Insecticidal potential of Streptomyces sp. dichloromethane extracts against the cactus cochineal Dactylopius opuntiae (Cockerell)

Destructive damages caused by Dactylopius opuntiae (Cockerell) to cactus worldwide require an ecofriendly IPM approach. Streptomyces sp. produce wide range of biologically active secondary metabolites that can be an interesting alternative to chemical insecticides for pest control, as they are less toxic and easily biodegradable. The efficacy of dichloromethane extracts of four Moroccan Streptomyces sp. strains: Streptomyces bellus- E23-2, Streptomyces galilaeus- E23-9, Streptomyces africanus- E23-3, and Streptomyces bellus- E25-12 (applied at 11, 13, 15, 17 and 20 mg mL-1) against D. opuntiae nymphs and adult females was evaluated under laboratory and greenhouse conditions. Results showed that Streptomyces bellus- E23-2 and Streptomyces galilaeus- E23-9 dichloromethane extracts applied at 20 mg mL-1 were more effective, causing higher mortality against nymphs (92% and 91%, respectively) and adult females (90% and 95%, respectively) after 8 days of exposure, resulting in an LT50 value of 3.0 days (nymph), and 3.0 and 6.0 days (adult female), respectively. Streptomyces bellus- E25-12 extract had the lowest mortalities [88% (nymph) and 68% (adult female)]. In greenhouse experiment, the highest first instar nymph mortality was achieved by Streptomyces bellus- E23-2 (55.5%) and Streptomyces galilaeus- E23-9 (50.5%) dichloromethane extracts at 20 mg mL-1. The metabolites found in dichloromethane extracts of Streptomyces bellus- E23-2 and Streptomyces galilaeus- E23-9 show considerable potential to be used in the development of new biopesticide formulations for use in integrated pest management programs against D. opuntiae

Antimicrobial potential of Streptomyces coeruleofuscus SCJ isolated from microbiologically unexplored garden soil in Northwest Morocco

Abstract Research on microorganisms in various biotopes is required to identify new, natural potent molecules. These molecules are essential to control the development of multi-drug resistance (MDR). In the present study, a Streptomyces sp., namely SCJ, was isolated from a soil sample collected from a Moroccan garden. SCJ isolate was identified on the basis of a polyphasic approach, which included cultural, micro-morphological, biochemical, and physiological characteristics. The sequence of the 16S rRNA gene of the SCJ strain showed 99.78% similarity to strains of Streptomyces coeruleofuscus YR-T (KY753282.1). The preliminary screening indicated that the SCJ isolate exhibited activity against Candida albicans ATCC 60,193, Escherichia coli ATCC 25,922, Staphylococcus aureus CECT 976, Staphylococcus aureus ATCC 25,923, Bacillus cereus ATCC 14,579, Pseudomonas aeruginosa ATCC 27,853, as well as various other clinical MDR bacteria and five phytopathogenic fungi. The ethyl acetate extract of the isolated strain demonstrated highly significant (p < 0.05) antimicrobial activity against multi-resistant bacteria and phytopathogenic fungi. The absorption spectral analysis of the ethyl acetate extract of the SCJ isolate obtained showed no absorption peaks characteristic of polyene molecules. Moreover, no hemolytic activity against erythrocytes was observed in this extract. GC–MS analysis of the ethyl acetate extract of the SCJ isolate revealed the presence of 9 volatile compounds including 3,5-Dimethylpyrazole, and pyrrolizidine derivatives (Pyrrolo[1,2-a]pyrazine 1,4-dione, hexahydro-3-(2-methylpropyl)), which could potentially explain the antimicrobial activity demonstrated in this study