Publications

4442

Abstract Culicoides biting midges (Diptera: Ceratopogonidae) are vectors responsible for the transmission of several viruses of veterinary importance. Previous screens of Culicoides have described the presence of the endosymbiont Candidatus Cardinium hertigii (Bacteroidetes). However, any impacts of this microbe on vectorial capacity, akin to those conferred by Wolbachia in mosquitoes, are yet to be uncovered and await a suitable system to study Cardinium ‐midge interactions. To identify potential candidate species to investigate these interactions, accurate knowledge of the distribution of the endosymbiont within Culicoides populations is needed. We used conventional and nested PCR assays to screen Cardinium infection in 337 individuals of 25 Culicoides species from both Palearctic and Afrotropical regions. Infections were observed in several vector species including C. imicola and the Pulicaris complex ( C. pulicaris , C. bysta , C. newsteadi and C. punctatus ) with varying prevalence. Phylogenetic analysis based on the Gyrase B gene grouped all new isolates within ‘group C’ of the genus, a clade that has to date been exclusively described in Culicoides . Through a comparison of our results with previous screens, we suggest C. imicola and C. sonorensis represent good candidates for onward study of Cardinium‐ midge interactions.

Abstract“Candidatus Liberibacter asiaticus” (Ca. L. asiaticus) is the causal agent of Huanglongbing disease of citrus and current study focuses on the discovery of novel small‐molecule inhibitors against SecA protein of Ca. L. asiaticus. In this study, homologous modeling was used to construct the three‐dimensional structure of SecA. Then, molecular docking‐based virtual screening and two rounds of in vitro bacteriostatic experiments were utilized to identify novel small‐molecule inhibitors of SecA. Encouragingly, 93 compounds were obtained and two of them (P684‐2850, P684‐3808) showed strong antimicrobial activities against Liberibacter crescens BT‐1 in bacteriostatic experiments. Finally, molecular dynamics simulations were employed to explore the binding modes of the receptor–ligand complexes. Results in MD simulations showed that compound P684‐3808 was relatively stable during simulation, while compound P684‐2850 left the binding pocket. Compound P684‐3808 might be suitable as a lead compound for further development of antimicrobial compounds against SecA of Ca. L. asiaticus.

The potato psyllid Bactericera cockerelli (Šulc) (Hemiptera: Triozidae) is a pest of solanaceous crops (order Solanales), including potato (Solanum tuberosum L.) and tomato (S. lycopersicum L.). Feeding by high populations of nymphs causes psyllid yellows while adults and nymphs are vectors of the plant pathogen ‘Candidatus Liberibacter solanacearum’. Foliar symptoms that were consistent with either ‘Ca. L. solanacearum’ infection or psyllid yellows were observed in 2019 on tomatillo (Physalis ixocarpa Brot.; family Solanaceae) grown within an experimental plot located near Saltillo, Mexico. This study had three primary objectives: 9i) determine whether the foliar symptoms observed on tomatillo were associated with ‘Ca. L. solanacearum’ infection, (ii) identify the haplotypes of ‘Ca. L. solanacearum’ and potato psyllids present in the symptomatic plot, and (iii) use gut content analysis to infer the plant sources of ‘Ca. L. solanacearum’-infected psyllids. Results confirmed that 71% of symptomatic plants and 71% of psyllids collected from the plants were infected with ‘Ca. L. solanacearum’. The detection of ‘Ca. L. solanacearum’ in plants and psyllids and the lack of nymphal populations associated with psyllid yellows strongly suggests that the observed foliar symptoms were caused by ‘Ca. L. solanacearum’ infection. All infected plants and insects harbored the more virulent ‘Ca. L. solanacearum’ haplotype B but one psyllid was also coinfected with haplotype A. The potato psyllids were predominantly of the central haplotype but one psyllid was identified as the western haplotype. Molecular gut content analysis of psyllids confirmed the movement of psyllids between noncrop habitats and tomatillo and indicated that ‘Ca. L. solanacearum’ infection of psyllids was associated with increased plant diversity in their diet.

Recent advances in sequencing technology promoted the blowout discovery of super tiny microbes in the Diapherotrites , Parvarchaeota , Aenigmarchaeota , Nanoarchaeota , and Nanohaloarchaeota (DPANN) superphylum. However, the unculturable properties of the majority of microbes impeded our investigation of their behavior and symbiotic lifestyle in the corresponding community.

ABSTRACTA mesophilic filamentous anoxygenic phototrophic bacterium, designated M50-1, was isolated from a microbial mat of the Chukhyn Nur soda lake (northeastern Mongolia) with salinity of 5−14 g/L and pH 8.0−9.3. The organism is a strictly anaerobic phototrophic bacterium, which required sulfide for phototrophic growth. The cells formed short undulate trichomes surrounded by a thin sheath and containing gas vesicles. Motility of the trichomes was not observed. The cells contained chlorosomes. The antenna pigments were bacteriochlorophyll d and β- and γ-carotenes. Analysis of the genome assembled from the metagenome of the enrichment culture revealed all the enzymes of the 3-hydroxypropionate bi-cycle for autotrophic CO2 assimilation. The genome also contained the genes encoding a type IV sulfide:quinone oxidoreductase (sqrX). The organism had no nifHDBK genes, encoding the proteins of the nitrogenase complex responsible for dinitrogen fixation. The DNA G + C content was 58.6%. The values for in silico DNA‒DNA hybridization and average nucleotide identity between M50-1 and a closely related bacterium ‘Ca. Chloroploca asiatica’ B7-9 containing bacteriochlorophyll c were 53.4% and 94.0%, respectively, which corresponds to interspecies differences. Classification of the filamentous anoxygenic phototrophic bacterium M50-1 as a new ‘Ca. Chloroploca’ species was proposed, with the species name ‘Candidatus Chloroploca mongolica’ sp. nov.

SAP11 is an effector protein that has been identified in various phytoplasma species. It localizes in the plant nucleus and can bind and destabilize TEOSINE BRANCHES/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factors. Although SAP11 of different phytoplasma species share similar activities, their protein sequences differ greatly. Here, we demonstrate that the SAP11-like protein of ‘Candidatus Phytoplasma mali’ (‘Ca. P. mali’) strain PM19 localizes into the plant nucleus without requiring the anticipated nuclear localization sequence (NLS). We show that the protein induces crinkled leaves and siliques, and witches’ broom symptoms, in transgenic Arabidopsis thaliana (A. thaliana) plants and binds to six members of class I and all members of class II TCP transcription factors of A. thaliana in yeast two-hybrid assays. We also identified a 17 amino acid stretch previously predicted to be a nuclear localization sequence that is important for the binding of some of the TCPs, which results in a crinkled leaf and silique phenotype in transgenic A. thaliana. Moreover, we provide evidence that the SAP11-like protein has a destabilizing effect on some TCPs in vivo.