Drought-Adapted Mediterranean Diet Plants: A Source of Bioactive Molecules Able to Give Nutrigenomic Effects per sè or to Obtain Functional Foods.

The Mediterranean diet features plant-based foods renowned for their health benefits derived from bioactive compounds. This review aims to provide an overview of the bioactive molecules present in some representative Mediterranean diet plants, examining their human nutrigenomic effects and health benefits as well as the environmental advantages and sustainability derived from their cultivation. Additionally, it explores the facilitation of producing fortified foods aided by soil and plant microbiota properties. Well-studied examples, such as extra virgin olive oil and citrus fruits, have demonstrated significant health advantages, including anti-cancer, anti-inflammatory, and neuroprotective effects. Other less renowned plants are presented in the scientific literature with their beneficial traits on human health highlighted. Prickly pear's indicaxanthin exhibits antioxidant properties and potential anticancer traits, while capers kaempferol and quercetin support cardiovascular health and prevent cancer. Oregano and thyme, containing terpenoids like carvacrol and γ-terpinene, exhibit antimicrobial effects. Besides their nutrigenomic effects, these plants thrive in arid environments, offering benefits associated with their cultivation. Their microbiota, particularly Plant Growth Promoting (PGP) microorganisms, enhance plant growth and stress tolerance, offering biotechnological opportunities for sustainable agriculture. In conclusion, leveraging plant microbiota could revolutionize agricultural practices and increase sustainability as climate change threatens biodiversity. These edible plant species may have crucial importance, not only as healthy products but also for increasing the sustainability of agricultural systems.

Temporal dynamic of biofilms enhances the settlement of the central-Mediterranean reef-builder Dendropoma cristatum (Biondi, 1859).

Research on marine invertebrate settlement provides baseline knowledge for restoration technique implementation, especially for biogenic engineers with limited dispersion ability. Previously, we determined that the maturity of a biofilm strongly enhances the settlement of the vermetid reef-builder Dendropoma cristatum. To elucidate settlement-related biofilm features, here we analyse the structure and composition of marine biofilms over time, through microscopic observations, eukaryotic and prokaryotic fingerprinting analyses and 16S rDNA Illumina sequencing. The vermetid settlement temporal increase matched with the higher biofilm coverage on the substratum and the reduction of the eukaryotic abundance and diversity. The prokaryotic assemblage become, over time, more similar to that found on the reef-associated biofilm. Vermetids may detect these differences and selectively settle on those biofilms which show an advantageous structure and composition. These outcomes may support the production of ideal substrates for vermetid colonization and their further translocation to repopulate degraded reefs.

Metagenome Assembled Genome of a Novel Verrucomicrobial Methanotroph From Pantelleria Island.

Verrucomicrobial methanotrophs are a group of aerobic bacteria isolated from volcanic environments. They are acidophiles, characterized by the presence of a particulate methane monooxygenase (pMMO) and a XoxF-type methanol dehydrogenase (MDH). Metagenomic analysis of DNA extracted from the soil of Favara Grande, a geothermal area on Pantelleria Island, Italy, revealed the presence of two verrucomicrobial Metagenome Assembled Genomes (MAGs). One of these MAGs did not phylogenetically classify within any existing genus. After extensive analysis of the MAG, we propose the name of "Candidatus Methylacidithermus pantelleriae" PQ17 gen. nov. sp. nov. The MAG consisted of 2,466,655 bp, 71 contigs and 3,127 predicted coding sequences. Completeness was found at 98.6% and contamination at 1.3%. Genes encoding the pMMO and XoxF-MDH were identified. Inorganic carbon fixation might use the Calvin-Benson-Bassham cycle since all genes were identified. The serine and ribulose monophosphate pathways were incomplete. The detoxification of formaldehyde could follow the tetrahydrofolate pathway. Furthermore, "Ca. Methylacidithermus pantelleriae" might be capable of nitric oxide reduction but genes for dissimilatory nitrate reduction and nitrogen fixation were not identified. Unlike other verrucomicrobial methanotrophs, genes encoding for enzymes involved in hydrogen oxidation could not be found. In conclusion, the discovery of this new MAG expands the diversity and metabolism of verrucomicrobial methanotrophs.

Methylacidimicrobium thermophilum AP8, a Novel Methane- and Hydrogen-Oxidizing Bacterium Isolated From Volcanic Soil on Pantelleria Island, Italy.

The Favara Grande is a geothermal area located on Pantelleria Island, Italy. The area is characterized high temperatures in the top layer of the soil (60°C), low pH (3-5) and hydrothermal gas emissions mainly composed of carbon dioxide (CO2), methane (CH4), and hydrogen (H2). These geothermal features may provide a suitable niche for the growth of chemolithotrophic thermoacidophiles, including the lanthanide-dependent methanotrophs of the phylum Verrucomicrobia. In this study, we started enrichment cultures inoculated with soil of the Favara Grande at 50 and 60°C with CH4 as energy source and medium containing sufficient lanthanides at pH 3 and 5. From these cultures, a verrucomicrobial methanotroph could be isolated via serial dilution and floating filters techniques. The genome of strain AP8 was sequenced and based on phylogenetic analysis we propose to name this new species Methylacidimicrobium thermophilum AP8. The transcriptome data at µmax (0.051 ± 0.001 h-1, doubling time ~14 h) of the new strain showed a high expression of the pmoCAB2 operon encoding the membrane-bound methane monooxygenase and of the gene xoxF1, encoding the lanthanide-dependent methanol dehydrogenase. A second pmoCAB operon and xoxF2 gene were not expressed. The physiology of strain AP8 was further investigated and revealed an optimal growth in a pH range of 3-5 at 50°C, representing the first thermophilic strain of the genus Methylacidimicrobium. Moreover, strain AP8 had a KS(app) for methane of 8 ± 1 µM. Beside methane, a type 1b [NiFe] hydrogenase enabled hydrogen oxidation at oxygen concentrations up to 1%. Taken together, our results expand the knowledge on the characteristics and adaptations of verrucomicrobial methanotrophs in hydrothermal environments and add a new thermophilic strain to the genus Methylacidimicrobium.

Critical range of soil organic carbon in southern Europe lands under desertification risk.

Soil quality is fundamental for ecosystem long term functionality, productivity and resilience to current climatic changes. Despite its importance, soil is lost and degraded at dramatic rates worldwide. In Europe, the Mediterranean areas are a hotspot for soil erosion and land degradation due to a combination of climatic conditions, soils, geomorphology and anthropic pressure. Soil organic carbon (SOC) is considered a key indicator of soil quality as it relates to other fundamental soil functions supporting crucial ecosystem services. In the present study, the functional relationships among SOC and other important soil properties were investigated in the topsoil of 38 sites under different land cover and management, distributed over three Mediterranean regions under strong desertification risk, with the final aim to define critical SOC ranges for fast loss of important soil functionalities. The study sites belonged to private and public landowners seeking to adopt sustainable land management practices to support ecosystem sustainability and productivity of their land. Data showed a very clear relationship between SOC concentrations and the other analyzed soil properties: total nitrogen, bulk density, cation exchange capacity, available water capacity, microbial biomass, C fractions associated to particulate organic matter and to the mineral soil component and indirectly with net N mineralization. Below 20 g SOC kg-1, additional changes of SOC concentrations resulted in a steep variation of all the analyzed soil indicators, an order of magnitude higher than the changes occurring between 50 and 100 g SOC kg-1 and 3-4 times the changes observed at 20-50 g SOC kg-1. About half of the study sites showed average SOC concentration of the topsoil centimetres <20 g SOC kg-1. For these areas the level of SOC might hence be considered critical and immediate and effective recovery management plans are needed to avoid complete land degradation in the next future.

Draft genome of a novel methanotrophic Methylobacter sp. from the volcanic soils of Pantelleria Island.

The genus Methylobacter is considered an important and often dominant group of aerobic methane-oxidizing bacteria in many oxic ecosystems, where members of this genus contribute to the reduction of CH4 emissions. Metagenomic studies of the upper oxic layers of geothermal soils of the Favara Grande, Pantelleria, Italy, revealed the presence of various methane-oxidizing bacteria, and resulted in a near complete metagenome assembled genome (MAG) of an aerobic methanotroph, which was classified as a Methylobacter species. In this study, the Methylobacter sp. B2 MAG was used to investigate its metabolic potential and phylogenetic affiliation. The MAG has a size of 4,086,539 bp, consists of 134 contigs and 3955 genes were found, of which 3902 were protein coding genes. All genes for CH4 oxidation to CO2 were detected, including pmoCAB encoding particulate methane monooxygenase (pMMO) and xoxF encoding a methanol dehydrogenase. No gene encoding a formaldehyde dehydrogenase was present and the formaldehyde to formate conversion follows the tetrahydromethanopterin (H4MPT) pathway. "Ca. Methylobacter favarea" B2 uses the Ribulose-Mono-Phosphate (RuMP) pathway for carbon fixation. Analysis of the MAG indicates that Na+/H+ antiporters and the urease system might be important in the maintenance of pH homeostasis of this strain to cope with acidic conditions. So far, thermoacidophilic Methylobacter species have not been isolated, however this study indicates that members of the genus Methylobacter can be found in distinct ecosystems and their presence is not restricted to freshwater or marine sediments.

Geothermal Gases Shape the Microbial Community of the Volcanic Soil of Pantelleria, Italy.

Volcanic and geothermal environments are characterized by low pH, high temperatures, and gas emissions consisting of mainly CO2 and varied CH4, H2S, and H2 contents which allow the formation of chemolithoautotrophic microbial communities. To determine the link between the emitted gases and the microbial community composition, geochemical and metagenomic analysis were performed. Soil samples of the geothermic region Favara Grande (Pantelleria, Italy) were taken at various depths (1 to 50 cm). Analysis of the gas composition revealed that CH4 and H2 have the potential to serve as the driving forces for the microbial community. Our metagenomic analysis revealed a high relative abundance of Bacteria in the top layer (1 to 10 cm), but the relative abundance of Archaea increased with depth from 32% to 70%. In particular, a putative hydrogenotrophic methanogenic archaeon, related to Methanocella conradii, appeared to have a high relative abundance (63%) in deeper layers. A variety of [NiFe]-hydrogenase genes were detected, showing that H2 was an important electron donor for microaerobic microorganisms in the upper layers. Furthermore, the bacterial population included verrucomicrobial and proteobacterial methanotrophs, the former showing an up to 7.8 times higher relative abundance. Analysis of the metabolic potential of this microbial community showed a clear capacity to oxidize CH4 aerobically, as several genes for distinct particulate methane monooxygenases and lanthanide-dependent methanol dehydrogenases (XoxF-type) were retrieved. Analysis of the CO2 fixation pathways showed the presence of the Calvin-Benson-Bassham cycle, the Wood-Ljungdahl pathway, and the (reverse) tricarboxylic acid (TCA) cycle, the latter being the most represented carbon fixation pathway. This study indicates that the methane emissions in the Favara Grande might be a combination of geothermal activity and biological processes and further provides insights into the diversity of the microbial population thriving on CH4 and H2 IMPORTANCE The Favara Grande nature reserve on the volcanic island of Pantelleria (Italy) is known for its geothermal gas emissions and high soil temperatures. These volcanic soil ecosystems represent "hot spots" of greenhouse gas emissions. The unique community might be shaped by the hostile conditions in the ecosystem, and it is involved in the cycling of elements such as carbon, hydrogen, sulfur, and nitrogen. Our metagenome study revealed that most of the microorganisms in this extreme environment are only distantly related to cultivated bacteria. The results obtained profoundly increased the understanding of these natural hot spots of greenhouse gas production/degradation and will help to enrich and isolate the microbial key players. After isolation, it will become possible to unravel the molecular mechanisms by which they adapt to extreme (thermo/acidophilic) conditions, and this may lead to new green enzymatic catalysts and technologies for industry.

Hydrogen and Carbon Monoxide-Utilizing Kyrpidia spormannii Species From Pantelleria Island, Italy.

Volcanic and geothermal areas are hot and often acidic environments that emit geothermal gasses, including H2, CO and CO2. Geothermal gasses mix with air, creating conditions where thermoacidophilic aerobic H2- and CO-oxidizing microorganisms could thrive. Here, we describe the isolation of two Kyrpidia spormannii strains, which can grow autotrophically by oxidizing H2 and CO with oxygen. These strains, FAVT5 and COOX1, were isolated from the geothermal soils of the Favara Grande on Pantelleria Island, Italy. Extended physiology studies were performed with K. spormannii FAVT5, and showed that this strain grows optimally at 55°C and pH 5.0. The highest growth rate is obtained using H2 as energy source (µmax 0.19 ± 0.02 h-1, doubling time 3.6 h). K. spormannii FAVT5 can additionally grow on a variety of organic substrates, including some alcohols, volatile fatty acids and amino acids. The genome of each strain encodes for two O2-tolerant hydrogenases belonging to [NiFe] group 2a hydrogenases and transcriptome studies using K. spormannii FAVT5 showed that both hydrogenases are expressed under H2 limiting conditions. So far no Firmicutes except K. spormannii FAVT5 have been reported to exhibit a high affinity for H2, with a Ks of 327 ± 24 nM. The genomes of each strain encode for one putative CO dehydrogenase, belonging to Form II aerobic CO dehydrogenases. The genomic potential and physiological properties of these Kyrpidia strains seem to be quite well adapted to thrive in the harsh environmental volcanic conditions.

Innovative, ecofriendly biosorbent-biodegrading biofilms for bioremediation of oil- contaminated water.

Immobilization of microorganisms capable of degrading specific contaminants significantly promotes bioremediation processes. In this study, innovative and ecofriendly biosorbent-biodegrading biofilms have been developed in order to remediate oil-contaminated water. This was achieved by immobilizing hydrocarbon-degrading gammaproteobacteria and actinobacteria on biodegradable oil-adsorbing carriers, based on polylactic acid and polycaprolactone electrospun membranes. High capacities for adhesion and proliferation of bacterial cells were observed by scanning electron microscopy. The bioremediation efficiency of the systems, tested on crude oil and quantified by gas chromatography, showed that immobilization increased hydrocarbon biodegradation by up to 23 % compared with free living bacteria. The resulting biosorbent biodegrading biofilms simultaneously adsorbed 100 % of spilled oil and biodegraded more than 66 % over 10 days, with limited environmental dispersion of cells. Biofilm-mediated bioremediation, using eco-friendly supports, is a low-cost, low-impact, versatile tool for bioremediation of aquatic systems.

A modified culture medium for improved isolation of marine vibrios.

Marine Vibrio members are of great interest for both ecological and biotechnological research, which often relies on their isolation. Whereas many efforts have been made for the detection of food-borne pathogenic species, much less is known about the performances of standard culture media toward environmental vibrios. We show that the isolation/enumeration of marine vibrios using thiosulfate-citrate-bile salts-sucrose agar (TCBS) as selective medium may be hampered by the variable adaptability of different taxa to the medium, which may result even in isolation failure and/or in substantial total count underestimation. We propose a modified TCBS as isolation medium, adjusted for marine vibrios requirements, which greatly improved their recovery in dilution plate counts, compared with the standard medium. The modified medium offers substantial advantages over TCBS, providing more accurate and likely estimations of the actual presence of vibrios. Modified TCBS allowed the recovery of otherwise undetected vibrios, some of which producing biotechnologically valuable enzymes, thus expanding the isolation power toward potentially new enzyme-producers Vibrio taxa. Moreover, we report a newly designed Vibrio-specific PCR primers pair, targeting a unique rpoD sequence, useful for rapid confirmation of isolates as Vibrio members and subsequent genetic analyses.

Microbial communities of polluted sub-surface marine sediments.

Microbial communities of coastal marine sediment play a key role in degradation of petroleum contaminants. Here the bacterial and archaeal communities of sub-surface sediments (5-10 cm) of the chronically polluted Priolo Bay (eastern coast of Sicily, Italy), contaminated mainly by n-alkanes and biodegraded/weathered oils, were characterized by cultural and molecular approaches. 16S-PCR-DGGE analysis at six stations, revealed that bacterial communities are highly divergent and display lower phylogenetic diversity than the surface sediment; sub-surface communities respond to oil supplementation in microcosms with a significant reduction in biodiversity and a shift in composition; they retain high biodegradation capacities and host hydrocarbon (HC) degraders that were isolated and identified. HC-degrading Alfa, Gamma and Epsilon proteobacteria together with Clostridia and Archaea are a common feature of sub-surface communities. These assemblages show similarities with that of subsurface petroleum reservoirs also characterized by the presence of biodegraded and weathered oils where anaerobic or microaerophilic syntrophic HC metabolism has been proposed.

Settlement performance of the Mediterranean reef-builders Dendropoma cristatum (Biondi 1859) in response to natural bacterial films.

The gastropod Dendropoma cristatum is a biogenic engineer of the central Mediterranean, forming reefs along the lower rocky intertidal fringe with a remarkable ecological role. To understand whether reef-associated biofilm cultivable bacterial and biofilm ageing may trigger the settlement of the juvenile snails, a combination of laboratory techniques and field experiments was used. Reef-associated biofilm cultivable bacteria were isolated, and a settlement-choice experiment was performed in situ on artificial biofilms composed of i) a mixture of six biofilm-forming selected isolates, ii) all the cultivable bacteria, and iii) 13-, 23-, 32-day old biofilms formed under natural conditions. Overall, settlement rate significantly differed among biofilm treatments (p < 0.0001). A significant positive correlation between biofilm ageing and juvenile D. cristatum settlement was assessed (r = 0.69 (p < 0.001), whereas the biofilm bacterial composition (relatively to the cultivable fraction) did not show any effect on the vermetid's settlement rate.

Bacterial communities in sediment of a Mediterranean marine protected area.

Biodiversity is crucial in preservation of ecosystems, and bacterial communities play an indispensable role for the functioning of marine ecosystems. The Mediterranean marine protected area (MPA) "Capo Gallo-Isola delle Femmine" was instituted to preserve marine biodiversity. The bacterial diversity associated with MPA sediment was compared with that from sediment of an adjacent harbour exposed to intense nautical traffic. The MPA sediment showed higher diversity with respect to the impacted site. A 16S rDNA clone library of the MPA sediment allowed the identification of 7 phyla: Proteobacteria (78%), Firmicutes (11%), Acidobacteria (3%), Actinobacteria (3%), Bacteroidetes (2%), Planctomycetes (2%), and Cyanobacteria (1%). Analysis of the hydrocarbon (HC)-degrading bacteria was performed using enrichment cultures. Most of the MPA sediment isolates were affiliated with Gram-positive G+C rich bacteria, whereas the majority of taxa in the harbour sediment clustered with Alpha- and Gammaproteobacteria; no Gram-positive HC degraders were isolated from the harbour sediment. Our results show that protection probably has an influence on bacterial diversity, and suggest the importance of monitoring the effects of protection at microbial level as well. This study creates a baseline of data that can be used to assess changes over time in bacterial communities associated with a Mediterranean MPA.

Intrinsic bioremediation potential of a chronically polluted marine coastal area.

A microbiological survey of the Priolo Bay (eastern coast of Sicily, Ionian Sea), a chronically polluted marine coastal area, was carried out in order to discern its intrinsic bioremediation potential. Microbiological analysis, 16S rDNA-based DGGE fingerprinting and PLFAs analysis were performed on seawater and sediment samples from six stations on two transects. Higher diversity and variability among stations was detected by DGGE in sediment than in water samples although seawater revealed higher diversity of culturable hydrocarbon-degrading bacteria. The most polluted sediment hosted higher total bacterial diversity and higher abundance and diversity of culturable HC degraders. Alkane- and PAH-degrading bacteria were isolated from all stations and assigned to Alcanivorax, Marinobacter, Thalassospira, Alteromonas and Oleibacter (first isolation from the Mediterranean area). High total microbial diversity associated to a large selection of HC degraders is believed to contribute to natural attenuation of the area, provided that new contaminant contributions are avoided.

Comprehensive Analysis of a Vibrio parahaemolyticus Strain Extracellular Serine Protease VpSP37.

Proteases play an important role in the field of tissue dissociation combined with regenerative medicine. During the years new sources of proteolytic enzymes have been studied including proteases from different marine organisms both eukaryotic and prokaryotic. Herein we have purified a secreted component of an isolate of Vibrio parahaemolyticus, with electrophoretic mobilities corresponding to 36 kDa, belonging to the serine proteases family. Sequencing of the N-terminus enabled the in silico identification of the whole primary structure consisting of 345 amino acid residues with a calculated molecular mass of 37.4 KDa. The purified enzyme, named VpSP37, contains a Serine protease domain between residues 35 and 276 and a canonical Trypsin/Chimotrypsin 3D structure. Functional assays were performed to evaluate protease activity of purified enzyme. Additionally the performance of VpSP37 was evaluated in tissue dissociations experiments and the use of such enzyme as a component of enzyme blend for tissue dissociation procedures is strongly recommended.

The gut microbiota of larvae of Rhynchophorus ferrugineus Oliver (Coleoptera: Curculionidae).

BACKGROUND: The red palm weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) is one of the major pests of palms. The larvae bore into the palm trunk and feed on the palm tender tissues and sap, leading the host tree to death. The gut microbiota of insects plays a remarkable role in the host life and understanding the relationship dynamics between insects and their microbiota may improve the biological control of insect pests. The purpose of this study was to analyse the diversity of the gut microbiota of field-caught RPW larvae sampled in Sicily (Italy). RESULTS: The 16S rRNA gene-based Temporal Thermal Gradient Gel Electrophoresis (TTGE) of the gut microbiota of RPW field-trapped larvae revealed low bacterial diversity and stability of the community over seasons and among pools of larvae from different host trees. Pyrosequencing of the 16S rRNA gene V3 region confirmed low complexity and assigned 98% of the 75,564 reads to only three phyla: Proteobacteria (64.7%) Bacteroidetes (23.6%) and Firmicutes (9.6%) and three main families [Enterobacteriaceae (61.5%), Porphyromonadaceae (22.1%) and Streptococcaceae (8.9%)]. More than half of the reads could be classified at the genus level and eight bacterial genera were detected in the larval RPW gut at an abundance ≥1%: Dysgonomonas (21.8%), Lactococcus (8.9%), Salmonella (6.8%), Enterobacter (3.8%), Budvicia (2.8%), Entomoplasma (1.4%), Bacteroides (1.3%) and Comamonas (1%). High abundance of Enterobacteriaceae was also detected by culturing under aerobic conditions. Unexpectedly, acetic acid bacteria (AAB), that are known to establish symbiotic associations with insects relying on sugar-based diets, were not detected. CONCLUSIONS: The RPW gut microbiota is composed mainly of facultative and obligate anaerobic bacteria with a fermentative metabolism. These bacteria are supposedly responsible for palm tissue fermentation in the tunnels where RPW larvae thrive and might have a key role in the insect nutrition, and other functions that need to be investigated.

Differential proteomic analysis of an engineered Streptomyces coelicolor strain reveals metabolic pathways supporting growth on n-hexadecane.

The alkB gene, encoding an alkane monooxygenase in the actinomycete Gordonia sp. SoCg, was expressed in the non-alkane-degrading actinomycete Streptomyces coelicolor M145. The resulting engineered strain, M145-AH, can grow on n-hexadecane as sole carbon source. To unravel proteins associated with growth on n-alkanes, proteome of M145-AH after 6, 24, and 48 h of incubation in the Bushnell-Haas (BH) mineral medium containing n-hexadecane as sole carbon source (H condition) and in BH without any carbon source (0 condition) were compared using 2D-differential gel electrophoresis. Proteome analysis revealed significant changes only at 48 h, showing 48 differentially abundant proteins identified by mass spectrometry procedures. To asses if these proteins were specifically related to n-hexadecane metabolism, their expression was investigated, comparing H proteome with that of M145-AH incubated in BH with glucose as sole carbon source (G condition). Thus, protein expression profiles at 6, 24, and 48 h under H, 0, and G conditions were combined, revealing that M145-AH regulates in a temporally- and carbon source-dependent manner the expression of proteins involved in regulatory events, central carbon metabolism, respiration, ß-oxidation, membrane transport, and amino acid and protein metabolism. Interestingly, 21 % of them, mostly involved in membrane transport and protein metabolism, showed a n-hexadecane-dependent regulation with regulatory proteins such as CRP likely to have a key role in M145-AH n-hexadecane growth. These results, expanding the knowledge on n-alkane utilization in Gram-positive bacteria, reveal genes to be targeted to develop an efficient S. coelicolor M145-AH-based bioremediation system.

Degradation of long-chain n-alkanes in soil microcosms by two actinobacteria.

The ability of two recently isolated actinobacteria, that degrade medium and long chain n-alkanes in laboratory water medium, was investigated in soil microcosms using different standard soils that were artificially contaminated with n-alkanes of different length (C(12)- C(20)- C(24)- C(30)). The two strains, identified as Nocardia sp. SoB and Gordonia sp. SoCp, revealed a similar high HC degradation efficiency with an average of 75% alkane degraded after 28 days incubation. A selectivity of bacteria towards n-alkanes of different length was detected as well as a consistent effect of soil texture and other soil physical chemical characteristics on degradation. It was demonstrated the specific aptitude of these selected strains towards specific environmental conditions.

Involvement of an alkane hydroxylase system of Gordonia sp. strain SoCg in degradation of solid n-alkanes.

Enzymes involved in oxidation of long-chain n-alkanes are still not well known, especially those in gram-positive bacteria. This work describes the alkane degradation system of the n-alkane degrader actinobacterium Gordonia sp. strain SoCg, which is able to grow on n-alkanes from dodecane (C(12)) to hexatriacontane (C(36)) as the sole C source. SoCg harbors in its chromosome a single alk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by both n-hexadecane and n-triacontane, which were chosen as representative long-chain liquid and solid n-alkane molecules, respectively. Biotransformation of n-hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. The Gordonia SoCg alkB was heterologously expressed in Escherichia coli BL21 and in Streptomyces coelicolor M145, and both hosts acquired the ability to transform n-hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected on n-triacontane. However, the recombinant S. coelicolor M145-AH, expressing the Gordonia alkB gene, was able to grow on n-triacontane as the sole C source. A SoCg alkB disruption mutant that is completely unable to grow on n-triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solid n-alkanes.

Diversity of rhizobia nodulating wild shrubs of Sicily and some neighbouring islands.

Legume shrubs have great potential for rehabilitation of semi-arid degraded soils in Mediterranean ecosystems as they establish mutualistic symbiosis with N-fixing rhizobia. Eighty-eight symbiotic rhizobia were isolated from seven wild legume shrubs native of Sicily (Southern Italy) and grouped in operational taxonomic units (OTU) by analysis of the ribosomal internal transcribed spacer (ITS) polymorphism. Partial sequencing of 16S rRNA gene of representative isolates of each OTU revealed that most Genisteae symbionts are related to Bradyrhizobium canariense, B. japonicum and B. elkanii. Teline monspessulana was the only Genistea nodulated by Mesorhizobium strains, and Anagyris foetida (Thermopsideae) was promiscuosly nodulated by Rhizobium, Mesorhizobium, Agrobacterium and Bradyrhizobium strains. Analysis of the nodulation gene nodA assigned most Mediterranean Genisteae bradyrhizobia to clade II but also to clades IV, I and III, which included, so far, sequences of (sub)tropical and Australian isolates. The high diversity and low host specificity observed in most wild legumes isolates suggest that preferential associations may establish in the field depending on differences in the benefits conferred to the host and on competition ability. Once identified, these beneficial symbiosis can be exploited for rehabilitation of arid, low productive and human-impacted soils of the Mediterranean countries.