Publications

4596

Abstract Background ‘ Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited bacterial pathogen causing significant diseases in solanaceous crops. In the United States, haplotypes A and B are transmitted by the potato psyllid Bactericera cockerelli . We previously identified differences in their acquisition and transmission between adults and nymphs. The present study characterized the dynamics of LsoA and LsoB acquisition and transmission by nymphs and examined the transcriptional responses of the nymphal gut upon their acquisition. Methods and results Nymphs were exposed to LsoA- or LsoB-infected plants for 1, 3, 5, or 7 days to measure the bacterial accumulation and for 8 days to assess the transmission efficiency following sequential inoculation of tomato plants. Quantitative PCR showed that LsoB accumulated to higher levels than LsoA after 3 days of acquisition. Following the sequential inoculation, LsoB was transmitted earlier than LsoA indicating a shorter latency period. RNA-seq analysis of the guts following a 1- and 5-day acquisition access periods revealed a greater transcriptional regulation at 5 days than at 1 day. Furthermore, the responses were haplotype-specific: LsoA primarily affected genes involved in protein translation, ER stress, and cell cycle regulation, whereas LsoB regulated genes involved in autophagy, apoptosis, and immune pathways. Conclusions This study revealed haplotype-specific gene regulation potentially leading to LsoB being transmitted more efficiently by psyllid nymphs.

Abstract Bovine hemoplasmas, including Mycoplasma wenyonii (M. wenyonii) and Candidatus Mycoplasma haemobos (C. M. haemobos) , are vector-borne pathogens that can cause significant clinical diseases in cattle. This case report from Türkiye describes the clinical findings, hematological analysis, and serum biochemistry results of a cow presenting with hemoglobinuria caused by C. M. haemobos . Blood samples from the infected animal were analyzed using hematological, biochemical, microscopic, and molecular methods. Multiplex polymerase chain reaction assay confirmed the infection, and microscopic analysis revealed a parasitemia rate of 6.99%. Clinical signs included hemoglobinuria, icterus, and anemia. The treatment included fluid therapy, antibiotic (oxytetracycline), and antianemic drugs. The cattle died 1 month post-treatment, reportedly due to a lower respiratory tract infection. This case report describes the diagnostic methods, clinical findings, and laboratory results. A widescale molecular survey of C. M. haemobos in cattle is warranted, with investigation of its pathogenicity and pathogenies.

Chokecherry (Prunus virginiana L.) is a native shrub that is widely found across North America and is a host of ‘Candidatus Phytoplasma pruni’ associated with X-disease of stone fruits. This pathogen is of major concern to U.S. cherry and peach growers, with the most recent and ongoing outbreak in the Pacific Northwest causing major economic harm. To investigate the role of chokecherry as a potential reservoir and source of orchard-associated strains, we surveyed wild chokecherry trees across 12 U.S. states, and compared the strains present to those in commercially cultivated Prunus species. Approximately 47% of chokecherry sampled tested positive for a ‘Ca. P. pruni’-related strain and phylogenetic analysis revealed high strain diversity, including six distinct clades and four newly identified lineages. In contrast, ‘Ca. P. pruni’ strains isolated from cultivated cherry and peach trees exhibited lower diversity and were infected by known disease outbreak-associated strains such as NWX. These data suggest limited transmission between wild and cultivated hosts in the western U.S., with patterns indicating spillover from orchards into nearby chokecherry populations rather than the reverse. However, in states east of the Rocky Mountains, chokecherry likely functions as a reservoir for orchard infections.

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 The Sphaerotilus-Leptothrix group of bacteria includes one of the first described microorganisms, Leptothrix ochracea , an uncultured type strain, plus isolates of Leptothrix and Sphaerotilus . This group is unified by the ability to form sheaths and oxidize metals, although L. ochracea exhibits obvious ecological, morphological, and functional differences from the rest of Sphaerotilus-Leptothrix . Recently, there have been calls to combine the group into one genus, Sphaerotilus ; however, these studies lacked adequate genomic representation of L. ochracea . Here, we present a comprehensive comparative genomic analysis of the Sphaerotilus-Leptothrix group, including expanded representation of L. ochracea , a closely related novel species, Leptothrix toolikensis , and two new isolates ( Leptothrix mechoopdaensis ). Analysis of 38 genomes resolves three phylogenetic and functional groups: the ochracea -type Leptothrix (Group 1), the mobilis -type Leptothrix (Group 2), and Sphaerotilus (Group 3). Group 1 genomes form a separate genus based on average nucleotide identity and alignment fraction. The genomes clearly diverge from the rest of Sphaerotilus-Leptothrix in phylogeny, size, and metabolic potential. Group 1 genomes are much smaller (2.59–3.04 Mb) than those of Groups 2 (4.55–6.06 Mb) and 3 (3.94–5.07 Mb), while encoding more metal oxidases and fewer carbohydrate-active enzymes. Group 2 clusters with Group 3 phylogenetically and is similar in organic carbon metabolisms but maintains more metal oxidation genes. Group 2 members lack homogeneity in phenotype and genotype, suggesting that additional isolates and genomes are needed for confident classification. However, Group 1 genomes ( L. ochracea and L. toolikensis ) show clear divergence, precluding their inclusion in Sphaerotilus and supporting the retention of the genus Leptothrix . IMPORTANCE Researchers have long noted differences in metal oxidation, morphology, and ecology among Sphaerotilus-Leptothrix , but longstanding confusion over phylogeny and genus boundaries led to inconsistent taxonomic classification between the two genera. This confusion stems from previous work that used isolates that are unavailable or lost distinguishing traits in culture, and from limited genomic data. Furthermore, the Leptothrix type strain L. ochracea has never been isolated. This study provides molecular evidence that substantiates calls to reassign some Leptothrix members to the genus Sphaerotilus but adds to an emerging body of evidence that Group 1 L. ochracea and now L. toolikensis represent a functionally distinct lineage. While genomic similarity metrics left taxonomic divisions unclear, integrating metabolic potential with phylogeny resolved genus boundaries based on clear functional groupings. This polyphasic approach for delineating genera clarifies longstanding taxonomic confusion and refines our understanding of functional diversity both across and within Sphaerotilus-Leptothrix lineages.

Soils are critical microbial habitats that support terrestrial ecosystem functioning and harbor numerous uncultured and functionally uncharacterized microbial groups. The black soil region in northeast China is a key agricultural ecosystem globally, yet the classification and functional understanding of its crucial microbial groups remain underexplored. In this study, we identified three high-completeness metagenome-assembled genomes (MAGs) from the Global Mollisols Genomic Atlas (GMGA). Phylogenetic and comparative genomic analyses identified these genomes as representing a novel evolutionary branch within the genus Flavobacterium, classified under the phylum Bacteroidota. Their novel taxonomic position is further supported by average nucleotide identity (ANI) and average amino acid identity (AAI) thresholds, demonstrating significant divergence from all known reference genomes. Functional annotation indicated that this species possesses strong plant polysaccharide degradation potential and a chemoheterotrophic lifestyle, together with environmental stress tolerance and a specialized nitrogen metabolic network adapted to agricultural inputs, thereby conferring a metabolic advantage in black soil environments characterized by high organic matter input and marked seasonal fluctuations. In addition, global distribution analysis showed that this lineage is widely distributed across diverse ecosystems and is significantly enriched in soil habitats, particularly in environments with fluctuating carbon sources and high organic matter inputs. The new species is most abundant in temperate soils, with the northeast black soil region of China emerging as a key hotspot. Based on these findings, and because no pure culture is currently available, we propose Candidatus Flavobacterium genomatis based on genome-resolved metagenomic evidence and in alignment with the International Code of Nomenclature of Prokaryotes rules for uncultivated prokaryotes. Our results expand the known species diversity of the genus Flavobacterium and suggest potential ecological roles of uncultured black-soil microbes in carbon and nitrogen cycling, including possible involvement in N2O reduction under suitable environmental conditions.

GroE is a chaperonin folding system consisting of GroEL (Cpn60, a 60 kDa chaperonin), and the smaller co-chaperonin GroES (Cpn10). Many ‘client’ proteins require GroE to fold properly, including several that are essential for cell viability. GroE is found in nearly all bacteria and eukaryotes. Mollicutes are the only micro-organisms that lack GroE in almost all cases. Only two clades of Mollicutes have retained the ancestral GroE system, or perhaps reacquired one; these exceptions include the family Acholeplasmataceae , consisting of the genera Acholeplasma and ‘ Candidatus Phytoplasma’. The role of GroEL in these unique Mollicutes is a source of speculation, given how many non-canonical ‘moonlighting’ roles have been ascribed to this protein. GroEL has been suggested to play a role in pathogenesis in plant and animal pathogenic Mollicutes by binding to host cells and facilitating invasion. However, in one further layer of exception, the phytopathogenic taxon ‘ Candidatus Phytoplasma pruni’ (ribosomal group 16SrIII) was reported in 2012 to lack a GroE system. This study confirms the lack of a functional GroE system in 16SrIII by providing two new, high-quality, non-fragmented genome assemblies, as well as a thorough survey of other 16SrIII genomes for genes encoding GroEL/GroES, including those that may not resemble phytoplasma GroEL (i.e. acquired by horizontal gene transfer, HGT). We discuss the implications of a clearly phytopathogenic, invasive group of Mollicutes that nevertheless lacks GroE, in light of the presumed role of GroEL for this species. We determined that multiple genomes of 16SrIII contain short, non-functional groEL pseudogenes, while most of the reported genomes lack any semblance of a GroE system. Examination of the new assemblies allowed us to rule out HGT as a means of GroE acquisition.