Xylella fastidiosa (Xf), a gram-negative phytopathogenic bacterium (Wells et al., 1987), has a very broad host range, causing different diseases in important crops (Hopkins, 1989) and in many urban shade trees (Sherald & Kostka, 1992). Xf symptoms may not be evident and many hosts can carry symptomless infections, making this pathogen difficult to manage. The pathogen is transmitted by xylem sap-feeding insects and colonizes host xylem vessels, causing typical leaf scorching. Xf is an endemic pathogen in America and was only recently identified in southern Italy on olive trees (Saponari et al., 2013), in Corsica, and in the south-east Mediterranean coast

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Microbiological methodologies allow understanding the causes that lead to the development of a certain microbial community colonizing an artistic surface, to characterize its composition and describe its role in the deterioration of the constituent materials. Metagenomics allows identifying microbial communities directly in their natural environments, bypassing the need for isolation and cultivation of individual species, thus providing a more comprehensive picture of the biodiversity present on a surface compared with standard cultivation methods. Furthermore, molecular analyses require small amounts of material, favoring the preservation of the artistic surface during sampling. Here, we verified the suitability of a protocol consisting in DNA extraction with micro-invasive sampling, using adhesive tape, PCR amplification with universal primers [bacteria (16S), fungi (ITS), and Viridiplantae (18S)], and amplicon sequencing by Oxford Nanopore Technologies (ONT) in the hypogeum of Basilica di San Nicola in Carcere Church (Rome, Italy). Sequence data were analyzed with a bioinformatic pipeline customized for pinpointing cultural heritage spoiling organisms, named "AmpLIcon SequencIng Analysis" (ALISIA). These data were integrated with traditional microbiology techniques that allowed the isolation of cultivable bacteria; three species were also characterized through their capability of biofilm formation and antibiotic resistance. Further, Fourier-transform infrared spectroscopy (FTIR) spectroscopy was performed to characterize the main products present on the masonry surface providing indications on the type of decay present. This novel biological workflow represents a powerful opportunity to investigate the microbial colonization of artistic surfaces aimed at implementing preservation strategies of cultural heritage from bio-spoilage.

SummaryXylella fastidiosa (Xf) is a polyphagous gram-negative bacterial plant pathogen that can infect more than 300 plant species. It is endemic in America while, in 2013, Xf subsp. pauca was for the first time reported in Europe on olive tree in the Southern Italy. The availability of fast and reliable diagnostic tools is indispensable for managing current and future outbreaks of Xf.In this work, we used the Oxford Nanopore Technologies (ONT) device MinION platform for detecting and identifying Xf at species, subspecies and Sequence Type (ST) level straight from infected plant material. The study showed the possibility to detect Xf by direct DNA sequencing and identify the subspecies in highly infected samples. In order to improve sensitivity, Nanopore amplicon sequencing was assessed. Using primers within the set of the seven MLST officially adopted for identifying Xf at type strain level, we developed a workflow consisting in a multiple PCR and an ad hoc pipeline to generate MLST consensus after Nanopore-sequencing of the amplicons. The here-developed combined approach achieved a sensitivity higher than real-time PCR allowing within few hours, the detection and identification of Xf at ST level in infected plant material, also at low level of contamination.Originality Significance StatementIn this work we developed a methodology that allows the detection and identification of Xylella fastidiosa in plant using the Nanopore technology portable device MinION. The approach that we develop resulted more sensitive than methods currently used for detecting X. fastidiosa, like real-time PCR. This approach can be extensively used for X. fastidiosa detection and it may pave the road for the detection of other tedious vascular pathogens.

Fusarium verticillioides causes ear rot disease in maize and its contamination with fumonisins, mycotoxins harmful for humans and livestock. Lipids, and their oxidized forms, may drive the fate of this disease. In a previous study, we have explored the role of oxylipins in this interaction by deleting by standard transformation procedures a linoleate diol synthase-coding gene, lds1, in F. verticillioides. A profound phenotypic diversity in the mutants generated has prompted us to investigate more deeply the whole genome of two lds1-deleted strains. Bioinformatics analyses pinpoint significant differences in the genome sequences emerged between the wild type and the lds1-mutants further than those trivially attributable to the deletion of the lds1 locus, such as single nucleotide polymorphisms, small deletion/insertion polymorphisms and structural variations. Results suggest that the effect of a (theoretically) punctual transformation event might have enhanced the natural mechanisms of genomic variability and that transformation practices, commonly used in the reverse genetics of fungi, may potentially be responsible for unexpected, stochastic and henceforth off-target rearrangements throughout the genome.