Publications

4580

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.

Insecticide applications are commonly recommended for managing Diaphorina citri, the vector of huanglongbing (HLB), but their effectiveness in reducing transmission of ‘Candidatus Liberibacter asiaticus’ (CLas), especially during continuous psyllid influx and shoot growth, remains unclear. This study evaluated the efficacy of foliar application of thiamethoxam and spinetoram in reducing CLas transmission in sweet orange seedlings. Two experiments were conducted up to 13 days after first spray. In experiment 1, CLas-positive psyllids were confined in seedlings every 2 days. Treatments were: control; S14, one spray at day 0; and S7, sprays at days 0 and 7. In experiment 2, psyllids were released for free choice within a screenhouse every 2 days. Treatments were: control, S14, S7, and S3, sprays at day 0 and every 3 days. Sprays on day 0 were over unfolded leaves (V2 stage). Psyllid mortality was assessed in experiment 1. Psyllid occupancy (percentage of seedlings with at least one psyllid) and abundance (number of psyllids per seedling) were assessed in experiment 2. After 6 months, seedlings were tested for CLas by qPCR. In experiment 1, cumulative psyllid mortality was higher in sprayed treatments than in the control for both insecticides, but HLB incidence was similar. In experiment 2, both psyllid occupancy and abundance decreased with shorter spray intervals, with the lowest HLB incidence in S3. These findings suggest that reducing spray intervals can limit CLas transmission during periods of shoot growth and continuous vector pressure. However, CLas transmission was not entirely prevented, highlighting the need for integrated, area-wide management strategies.

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.

“Candidatus Sarcina troglodytae” (“Ca. S. troglodytae”), a proposed bacterial species in the family Clostridiaceae, has been epidemiologically associated with a lethal disease in sanctuary chimpanzees in Sierra Leone, epizootic neurologic and gastroenteric syndrome (ENGS). As sarcinae are known to be difficult to culture, a lack of viable in vitro growth conditions has limited further characterization of this bacterium. Such studies are critical to elucidating the relationship between “Ca. S. troglodytae” and ENGS.  Here, we isolate a Gram-stain-positive, endospore-forming, coccus and anaerobic bacterial strain, designated JB3T, from brain tissue of a western chimpanzee (Pan troglodytes verus) using a reinforced clostridial medium. We describe the growth of strain JB3T at a pH range of 6 to 9 (optimum 6) at 37°C in an atmosphere composed of 5% H2, 5% CO2, and 90% N2 and demonstrate endospore production under alkaline conditions, suggesting the possibility of an environmental reservoir. We identify ethanol as the primary non-gaseous fermentation byproduct which we hypothesize to have relevance for ENGS. Antibiotic susceptibility testing shows susceptibility to common antimicrobial agents with notable resistance to ceftriaxone. By establishing in vitro conditions for the viable culture, propagation, and storage of “Ca. S. troglodytae”, this study lays the groundwork for future infection studies to test hypotheses about pathogenic mechanisms and prevention/treatment measures for ENGS.

‘Candidatus Liberibacter asiaticus’ (CLas), the causal agent of citrus huanglongbing, is transmitted by the Asian citrus psyllid Diaphorina citri. While CLas-positive (CLas+) females exhibit increased fecundity and metabolic demands, their neuroendocrine regulation mechanisms remain unclear. We propose CLas manipulates dopamine (DA) signaling to enhance psyllid fecundity and CLas proliferation. Metabolomics revealed elevated DA in CLas+ females. Silencing DA synthesis genes and receptor DcDop2 via RNAi reduced lipid reserves, fecundity, and ovarian CLas titers. Through combined in vivo and in vitro experiments, we demonstrated that the microRNA miR-31a suppresses DcDop2 expression by binding to its 3’ untranslated region. Overexpression of miR-31a resulted in decreased DcDop2 expression and CLas titers in the ovaries, eliciting phenotypic defects akin to DcDop2 knockdown. Furthermore, DcDop2 knockdown and miR-31a overexpression reduced juvenile hormone (JH) levels and adipokinetic hormone (AKH) signaling in fat bodies and ovaries. Consequently, CLas regulates the DA-DcDop2 signaling axis to improve D. citri lipid metabolism and fecundity, while simultaneously promoting its replication. These findings reveal a coevolution between CLas proliferation and ovarian development in the insect host. This discovery enhances our understanding of the molecular interplay between plant pathogens and vector insects and offers novel targets and strategies for HLB field management.

In 2024, an infestation of corn leafhoppers, Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae), was detected in several commercial corn fields across Oklahoma (OK) (Faris et al. 2024). Corn hybrids in the infested field showed symptoms resembling maize bushy stunt, including chlorotic striping, reddening of leaves, production of multiple ears, and stunting. Visual disease incidence ranged from 25% to 100% among affected fields. Leaf samples from symptomatic plants were collected from 15 commercial corn fields across seven counties in OK (Payne, Logan, Caddo, Kay, Texas, Pottawatomie, and Grady) during September, October, and November of 2024. Each sample consisted of 3-4 symptomatic corn leaves randomly collected in each field. In addition, 43 corn leafhopper samples were collected from the symptomatic fields using handheld vacuums. Each corn leafhopper sample consisted of a minimum of 10 corn leafhoppers per field. In the laboratory, the corn leafhoppers were identified as D. maidis based on morphological characteristics as described (Faris et al. 2024). DNA from the 15 leaf samples was extracted from the leaf midrib and blade tissues using the DNeasy® Plant Mini Kit. Insect DNA was extracted using a CTAB-based method (Gorayeb et al. 2023), with each sample consisting of five pooled insects per field. DNA samples from plants and insects were initially screened using the R16F2n/R16R2 primer pair (Gundersen and Lee, 1996) for the presence of phytoplasmas. Seventeen insect and five plant samples tested positive for phytoplasma. Subsequent phytoplasma screening was performed on insect and plant samples collected from the same fields on the same dates, comprising a total of four insect and five plant samples. To further characterize the phytoplasma, a semi-nested PCR targeting the 16S rRNA gene was performed on these samples (four insect and five plant samples) using primer pairs P1/16S-SR followed by P1A/16S-SR (Wei et al. 2021), yielding an expected amplicon of approximately 1.5 Kb. An additional gene marker, the ribosomal protein (rp) gene, was also amplified using universal primers rpF1/rpR1 (Lee et al. 1998), producing 1.2 Kb PCR amplicons. PCR products were subjected to Sanger sequencing, and 16S rRNA and rp gene sequences were deposited in GenBank under accession numbers PX927497–PX927505 and PX993703-PX993711, respectively. BLASTn analysis of the 16S rRNA sequences showed 99.14–99.93% nucleotide identity with reference strains of ‘Candidatus Phytoplasma asteris’ associated with maize bushy stunt (accessions MW578284 and CP015149). Similarly, the rp gene sequences shared 99.91–100% nucleotide identity with the same reference strains. Using the iPhyClassifier tool (Zhao et al. 2013), the 16S rRNA gene sequences were classified within 16Sr group I, subgroup B, with a similarity coefficient of 1.0 (AP006628). The pairwise comparison and subsequent phylogenetic analysis showed that the OK isolates clustered within the 16SrI-B clade. This finding represents the first report of a 16SrI-B phytoplasma (‘Candidatus Phytoplasma asteris’) associated with maize bushy stunt in OK. Although currently classified as ‘Candidatus Phytoplasma asteris’, a proposal to establish a novel phytoplasma species, ‘Candidatus Phytoplasma zeae’, has been made based on ecological distinctiveness, vector specificity, whole-genome comparisons, and community consensus (Pellegrinetti et al. 2025).