Endosymbiotic Bacteria Associated with the Mealy Bug, Rhizoecus amorphophalli (Hemiptera: Pseudococcidae)

Impact of diet and bacterial supplementation regimes on Orius strigicollis microbiota and life history performance

Given the growing interest in manipulating microbiota to enhance the fitness of mass-reared insects for biological control, this study investigated the impact of an artificial diet on the microbiota composition and performance of Orius strigicollis. We compared the microbiota of O. strigicollis fed on an artificial diet and moth eggs via culturing and 16S rRNA gene amplicon sequencing. Subsequently, we assessed life history traits and immune gene expression of O. strigicollis fed on the artificial diet supplemented with Pantoea dispersa OS1. Results showed that microbial diversity remained largely unaffected by the artificial diet, with similar microbiota compositions in both diet groups. OS1, a minor member of the microbiota but significantly enriched in bugs fed on the artificial diet, improved nymphal survival rates and shifted adult longevity-reproduction life history in females. Additionally, OS1 supplementation elevated the transcription of antimicrobial peptide diptericin. According to population parameters, the group receiving OS1 only during the nymphal stage showed higher population growth potential compared to the group supplemented across all life stages. These findings reveal the resilience of O. strigicollis microbiota under distinct dietary conditions and highlight the potential of using natural symbionts and specific supplementation regimes to improve Orius rearing for future biocontrol programs.

Role of gut symbionts of insect pests: A novel target for insect-pest control

Insects possess beneficial and nuisance values in the context of the agricultural sector and human life around them. An ensemble of gut symbionts assists insects to adapt to diverse and extreme environments and to occupy every available niche on earth. Microbial symbiosis helps host insects by supplementing necessary diet elements, providing protection from predators and parasitoids through camouflage, modulation of signaling pathway to attain homeostasis and to trigger immunity against pathogens, hijacking plant pathways to circumvent plant defence, acquiring the capability to degrade chemical pesticides, and degradation of harmful pesticides. Therefore, a microbial protection strategy can lead to overpopulation of insect pests, which can drastically reduce crop yield. Some studies have demonstrated increased insect mortality via the destruction of insect gut symbionts; through the use of antibiotics. The review summarizes various roles played by the gut microbiota of insect pests and some studies that have been conducted on pest control by targeting the symbionts. Manipulation or exploitation of the gut symbionts alters the growth and population of the host insects and is consequently a potential target for the development of better pest control strategies. Methods such as modulation of gut symbionts via CRISPR/Cas9, RNAi and the combining of IIT and SIT to increase the insect mortality are further discussed. In the ongoing insect pest management scenario, gut symbionts are proving to be the reliable, eco-friendly and novel approach in the integrated pest management.

Description of Novosphingopyxis iocasae sp. nov., isolated from deep sea sediment from the Mariana Trench, and emended description of the genus Novosphingopyxis

In this study, we reported a Gram-stain-negative, orange-coloured, rod-shaped, motile and faculatively anaerobic bacterium named strain PB63^T, which was isolated from the deep-sea sediment from the Mariana Trench. Growth of PB63^T occurred at 10-35 °C (optimum, 28 °C), pH 5.0-8.0 (optimum, 5.0-6.0) and with 0-7 % (w/v) NaCl (optimum, 2-3 %). The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that PB63^T represented a member of the genus Novosphingopyxis and was closely related to Novosphingopyxis baekryungensis DSM 16222^T (97.9 % sequence similarity). PB63^T showed tolerance to a variety of heavy metals, including Co²⁺, Zn²⁺, Mn²⁺ and Cu²⁺. The complete genome of PB63^T was obtained, and many genes involved in heavy metal resistance were found. The genomic DNA G+C content of PB63^T was 62.8 mol%. The predominant respiratory quinone of PB63^T was ubiquinone-10 (Q-10). The polar lipids of PB63^T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, glycolipid, phosphatidylcholines and three unidentified lipids. The major fatty acids of PB63^T included summed feature 8 (C_{18 : 1}ω7c or/and C_{18 : 1}ω6c), C_{14 : 0} 2-OH, 11-methyl C_{18 : 1}ω7c, C_{16 : 0}, summed feature 3 (C_{16 : 1}ω7c and/or C_{16 : 1}ω6c) and C_{17 : 1}ω6c. The results of phylogenetic, physiological, biochemical and morphological analyses indicated that strain PB63^T represents a novel species of the genus Novosphingopyxis, and the name Novosphingopyxis iocasae sp. nov. is proposed with the type species PB63^T (=CCTCC AB 2019195^T=JCM 34178^T).

Degradation of chlorpyriphos and polyethylene by endosymbiotic bacteria from citrus mealybug

Chlorpyriphos is one of the major organophosphorus pesticides used widely to control a range of insect pests across several crops. This insecticide is hazardous to the environment and toxic to mammals, thus, it is essential to remove the same from the environment. Similarly, use of polythene is also increasing day by day. Therefore, it is highly important to identify ways to degrade chlorpyriphos and other pesticides from the environment. We studied the degradation of chlorpyriphos and polyethylene by Citrus mealybug (Planococcus citri) bacterial endosymbionts such as Bacillus licheniformis, Pseudomonas cereus, Pseudomonas putida and Bacillus subtilis. This investigation revealed that bacterial endosymbionts use the polythene as a source of carbon and solubilize them by their enzymatic machinery. The degradation of polyethylene by endosymbionts showed a significant reduction in weight of polyethylene sheet after 15, 30 and 45 days of treatment. The SEM images showed localized degradation of the polyethylene around the bacterial cells in the biofilm. Further, the tensile strength (percentage elongation) was significantly reduced after 45 days of incubation. The weight of paraffin wax showed significant reduction in B. cereus. A significant reduction in total amount of chlorpyriphos in soil was observed at an interval of 7, 14 and 21 days after treatment by the bacterial isolates. Among the bacteria, B. cereus and P. putida were found to be most effective. The results from this study show that endosymbionts can be significantly implicated in degrading chlorpyriphos and polyethylene from the environment.

Symbiont Genomic Features and Localization in the Bean Beetle Callosobruchus maculatus

A pervasive pest of stored leguminous products, the bean beetle Callosobruchus maculatus (Coleoptera: Chrysomelidae) associates with a simple bacterial community during adulthood. Despite its economic importance, little is known about the compositional stability, heritability, localization, and metabolic potential of the bacterial symbionts of C. maculatus. In this study, we applied community profiling using 16S rRNA gene sequencing to reveal a highly conserved bacterial assembly shared between larvae and adults. Dominated by Firmicutes and Proteobacteria, this community is localized extracellularly along the epithelial lining of the bean beetle's digestive tract. Our analysis revealed that only one species, Staphylococcus gallinarum (phylum Firmicutes), is shared across all developmental stages. Isolation and whole-genome sequencing of S. gallinarum from the beetle gut yielded a circular chromosome (2.8 Mb) and one plasmid (45 kb). The strain encodes complete biosynthetic pathways for the production of B vitamins and amino acids, including tyrosine, which is increasingly recognized as an important symbiont-supplemented precursor for cuticle biosynthesis in beetles. A carbohydrate-active enzyme search revealed that the genome codes for a number of digestive enzymes, reflecting the nutritional ecology of C. maculatus. The ontogenic conservation of the gut microbiota in the bean beetle, featuring a "core" community composed of S. gallinarum, may be indicative of an adaptive role for the host. In clarifying symbiont localization and metabolic potential, we further our understanding and study of a costly pest of stored products. IMPORTANCE From supplementing essential nutrients to detoxifying plant secondary metabolites and insecticides, bacterial symbionts are a key source of adaptations for herbivorous insect pests. Despite the pervasiveness and geographical range of the bean beetle Callosobruchus maculatus, the role of microbial symbioses in its natural history remains understudied. Here, we demonstrate that the bean beetle harbors a simple gut bacterial community that is stable throughout development. This community localizes along the insect's digestive tract and is largely dominated by Staphylococcus gallinarum. In elucidating symbiont metabolic potential, we highlight its possible adaptive significance for a widespread agricultural pest.

Characterization of the bacterial communities of psyllids associated with Rutaceae in Bhutan by high throughput sequencing

Background

Several plant-pathogenic bacteria are transmitted by insect vector species that often also act as hosts. In this interface, these bacteria encounter plant endophytic, insect endosymbiotic and other microbes. Here, we used high throughput sequencing to examine the bacterial communities of five different psyllids associated with citrus and related plants of Rutaceae in Bhutan: Diaphorina citri, Diaphorina communis, Cornopsylla rotundiconis, Cacopsylla heterogena and an unidentified Cacopsylla sp.

Results

The microbiomes of the psyllids largely comprised their obligate P-endosymbiont ‘Candidatus Carsonella ruddii’, and one or two S-endosymbionts that are fixed and specific to each lineage. In addition, all contained Wolbachia strains; the Bhutanese accessions of D. citri were dominated by a Wolbachia strain first found in American isolates of D. citri, while D. communis accessions were dominated by the Wolbachia strain, wDi, first detected in D. citri from China. The S-endosymbionts from the five psyllids grouped with those from other psyllid taxa; all D. citri and D. communis individuals contained sequences matching ‘Candidatus Profftella armatura’ that has previously only been reported from other Diaphorina species, and the remaining psyllid species contained OTUs related to unclassified Enterobacteriaceae. The plant pathogenic ‘Candidatus Liberibacter asiaticus’ was found in D. citri but not in D. communis. Furthermore, an unidentified ‘Candidatus Liberibacter sp.’ occurred at low abundance in both Co. rotundiconis and the unidentified Cacopsylla sp. sampled from Zanthoxylum sp.; the status of this new liberibacter as a plant pathogen and its potential plant hosts are currently unknown. The bacterial communities of Co. rotundiconis also contained a range of OTUs with similarities to bacteria previously found in samples taken from various environmental sources.

Conclusions

The bacterial microbiota detected in these Bhutanese psyllids support the trends that have been seen in previous studies: psyllids have microbiomes largely comprising their obligate P-endosymbiont and one or two S-endosymbionts. In addition, the association with plant pathogens has been demonstrated, with the detection of liberibacters in a known host, D. citri, and identification of a putative new species of liberibacter in Co. rotundiconis and Cacopsylla sp.

In Vitro Anticancer Activity of Staphyloxanthin Pigment Extracted from Staphylococcus gallinarum KX912244, a Gut Microbe of Bombyx mori

The present study reports the in vitro biological nature of the pigment produced by Staphylococcus gallinarum KX912244, isolated as the gut microflora bacterium of the insect Bombyx mori. The purified pigment was characterized as Staphyloxanthin based on bio-physical characterization techniques like Fourier transform infrared spectroscopy, high performance liquid chromatography, Proton nuclear magnetic resonance spectroscopy (¹H NMR), Liquid chromatography-Mass spectroscopy and Gas chromatography-Mass spectroscopy. The Staphyloxanthin pigment presented considerable biological properties including in vitro antimicrobial activity against pathogens Staphylococcus aureus, Escherichia coli and Candida albicans; in vitro antioxidant activity by % DPPH free radical scavenging activity showing IC₅₀ value of 54.22 µg/mL; DNA damage protection activity against reactive oxygen species and anticancer activity evaluated by cytotoxicity assay against 4 different cancer cell lines like the Dalton's lymphoma ascites with IC₅₀ value 6.20 ± 0.02 µg/mL, Ehrlich ascites carcinoma having IC₅₀ value 6.48 ± 0.15 µg/mL, Adenocarcinomic human alveolar basal epithelial cells (A549 Lung carcinoma) bearing IC₅₀ value 7.23 ± 0.11 µg/mL and Mus mucus skin melanoma (B16F10) showing IC₅₀ value 6.58 ± 0.38 µg/mL and less cytotoxicity towards non-cancerous human fibroblast cell lines (NIH3T3) with IC₅₀ value of 52.24 µg/mL. The present study results suggest that Staphyloxanthin acts as a potential therapeutic agent especially due to its anticancer property.

Can social partnerships influence the microbiome? Insights from ant farmers and their trophobiont mutualists

Mutualistic interactions with microbes have played a crucial role in the evolution and ecology of animal hosts. However, it is unclear what factors are most important in influencing particular host–microbe associations. While closely related animal species may have more similar microbiota than distantly related species due to phylogenetic contingencies, social partnerships with other organisms, such as those in which one animal farms another, may also influence an organism's symbiotic microbiome. We studied a mutualistic network of Brachymyrmex and Lasius ants farming several honeydew‐producing Prociphilus aphids and Rhizoecus mealybugs to test whether the mutualistic microbiomes of these interacting insects are primarily correlated with their phylogeny or with their shared social partnerships. Our results confirm a phylogenetic signal in the microbiomes of aphid and mealybug trophobionts, with each species harbouring species‐specific endosymbiont strains of Buchnera (aphids), Tremblaya and Sodalis (mealybugs), and Serratia (both mealybugs and aphids) despite being farmed by the same ants. This is likely explained by strict vertical transmission of trophobiont endosymbionts between generations. In contrast, our results show the ants’ microbiome is possibly shaped by their social partnerships, with ants that farm the same trophobionts also sharing strains of sugar‐processing Acetobacteraceae bacteria, known from other honeydew‐feeding ants and which likely reside extracellularly in the ants’ guts. These ant–microbe associations are arguably more “open” and subject to horizontal transmission or social transmission within ant colonies. These findings suggest that the role of social partnerships in shaping a host's symbiotic microbiome can be variable and is likely dependent on how the microbes are transmitted across generations.

Looking for phosphate-accumulating bacteria in activated sludge processes: a multidisciplinary approach

Over the past decades, an increasing need in renewable resources has progressively appeared. This trend concerns not only fossil fuels but also mineral resources. Wastewater and sewage sludge contain significant concentrations in phosphate and can be considered as a fertilizer source of the utmost importance. In wastewater treatment plants, the biological uptake of phosphate is performed by a specific microbiota: the phosphate-accumulating organisms. These microorganisms are recovered in sewage sludge. Here, we aimed to investigate the occurrence of phosphate accumulators in four wastewater treatment plants. A 16S metagenetic analysis identified the main bacterial phyla extracted from the aerobic treatment: α-Proteobacteria, β-Proteobacteria, and Sphingobacteria. An enrichment stage was performed to stimulate the specific growth of phosphate-accumulating bacteria in an acetate medium. An analysis of metabolic activities of sulfur and phosphorus highlighted strong modifications related to phosphorus and much less distinguishable effects with sulfur. A solid acetate medium containing 5-Br-4-Cl-3-indolyl phosphate was used to select potential phosphate-accumulating bacteria from the enriched consortia. The positive strains have been found to belong in the genera Acinetobacter, Corynebacterium, and Pseudomonas. Finally, electron microscopy was applied to the strains and allowed to confirm the presence of polyphosphate granules. Some of these bacteria contained granules the size of which exceeded 100 nm.

Biological Control Potential of Bacillus amyloliquefaciens KB3 Isolated from the Feces of Allomyrina dichotoma Larvae

Most biocontrol agents for plant diseases have been isolated from sources such as soils and plants. As an alternative source, we examined the feces of tertiary larvae of the herbivorous rhino beetle, Allomyrina dichotoma for presence of biocontrol-active microbes. The initial screen was performed to detect antifungal activity against two common fungal plant pathogens. The strain with strongest antifungal activity was identified as Bacillus amyloliquefaciens KB3. The inhibitory activity of this strain correlated with lipopeptide productions, including iturin A and surfactin. Production of these surfactants in the KB3 isolate varied with the culture phase and growth medium used. In planta biocontrol activities of cell-free culture filtrates of KB3 were similar to those of the commercial biocontrol agent, B. subtilis QST-713. These results support the presence of microbes with the potential to inhibit fungal growth, such as plant pathogens, in diverse ecological niches.