Chemical Profile, In Vitro Biological Activity and Comparison of Essential Oils from Fresh and Dried Flowers of Lavandula angustifolia L.

The chemical composition of essential oils (EOs) from dried and fresh flowers of Lavandula angustifolia L. (lavender), named LA 2019 and LA 2020, respectively, grown in central Italy was analyzed and compared by GC and GC-MS. For both samples, 61 compounds were identified, corresponding to 97.9% and 98.1% of the total essential oils. Explorative data analysis, performed to compare the statistical composition of the samples, resulted in a high level of global similarity (around 93%). The compositions of both samples were characterized by 10 major compounds, with a predominance of Linalool (35.3-36.0%), Borneol (15.6-19.4%) and 1,8-Cineole (11.0-9.0%). The in vitro antibacterial activity assay by disk diffusion tests against Bacillus subtilis PY79 and Escherichia coli DH5α showed inhibition of growth in both indicator strains. In addition, plate counts revealed a bactericidal effect on E. coli, which was particularly noticeable when using oil from the fresh lavender flowers at the highest concentrations. An in vitro antifungal assay showed that the EOs inhibited the growth of Sclerotium rolfsii, a phytopathogenic fungus that causes post-harvest diseases in many fruits and vegetables. The antioxidant activity was also assessed using the ABTS free radical scavenging assay, which showed a different antioxidant activity in both EOs. In addition, the potential application of EOs as a green method to control biodeterioration phenomena on an artistic wood painting (XIX century) was evaluated.

Winter survival of microbial contaminants in soil: an in situ verification.

The aim of the research was to evaluate, at site scale, the influence of freezing and freeze/thaw cycles on the survival of faecal coliforms and faecal enterococci in soil, in a climate change perspective. Before the winter period and during grazing, viable cells of faecal coliforms and faecal enterococci were detected only in the first 10 cm below ground, while, after the winter period and before the new seasonal grazing, a lower number of viable cells of both faecal indicators was detected only in some of the investigated soil profiles, and within the first 5 cm. Taking into consideration the results of specific investigations, we hypothesise that the non-uniform spatial distribution of grass roots within the studied soil can play an important role in influencing this phenomenon, while several abiotic factors do not play any significant role. Taking into account the local trend in the increase of air temperature, a different distribution of microbial pollution over time is expected in spring waters, in future climate scenarios. The progressive increase in air temperature will cause a progressive decrease in freeze/thaw cycles at higher altitudes, minimising cold shocks on microbial cells, and causing spring water pollution also during winter.

Role and potentialities of bacteria associated with Tuber magnatum: A mini-review.

Among the hypogeous ectomycorrhizal fungi, the white truffle Tuber magnatum Picco is the species of greatest interest, both from an ecological and economic point of view. The increasing market demand of the precious white truffle along with the fall in its natural production led to a growing interest in cultivation techniques and encouraged truffle growers and researchers to deeper investigate factors that could affect and improve T. magnatum productivity. In this context, microbial communities play a central role. Indeed, in the last few years, the hypothesis of a potential link between microbial community composition and truffle orchard productivity is arousing a greater attention. Moreover, since the value of the prized T. magnatum can vary in relation to its provenience, the need to define a reliable tracking system is also emerging and bacteria appear to be a promising tool. Accordingly, the present mini-review summarises the knowledge currently available on T. magnatum microbial communities, focusing on the role of truffle-associated bacteria and highlighting similarities and differences between samples of different origin, to address the following issues: (i) Is there a correlation between microbial taxa and truffle ground productivity? (ii) Can bacteria actually be used as markers of T. magnatum geographic origin? The identification of microorganisms able to promote T. magnatum formation may represent an important advance in the field of truffle farming. Similarly, the detection of bacterial taxa that can be used as markers of T. magnatum origin could have a considerable impact on truffle industry and trade, even at local scale.

How do turbidite systems behave from the hydrogeological point of view? New insights and open questions coming from an interdisciplinary work in southern Italy.

Turbidite successions can behave either as aquitards or aquifers depending on their lithological and hydraulic features. In particular, post-depositional processes can increase rock permeability due to fracture development in the competent layers. Thus, at a local scale, turbidite systems warrant further detailed investigations, aimed at reconstructing reliable hydrogeological models. The objective of this work was to investigate from the hydrogeological perspective a turbiditic aquifer located in southern Italy, where several perennial and seasonal springs were detected. Considering the complex hydrodynamics of these systems at the catchment scale, to reach an optimal characterization, a multidisciplinary approach was adopted. The conceptual framework employed microbial communities as groundwater tracers, together with the physicochemical features and isotopic signature of springs and streams from water samples. Meanwhile, geophysical investigations coupled with the geological survey provided the contextualization of the hydrogeological data into the detailed geological reconstruction of the study area. This modus operandi allowed us to typify several differences among the samples, allowing identification of sources and paths of surface water and groundwater, along with diffuse groundwater outflow along streams. As a final result, a hydrogeological conceptual model was reconstructed, underlining how at a very local scale the lithologic, hydraulic, and geomorphological heterogeneity of the studied relief can lead to an improved hydrogeological conceptual model compared to that of other turbidite systems. These results open new questions about the hydrogeological behavior of turbiditic aquifers, which could be pivotal in future research. In fact, these systems could support relevant ecosystems and anthropic activities, especially where climate change will force the research of new (and probably less hydrogeologically efficient) water sources.

Heterogeneity of the white truffle Tuber magnatum in a limited geographic area of Central-Southern Italy.

Molise region (Central-Southern Italy) is one of the Italian richest areas of truffles and contributes significantly to the national production of the precious Tuber magnatum. Nevertheless, Molise truffle has received little scientific attention. Accordingly, in the present study, two T. magnatum populations collected in two different sites of Molise region were characterised from a morphological, genetic and microbiological point of view. A considerable variability between and within the two analysed groups emerged, suggesting an interesting heterogeneity of Molise white truffle populations. Ascocarps of the two groups significantly differed in size and maturation degree, although no linear correlation between weight and maturity was found. Genetic investigations focused on the Sequence-Characterised Amplified Region SCAR A21-inf. Three haplotypes, randomly distributed within the two truffle groups regardless of their collection sites, were detected. The 16S rRNA gene amplicon high-throughput sequencing provided an overview of the composition of the ascocarp-associated bacterial communities. A predominance of α-Proteobacteria was observed, with Bradyrhizobium among the main genera. However, some truffles showed unusual microbial profiles, with Pedobacter, Polaromonas and other bacterial genera as dominant taxa.

The rhizosphere of Salix viminalis plants after a phytostabilization process assisted by biochar, compost, and iron grit: chemical and (micro)-biological analyses.

Amendments, such as biochar, compost, and iron grit, used in phytostabilization studies, showed positive effects on soil physico-chemical properties, plant growth, and the microbial community. However, assisted phytostabilization studies do not always focus on the rhizosphere area where soil, plants, and microorganisms are affected by the amendments and plants and microorganisms can also interact with each other. The aims of this study were to evaluate the effects of amendment application on the exudation of organic acids by Salix viminalis plant roots, as well as the effects of amendments and plant development on the soil CHNS contents and the microbial community activity and diversity, assessed by measuring enzyme activities and using Biolog EcoPlatesTM tests and next-generation sequencing analyses. The results of the mesocosm experiment showed that soil C, H, and N contents were increased by amendment application, especially biochar and compost, while the one of S decreased. Enzyme activities, microbial activity, and diversity were also increased by the addition of amendments, except iron grit alone. Finally, the quantity of organic acids exuded by roots were little affected by amendments, which could in part explain the reduced effect of plant development on soil chemical and microbiological parameters. In conclusion, this study showed in particular that biochar and compost were beneficial for the soil CHN contents and the microbial community while affecting poorly Salix viminalis root exudates.

Evaluation of direct and biochar carrier-based inoculation of Bacillus sp. on As- and Pb-contaminated technosol: effect on metal(loid) availability, Salix viminalis growth, and soil microbial diversity/activity.

Phytomanagement manipulates the soil-plant system to lower the risk posed by contaminated soils. In this process, the addition of amendments, such as biochar, and bacteria can improve the fertility of poor contaminated soils and consequently ameliorate plant growth. A number of studies based on the inoculation of soil with microorganisms of the genus Bacillus, previously isolated from contaminated sites, revealed positive effects on soil properties and plant growth. Furthermore, when the Bacillus isolates were used in association with biochar, better results were obtained, as biochar can ameliorate soil properties and serve as habitat for microorganisms. Accordingly, a mesocosm study was set-up using a mining technosol amended with biochar and inoculated with an endogenous Bacillus isolate, to evaluate the effect of inoculation on soil properties, metal(loid) immobilization, and Salix viminalis growth. Two inoculation methods were compared: (1) direct inoculation of bacteria (Bacillus sp.) and (2) inoculation using biochar as a carrier. Results showed that the Bacillus isolate modified soil properties and ameliorated plant growth, while having a reduced effect on metal(loid) accumulation. The microbial activity was also stimulated, and the community composition was shifted, more importantly when biochar was used as a carrier. In conclusion, this research revealed an improvement of the plant growth and microbial activity after the addition of the endogenous bacterium to the analyzed former mining soil, with better results recorded when a carrier was used.

Unraveling the Composition of the Root-Associated Bacterial Microbiota of Phragmites australis and Typha latifolia.

Phragmites australis and Typha latifolia are two macrophytes commonly present in natural and artificial wetlands. Roots of these plants engage in interactions with a broad range of microorganisms, collectively referred to as the microbiota. The microbiota contributes to the natural process of phytodepuration, whereby pollutants are removed from contaminated water bodies through plants. The outermost layer of the root corpus, the rhizoplane, is a hot-spot for these interactions where microorganisms establish specialized aggregates designated biofilm. Earlier studies suggest that biofilm-forming members of the microbiota play a crucial role in the process of phytodepuration. However, the composition and recruitment cue of the Phragmites, and Typha microbiota remain poorly understood. We therefore decided to investigate the composition and functional capacities of the bacterial microbiota thriving at the P. australis and T. latifolia root-soil interface. By using 16S rRNA gene Illumina MiSeq sequencing approach we demonstrated that, despite a different composition of the initial basin inoculum, the microbiota associated with the rhizosphere and rhizoplane of P. australis and T. latifolia tends to converge toward a common taxonomic composition dominated by members of the phyla Actinobacteria, Firmicutes, Proteobacteria, and Planctomycetes. This indicates the existence of a selecting process acting at the root-soil interface of these aquatic plants reminiscent of the one observed for land plants. The magnitude of this selection process is maximum at the level of the rhizoplane, where we identified different bacteria enriched in and discriminating between rhizoplane and rhizosphere fractions in a species-dependent and -independent way. This led us to hypothesize that the structural diversification of the rhizoplane community underpins specific metabolic capabilities of the microbiota. We tested this hypothesis by complementing the sequencing survey with a biochemical approach and scanning electron microscopy demonstrating that rhizoplane-enriched bacteria have a bias for biofilm-forming members. Together, our data will be critical to facilitate the rational exploitation of plant-microbiota interactions for phytodepuration.

Role of organic matter and clay fraction on migration of Escherichia coli cells through pyroclastic soils, southern Italy.

A comparative study on the adsorption of Escherichia coli cells to two different pyroclastic soils collected in southern Italy (carbonate Apennines) was performed in laboratory using surfactant-free solutions and solutions with the surfactants sodium dodecyl sulphate (SDS, anionic) and octylphenoxypolyethoxyethanol (Triton X-100, non-ionic). Both soils are rich in organic matter (up to 35%), but only one contains a clay fraction (2-5%). The experiments demonstrated that E. coli cells are significantly adsorbed to the clay fraction of the soil, while the organic matter content does not play a significant role. The pore size exclusion phenomenon is another factor to consider when analyzing the retention of E. coli cells within such soils. However, despite the existence of different factors that enhance bacterial cells retention, a high percent of E. coli cells is transported through soil media. The not absolute protection of such soils against microbial pollution is supported not only by the results of the column experiments at lab scale, but also by the findings of a field monitoring at site scale.