Publications

4780

Abstract Phytoplasmas are wall-less, phloem-limited unculturable bacteria that are naturally spread by sap-sucking insects. 'Candidatus Phytoplasma australiense', subgroup 16SrXII-B, is associated with a wide range of diseases in Australia and New Zealand. Important commercial crop hosts of 'Ca. Phytoplasma australiense' include grapevine, papaya and strawberry. This phytoplasma is associated with rapid death of its papaya and cabbage tree hosts. In New Zealand, the insect vectors have been confirmed to be the endemic Cixiid planthoppers, Zeoliarus atkinsoni and Z. oppositus, while in Australia no vector has yet been determined, although the leafhopper, Orosius argentatus, has been implicated. Long distance spread of the phytoplasma is possible through infected vegetative propagating material. 'Ca. Phytoplasma australiense' is on the A1 list of regulated organisms for Canada and Bahrain, and is listed as a quarantine pest for the USA.

Abstract The Atlantic tall, the most prevalent coconut ecotype throughout the Caribbean region and Atlantic coast of the Americas (Harries, 1978a), is highly susceptible to LY disease. During the past three decades, at least 50% of Florida's estimated one million coconut palms and over 80% of Jamaica's five million coconut palms have been eliminated by LY (McCoy et al., 1983). Similar epidemic losses of coconut to LY continued along the Atlantic coasts of southern Mexico and Honduras (Oropeza and Zizumbo, 1997). Although rarely affecting palms less than 5 years old, the disease prevents any re-establishment of highly susceptible coconut ecotypes in LY-endemic locations such as Florida and Jamaica.

Abstract Hal.ec.to.sym.bi.o'ta. Gr. masc. n. hals , halos salt, salt water; Gr. prep. ektos outside; N.L. masc. n. symbiota (from Gr. n. symbiotes ) one who lives with a companion, partner; N.L. masc. n. Halectosymbiota an ectosymbiont from salt water organisms. The genus Candidatus Halectosymbiota corrig., originally described as Ca . Haloectosymbiotes, was established based on a 16S rRNA taxonomic marker gene sequence of the only identified species in this genus, Candidatus Halectosymbiota riaformosensis. Ca . Halectosymbiota riaformosensis was observed to live as ectosymbiont on a halophile scuticociliate, which was isolated from a thalassohaline solar saltern pond (12% salinity) in Faro, Portugal. Comparisons of 16S rRNA gene sequences showed that Ca . Halectosymbiota is phylogenetically affiliated to the genera Halolamina (sequence similarity to H. pelagica : 87%) and Halobaculum (sequence similarity to H. magnesiiphilum 85%). Based on scanning electron microscopy micrographs and fluorescence in situ hybridization, cells are rod‐shaped and approximately 1.8 × 0.6 μm in size. Cells are densely covering the surface of the host, with approximately 0.52 epibiotic cells per μm 2 . Free‐living forms were not observed. Candidatus Halectosymbiota riaformosensis is sensitive to anisomycin. Known habitats are aquatic hypersaline environments. Type species : Not applicable. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Halectosymbiota is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Methanobacteriati / Methanobacteriota / Halobacteria / Halobacteriales / Halobacteriaceae / Candidatus Halectosymbiota Candidatus Halectosymbiota could not be recovered in GTDB ** . * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

The exploration of deep marine sediments has unearthed many new lineages of microbes. The finding of this novel phylum of Asgard archaea is important, since understanding the diversity and evolution of Asgard archaea may inform also about the evolution of eukaryotic cells. The comparison of metabolic potentials of the Asgard archaea can help inform about selective pressures the lineages have faced during evolution.

AbstractCandidatusLiberibacter asiaticus (CLas) is one the causative agents of greening disease in citrus, an unccurable, devastating disease of citrus worldwide. CLas is vectored byDiaphorina citri, and the understanding of the molecular interplay between vector and pathogen will provide additional basis for the development and implementation of successful management strategies. We focused in the molecular interplay occurring in the gut of the vector, a major barrier for CLas invasion and colonization. We investigated the differential expression of vector and CLas genes by analyzing ade novoreference metatranscriptome of the gut of adult psyllids fed of CLas-infected and healthy citrus plants for 1-2, 3-4 and 5-6 days. CLas regulates the immune response of the vector affecting the production of reactive species of oxygen and nitrogen, and the production of antimicrobial peptides. Moreover, CLas overexpressedperoxiredoxinin a protective manner. The major transcript involved in immune expression was related to melanization, aCLIP-domain serine proteasewe believe participates in the wounding of epithelial cells damaged during infection, which is supported by the down-regulation ofpangolin. We also detected that CLas modulates the gut peristalsis of psyllids through the down-regulation oftitin, reducing the elimination of CLas with faeces. The up-regulation of the neuromodulatorarylalkylamine N-acetyltransferaseimplies CLas also interferes with the double brain-gut communication circuitry of the vector. CLas colonizes the gut by expressing twoType IVb pilin flpgenes and several chaperones that can also function as adhesins. We hypothesized biofil formation occurs by the expression of the cold shock protein of CLas. We also describe the interplay during cell invasion and modification, and propose mechanisms CLas uses to invade the host hemocel. We identified several specific targets for the development of strategies directed to interfere with the successful utilization of the psyllid vector by this pathogen.Author SummaryHuanglongbing (HLB) or greening is an incurable disease causing severe damage to citrus production, making citrus industrial activity unsustainable in several countries around the world. HLB is caused by three species ofCandidatusLiberibacter.Ca.L. asiaticus (CLas), vectored by the psyllidDiaphorina citri, is the prevalent species. Attempts to apply new technologies in the development of strategies for disease and pest management are been made. However, we still miss basic information on this system to efficiently apply the current technologies and envisage the implementation of new approaches for pest control, despite the relevant scientific contribution available. One major gap is regarded to the molecular interplay between CLas and its vector. We focused our attention in the molecular interplay occurring at the first relevant interaction of CLas andD. citri, represented by the gut barrier. We report the transcriptional activity of CLas during the invasion and establishment of the infection in the gut of the vector, as well as the transcriptional activity of the vector in response to the infection. We identified several host genes that are targeted and regulated by CLas as well as several CLas genes that are promising targets for the application of new management strategies.

Background The chicken is the most abundant food animal in the world. However, despite its importance, the chicken gut microbiome remains largely undefined. Here, we exploit culture-independent and culture-dependent approaches to reveal extensive taxonomic diversity within this complex microbial community. Results We performed metagenomic sequencing of fifty chicken faecal samples from two breeds and analysed these, alongside all (n = 582) relevant publicly available chicken metagenomes, to cluster over 20 million non-redundant genes and to construct over 5,500 metagenome-assembled bacterial genomes. In addition, we recovered nearly 600 bacteriophage genomes. This represents the most comprehensive view of taxonomic diversity within the chicken gut microbiome to date, encompassing hundreds of novel candidate bacterial genera and species. To provide a stable, clear and memorable nomenclature for novel species, we devised a scalable combinatorial system for the creation of hundreds of well-formed Latin binomials. We cultured and genome-sequenced bacterial isolates from chicken faeces, documenting over forty novel species, together with three species from the genus Escherichia, including the newly named species Escherichia whittamii. Conclusions Our metagenomic and culture-based analyses provide new insights into the bacterial, archaeal and bacteriophage components of the chicken gut microbiome. The resulting datasets expand the known diversity of the chicken gut microbiome and provide a key resource for future high-resolution taxonomic and functional studies on the chicken gut microbiome.

AbstractAnaplasmosis, caused by infection with bacteria of the genusAnaplasmais an important veterinary and zoonotic disease. The characterization of transmission has concentrated on ticks and little is known about non-tick vectors of livestock anaplasmosis. This study investigated the presence ofAnaplasmaspp. in camels in northern Kenya and whether the hematophagous camel ked,Hippobosca camelina, acts as a vector. Camels (n =976) and > 10,000 keds were sampled over a three-year study period and the presence ofAnaplasmaspecies was determined by PCR-based assays targeting theAnaplasmataceae16S rRNA gene. Camels were infected by‘CandidatusAnaplasma camelii’occurring from 63 - 78% during the dry (September 2017), wet (June-July 2018), and late wet seasons (July-August 2019). 10 - 29% of camel keds harbored ‘Ca. Anaplasma camelii’ acquired from infected camels during blood feeding. We determined whetherAnaplasmapositive camel keds could transmit ‘Ca. Anaplasma camelii’ to small laboratory animals via blood-feeding. We show competence in pathogen transmission and subsequent infection in mice and rabbits by both direct detection in blood smears and subsequent molecular identification by PCR. Transmission of ‘Ca. Anaplasma camelii’ to mice (8 - 47%) and rabbits (25%) occurred readily after ked bites. Hence, we demonstrate, for the first time, the potential ofH. camelinaas a vector of anaplasmosis. This key finding provides the basis for establishing ked control programmes for improvement of livestock and human health.Author summaryHematophagous flies such as Tabanids andStomoxys, among other biting flies, are mechanical transmitters of various pathogens such as African trypanosomes andAnaplasmaspecies. However, little is known about the role of common camel-specific biting keds (also known as camel flies or louse flies, genusHippobosca) in pathogen transmission. Keds inflict painful bites to access host blood, and in the process may transmit bacterial hemopathogens frequently detected in both camels and their keds. We confirmed by experimental blood-feeding, gene amplification, and amplicon sequencing that camel keds can transmit “CandidatusAnaplasma camelii” from naturally-infected camels to healthy mice and rabbits. The high prevalence of camel anaplasmosis throughout the year in northern Kenya could be explained by the infestation camel-specificH. camelina, whose capacity as efficient fliers, unlike ticks, promotes disease transmission and maintenance within and among camel herds. Although this study focused on the transmission ofAnaplasmasp. by camel keds, it is possible that other hemopathogens could also be transmitted by these flies through a similar mechanism. Notably, in the absence of their preferred hosts, keds occasionally bite humans and other vertebrates they come across in order to acquire bloodmeals, and in the process could transmit zoonotic pathogens.

Melatonin is synthesized from the amino acid L-tryptophan via the shikimic acid pathway and ubiquitously distributed in both prokaryotes and eukaryotes. Although most of melatonin biosynthesis genes were characterized in several plants and animal species including the insect model, Drosophila melanogaster, none of these enzymes have been identified from the Asian citrus psyllid, Diaphorina citri. We used comprehensive in silico analysis and gene expression techniques to identify the melatonin biosynthesis-related genes of D. citri and to evaluate the expression patterns of these genes within the adults of D. citri with gradient infection rates (0, 28, 34, 50, 58, and 70%) of the phytopathogenic bacterium Candidatus Liberibacter asiaticus and after the treatment with exogenous melatonin. We showed that the D. citri genome possesses six putative melatonin biosynthesis-related genes including two putative tryptophan 5-hydroxylase (DcT5H-1 and DcT5H-2), a putative aromatic amino acid decarboxylase (DcAADC), two putative arylalkylamine N-acetyltransferase (DcAANAT-1 and DcAANAT-2), and putative N-acetylserotonin O-methyltransferase (DcASMT). The infection with Ca. L. asiaticus decreased the transcript levels of all predicted genes in the adults of D. citri. Moreover, melatonin supplementation induced their expression levels in both healthy and Ca. L. asiaticus-infected psyllids. These findings confirm the association of these genes with the melatonin biosynthesis pathway.