Aug 2026· Pest Management Science· 0 citations· 49 references
Medicine
TL;DR
A virulent Serratia nematodiphila named BPH1 is isolated from diseased N. lugens and characterized its insecticidal activity, genomic features, and virulence-associated phenotypes, revealing genomic and phenotypic features potentially associated with pathogenicity.
Abstract
Background
Delphacid planthoppers (Hemiptera: Delphacidae), including the brown planthopper (Nilaparvata lugens), pose a significant threat to global rice production, highlighting the urgent need for sustainable and effective biological control agents. Here, we isolated a virulent strain of Serratia nematodiphila named BPH1 from diseased N. lugens and characterized its insecticidal activity, genomic features, and virulence-associated phenotypes.
Results
S. nematodiphila BPH1 exhibited median lethal concentrations (LC50) of 5.5 × 104 and 2.4 × 108 CFU/mL for N. lugens adults and nymphs, respectively. At a concentration of 108 CFU/mL, the median lethal time (LT50) was approximately 15 h for adults and 45 h for nymphs. Whole-genome sequencing revealed a 5.15 Mb draft genome assembly containing a complete prodigiosin biosynthetic gene cluster and multiple serralysin metalloprotease genes, representing candidate virulence-associated genomic features. The strain exhibited extracellular protease activity and swimming and swarming motility in vitro, which are commonly associated with bacterial entomopathogenicity. In insecticidal-spectrum assays, the strain caused mortality in two additional delphacid planthoppers, Laodelphax striatellus and Sogatella furcifera, and in the mosquito Aedes albopictus, whereas it showed no pathogenicity toward the green peach aphid Myzus persicae under the tested conditions.
Bemisia tabaci (Gennadius) and Aphis gossypii (Glover) are two notorious pests of vegetables grown in greenhouses and their outbreaks can be devastating and cause a significant loss in yield and quality. The prevail and effective control of the pests mainly relies on frequent applications of pesticides, which is likely to negatively impact environments and human health through residue, resurgence, and resistance. To avoid negative “3R” issues brought forth by chemicals, entomopathogenic fungus such as Metarhizium sp. are widely used as biocontrol agents even if they are different in their population, adaptability and pathogenicity among various species and isolates collected from different insect hosts and environments. To screen for the entomopathogenic fungi with optimal pathogenicity against the piercing-sucking pests B. tabaci and A. gossypii, we have isolated, purified four strains (SG-A, SG-B, SG-C, and SG-D) of Metarhizium sp. using yellow mealworms (Tenebrio molitor) as the bait, and identified them as Metarhizium pinghaense morphologically and molecularly. Bioassay results have indicated that four isolates of M. pingshaense infected both B. tabaci and A. gossypii with some differences in the virulence and median lethal time. Both B. tabaci and A. gossypii nymphs showed an increase in the mortality rate as the spore concentration rose. Four M. pingshaense strains also exhibited the different pathogenicity against B. tabaci and A. gossypii at various levels: At an inoculum concentration of 1 × 108 conidia/mL, the cumulative corrected mortality of B. tabaci nymphs 8 days post-treatment ranked in the order: SG‑A > SG‑C > SG‑B = SG‑D. For A. gossypii, the cumulative corrected mortality followed the order: SG‑A > SG‑B > SG‑D > SG‑C.Strain SG-A demonstrated the maximized pathogenicity against nymphs of B. tabaci and A. gossypii 8 days after the treatment (LC50 = 7.00 × 104 and 4.21 × 105 conidia/mL, respectively). At the spore concentration at 1 × 108 conidia/mL, its cumulatively corrected mortality reached 94.44% and 96.67% (LT50 = 4.13 d and 2.61 d, respectively). Strain SG-C showed an optimal pathogenicity against B. tabaci nymphs only with a cumulative corrected mortality of 87.78% and an LT50 at 4.30 d 8 days after the treatment. In contrast, strain SG-B exhibited relatively high pathogenicity against A. gossypii nymphs only with a cumulative corrected mortality of 72.22% and an LT50 at 2.31 d 8 days after the treatment. Therefore, M. pinghaense SG-A should be a potential biocontrol agent to manage whiteflies and aphids at their nymph stage during the vegetable production season.
Haiyan Hu, Yali Wang, Chunyan Li et al.· PLoS ONE· 0 citations
Background Innovative vector control strategies are urgently needed to combat malaria transmission by Anopheles gambiae, given the limitations of current insecticides—namely resistance, human toxicity, environmental damage, and high costs. This study evaluated the larvicidal efficacy of endophytic bacteria isolated from Cola nitida against third-instar larvae of Anopheles gambiae. Methods Endophytic bacteria were isolated from nine Cola nitida plant parts (leaves, roots, stems, fruits, flowers, stem bark, branches, root bark, whole plant extracts) using standard surface sterilization and culturing protocols. Thirty-two morphologically distinct strains were purified and screened for larvicidal activity against third-instar An. gambiae larvae using the WHO-recommended turbidity method at McFarland 4 standard. Six active isolates underwent dose-response testing (McFarland 0.5-4) with mortality recorded at 24 and 48 hours. Environmental safety was assessed via Lemna minor growth inhibition, and molecular identification employed the API 20E biochemical gallery. Results Screening identified six strains with significant larvicidal activity (LC₅₀ < McFarland 2). At McFarland 2 concentration, all six strains achieved >50% mortality within 24-48 hours, with Lemna minor EC₅₀ >100% indicating minimal phytotoxicity. API 20E identification (96-99.99% similarity) revealed three strains (6164, 6211, 6501) matching Photobacterium damselae, two (6186-1, 6512-1) matching Salmonella enterica subsp. arizonae, and one (6600) matching Pseudomonas sp., confirmed by distinctive biochemical profiles. Conclusion This study provides the first evidence of potent, environmentally safe larvicidal activity from Cola nitida endophytic bacteria against Anopheles gambiae. These strains represent promising biocontrol candidates to address insecticide resistance, offering a sustainable alternative for malaria vector management in endemic regions.
Jean Baptiste Hzounda Fokou, S. V. Olugu, C. Ndo et al.· bioRxiv· 0 citations
The rapid evolution of pesticide resistance in Plutella xylostella has reduced the effectiveness of conventional pest control methods in cruciferous crops. This study investigated the virulence of Serratia marcescens PXG6 against P. xylostella and identified two putative virulence factors, ser (serralysin) and shlB (hemolysin transporter). Whole-genome sequencing revealed a GC content of 59.65%, 4650 predicted genes, multiple secretion systems (types I, V, and VI), and 715 putative virulence-related genes. Bioinformatic analyses predicted type IV pili, serralysin, hemolysin, and flagella as pathogenic determinants. Purified prodigiosin exhibited concentration-dependent insecticidal activity, whereas bacterial proteins alone caused little larval mortality, indicating that full virulence depends on live bacterial cells. Gene knockout mutants Δser and ΔshlB exhibited altered growth, motility, biofilm formation, and stress tolerance. Deletion of shlB significantly reduced hemolytic activity, protein secretion, and virulence against P. xylostella, whereas Δser had minimal impact on larval survival. Overall, PXG6 pathogenicity involves multiple bacterial components, with shlB playing a key role in virulence. These findings improve our understanding of the pathogenic mechanisms of PXG6 and support the development of S. marcescens-based biocontrol strategies against P. xylostella.
Muhammad Rehan Akhtar, Jun Ma, Yan Sun et al.· Environmental Microbiology· 0 citations
In vitro fungicide sensitivity assays, performed using the hyphal growth inhibition method against six common fungicides, demonstrated that Carbendazim was the most effective agent, indicating significant selectivity.
Fang Wu, Jing Tu, Zhu-Xiang Liu et al.· Plant Disease· 0 citations
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