoding for sugar moieties are located  in distant loci, le sugar backbone is synthesized completely first and decorated later.