Publications

4616

AbstractHere a stable glycogen accumulating organisms (GAOs) system was operated by anaerobic–aerobic mode in the sequencing batch reactor. We focused on the metabolic mechanisms of PHAs storage from GAOs. Our system showed the classic characteristic of glycogen accumulating metabolism (GAM). Glycogen consumption was followed by acetic acid uptake to synthesize poly-β-hydroxyalkanoates (PHAs) during the anaerobic period, and glycogen was synthesized by PHAs degradation in the aerobic stage. Microbial community structure indicated that Candidatus Contendobacter was the most prevalent GAOs. We found that the ethylmalonyl-CoA (EMC) pathway was the crucial pathway supplying the core substance propionyl-CoA for poly-β-hydroxyvalerate (PHV) synthesis in Candidatus Contendobacter. All genes in EMC pathway were mainly located in Candidatus Contendobacter by gene source analysis. The key genes expression of EMC pathway increased with Candidatus Contendobacter enrichment, further validating that propionyl-CoA was synthesized by Candidatus Contendobacter predominantly via EMC pathway. Our work revealed the novel mechanisms underlying PHV synthesis through EMC pathway and further improved the intercellular storage metabolism of GAOs.

Abstract The previously uncultured phylum “Candidatus Eremiobacterota” is globally distributed and often abundant in oligotrophic environments. Although it includes lineages with the genetic potential for photosynthesis, one of the most important metabolic pathways on Earth, the absence of pure cultures has limited further insights into its ecological and physiological traits. We report the first successful isolation of a “Ca. Eremiobacterota” strain from a fumarolic ice cave on Mt. Erebus volcano (Antarctica). Polyphasic analysis revealed that this organism is an aerobic anoxygenic photoheterotrophic bacterium with a unique lifestyle, including bacteriochlorophyll a production, CO2 fixation, a high CO2 requirement, and phototactic motility using type IV-pili, all of which are highly adapted to polar and fumarolic environments. The cells are rods or filaments with a vesicular type intracytoplasmic membrane system. The genome encodes novel anoxygenic Type II photochemical reaction centers and bacteriochlorophyll synthesis proteins, forming a deeply branched monophyletic clade distinct from known phototrophs. The first cultured strain of the eighth phototrophic bacterial phylum which we name Vulcanimicrobium alpinus gen. nov., sp. nov. advances our understanding of ecology and evolution of photosynthesis.

AbstractBACKGROUNDAsian citrus psyllid (ACP), also known as Diaphorina citri, is the natural vector of Candidatus Liberibacter asiaticus (CLas), which is responsible for Huanglongbing (HLB), a devastating citrus disease. Previously, the pathogen was successfully excluded from diseased citrus plants by using the indigenous endophyte Bacillus subtilis L1‐21. However, the pathogen elimination and colonization potential of B. subtilis L1‐21 in the carrier vector ACP, as well as the recruitment of native microbial communities of psyllid in the presence of endophytes, are still unknown.RESULTSInitially, we suggested that endophyte L1‐21 reduced the CLas copies in ACP from 6.58 × 106 to 5.04 × 104 per insect after 48 h, however, the pathogen copies remained stable in the negative control. The endophyte was stable for 48 h after application. Among the bacterial genera those highlighted in ACP were Candidatus Liberibacter, Pseudomonas, Candidatus Profftella, Methylobacterium‐Methylorubrum, Pantoea, Curtobacterium, Wolbachia, Actinomycetospora, and Bacillus. Interestingly, B. subtilis L1‐21 easily colonizes the midgut of ACP but cannot be detected in eggs. When ACP with endophyte L1‐21 was allowed to feed on new citrus leaves, the highest colonization was observed. We also found that psyllids carrying endophyte L1‐21 after feeding on citrus leaves reduced the CLas copies in leaves on the 0, 3rd and 5th day from 8.18 × 10,4 2.6 × 10,3 and 0 pathogen copies/g fresh midvein, respectively.CONCLUSIONSWe propose that B. subtilis L1‐21 is a native endophyte in citrus and psyllid, which efficiently reduces the CLas pathogen in both citrus and psyllids, provides a more protective effect by increasing the number of cultivable endophytes, and successfully colonizes the midgut of ACP. © 2022 Society of Chemical Industry.

AbstractThe endosymbiotic Wolbachia is one of the most common intracellular bacteria known in arthropods and nematodes. Its ability for reproductive manipulation can cause unequal inheritance to male and female offspring, allowing the manipulator to spread, but potentially also impact the evolutionary dynamics of infected hosts. Estimated to be present in up to 66% of insect species, little is known about the phenotypic impact of Wolbachia within the order Coleoptera. Here, we describe the reproductive manipulation by the Wolbachia strain wSur harboured by the sawtoothed grain beetle Oryzaephilus surinamensis (Coleoptera, Silvanidae), through a combination of genomics approaches and bioassays. The Wolbachia strain wSur belongs to supergroup B that contains well‐described reproductive manipulators of insects and encodes a pair of cytoplasmic incompatibility factor (cif) genes, as well as multiple homologues of the WO‐mediated killing (wmk) gene. A phylogenetic comparison with wmk homologues of wMel of Drosophila melanogaster identified 18 wmk copies in wSur, including one that is closely related to the wMel male‐killing homologue. However, further analysis of this particular wmk gene revealed an eight‐nucleotide deletion leading to a stop‐codon and subsequent reading frame shift midsequence, probably rendering it nonfunctional. Concordantly, utilizing a Wolbachia‐deprived O. surinamensis population and controlled mating pairs of wSur‐infected and noninfected partners, we found no experimental evidence for male‐killing. However, a significant ~50% reduction of hatching rates in hybrid crosses of uninfected females with infected males indicates that wSur is causing cytoplasmic incompatibility. Thus, Wolbachia also represents an important determinant of host fitness in Coleoptera.

Abstract Background The human louse (Pediculus humanus) is a haematophagous ectoparasite that is intimately related to its host. It has been of great public health concern throughout human history. This louse has been classified into six divergent mitochondrial clades (A, D, B, F, C and E). As with all haematophagous lice, P. humanus directly depends on the presence of a bacterial symbiont, known as “Candidatus Riesia pediculicola”, to complement their unbalanced diet. In this study, we evaluated the codivergence of human lice around the world and their endosymbiotic bacteria. Using molecular approaches, we targeted lice mitochondrial genes from the six diverged clades and Candidatus Riesia pediculicola housekeeping genes. Methods The mitochondrial cytochrome b gene (cytb) of lice was selected for molecular analysis, with the aim to identify louse clade. In parallel, we developed four PCR primer pairs targeting three housekeeping genes of Candidatus Riesia pediculicola: ftsZ, groEL and two regions of the rpoB gene (rpoB-1 and rpoB-2). Results The endosymbiont phylogeny perfectly mirrored the host insect phylogeny using the ftsZ and rpoB-2 genes, in addition to showing a significant co-phylogenetic congruence, suggesting a strict vertical transmission and a host–symbiont co-speciation following the evolutionary course of the human louse. Conclusion Our results unequivocally indicate that louse endosymbionts have experienced a similar co-evolutionary history and that the human louse clade can be determined by their endosymbiotic bacteria. Graphical Abstract

Huanglongbing (HLB) is a destructive citrus disease that affects citrus production worldwide. ‘Candidatus Liberibacter asiaticus’ (CLas), a phloem-limited bacterium, is the associated causal agent of HLB. The current standard for detection of CLas is real-time quantitative polymerase chain reaction (qPCR) using either the CLas 16S rRNA gene or the ribonucleotide reductase (RNR) gene-specific primers/probe. qPCR requires well-equipped laboratories and trained personnel, which is not convenient for rapid field detection of CLas-infected trees. Recombinase polymerase amplification (RPA) assay is a fast, portable alternative to PCR-based diagnostic methods. In this study, an RPA assay was developed to detect CLas in crude citrus extracts utilizing isothermal amplification, without the need for DNA purification. Primers were designed to amplify a region of the CLas RNR gene, and a fluorescent labeled probe allowed for detection of the amplicon in real-time within 8 mins at 39°C. The assay was specific to CLas, and the sensitivity was comparable to qPCR, with a detection limit cycle threshold of 34. Additionally, the RPA assay was combined with a lateral flow device for a point-of-use assay that is field deployable. Both assays were 100% accurate in detecting CLas in fresh citrus crude extracts from leaf midribs and roots from five California strains of CLas tested in the Contained Research Facility in Davis, California. This assay will be important for distinguishing CLas-infected trees in California from those infected by other pathogens that cause similar disease symptoms and can help control HLB spread.