Evaluation of Actinomycetes secondary metabolites for Larvicidal activity against Culex quinquefasciatus.

Jeya Preethi S, Karpagavalli C and Ponmurugan P

Biomedical Research Laboratory, Botany department, Bharathiar University, Coimbatore – 641046, Tamil Nadu, India

Abstract

Six actinomycetes samples, including Nocardiopsis alba, Streptomyces euisocasilis, Streptomyces dot, Streptomyces mutabilis, R1 and R2 strains, were employed in our investigation.  These secondary metabolites of actinobacteria may be used to create novel, secure C. quinquefasciatus control products. After being inoculated into a 500 ml conical flask with 200 ml of starch casein broth, the pure Actinobacteria isolates were shaker-incubated for 7 days at 28 ± 2 °C. Every secondary metabolite produced by Actinobacteria was found to be harmful to Culex quinquefasciatus larvae. All of the isolates demonstrated larvicidal efficacy against the larvae of the Culex quinquefasciatus mosquito.

Introduction

Actinomycetes are Gram-positive, unicellular bacteria that are members of the Actinomycetales Order. This group's members are extensively dispersed across nature and can be found in many different types of environments worldwide.  Greek terms "mykes/mukes" (meaning fungi) and "atkis" (meaning ray) are the source of the name Actinomycetes. It has been demonstrated that they produce the same disease as fungus and share certain traits with them, such as mycelial development. Actinomycetes are not only extensively spread but also adaptable in terms of feeding and have the ability to produce a variety of spores. Due to these traits, the group has been able to successfully compete with nearby creatures. Although some of the members of this group are pathogenic (e.g., Actinomyces israelii causes actinomycosis), they are also important soil organisms that break down a variety of resistant organic compounds and produce biologically active compounds that find application in the pharmaceutical and insecticidal industries. The majority of naturally occurring secondary metabolites have been shown to have strong potential antagonistic action. One such organism is the actinomycetes, which are distinguished by their capacity to generate significant secondary metabolites. Among these, the genus Streptomyces is the most prolific producer of antibiotics, making up around 80% of the natural compounds derived from actinomycetes that have been documented (Jensen et al., 2005). Despite the fact that thousands of antibiotics have been identified, it is believed that these only make up a small portion of the repertory of bioactive substances that Streptomyces species can create (Watve et al., 2001).          

Conclusions

Six actinomycetes samples were employed in our investigation, including R1 and R2 strains of Streptomyces mutabilis, Streptomyces euisocasilis, Streptomyces alba, and Dot from the Microbial Type Culture Collection (MTCC) at the Institute of Microbial Technology (IMTECH), Chandigarh, India. After being inoculated into a 500 ml conical flask with 200 ml of starch casein broth, the pure Actinobacteria isolates were cultured for 7 days at 28 ± 2 °C in a shaker incubator. The supernatant from the cell-free culture filtrates was removed, dissolved in an equal volume of ethyl acetate, and thoroughly mixed in a separating funnel for one hour. After being taken out and properly dried, the solvent extract was diluted in DMSO and employed in the larvicidal bioassay.

Six Actinobacterial secondary metabolites in total were employed in this investigation to evaluate the larvicidal activity. All of the isolates demonstrated larvicidal efficacy against the larvae of the Culex quinquefasciatus mosquito. Every secondary metabolite produced by Actinobacteria was found to be harmful to Culex quinquefasciatus larvae. The results of this investigation demonstrated some Actinobacteria's larvicidal properties at different concentrations and exposure times.

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