Aims: To investigate the petroleum hydrocarbon (HC)‐degrading potential of indigenous micro‐organisms in a sandy Mediterranean coast, accidentally contaminated with petroleum‐derived HCs.
Methods and Results: Using culturable methods, a population of Gram‐positive n‐alkane degraders was detected in the contaminated soil. Five isolates, identified as one Nocardia, two Rhodococcus and two Gordonia strains, were able to degrade medium‐ and long‐chain n‐alkanes up to C36 as assessed by growth assays and gas chromatography‐mass spectrometry analysis. Diverging alkane hydroxylase‐encoding genes (alkB) were detected by PCR, using degenerated primers, in all the strains; multiple sequences were obtained from the Nocardia strain, while only one alkB gene was detected in the Rhodococcus and Gordonia strains. The majority of the alkB sequences were related to Rhodococcus alkB2, but none was identical to it.
Conclusions: Actinomycetes might have a key role in bioremediation of n‐alkane‐contaminated sites under dry, resource‐limited conditions, such as those found in the Mediterranean shorelines.
Significance and Impact of the Study: To our knowledge, this is the first study on the bioremediation potential in Mediterranean contaminated beaches.
The current climatic scenario requires the use of innovative solutions to increase the production of electricity from renewable energy sources. Multilevel Power Inverters are a promising solution to improve the penetration of renewable energy sources into the electrical grid. Moreover, the performance of MPIs is a function of the modulation strategy employed and of its features (modulation index and switching frequency). This paper presents an extended and experimental analysis of three-phase five-level Cascaded H-Bridges Multilevel Inverter performance in terms of efficiency and harmonic content considering several MC PWM modulation strategies. In detail, the CHBMI performance is analyzed by varying the modulation index and the switching frequency. For control purposes, the NI System On Module sbRIO-9651 control board, a dedicated FPGA-based control board for power electronics and drive applications programmable in the LabVIEW environment, is used. The paper describes the modulation strategies implementation, the test bench set-up, and the experimental investigations carried out. The results obtained in terms of Total Harmonic Distorsion (THD) and efficiency are analyzed, compared, and discussed.
Aims: The molecular diversity of 25 strains of rhizobia, isolated in Sicily from root nodules of the Mediterranean shrubby legume Spanish broom (Spartium junceum L.), is presented in relation to the known rhizobial reference strains. Methods and Results: Our approach to the study of the S. junceum rhizobial diversity combined the information given by the 16S and the intergenic spacer (IGS) 16S±23S rDNA polymorphic region by obtaining them in a single polymerase chain reaction (PCR) step. The PCR fragment size of the S. junceum isolates was 2400±2500 bp and that of the reference strains varied from 2400 in Bradyrhizobium strains to 2800 in Sinorhizobium strains. Inter-and intrageneric length variability was found among the reference strains. Restriction fragment length polymorphisms (RFLP) analysis allowed us to identify eight genotypes among the S. junceum rhizobia that were clustered into two groups, both related to the Bradyrhizobium lineage. Sequencing of representative strains of the two clusters con®rmed these data. The 16S±IGS PCR±RFLP approach, when applied to rhizobial reference strains, allowed very close species (i.e. Rhizobium leguminosarum/R. tropici) to be separated with any of the three enzymes used; however, cluster analysis revealed inconsistencies with the 16S-based phylogenesis of rhizobia. Conclusions: Rhizobia nodulating S. junceum in the Mediterranean region belong to the Bradyrhizobium lineage. Our results con®rm the resolution power of the 16S±23S rDNA in distinguishing among rhizobia genera and species, as well as the usefulness of the PCR±RFLP method applied to the entire 16S±IGS region for a rapid tracking of the known relatives of new isolates. Signi®cance and Impact of the Study: The present paper is, to our knowledge, the ®rst report on rhizobia nodulating a Mediterranean wild woody legume.
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