The atypical hemolytic uremic syndrome (aHUS) is a paradigm of a disease, caused by overactivation of the alternative complement pathway secondary to a not well-understood trigger event. About 60 % of the patients present genetic or acquired abnormalities in the proteins of the alternative complement pathway. In 40 % of the cases the affected protein is the complement regulator Factor H (FH)-30 % due to mutations and 10 % because of anti-FH autoantibodies. Here we describe the detailed protocol for a rapid test to analyse the functional defect associated with genetic or acquired FH-related abnormalities. It can be applied for the characterization of the underlying complement defect in aHUS, based on spontaneous lysis of non-sensitized sheep erythrocytes in contact with patients' plasma or serum.

Vibrio bacteria, and particularly members of the Harveyi clade, are the causative agents of vibriosis. This disease is responsible for mass mortality events and important economic losses on aquaculture farms. Improvements in surveillance and diagnosis are needed to successfully manage vibriosis outbreaks. 16S rRNA gene sequencing is generally considered to be the gold standard for bacterial identification but the cost and long processing time make it difficult to apply for routine identification. In contrast, MALDI-TOF MS offers rapid diagnosis and is commonly used in veterinary laboratories today. The major limiting factor for using this technique is the low environmental bacterial diversity in the commonly available databases. Here, we demonstrate that the sole use of the commercially available Bruker BioTyper database is not fully adequate for identifying Vibrio bacteria isolated from aquaculture farms. We therefore developed a new in-house database named Luvibase, composed of 23 reference MALDI-TOF mass spectra profiles obtained from Vibrio collection strains, mostly belonging to the Harveyi clade. The comparison of the accuracy of MALDI-TOF MS profiling and 16S rRNA gene sequencing revealed a lack of resolution for 16S rRNA gene sequencing. In contrast, MALDI-TOF MS profiling proved to be a more reliable tool for resolving species-level variations within the Harveyi clade. Finally, combining the Luvibase with the Bruker ver.9.0.0.0 database, led to successful identification of 47 Vibrio isolates obtained from moribund abalone, seabass and oysters. Thus, the use of Luvibase allow for increased confidence in identifying Vibrio species belonging to the Harveyi clade.

BackgroundPhytophthora infestans is responsible for late blight, one of the most important potato diseases. Phenazine-1-carboxylic acid (PCA)-producing Pseudomonas fluorescens strain LBUM223 isolated in our laboratory shows biocontrol potential against various plant pathogens. To characterize the effect of LBUM223 on the transcriptome of P. infestans, we conducted an in vitro time-course study. Confrontational assay was performed using P. infestans inoculated alone (control) or with LBUM223, its phzC- isogenic mutant (not producing PCA), or exogenically applied PCA. Destructive sampling was performed at 6, 9 and 12 days and the transcriptome of P. infestans was analysed using RNA-Seq. The expression of a subset of differentially expressed genes was validated by RT-qPCR.ResultsBoth LBUM223 and exogenically applied PCA significantly repressed P. infestans’ growth at all times. Compared to the control treatment, transcriptomic analyses showed that the percentages of all P. infestans’ genes significantly altered by LBUM223 and exogenically applied PCA increased as time progressed, from 50 to 61% and from to 32 to 46%, respectively. When applying an absolute cut-off value of 3 fold change or more for all three harvesting times, 207 genes were found significantly differentially expressed by PCA, either produced by LBUM223 or exogenically applied. Gene ontology analysis revealed that both treatments altered the expression of key functional genes involved in major functions like phosphorylation mechanisms, transmembrane transport and oxidoreduction activities. Interestingly, even though no host plant tissue was present in the in vitro system, PCA also led to the overexpression of several genes encoding effectors. The mutant only slightly repressed P. infestans’ growth and barely altered its transcriptome.ConclusionsOur study suggests that PCA is involved in P. infestans’ growth repression and led to important transcriptomic changes by both up- and down-regulating gene expression in P. infestans over time. Different metabolic functions were altered and many effectors were found to be upregulated, suggesting their implication in biocontrol.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4852-1) contains supplementary material, which is available to authorized users.

The phenazine-1-carboxylic acid (PCA)-producing Pseudomonas fluorescens strain LBUM223 shows biocontrol potential against Streptomyces scabies, which causes common scab of potato. To better characterize the impact of inoculating this specific biocontrol agent under field conditions, the microbiomes of the rhizosphere and the geocaulosphere of potato plants were characterized using next-generation sequencing. A single initial application or biweekly applications of LBUM223 were performed up to 11 weeks after planting. Rhizosphere and geocaulosphere soils (when potato tubers were produced) were sampled every 2 weeks. Following soil DNA extractions, 16S rRNA gene amplification and sequencing were performed using the Illumina MiSeq technology. The QIIME pipeline was used for data analyses. Results were generated from 45 rhizosphere and 27 geocaulosphere samples, for which 63,502 and 44,469 different operational taxonomical units were observed. Diversity comparisons between both datasets were performed. To our knowledge, this is the first time that the geocaulosphere microbiome is characterized and compared with the rhizosphere microbiome following inoculation with a specific microorganism. Eleven phyla accounted for 95% of the diversity, with Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria being the most abundant ones. Overall, the results obtained suggest that P. fluorescens strain LBUM223 does not significantly alter the autochthonous rhizosphere nor geocaulosphere microbiomes.

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Vibrio harveyi is a particularly problematic Gram-negative bacterium because it can form biofilms on aquaculture facility surfaces, leading to resistance of bacteria against antibiotics and water sanitizers. A SYBR Green I quantitative real-time PCR method was developed to detect V. harveyi directly from environmental samples, including seawater and biofilm. Specific primers targeting the mreB gene were designed. The exclusivity and inclusivity of the newly designed primers were evaluated using a panel of 85 bacteria: 58 V. harveyi from multiples origins and 27 non-V. harveyi isolates, and compared with two pairs of primers targeting the topA and toxR genes that were designed previously. All sets of primers were able to distinguish V. harveyi from closely related species belonging to the Harveyi clade. However, the mreB primers showed better inclusivity and were thus used to develop the real-time PCR assay. A quantification curve was obtained from pure culture of V. harveyi and exhibited excellent efficacy with detection levels as low as 5 genome copies in the PCR reaction. After selection of the extraction kit allowing the best DNA quantity and purity, validation was performed on both seawater and biofilm samples collected from a fish farm. The presence of inhibitors in the DNA templates was evaluated and a 10-fold dilution of template DNA was recommended in order to avoid their effects. The assay was able to detect V. harveyi from environmental samples, confirming the validity of the method. This real-time PCR method will help to evaluate the dynamics of V. harveyi in aquaculture facilities. Suitable prophylactic control measures could be designed using this method, instead of the use of curative methods such as antibiotics

The discovery of novel specific ribosome-associated factors challenges the assumption that translation relies on standardized molecular machinery. In this work, we demonstrate that Tma108, an uncharacterized translation machinery-associated factor in yeast, defines a subpopulation of cellular ribosomes specifically involved in the translation of less than 200 mRNAs encoding proteins with ATP or Zinc binding domains. Using ribonucleoparticle dissociation experiments we established that Tma108 directly interacts with the nascent protein chain. Additionally, we have shown that translation of the first 35 amino acids of Asn1, one of the Tma108 targets, is necessary and sufficient to recruit Tma108, suggesting that it is loaded early during translation. Comparative genomic analyses, molecular modeling and directed mutagenesis point to Tma108 as an original M1 metallopeptidase, which uses its putative catalytic peptide-binding pocket to bind the N-terminus of its targets. The involvement of Tma108 in co-translational regulation is attested by a drastic change in the subcellular localization of ATP2 mRNA upon Tma108 inactivation. Tma108 is a unique example of a nascent chain-associated factor with high selectivity and its study illustrates the existence of other specific translation-associated factors besides RNA binding proteins.

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