ANTAGONISTIC AND INSECTICIDAL ACTIVITIES OF SOME STREPTOMYCES ISOLATES

Abstract

Fifteen local isolates of Streptomyces named, S01, S02, S03, S04, S05, S06, S07,
S08, S09, S10, S11, S12, S13, S14, and S15, isolated from different soils and geographical
areas in Egypt were used in this investigation. These isolates were propagated for screening
studies and to evaluate their efficiency as antagonistic agents against some phytopathogenic
fungi (such as, Rhizopus nigricans, Aspergillus niger, Fusarium oxysporum and
Helminthisporum gramenium) and insect pest, (cotton leaf worm, Spodopetra littoralis).
The Streptomyces isolates were grown on starch nitrate broth medium under shaking
condition at 28oC for 6 days. Culture filtrates were then tested against the five
phytopathogenic fungi. Results revealed that most of the isolates were varied in their
antagonistic activities. Isolate S08 was active against R. nigricans, A. niger and F.
oxysporum while isolates S01, S05, S11 and S14 were active against A. niger and F.
oxysporum and isolates S04, S09 and S13 were active against R. nigricans and A. niger. On
the other hand, no antifungal activity was found against Helminthisporum sp. The
insecticidal activity of both culture filtrates and cell pellets were tested against cotton leaf
worm. The experimental results showed that the pellets of some Streptomyces isolates were
more active against cotton leaf worm than culture filtrates. Generally, isolates S05, S08,
S10 and S15 showed 80, 100, 70 and 80% mortality against cotton leaf worm, respectively.
The protein(s) of isolate S08 cells was purified through ammonium sulfate saturation 40, 60
and 80%. Results of SDS-PAGE analysis showed that a 40 KDa protein was purified and
showed high activity against four instars of the cotton leaf worm. This result demonstrated
the ability to use such Streptomyces isolates as effective biopesticide agents