Publications

4855

Abstract De novo assembly of ancient and modern bacterial metagenomes can shed light on evolution and ecology of bacterial species that are challenging to culture. Tannerella and Porphyromonas are bacterial genera linked to periodontal disease, and understanding their evolution may reveal insights into their role in oral disease development. We performed pangenomic and phylogenetic analyses on a global set of isolates and metagenome-assembled genomes of the genera Tannerella (n = 238) and Porphyromonas (n = 976), including 66 genomes from ancient dental calculus samples (up to 14,800 years old), and modern oral samples from present-day living populations. We identify a novel species of oral Tannerella in modern and ancient humans, which we call Ca. Tannerella abscondita, that is related to and often mistaken for Tannerella forsythia but differs in its virulence repertoire. We reveal distinct niche tropism in Tannerella species and Porphyromonas pasteri, but not Porphyromonas gingivalis. There is limited phylogeographic structuring, and virulence genes are homogeneously distributed across continents and oral niches. Saliva-derived strains of T. forsythia and P. gingivalis from Oceania and T. serpentiformis and P. pasteri from Asia show enrichment of pseudogenes related to ecological niche transitions. A phylogenetic analysis of the P. gingivalis major fimbrial protein gene fimA reveals the genes cluster by genotypes, and that no ancient genes are found in genotypes I and Ib. Using de novo assembly for bacterial pangenomics improves the representation of oral genera found in reference databases and enhances our ability to study the evolutionary history of these taxa.

Lethal wilt (LW), known as “Marchitez Letal” in Colombia, is an endemic disease affecting oil palms (Elaeis guineensis Jacq.) and a leading cause of crop loss. The disease is characterized by the drying of leaflets from the tip to the base, primarily impacting the lower third of the plant and progressively moving upward. This progression leads to physiological disturbances, including necrosis at the tips of immature inflorescence bracts (spines) and the detachment of bunch fruits, ultimately causing wilting. As a phytosanitary measure, infected palms are eradicated to prevent further spread of the disease. The primary goal of this research was to identify the bacteria associated with LW and to validate a molecular detection method. A 16S amplicon-based analysis was employed to identify and compare the microbial diversity in LW-affected palm tissues with those of healthy plants. Among the 16 OTUs corresponding to different bacterial genera found in all LW samples, taxonomic classification and symptomatology suggested that the bacteria closely associated with LW belong to the genus ‘Candidatus Liberibacter’. Further phylogenetic analysis indicated that these bacteria are part of the Rhizobiaceae family, grouping closely with other species of the genus ‘Ca. Liberibacter’. The concentration of the pathogen in different oil palm tissues was determined using droplet digital PCR and quantitative PCR, expressed in copies/μl in the LW samples. This study represents the first report of ‘Ca. Liberibacter’ sp. being associated with lethal wilt in oil palms of the Arecaceae family in Colombia. The findings from this research could contribute significantly to the development of effective management strategies to prevent crop losses. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Abstract Since 2025, EFSA has conducted expert knowledge elicitations to estimate survey parameters for the detection of EU priority pests listed in Commission Delegated Regulation (EU) 2019/1702, in cases where pest‐specific information is lacking in the scientific literature. The design and implementation of statistically sound and risk‐based surveys require quantitative parameters such as sampling effectiveness, design prevalence and relative risk. This report presents the estimated values for Bactericera cockerelli and ‘Candidatus Liberibacter solanacearum’, together with the supporting evidence and expert rationale. These values will be integrated into the EFSA Plant Pest Survey Toolkit to guide EU Member States in designing harmonised pest surveys across the EU.

Candidatus Liberibacter solanacearum (CLso), a pathogen of concern to the potato industry, which causes zebrachip disease, is vectored by the tomato/potato psyllid [ Bactericera cockerelli (Šulc)]. This study investigated whether Lycium ferocissimum acts as an overwintering green bridge enabling pathogen survival, while potatoes are absent. The potential of L. ferocissimum to act as a green bridge for other pathogens was also investigated. African boxthorn leaf samples were taken in Feb, Mar, and Apr 2023 in Canterbury, New Zealand, and endophytes were isolated and cultured. DNA was extracted from these pure-cultured endophytes as well as from leaves. Molecular methods were used to identify the cultured endophytes and to determine the presence of CLso. This study found several potentially pathogenic endophytes including Alternaria porri, Stemphylium eturmiunum , Stemphylium vesicarium, Pseudomonas spp., Erwinia spp. , Pantoea sp. , and Candidatus Liberibacter solanacearum. The percentage of leaves which tested positive for CLso increased from 2% in Feb 2023 to 39% in Apr 2023. CLso was found in leaves without evidence of psyllid feeding, which may indicate systemic infection of African Boxthorn, suggesting the plant acts as a green bridge plant. It is highly recommended that this plant be eradicated within the vicinity of potatoes and other Solanaceous crops.

Candidatus Saccharibacteria (TM7) is an underexplored bacterial group within the human oral microbiome. These ultra-small, host-dependent organisms, despite their reduced genomes, significantly influence microbial balance and host immunity, exhibiting dual roles in oral health and disease and emerging as a key focus in microbiome research. This systematic review aimed to synthesize evidence on the prevalence, host interactions, genomic features, and ecological roles of TM7 in the oral cavity. A total of 13 peer-reviewed studies published between 2020 and 2025 were selected for detailed review based on predefined inclusion criteria, including clinical, laboratory, and metagenomic analyses focusing on TM7 detection, isolation, host specificity, and interactions with oral microbial communities. TM7 was found to be predominantly oral-adapted, exhibiting site-specific colonization with higher abundance in saliva. Coculture experiments demonstrated strict host dependence, particularly on Actinomyces, Schaalia, and Arachnia species, with strain-specific variations affecting host viability and microbial networks. TM7 genomes are highly reduced, with specialized adaptations including type IV pili and arginine deiminase pathways. Interactions with the immune system were context-dependent, with both immunomodulatory and pro-inflammatory outcomes observed. Detection methods significantly influenced TM7 prevalence and functional interpretation. Overall, TM7 represents a host-dependent, ecologically influential oral bacterium with genomic specialization, strain-level variability, and complex interactions within microbial communities. These findings highlight its potential roles in oral health and disease and emphasize the need for advanced multi-modal analytical approaches.