Publications

4039

Citrus HLB, caused by Candidatus Liberibacter asiaticus (CLas), is the most devastating citrus disease worldwide. Usually 10% of total genes in bacteria are regulatory genes, but only 2% of CLas genes encode transcriptional factors. Here, 20 transcriptional regulators were predicted including eight genes (lsrB, ldtR, rem, visR, visN, ctrA, mucR, pelD, and atoC) directly or indirectly involved in regulating motility, and five genes (i.e., rpoH, prbP, phrR, rirA, and lsrB) involved in oxidative stress response. We demonstrated that rem, lsrB, and visNR of CLas can complement the corresponding mutants of S. meliloti in their reduced motility. We further investigated traits controlled by Rem in S. meliloti and CLas using RNA-seq analyses of rem mutant vs. complementation strains with remSmc or remLas. Transcriptomic analysis showed RemLas significantly regulates the expression of genes in S. meliloti, which was used to infer its regulation of CLas genes by identification of homologous genes. We found Rem is involved in regulating motility, chemotaxis, transporters, and oxidative phosphorylation in S. meliloti and regulating flagellar and transporter genes in CLas. Among the 39 putative RemLas-regulated genes in CLas, 16 contain Rem binding motif, including 10 genes involved in flagellar assembly. Taken together, this study offers valuable insights regarding regulatory genes of CLas with many of them involved in regulating motility and oxidative stress response. The regulation of flagellar genes by Rem in CLas unravels critical information regarding motility in CLas infection of hosts.

A Gram-stain-negative, aerobic and rod-shaped bacterium, designated as HZG-20T, was isolated from a tidal flat in Zhoushan, Zhejiang Province, China. The 16S rRNA sequence similarities between strain HZG-20T and Pikeienuella piscinae RR4-56T, Coraliihabitans acroporae NNCM2T, Parvibaculum indicum P31T and Zhengella mangrovi X9-2-2T were 98.9, 91.7, 91.0 and 91.0%, respectively. Colonies of strain HZG-20T were 1.4 mm in diameter, milky white, round, smooth and convex after cultivating on marine agar at 30 °C for 48 h. Cells were catalase and oxidase-negative. Growth occurred at 15–37 ℃ (optimum, 28 ℃), pH 5.0–9.0 (optimum, pH 6.0–8.0) and with 0–8% (w/v) NaCl (optimum, 1–3%). It contained Menaquinone-8 (H2) as the sole respiratory quinone, and C16:0 (11.8–13.6%), C18:1  ω9c (6.8–13.3%) and C15:0 anteiso (10.9–27.7%) as the major cellular fatty acids. The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, one unidentified phospholipid, one unidentified aminolipid, one unidentified phosphoglycolipid, two unidentified glycolipids (GL1–GL2) and three unidentified lipids (L1–L3). The genome of strain HZG-20T was 3 835 886 bp in length, comprised 3746 protein-coding genes, with DNA G+C content of 67.1 mol%. The phylogenetic and phylogenomic trees indicated that strain HZG-20T formed an independent and stable clade with P. piscinae RR4-56T. However, the average nucleotide identity, digit DNA–DNA hybridization and average amino acid identity values between strain HZG-20T and P. piscinae RR4-56T, C. acroporae NNCM2T, P. indicum P31T and Z. mangrovi X9-2-2T were 81.6, 71.1, 68.7 and 69.5%; 23.0, 18.5, 17.9 and 17.5%; and 78.2, 56.8, 56.5 and 61.9%, respectively, together with distinct chemotaxonomic features, indicating strain HZG-20T should not be assigned to known genera. As a result, a novel species of a novel genus within the family Paracoccaceae, designated as Paludibacillus litoralis gen. nov., sp. nov., was proposed. The type strain is HZG-20T (MCCC 1K08468T=KCTC 82692T).

AbstractThis study reports the draft genome ofCandidatusPhytoplasma pyri strain P1, isolated from Argentina, marking the first global sequencing of this species. The genome assembly consisted of 16 contigs, with a total length of 575,431 bp, a GC content of 20.35%, and 125X coverage. A total of 536 genes were annotated, including those related to metabolism, genetic information processing, and signaling. Phylogenetic analysis placed ‘CandidatusPhytoplasma pyri’ within the 16SrX group, supporting its classification as a distinct species from ‘CandidatusPhytoplasma mali’ and ‘CandidatusPhytoplasma prunorum’, despite their close evolutionary proximity. The investigation also identified 17 secreted proteins, including homologs of known effectors such as SAP39 and SAP41, as well as conserved proteins associated with virulence mechanisms. A homologue of the Imp immunodominant membrane protein was also characterized, revealing conserved gene organization across related strains. These findings contribute to the understanding of ‘CandidatusPhytoplasma pyri’ pathogenic and provide valuable genomic data for future research. This study highlights the importance of expanding phytoplasma genomics, as it provides a crucial first step in understanding ‘CandidatusPhytoplasma pyri’ and its role in plant pathology

ABSTRACT The complete genome of “ Candidatus Phytoplasma solani” GOE was obtained from the infected vector Pentastiridius leporinus by single-molecule real-time sequencing. This 16SrXII-P phytoplasma is associated with the economically important sugar beet disease “syndrome basses richesses.” The genome sequence is an essential resource for diagnosis and understanding pathogen–host interaction.

An ongoing outbreak of X-Disease, associated with ‘Candidatus Phytoplasma pruni’ has resulted in severe economic losses for cherry and stone fruit growers in the U.S. Pacific Northwest in the last decade. Given that this pathogen is transmitted by polyphagous leafhopper species, primarily Colladonus montanus ssp. reductus and C. geminatus in the PNW, alternative plant hosts present a significant management concern. Here we surveyed phytoplasma incidence in non-Prunus plants found in and around stone fruit orchard borders and compared these results to the leafhopper feeding patterns through gut content analysis. We confirmed ‘Ca. P. pruni’ infection in 21 plant species from 15 families. Of these, 15 species were commonly found in the diets of phytoplasma-carrying leafhoppers. Due to the abundance of common species, including Taraxacum, Malva, and Trifolium spp., alternative hosts were found across all growing seasons, although ‘Ca. P. pruni’ titer was low (<102 cells) in most of these hosts. No geographic patterns were identified, instead phytoplasma incidence and spread at individual orchards was related to the management of annual and biennial host species, thus removing preferred leafhopper feeding hosts. These data suggest alternative host removal, along with removal of infected trees, is an effective means of slowing disease spread.

ABSTRACTThis study explores the metabolic implications of dual substrate uptake in“Candidatus Accumulibacter”, focusing on the co-consumption of volatile fatty acids and amino acids under conditions typical of enhanced biological phosphorus removal (EBPR) systems. Combining batch tests from highly enriched “Ca.Accumulibacter” cultures with conditional flux balance analysis (cFBA) predictions, we demonstrated that co-consumption of acetate and aspartate leads to synergistic metabolic interactions, lowering ATP loss compared to individual substrate consumption. The metabolic synergy arises from the complementary roles of acetate and aspartate uptake: acetate uptake provides acetyl-CoA to support aspartate metabolism, while aspartate conversion generates NADH, reducing the need for glycogen degradation during acetate uptake. We termed this type of metabolic interaction as reciprocal synergy. We further expanded our predictions to uncover three types of interactions between catabolic pathways when substrates are co-consumed by “Ca.Accumulibacter”: (i) neutral, (ii) one-way synergistic and (iii) reciprocal synergistic interactions. Our results highlight the importance of network topology in determining metabolic interactions and optimizing resource use. These findings provide new insights into the metabolism “Ca.Accumulibacter” and suggest strategies for improving EBPR performance in wastewater treatment plants, where the influent typically contains a mixture of organic carbon compounds.SynopsisThis research demonstrates how dual substrate uptake by “Ca.Accumulibacter” enhances metabolic efficiency in EBPR by reducing global ATP losses through optimization of storage polymer usage.

Small, obligately anaerobic strains 13CB8CT, 13CB11CT, 13CB18CT and 13GAM1GT were isolated from a faecal sample in a patient with Parkinson’s disease with a history of duodenal resection. After conducting a comprehensive polyphasic taxonomic analysis including genomic analysis, we propose the establishment of one new genus and four new species. The novel bacteria are Desulfovibrio falkowii sp. nov. (type strain JCM 36128T = DSM 116810T), Porphyromonas miyakawae sp. nov. (type strain JCM 36129T = DSM 116947T), Mediterraneibacter flintii sp. nov. (type strain JCM 36130T = DSM 116866T) and Owariibacterium komagatae gen. nov. sp. nov. (type strain JCM 36131T = DSM 116982T), respectively.