Publications

4508

AbstractCandidatus Branchiomonas cysticola is recognized as the most prevalent bacterial agent causing epitheliocystis in Atlantic salmon (Salmo salar). Based on its partial 16S rRNA sequence, the bacterium has previously been found to be a member of Burkholderiales in the class Betaproteobacteria. Multilocus Sequence Analysis (MLSA) of the bacterium and 60 type strains of Betaproteobacteria using newly identified housekeeping genes (dnaK, rpoC, and fusA) and ribosomal subunit sequences (16S and 23S), instead supported the bacterium’s affiliation to Nitrosomodales. Taxonomic rank normalization by Relative Evolutionary Divergence (RED) showed the phylogenetic distinction between Cand. B. cysticola and its closest related type strain to be at the family level. A novel bacterial family named Branchiomonaceae has thus been proposed to include a monophyletic clade of Betaproteobacteria exclusively associated with epitheliocystis in fish.

AbstractA 9‐year‐old neutered male cat, previously test‐positive for feline immunodeficiency virus (FIV), was presented with an history of vomiting, hyporexia, and weight loss. Panleukopenia was identified on complete blood counts, and bone marrow evaluation revealed ineffective granulocytic hyperplasia and rare neutro‐, erythro‐, and rubriphagocytosis. Prednisolone was initiated with no response, and progression to pancytopenia occurred. On abdominal ultrasonographic examination, splenomegaly was present. PCR testing was positive for Candidatus Mycoplasma haemominutum and IgG antibodies against Toxoplasma gondii were detected (titer 1:2560). Treatment with antibiotics, feline recombinant interferon‐ω, chlorambucil, mycophenolate, and raltegravir was implemented with no clinical improvement, and splenectomy was performed. Cytologic evaluation of splenic aspirates revealed exuberant neutro‐, erythro‐, and rubriphagocytosis. Histopathology of the spleen also showed many erythrophagocytic macrophages with no evidence of malignancy, and a diagnosis of hemophagocytic syndrome (HS) was made. The WBC count and hematocrit reached reference values 1 day and 3 months, respectively, after splenectomy. The cat was treated with cyclosporine and lomustine. Disease progression led to the development of septic hepatitis, and the cat was euthanized. To our knowledge, this is the first case of presumptive HS in cats that might have been associated with FIV, Toxoplasma gondii, and Candidatus Mycoplasma haemominutum co‐infection.

‘Candidatus Liberibacter asiaticus’ is the bacterium associated with the citrus disease known as huanglongbing (HLB). This study evaluated the influence of ‘Ca. L. asiaticus’ infection on a number of key plant physiological variables concerning photosynthesis, cell integrity, reactive oxygen species scavengers’ activity, and osmoregulation of two different species of citrus—the pomelo Citrus maxima and the mandarin C. reticulata ‘Tankan’—relative to their measured ‘Ca. L. asiaticus’ infection load. Results indicated that all measured physiological variables except soluble sugar were affected by increased ‘Ca. L. asiaticus’ infection titers, wherein the variety C. maxima proved overall more resistant than C. reticulata. ‘Ca. L. asiaticus’ infection was linked in both plants to decrease in chlorophyll concentration, cell membrane permeability, and malondialdehyde, as well as increased free proline and starch contents. Chlorophyll fluorescence measurements taken 9 months after grafting the mandarin C. reticulata with ‘Ca. L. asiaticus’ scions revealed a significant decrease in the photosynthesis variables maximum photochemical quantum yield of photosystem II (PSII), effective photochemical quantum yield of PSII, and coefficient of photochemical fluorescence quenching assuming interconnected PSII antennae, whereas nonphotochemical fluorescence quenching increased significantly; C. maxima plants, on the other hand, did not show significant differences until the 12th month from infection exposure. The variables superoxide dismutase, catalase, peroxidase, and soluble protein initially increased and later decreased. In addition, progression of ‘Ca. L. asiaticus’ replication in both citrus species was accompanied by rapid changes in three reactive oxygen species scavenging enzymes in C. maxima, while the pattern was different in C. reticulata. We hypothesize that the observed interspecific differences in physiological change are related to their relative resistance against ‘Ca. L. asiaticus’ infection. These results provide a scaffold for better describing the pathogenesis, selecting the most resistant breeds, or even validating pertaining omics research; ultimately, these detailed observations can facilitate the diagnosis of ‘Ca. L. asiaticus’ infection.

AbstractMethanogenic and methanotrophic archaea produce and consume the greenhouse gas methane, respectively, using the reversible enzyme methyl-coenzyme M reductase (Mcr). Recently, Mcr variants that can activate multicarbon alkanes have been recovered from archaeal enrichment cultures. These enzymes, called alkyl-coenzyme M reductase (Acrs), are widespread in the environment but remain poorly understood. Here we produced anoxic cultures degrading mid-chain petroleum n-alkanes between pentane (C5) and tetradecane (C14) at 70 °C using oil-rich Guaymas Basin sediments. In these cultures, archaea of the genus Candidatus Alkanophaga activate the alkanes with Acrs and completely oxidize the alkyl groups to CO2. Ca. Alkanophaga form a deep-branching sister clade to the methanotrophs ANME-1 and are closely related to the short-chain alkane oxidizers Ca. Syntrophoarchaeum. Incapable of sulfate reduction, Ca. Alkanophaga shuttle electrons released from alkane oxidation to the sulfate-reducing Ca. Thermodesulfobacterium syntrophicum. These syntrophic consortia are potential key players in petroleum degradation in heated oil reservoirs.

AbstractMany Rickettsia species of the spotted fever group (SFG) cause tick‐borne diseases known as “spotted fever.” One of the candidate SFG Rickettsia species is “Candidatus Rickettsia kotlanii,” which was first detected in Haemaphysalis concinna in Hungary in 2006. However, its precise phylogenetic position in the SFG is not clear because only single‐gene sequence–based phylogenetic analyses were performed using very limited genes. Here, we present the complete genome sequences of two Japanese “Ca. R. kotlanii” isolates, which differed only by a 135 bp insertion/deletion (InDel). Using these genomes and publicly available whole genome sequences of other Rickettsia species, the precise phylogenetic position of “Ca. R. kotlanii” in Rickettsia was determined to be in a clade of the SFG. The phylogenetic relationships and average nucleotide identity of “Ca. R. kotlanii” relative to the other species indicated that “Ca. R. kotlanii” is an independent taxon in the SFG. Notably, although the genomes of the two isolates were almost identical, the isolates were obtained from different tick species in different regions and years, suggesting extremely low genomic diversity in “Ca. R. kotlanii.” While the genome of “Ca. R. kotlanii” is the smallest in the transitional group and SFG Rickettsia sequenced to date, we identified genes uniquely present or absent in “Ca. R. kotlanii,” but most were apparently degraded. Therefore, analyses of differences at the sequence (single nucleotide polymorphisms and small InDels) or gene expression level will be required to understand the functional or physiological features unique to “Ca. R. kotlanii.”

‘Candidatus Liberibacter solanacearum’ (Lso) is the causal agent of zebra chip of potato (Solanum tuberosum), which can significantly reduce potato yield. In this study, a loop-mediated isothermal amplification (LAMP) method for the detection of Lso haplotypes A and B was developed and evaluated. Two sets of LAMP primers named LAMP-A and LAMP-B were designed and tested for specificity and sensitivity. Both LAMP-A and LAMP-B were specific to Lso in in silico analysis using the Primer-Blast tool. The LAMP-A and LAMP-B could only produce positive signals from DNA mixtures of Lso-infected tomato but not from the genomic DNA of 37 nontarget plant pathogens. The sensitivity of LAMP-A and LAMP-B on Lso haplotypes A and B were tested on gBlocks and genomic DNA from Lso-infected tomato. On the genomic DNA for LAMP-A, the lowest amount of template DNA for a positive LAMP reaction was 2 to 20 ng on four haplotype A strains and 20 to 80 ng on four haplotype B strains; for LAMP-B, the lowest amount of template DNA for a positive LAMP reaction was 0.02 to 2 ng on four haplotype B strains and 20 ng to no amplification on four haplotype A strains. On gBlocks for LAMP-A, the lowest number of copies for a positive LAMP reaction was 60 on haplotype A and 600 on haplotype B; for LAMP-B, the lowest number of copies for a positive LAMP reaction was 60 on haplotype B and 600 on haplotype A. Therefore, considering the convenience of the LAMP technique, as well as the high specificity and sensitivity, the LAMP-A and LAMP-B primers can be used together to test the probable Lso-infected plant or psyllid samples to rapidly, accurately, and directly differentiate haplotypes A and B. We highly recommend this LAMP system to plant pathology practitioners and diagnostic labs for routine detection of Lso and confirmation of zebra chip disease on potato or tomato.

An updated real-time multiplex quantitative polymerase chain reaction (qPCR) assay was designed and validated for the simultaneous detection of three ‘ Candidatus Liberibacter species’ (CLsp), ‘ Ca. Liberibacter asiaticus’ (CLas), ‘africanus’ (CLaf), and ‘americanus’ (CLam), associated with the huanglongbing disease of citrus. The multiplex assay was designed based on the qPCR assay published in 2006 by Li et al., considering all available CLsp 16S rRNA gene sequences in GenBank and the MIQE guidelines and workflow for qPCR optimization, which became available after 2006. When using the updated multiplex CLsp qPCR assay compared with singleplex qPCR, no significant increase in quantitative cycle (Cq) values was detected. The specificity and sensitivity of the updated qPCR assay was optimal, and measuring the intra- and interassay variations confirmed the reproducibility and repeatability of the assay. The assay was also successfully used with a large number of diverse samples at independent laboratories in four countries, thus demonstrating its transferability, applicability, practicability, and robustness as different qPCR reaction conditions or instruments had a minor effect on Cq values. This updated multiplex CLsp qPCR assay can be used in a variety of citrus surveys, germplasm, or nursery stock programs that require different pathogen detection tools for their successful operation. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .