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Additional file 1. Transmission electron microscope image of the silver nanoparticles used in the study. Nanoparticles were obtained in solid form from US Research Nanomaterials, Inc. (Houston, TX, USA), and were applied to soil in this form.

The vegetable waste biomass is produced by several production chains like agriculture, agro- and food industries. Such biomass represents the renewable feedstock for a waste-based biorefinery, an industrial model that plays a key role in a bio-economy system, an innovative economy model that is based on the sustainable use of renewable resources in agriculture and industry, and that takes in account biodiversity and environmental protection (1). In this frame, the identification of starting materials that are not in competition with food chain or other production chains coupled with the development of new technologies and processes, is one of the main issues for a waste- based biorefinery. Here we reported some examples for the re-use and valorization of two kinds of vegetable waste biomass: the energy crops' residues (2, 3) and the wastes of food industry (4, 5) The crops selected, i.e. the giant reed (Arundo donax) and the cardoon (Cynara cardunculus) are among the annual crops and perennial herbaceous species that are object of increasing interest in relation to their use as feedstock for lignocellulose-based biorefinery. The food wastes that have been investigated include the residues of the industrial transformation of tomato, lemon, carrot and fennel, i.e. some most typical cultivation of the Italian agro-industrial sector. This two types of waste biomass have been investigated for their potential as sources of value added molecules and bioenergy.

Halophiles are organisms that inhabit hypersaline environments and require hypersaline conditions to grow (from 2–5 % NaCl up to above 20–30 % NaCl). Halophiles are mostly prokaryotes, which are able to thrive in such harsh conditions because of their capability to balance the osmotic pressure of the environment through different mechanisms. Bacteria mainly produce high concentrations of compatible solutes, small water-soluble organic molecules, which do not interfere with cell metabolism (amino acids and their derivatives, sugar and polyols). Archaea and some halophilic anaerobic bacteria accumulate high concentration of salts intracellularly (KCl). Halophilic bacteria produce biomolecules with great potential for biotechnology: exopolysaccharides, compatible solutes (which can be used as stabilizers of biomolecules) and stable enzymes (with potential use as biocatalysts). Quorum sensing (QS) could influence the production of these biomolecules, thus a better understanding of halophilic bacterial communication mechanisms can help to improve the yields of these biotechnological processes. QS contributes to environmental adaptation via different models, by inducing the expression of genes that are required for the well-being of the organisms in a given milieu. To date, different kinds of autoinducers were detected in halophilic microorganisms (diketopiperazines, N-Acyl homoserine lactones, autoinducer-2), but the role of QS in this group of extremophiles needs to be elucidated yet. This chapter presents the recent advances in our understanding of bacterial intercommunication systems in halophilic bacteria.

Excerpt from Discission: Species-specific cell-cell signalling is involved in pathogenic or symbiotic interactions between a variety of bacteria and their plant and animal hosts [Parsek M.R. and Greenberg E.P. 2000]. It has been demonstrated that QS molecules are involved in attraction of zoospores of green seaweed Ulva and the detection of AHLs results in calcium influx into the zoospore. That was the first example of a calcium signalling event in a eukaryote in response to bacterial QS molecules [Joint I. et al. 2007]. Moreover, it has been showed that the interdial surfaces colonized by Ulva are dominated by α-Proteobacteria, and that this diverse assemblage both produces and degrades AHLs. These results suggested that AHLdegrading strains can affect bacterial community behaviour by interfering with QS between neighbouring bacteria [Tait K. et al. 2009]. It may therefore be the case that some kind of “communication” also exists between marine sponges and microorganisms that are specifically associated with them. From α- and γ-Proteobacteria isolated from marine sponges Mycale laxissima and Ircinia strobilina was detected a range of AHLs molecules, and among the bacteria tested, AHL production was more frequently observed for the Proteobacteria associated with M. laxissima than those with I. strobolina [Mohamed N.M. et al. 2008]. In the case of specific sponge-bacteria association, it is possible that specifically associated bacteria may thrive or at least survive with sponge. In fact a ribosomal RNA study of axenic cell cultures of Suberites domuncula showed a 16S rRNA band specific for bacteria [Thakur N.L. et al. 2003]. ...

Extreme environments, generally characterized by atypical temperatures, pH, pressure, salinity, toxicity, and radiation levels, are inhabited by various microorganisms specifically adapted to these particular conditions, called extremophiles. Among these, the microorganisms belonging to the Archaea domain are of significant biotechnological importance as their biopolymers possess unique properties that offer insights into their biology and evolution. Particular attention has been devoted to two main types of biopolymers produced by such peculiar microorganisms, that is, the extracellular polysaccharides (EPSs), considered as a protection against desiccation and predation, and the endocellular polyhydroxyalkanoates (PHAs) that provide an internal reserve of carbon and energy. Here, we report the composition, biosynthesis, and production of EPSs and PHAs by different archaeal species.

Pseudomonas aeruginosa is an opportunistic pathogen that causes high morbidity and mortality rates due to its biofilm form. Biofilm formation is regulated via quorum sensing (QS) mechanism and provides up to 1000 times more resistance against conventional antibiotics. QS related genes are expressed according to bacterial population density via signal molecules. QS inhibitors (QSIs) from natural sources are widely studied evaluating various extracts from extreme environments. It is suggested that extremely halophilic Archaea may also produce QSI compounds. For this purpose, we tested QS inhibitory potentials of ethyl acetate extracts from cell free supernatants and cells of Natrinema versiforme against QS and biofilm formation of P. aeruginosa. To observe QS inhibition, all extracts were tested on P. aeruginosa lasB-gfp, rhlA-gfp, and pqsA-gfp biosensor strains and biofilm inhibition was studied using P. aeruginosa PAO1. According to our results, QS inhibition ratios of cell free supernatant extract (CFSE) were higher than cell extract (CE) on las system, whereas CE was more effective on rhl system. In addition, anti-biofilm effect of CFSE was higher than CE. Structural analysis revealed that the most abundant compound in the extracts was trans 4-(2-carboxy-vinyl) benzoic acid.