Summary
Liberibacter asiaticus is the prevalent causative pathogen of Huanglongbing or citrus greening disease, which has resulted in a devastating crisis in the citrus industry. A thorough understanding of this pathogen's physiology and mechanisms to control cell survival is critical in the identification of therapeutic targets. YbeY is a highly conserved bacterial RNase that has been implicated in multiple roles. In this study, we evaluated the biochemical characteristics of the L. asiaticus YbeY (CLIBASIA_01560) and assessed its potential as a target for antimicrobials. YbeYLas was characterized as an endoribonuclease with activity on 3′ and 5′ termini of 16S and 23S rRNAs, and the capacity to suppress the E. coli ΔybeY phenotype. We predicted the YbeYLas protein:ligand interface and subsequently identified a flavone compound, luteolin, as a selective inhibitor. Site‐directed mutagenesis was subsequently used to identify key residues involved in the catalytic activity of YbeYLas. Further evaluation of naturally occurring flavonoids in citrus trees indicated that both flavones and flavonols had potent inhibitory effects on YbeYLas. Luteolin was subsequently examined for efficacy against L. asiaticus in Huanglongbing‐infected citrus trees, where a significant reduction in L. asiaticus gene expression was observed.
Pollution by petroleum hydrocarbons is one of the major environmental problems in ports and it is mainly associated with ship/boat traffic and related facilities. Ports are not closed systems and their pollution may impact adjacent coastal areas. Hydrocarbon degraders and particularly the obligate hydrocarbonoclastic bacteria carry out a fundamental and global activity in biological removal of hydrocarbons in marine habitats.This study was carried out within MAPMED, a multidisciplinary project aimed to improve the environmental sustainability of tourist ports in the Mediterranean Sea with regard to monitoring and reduction of hydrocarbon pollution.Three tourist ports were selected as case study sites: Cagliari (Italy), El Kantaoui (Tunisia), and Heraklion (Greece). The degradation potential of the autochthonous bacterial communities was evaluated enumerating heterotrophs and hydrocarbon degraders by MPN in the surface seawater. Heterotrophs were significantly more abundant in seawater from Cagliari port as compared to El Kantaoui and Heraklion ports. On the contrary, higher viable titles of diesel-and phenanthrene-degraders were found in seawater from El Kantaoui port compared to the other two areas. Hydrocarbon-degrading bacteria were isolated and characterized regarding their phylogenetic position and catabolic abilities. The hydrocarbon degradation activities were evaluated by GC-MS in aerobic batch reactors on diesel as carbon source. The majority of degraders from Cagliari were assigned to Pseudomonas whereas strains from El Kantaoui and Heraklion were assigned to Alcanivorax and Marinobacter.The selection of the most appropriate methodologies for the eco-efficient remediation of petroleum-hydrocarbon contamination of selected sites is currently in progress. http://dx.
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