Publications

4865

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).

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 the primary and most destructive disease affecting citrus, caused by a pathogen transmitted by an insect vector, Diaphorina citri. There are no curative methods for the disease, and rapid and accurate methods are needed for early detection in the field, even before symptoms appear. These will facilitate the faster removal of infected trees, preventing the spread of the bacteria through commercial citrus orchards.RESULTSIt was possible to determine ranges of hyperspectral bands that demonstrated significant differences in relative reflectance between treatments consisting of healthy and infected plants from the first days of evaluation, when plants infected with ‘Candidatus Liberibacter asiaticus’ (CLas) were still in the asymptomatic stage of the disease. From the Week 2 of evaluation [58 days after infection (DAI) of plants] until the last week, spectral differences were detected in the red edge region (660–750 nm). From the Week 6 onwards (86 DAI), spectral differences between healthy and symptomatic plants were observed in bands close to the visible region (520–680 nm).CONCLUSIONSpectral differences were detected in the leaves of C. sinensis infected by CLas before the appearance of symptoms, making it feasible to use the hyperspectral sensor to monitor the disease. Our results indicate the need for future studies to validate the use of hyperspectral sensors for managing and detecting HLB in commercial citrus orchards, contributing to the integrated management of the disease. © 2024 Society of Chemical Industry.

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.

AbstractBACKGROUNDThe brown marmorated stink bug Halyomorpha halys has become an invasive insect pest of many crops. A promising control strategy to manage the proliferation of H. halys is based on the suppression of its obligate and vertically transmitted uncultivated symbiotic bacterium Candidatus Pantoea carbekii through surface‐sterilization of H. halys eggs. Indeed, the application of antimicrobial formulations on the eggs of H. halys could cause mortality of endosymbiont and consequently of newly emerged nymphs.In this study, a microbial live/dead assay was applied directly on H. halys eggs to evaluate Ca. P. carbekii loss of viability after treatments with seven commercial formulations including fungicides (copper hydroxide, sulphur, sweet orange essential oil) and plant biostimulants (flavonoids and chestnut tannin extract) compared with two disinfectants for civil and industrial use (sodium hypochlorite/hydrated sodium/tetraborate decahydrate and peracetic acid/hydrogen peroxide). Impact of mode of application was also evaluated, as surface treatment of egg masses was performed through spraying and dipping in laboratory conditions. Antimicrobial activity data were finally complemented with observations of egg hatching and vitality of the nymphs.RESULTSThe optimization of live/dead staining is useful for evaluating Ca. P. carbekii mortality directly on eggs, providing a rapid and reliable culture‐independent approach. Sodium hypochlorite, copper, sulphur, tannins and sweet orange essential oil showed an antimicrobial effect against Ca. P. carbekii and a H. halys egg hatching reduction and nymph's vitality.CONCLUSIONSThe antimicrobial and insecticidal effects of these commercial products should be further studied to assess their in‐field efficiency as well as the impact of these substances on non‐target organisms. The approach followed in this study could be considered a robust pipeline of analyses to evaluate the effectiveness of antimicrobial eco‐friendly compounds in symbiotic control of H. halys. © 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’.