Publications

4526

AbstractGlyphosate is widely used as a herbicide, but recent studies begin to reveal its detrimental side effects on animals by targeting the shikimate pathway of associated gut microorganisms. However, its impact on nutritional endosymbionts in insects remains poorly understood. Here, we sequenced the tiny, shikimate pathway encoding symbiont genome of the sawtoothed grain beetleOryzaephilus surinamensis. Decreased titers of the aromatic amino acid tyrosine in symbiont-depleted beetles underscore the symbionts’ ability to synthesize prephenate as the precursor for host tyrosine synthesis and its importance for cuticle sclerotization and melanization. Glyphosate exposure inhibited symbiont establishment during host development and abolished the mutualistic benefit on cuticle synthesis in adults, which could be partially rescued by dietary tyrosine supplementation. Furthermore, phylogenetic analyses indicate that the shikimate pathways of many nutritional endosymbionts likewise contain a glyphosate sensitive 5-enolpyruvylshikimate-3-phosphate synthase. These findings highlight the importance of symbiont-mediated tyrosine supplementation for cuticle biosynthesis in insects, but also paint an alarming scenario regarding the use of glyphosate in light of recent declines in insect populations.

Human head and body lice host the obligate endosymbiotic bacterium “ Candidatus Riesia pediculicola.” In this announcement, we describe the complete genome sequence of a “ Ca. Riesia pediculicola” strain isolated from the human head louse, Pediculus humanus subsp. capitis . The inter- and intraspecific variations of endosymbiont genomes were investigated, and this strain was found to display high-level variations in its genome.

Abstract Whole‐genome sequencing of “ Candidatus Liberibacter asiaticus” (Las) indicated some polymorphic gene regions enabling the molecular characterization of this bacterium. Although the population diversity of Las in China has been previously studied, no reports have used a combination of a prophage region and short tandem repeat (STR) loci for phylogenetic relationship characterization. In this study, we investigated the genetic diversity and structure of 667 Las strains from nine provinces in southern China using multiple genetic loci including three type‐specific prophage loci, two STR loci, and a miniature inverted‐repeat transposable element (MITE) region. The results indicated that the genetic diversity varied according to the gene loci used. The prophage regions, including the MITEs, revealed significant genetic differences of Las populations in Yunnan and Guizhou from other provinces, while the STR loci only indicated a difference of Las population in Guizhou from those of other provinces. In particular, the Las population shown to be diverse in Jiangxi at the CLIBASIA_01215_STR locus was not diverse when measured using the other loci. Considering all loci, the Las populations from Yunnan and Guizhou were different, those from Guangdong and Guangxi were complex, while the Las population in Jiangxi was comparatively simple. Las populations from five neighbouring provinces, including Guangdong, Guangxi, Hunan, Fujian, and Jiangxi were grouped in a big cluster. The Las population structure changed with age according to the prophage type. This study evaluated the method used for studying the molecular diversity of Las populations and provided more detailed information on the geographical origin and epidemic trend of Chinese Las populations.

Citrus, mainly mandarin (Citrus reticulata Blanco), is an economically important fruit crop in Bhutan. Despite having favorable agroclimatic conditions for citrus cultivation, the early decline of fruit-bearing orchards coupled with low crop productivity is a major concern among citrus growers. During a recent survey, an association of ‘Candidatus Liberibacter asiaticus’ (citrus greening) and citrus tristeza virus (CTV), either singly or as mixed infections in declined citrus trees, was recorded in all four major citrus-growing districts (Tsirang, Dagana, Zhemgang, and Sarpang). Using PCR-based diagnosis, a higher incidence of citrus greening (27.45%) and tristeza (70.58%) was observed in symptomatic field samples. Detection and characterization of ‘Ca. L. asiaticus’ was performed based on the 16S ribosomal DNA, prophage gene, 50S ribosomal rplA-rplJ gene, and tandem repeats of the CLIBASIA_01645 locus. Similarly, the coat protein, p23, and p18 genes were used as genetic markers for the detection and characterization of Bhutanese CTV. The ‘Ca. L. asiaticus’ isolates from Bhutan segregated into classes II and III based on the CLIBASIA_01645 locus, analogous to Indian isolates from the northeast region and Term-A based on the CLIBASIA_05610 locus. CTV isolates of Bhutan were observed as closely related to the VT strain, which is considered to be the most devastating. To the best of our knowledge, this is the first study on molecular characterization of ‘Ca. L. asiaticus’ and CTV isolates and their association with citrus decline in Bhutan.

AbstractXylitol was first applied to enhance nitrogen removal from saline wastewater through “Candidatus Brocadia sinica”‐dominated anammox process under low temperature. The reactor was maintained at 15°C, and the salinity of wastewater was 35 g/L. Ammonium removal rate (ARR) and nitrite removal rate (NRR) were stable at around 0.27 kg/(m3 d) without xylitol addition. As an osmotic pressure regulator and cryoprotective agent, optimal ARR and NRR were 0.51 kg/(m3 d) and 0.63 kg/(m3 d) at 0.3 mM xylitol. At the addition of 1 mM high‐dosage xylitol, there existed dissimilatory reduction in nitrate to ammonium nitrogen and heterotrophic denitrification in the reactor. Remodified logistic model was suitable to simulate removal process with xylitol addition. As a result, xylitol dose should be controlled within 0.3 mM, which greatly promoted the nitrogen removal from saline wastewater under low temperature.Practitioner points Xylitol could be used as osmotic pressure regulator and cryoprotective agent to enhance nitrogen removal. The optimal dose was achieved at 0.3 mM xylitol for “Candidatus Brocadia sinica” in low‐temperature saline wastewater. High‐dosage xylitol could interfere with nitrogen removal efficiency due to the presence of DNAR and HB. Remodified logistic model was suitable for the analysis and prediction of nitrogen removal process with xylitol addition.