Publications

4728

A motile, rod-shaped and anaerobic strain WK13T was isolated from a secondary root canal infection of a human tooth. WK13T cells were Gram-stain-negative, catalase-positive and oxidase-negative. The major fatty acids (≥ 5.0%) were C16 : 0, C18 : 0, C16 : 1  ω7c, C18 : 1  ω9c and C18 : 2  ω6,9c. The DNA G+C content was 57.94 mol%. The major polar lipids were phosphatidylethanolamine, phosphatidylserine, diphosphatidylglycerol, phosphatidylcholine and lysophosphatidylcholine. There were no respiratory quinones detectable. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain WK13T belongs to the class Betaproteobacteria. WK13T showed a 93.6% and 93.5% 16S rRNA gene sequence similarity to the most closely related cultured species, Propionivibrio pelophilus strain DSM 12018T and Propionivibrio dicarboxylicus strain DSM 5885T, respectively. On the basis of physiological and biochemical data, the isolate is considered to represent a novel species of a new genus in the class Betaproteobacteria, for which we propose the name Dentiradicibacter hellwigii gen. nov., sp. nov. The type strain is WK13T (=DSM 112713T=NCTC 14938T).

This study describes a Gram-stain-negative, rod-shaped, facultatively anaerobic bacterial species isolated from the octocoral Litophyton sp. inhabiting the live coral aquarium at Oceanário de Lisboa in Portugal. Four strains, NE35, NE40T, NE41 and NE43, were classified into the genus Endozoicomonas by means of 16S rRNA gene and whole-genome sequence homologies. We then performed phylogenetic, phylogenomic and biochemical analyses to examine their novel species status within the Endozoicomonas genus, based on comparisons with the designated novel type strain NE40T. The closest 16S rRNA gene relatives to strain NE40T are Endozoicomonas montiporae CL-33T (98.2%), Endozoicomonas euniceicola EF212T (97.6%) and Endozoicomonas gorgoniicola PS125T (97.2%). The four strains show genome-wide average nucleotide identity scores above the species level cut-off (95%) with one another and below the cut-off with all Endozoicomonas type strains with publicly available genomes. Digital DNA–DNA hybridization further supported the classification of the strains as a novel species, showing values below 70% when compared with other Endozoicomonas type strains. The DNA G+C content of NE40T was 49.0 mol%, and its genome size was 5.45 Mb. Strain NE40T grows from 15 to 37 °C, with 1–5% (w/v) NaCl, and between pH 6.0 and 8.0 in marine broth and shows optimal growth at 28–32 °C, 2–3% NaCl and pH 7.0–8.0. The predominant cellular fatty acids are summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c), summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c), C16 :0 and C14 :0. Strain NE40T presents oxidase, catalase and β-galactosidase activities and can reduce nitrates to nitrites and degrade cellulose, chitin, agarose and xylan. Based on the polyphasic approach employed in this study, we propose the novel species name Endozoicomonas lisbonensis sp. nov. (type strain NE40T=DSM 118084T=UCCCB 212T).

Understanding the characteristics of microbes during long-term space missions is essential for safeguarding the health of astronauts and maintaining the functionality of spacecraft. In this study, a Gram-positive, aerobic, spore-forming, rod-shaped strain JL1B1071T was isolated from the surface of hardware on the China Space Station. This strain belongs to the genus Niallia, with its closest relative being Niallia circulans ATCC 4513T. The genome of JL1B1071T is 5 166 230 bp in size, with a G+C content of 35.6 mol%. The average nucleotide identity and digital DNA–DNA hybridization values between JL1B1071T and N. circulans ATCC 4513T are 83.3 and 27.5%, respectively, both below the recommended thresholds for species delineation. The major cellular fatty acids were anteiso-C15:0 and iso-C15:0. The major quinone was menaquinone-7 (MK-7). Notably, strain JL1B1071T demonstrates a unique ability to hydrolyse gelatin, suggesting that it can utilize gelatin as a substrate in nutrient-limited environments. Genomic analysis of JL1B1071T revealed two conserved signature indels in the GAF domain-containing protein and DNA ligase D protein, which are specific to the genus Niallia. Additionally, structural and functional differences in proteins BshB1 and SplA were identified, which may enhance biofilm formation, oxidative stress response and radiation damage repair, thereby aiding its survival in the space environment. Based on phenotypic, physiological and chemotaxonomic characteristics, as well as genome annotation, strain JL1B1071T was considered a novel species within the genus Niallia and is proposed to be named Niallia tiangongensis sp. nov. The type strain is JL1B1071T (=GDMCC 1.4642=KCTC 43715).

AbstractBACKGROUNDHuanglongbing (HLB) is a systemic disease of citrus caused by the bacterial pathogen Candidatus Liberibacter asiaticus (CLas) that limits citrus production worldwide. CLas is an obligate bacterial pathogen that multiplies in citrus trees and in the insect vector, the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. There is no cure for HLB currently and broad‐spectrum antibiotics represent one possible therapeutic against disease symptoms. Single‐stranded nucleic acid analogs, 2′‐deoxy‐2’‐Fluoro‐β‐D‐arabinonucleic antisense oligonucleotides (FANA ASOs), can modulate gene expression by enzymatic degradation or steric blocking of an RNA target. FANA ASOs recognize and bind to specific RNA forms, including mRNA, miRNA and long noncoding RNA, through complementary base‐pairing.RESULTSInjection of oxytetracycline (OTC) into mature citrus trees with HLB ameliorated symptoms of disease, increased fruit yield and quality of juice as compared with that produced by noninjected controls. Injection of trees with FANA ASOs reduced CLas abundance but did not improve fruit yield and quality above control levels at the injection dosage tested. Reduced pathogen relative abundance following OTC injection was coincident with lower CLas acquisition and inoculation by laboratory deployed and wild‐type D. citri collected from the field, respectively. However, injections of FANA ASOs did not consistently reduce CLas transmission as compared with noninjected controls.CONCLUSIONSTrunk injection of OTC may be useful in management of HLB by reducing CLas infection in trees and disrupting transmission. However, more research is needed to verify the potential usefulness of FANA ASOs. Optimizing FANA ASO dosage in trees and exploring the potential of multiplex FANA ASOs that simultaneously target multiple mRNAs could possibly enhance their efficacy against CLas. © 2024 Society of Chemical Industry.

ABSTRACT Biogas reactors operating at elevated ammonia levels are commonly susceptible to process disturbances, further augmented at thermophilic temperatures. The major cause is assumed to be linked to inhibition followed by an imbalance between different functional microbial groups, centred around the last two steps of the anaerobic digestion, involving acetogens, syntrophic acetate oxidisers (SAOB) and methanogens. Acetogens are key contributors to reactor efficiency, acting as the crucial link between the hydrolysis and fermentation steps and the final methanogenesis step. Their major product is acetate, at high ammonia levels further converted by SAOB and hydrogenotrophic methanogens to biogas. Even though these functionally different processes are well recognised, less is known about the responsible organism at elevated temperature and ammonia conditions. The main aim of this study was to garner insights into the penultimate stages in three thermophilic reactors (52°C) operated under high ammonia levels (FAN 0.7–1.0 g/L; TAN 3.6–4.4 g/L). The primary objective was to identify potential acetogens and SAOBs. Metagenomic data from the three reactors were analysed for the reductive acetyl‐CoA pathway (Wood–Ljungdahl Pathway) and glycine synthase reductase pathway. The results revealed a lack of true acetogens but uncovered three potential SAOB candidates that harbour the WLP, ‘ Candidatus Thermodarwinisyntropha acetovorans’, ‘ Candidatus Thermosyntrophaceticus schinkii’, ‘ Candidatus Thermotepidanaerobacter aceticum’, and a potential lipid‐degrader ‘ Candidatus Thermosyntrophomonas ammoiaca’.

The occurrence of ‘Candidatus Liberibacter’ spp. and ‘Ca. Phytoplasma’ spp. associated with blotchy mottle symptoms poses challenges to huanglongbing (HLB) diagnosis using molecular techniques. The ability to detect multiple targets simultaneously and specifically is a key aspect met by quantitative PCR (qPCR). A set of primers and hydrolysis probes useful in either single or multiplex reactions for the detection and quantification of HLB-associated bacteria were developed. Sequences from conserved genes of the ribosomal proteins for Liberibacter and phytoplasma circumvent the lack of specificity and cross-reactivity problems related to 16Sr DNA gene amplification, allowing precise and specific detection of HLB-associated bacteria in citrus and in the Liberibacter vector, Diaphorina citri. The triplex reaction exhibited high quality and precision as a robust tool for quantifying ‘Ca. L. asiaticus’ (CLas), ‘Ca. L. americanus’ (CLam), and 16Sr IX phytoplasma. Triplex qPCR showed consistent results and comparable sensitivity to the ribonuclease reductase test, although quantification cycle (Cq) values were higher when compared with 16SrDNA qPCR. Detection tests using field samples indicate that the qPCR triplex can identify HLB-associated bacteria in samples with varying levels of symptoms, ranging from typical to asymptomatic. Assessment of field samples from growers indicated more than 78.6% had Cq lower than 35.0, below the cutoff established for qPCR reactions used in this work. qPCR triplex is a safe, specific, and sufficiently sensitive technique for detecting CLas, CLam, and 16Sr IX phytoplasma simultaneously, in both citrus and D. citri samples. Its application is of importance in assisting growers in making decisions for HLB management.