Occurrence and diversity of bacterial communities in Tuber magnatum during truffle maturation

none9Tuber magnatum, an ascomycetous fungus and obligate ectomycorrhizal symbiont, forms hypogeous fruit bodies, commonly called Italian white truffles. The diversity of bacterial communities associated with T. magnatum truffles was investigated using culture-independent and -dependent 16S rRNA genebased approaches. Eighteen truffles were classified in three groups, representing different degrees of ascocarp maturation, based on the percentage of asci containing mature spores. The culturable bacterial fraction was 4.17 (+/- 1.61) x 10.000.000, 2.60 (+/- 1.22) x 10.000.000 and 1.86 (+/-1.32) x 1.000.000 cfu g-1 for immature, intermediate and mature ascocarps respectively. The total of bacteria count was two orders of magnitude higher than the cfu g-1 count. Sequencing results from the clone library showed a significant presence of alpha-Proteobacteria (634 of the 771 total clones screened, c. 82%) affiliated with Sinorhizobium, Rhizobium and Bradyrhizobium spp. The bacterial culturable fraction was generally represented by gamma-Proteobacteria (210 of the 384 total strains isolated, c. 55%), which were mostly fluorescent pseudomonads. Fluorescent in situ hybridization confirmed that alpha-Proteobacteria (85.8%) were the predominant components of truffle bacterial communities with beta-Proteobacteria (1.5%), gamma-Proteobacteria (1.9%), Bacteroidetes (2.1%), Firmicutes (2.4%) and Actinobacteria (3%) only poorly represented. Molecular approaches made it possible to identify alpha-Proteobacteria as major constituents of a bacterial component associated with T. magnatum ascoma, independently from the degree of maturation.openE. BARBIERI; C. GUIDI; J. BERTAUX; P. FREY-KLETT; J. GARBAYE; P. CECCAROLI; R. SALTARELLI; A. ZAMBONELLI; V. STOCCHIBarbieri, Elena; C., Guidi; J., Bertaux; P., FREY KLETT; J., Garbaye; Ceccaroli, Paola; Saltarelli, Roberta; A., Zambonelli; Stocchi, Vilbert

The Mineralosphere Concept: Mineralogical Control of the Distribution and Function of Mineral-associated Bacterial Communities

© 2015 Elsevier Ltd. Soil is composed of a mosaic of different rocks and minerals, usually considered as an inert substrata for microbial colonization. However, recent findings suggest that minerals, in soils and elsewhere, favour the development of specific microbial communities according to their mineralogy, nutritive content, and weatherability. Based upon recent studies, we highlight how bacterial communities are distributed on the surface of, and in close proximity to, minerals. We also consider the potential role of the mineral-associated bacterial communities in mineral weathering and nutrient cycling in soils, with a specific focus on nutrient-poor and acidic forest ecosystems. We propose to define this microbial habitat as the mineralosphere, where key drivers of the microbial communities are the physicochemical properties of the minerals

“I told you this last time, right?”: Re-visiting narratives of STEM education

The stories we tell ourselves and others - both as individuals and as a community - reflect how we make sense of our lives. Our work using narrative methods has explored how university graduates make sense of their learning experiences and how these fit within their wider learning trajectories. In this paper, we discuss work we conducted with a group of a dozen students who, when first interviewed, were in the second half of their undergraduate education at Olin College of Engineering. All twelve participants were re-interviewed four years later, after they had graduated, using the same narrative protocol that asked them to describe their learning 'life' as if it was a book, and to identify and describe individual chapters of their experience. The pairs of interviews were analysed with respect to their form and their content. In regard to form, a classification of these repeated stories is derived. Thematic analysis of the content examines a) how students come to study and practice computing and b) the continuing, and changing influence of a university education over time, as students construct an individual sense of coherence

Salmonella Biofilm Formation on Aspergillus niger Involves Cellulose – Chitin Interactions

Salmonella cycles between host and nonhost environments, where it can become an active member of complex microbial communities. The role of fungi in the environmental adaptation of enteric pathogens remains relatively unexplored. We have discovered that S. enterica Typhimurium rapidly attaches to and forms biofilms on the hyphae of the common fungus, Aspergillus niger. Several Salmonella enterica serovars displayed a similar interaction, whereas other bacterial species were unable to bind to the fungus. Bacterial attachment to chitin, a major constituent of fungal cell walls, mirrored this specificity. Pre-incubation of S. Typhimurium with N-acetylglucosamine, the monomeric component of chitin, reduced binding to chitin beads by as much as 727-fold and inhibited attachment to A. niger hyphae considerably. A cellulose-deficient mutant of S. Typhimurium failed to attach to chitin beads and to the fungus. Complementation of this mutant with the cellulose operon restored binding to chitin beads to 79% of that of the parental strain and allowed for attachment and biofilm formation on A. niger, indicating that cellulose is involved in bacterial attachment to the fungus via the chitin component of its cell wall. In contrast to cellulose, S. Typhimurium curli fimbriae were not required for attachment and biofilm development on the hyphae but were critical for its stability. Our results suggest that cellulose–chitin interactions are required for the production of mixed Salmonella-A. niger biofilms, and support the hypothesis that encounters with chitinaceous alternate hosts may contribute to the ecological success of human pathogens

Microbial analysis of in situ biofilm formation in drinking water distribution systems: implications for monitoring and control of drinking water quality.

Biofilm formation in drinking water distribution systems (DWDS) is influenced by the source water, the supply infrastructure and the operation of the system. A holistic approach was used to advance knowledge on the development of mixed species biofilms in situ, by using biofilm sampling devices installed in chlorinated networks. Key physico-chemical parameters and conventional microbial indicators for drinking water quality were analysed. Biofilm coverage on pipes was evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The microbial community structure, bacteria and fungi, of water and biofilms was assessed using pyrosequencing. Conventional wisdom leads to an expectation for less microbial diversity in groundwater supplied systems. However, the analysis of bulk water showed higher microbial diversity in groundwater site samples compared with the surface water site. Conversely, higher diversity and richness were detected in biofilms from the surface water site. The average biofilm coverage was similar among sites. Disinfection residual and other key variables were similar between the two sites, other than nitrates, alkalinity and the hydraulic conditions which were extremely low at the groundwater site. Thus, the unexpected result of an exceptionally low diversity with few dominant genera (Pseudomonas and Basidiobolus) in groundwater biofilm samples, despite the more diverse community in the bulk water, is attributed to the low-flow hydraulic conditions. This finding evidences that the local environmental conditions are shaping biofilm formation, composition and amount, and hence managing these is critical for the best operation of DWDS to safeguard water quality

Stratospheric aerosol - Observations, processes, and impact on climate

Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes