Preliminary assessment of insecticidal activity of Moroccan actinobacteria isolates against mediterranean fruit fly (Ceratitis capitata)

An Overview on Nocardiopsis Species Originating From North African Biotopes as a Promising Source of Bioactive Compounds and In Silico Genome Mining Analysis of Three Sequenced Genomes

Actinobacteria are renowned for their prolific production of diverse bioactive secondary metabolites. In recent years, there has been an increasing focus on exploring "rare" genera within this phylum for biodiscovery purposes, notably the Nocardiopsis genus, which will be the subject of the present study. Recognizing the absence of articles describing the research process of finding bioactive molecules from the genus Nocardiopsis in North African environments. We, therefore, present a historical overview of the discoveries of bioactive molecules of the genus Nocardiopsis originating from the region, highlighting their biological activities and associated reported molecules, providing a snapshot of the current state of the field, and offering insights into future opportunities and challenges for drug discovery. Additionally, we present a genome mining analysis of three genomes deposited in public databases that have been reported to be bioactive. A total of 36 biosynthetic gene clusters (BGCs) were identified, including those known to encode bioactive molecules. Notably, a substantial portion of the BGCs showed little to no similarity to those previously described, suggesting the possibility that the analyzed strains could be potential producers of new compounds. Further research on these genomes is essential to fully uncovering their biotechnological potential. Moving forward, we discuss the experimental designs adopted in the reported studies, as well as new avenues to guide the exploration of the Nocardiopsis genus in North Africa.

Bioinsecticidal activity of actinomycete secondary metabolites against the acetylcholinesterase of the legume’s insect pest Acyrthosiphon pisum: a computational study

Background

Acyrthosiphon pisum or pea aphid is an insect of the Aphididae family, which attacks various species of legumes such as beans and peas. This pest causes economically heavy crop losses around the world. The use of conventional chemical insecticides is the only way to control its development. However, the harmful consequences of these chemicals are well known. They pollute various compartments of the environment, thus constituting a major risk for human and environmental health. The search for a more ecological alternative, respectful of the environment is, therefore, a necessity. Actinomycetes represent a source of biologically active secondary metabolites, such as antibiotics and biopesticidal agents. In this study, 150 secondary metabolites of actinomycetes have made the objective of an in silico research by molecular docking, by screening their potential inhibitors against the enzyme acetylcholinesterase (AChE) of A. pisum.

Results

The 3D structure of AChE, unavailable in the PDB database, was first modeled using the Modeller program, then the stereochemical quality of the model was validated. The molecular docking performed by the Autodock Vina algorithm allowed the selection of two metabolites giving binding energy equal to or lower than that of the co-crystallized inhibitor tetrahydro-acridine (−10.3Kcal/mol). The top-two metabolites are diazepinomicine (−10.9 Kcal/mol), and hygromycin (−10.3 Kcal/mol). These components have shown numerous interactions with the key residues of the catalytic site of the AChE enzyme, indicating their potential to inhibit its biological activity. The environmental and health safety of these components, as well as their bioavailability, were also studied by the verification of several pharmacokinetic and ADMET criteria. Diazepinomicine has shown excellent results verifying most of the criteria studied. A 50-ns MD simulation was also performed in order to test the stability of the complexes formed.

Conclusions

In addition to its favorable pharmacokinetic properties, the special chemical structure of diazepinomicin allows this molecule to interact intensely with AChE notably through the involvement of its two groups farnesyl diphosphate and dibenzodiazepinone which ensure several hydrogen and hydrophobic interactions, that offers very high stability to the complex AChE diazepinomicin. In conclusion, diazepinomicin can be suggested as a potential bioinsecticidal agent against the pest A. pisum.

Chemical Composition and Insecticidal Properties of Moroccan Lavandula dentata and Lavandula stoechas Essential Oils Against Mediterranean Fruit Fly, Ceratitis capitata

The current study describes the chemical composition and insecticidal activities of the essential oils (EOs) extracted from Lavandula dentata L. and Lavandula stoechas L. against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), a worldwide fruit pest. Gas chromatography (GC) and GC-mass spectrophotometry (GC-MS) analyses revealed that L. dentata oil contained camphor (50.8%), 1,8-cineole (6.6%), β-selinene (5%), and borneol (3.2%) as major components. On the other hand, L. stoechas EO was characterized by high contents of camphor (44%), camphene (14.8%), fenchone (9.1%), and 1-10-diepi-cubenol (4.6%). The toxic impact of EOs against C. capitata was evaluated through ingestion and contact methods. All of the EOs were toxic to C. capitata, and insect mortality was dose and time-dependent. In ingestion toxicity assays, L. dentata was the most toxic oil with an LC₅₀ (lethal concentration for 50% mortality) of 6.54% for males and 10.21% for females. Topical applications revealed that all the EOs had a good insecticidal activity at 24 h. The results of this study show that L. dentata and L. stoechas EOs may reduce the risks associated with the use of synthetic insecticides and may also be considered as a potent source for the production of botanical insecticides against C. capitata.

Draft Genome Sequence of the Novonestmycin-Producing Strain Streptomyces sp. Z26, Isolated from Potato Rhizosphere in Morocco

Streptomyces sp. strain Z26 exhibited antifungal activity and turned out to be a producer of the secondary metabolites novonestmycin A and B. The 6.5-Mb draft genome gives insight into the complete secondary metabolite production capacity and builds the basis to find and locate the biosynthetic gene cluster encoding the novonestmycins.

Streptomyces sp. strain Z26 exhibited antifungal activity and turned out to be a producer of the secondary metabolites novonestmycin A and B. The 6.5-Mb draft genome gives insight into the complete secondary metabolite production capacity and builds the basis to find and locate the biosynthetic gene cluster encoding the novonestmycins.

Insecticidal activity of a Moroccan strain of Streptomyces phaeochromogenes LD-37 on larvae, pupae and adults of the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly (medfly), Ceratitis capitata, is considered the most important fruit pest worldwide. Its management is mainly based on the use of chemical insecticides. Although these conventional pesticides are effective at high doses, they cause considerable human health and environment problems. Thus, the aim of this study was to assess insecticidal activity of Moroccan actinobacteria against C. capitata. A total of 12 preselected actinobacteria isolated from various Moroccan habitats were screened for their insecticidal activity against larvae, pupae and adults of C. capitata. Four actinobacteria isolates were significantly active against the first-instar larvae, and nine were active against the medfly adult, while no significant mortality was obtained against the third-instar larval and pupal stages. Among the selected isolates, the biological screening revealed that strain Streptomyces LD-37, which showed 99.4% similarity with Streptomyces phaeochromogenes, exhibited the maximal corrected larval mortality of 98%. Moreover, the isolates AS1 and LD-37 showed the maximum significant corrected mortality against adults of 32.5 and 28.2%, respectively. The crude extract obtained from a fermented culture of strain S. phaeochromogenes LD-37 was separated into six fractions by thin layer chromatography. Fractions F3 and F4 caused a significant corrected larval mortality of 66.7 and 53.3%, respectively; whereas the maximum reduction in adult emergence was obtained with fraction F4. This finding could be useful for utilizing S. phaeochromogenes LD-37 as an alternative to chemical insecticides in pest management of C. capitata.