Host Specificity and Spatial Distribution Preference of Three Pseudomonas Isolates

Plant hosts recruit and maintain a distinct root-associated microbiota based on host and bacterium traits. However, past studies disregarded microbial strain-host specificity and spatial micro-heterogeneity of the root compartment. Using genetic manipulation, confocal laser scanning microscopy, real-time quantitative PCR, and genome sequencing we characterized the colonization patterns of three Pseudomonas spp. isolates native to wheat roots, on the micro-scale. Namely, isolates P. fluorescens NT0133, P. stutzeri NT124, and P. stutzeri NT128. All three isolates preferentially colonized wheat over cucumber roots that served as control for host specificity. Furthermore, not only had the isolates strong host specificity but each isolate had a distinct spatial distribution on the root, all within a few millimeters. Isolate P. stutzeri-NT0124 preferentially colonized root tips, whereas P. fluorescens-NT0133 showed a preference for zones distant from the tip. In contrast, isolate P. stutzeri-NT0128 had no preference for a specific niche on the root. While all isolates maintained genetic potential for motility and biofilm formation their phenotype varied significantly and corresponded to their niche preference. These results demonstrate the importance of spatial colonization patterns, governed by both niche and bacterial characteristics which will have great importance in future attempts to manipulate the plant microbiome by constructing synthetic microbial consortia

The potential of lignocellulosic ethanol production in the Mediterranean Basin

This review provides an overview of the potential of bioethanol fuel production from lignocellulosic residues in the Mediterranean Basin. Residues from cereal crops, olive trees, and tomato and grape processing are abundant lignocellulosic wastes in France, Italy, Spain, Turkey and Egypt, where their use as raw materials for ethanol production could give rise to a potential production capacity of 13 Mtoe of ethanol. Due to the lack of sufficient amounts of agricultural residues in all of the other Mediterranean countries, use of the cellulosic content of municipal solid waste (MSW) as feedstock for ethanol fuel production is also proposed. A maximum potential production capacity of 30 Mtoe of ethanol could be achieved from 50% of the 180 million tons of waste currently produced annually in the Mediterranean Basin, the management of which has become a subject of serious concern. However, to make large-scale ethanol production from agricultural residues and MSW a medium-term feasible goal in the Mediterranean Basin, huge efforts are needed to achieve the required progress in cellulose ethanol technologies and to overcome several foreseeable constraints.Fuel ethanol Mediterranean Lignocellulose Crop residue Municipal solid waste

Ecology of Root Colonizing <em>Massilia</em> (Oxalobacteraceae)

<div><h3>Background</h3><p>Ecologically meaningful classification of bacterial populations is essential for understanding the structure and function of bacterial communities. As in soils, the ecological strategy of the majority of root-colonizing bacteria is mostly unknown. Among those are <em>Massilia</em> (Oxalobacteraceae), a major group of rhizosphere and root colonizing bacteria of many plant species.</p> <h3>Methodology/Principal Findings</h3><p>The ecology of <em>Massilia</em> was explored in cucumber root and seed, and compared to that of <em>Agrobacterium</em> population, using culture-independent tools, including DNA-based pyrosequencing, fluorescence <em>in situ</em> hybridization and quantitative real-time PCR. Seed- and root-colonizing <em>Massilia</em> were primarily affiliated with other members of the genus described in soil and rhizosphere. <em>Massilia</em> colonized and proliferated on the seed coat, radicle, roots, and also on hyphae of phytopathogenic <em>Pythium aphanidermatum</em> infecting seeds. High variation in <em>Massilia</em> abundance was found in relation to plant developmental stage, along with sensitivity to plant growth medium modification (amendment with organic matter) and potential competitors. <em>Massilia</em> absolute abundance and relative abundance (dominance) were positively related, and peaked (up to 85%) at early stages of succession of the root microbiome. In comparison, variation in abundance of <em>Agrobacterium</em> was moderate and their dominance increased at later stages of succession.</p> <h3>Conclusions</h3><p>In accordance with contemporary models for microbial ecology classification, copiotrophic and competition-sensitive root colonization by <em>Massilia</em> is suggested. These bacteria exploit, in a transient way, a window of opportunity within the succession of communities within this niche.</p> </div