Screening of Secondary Metabolites Produced by Streptomyces Species from a Soil Sample that Can Produce Anti-Nematodal and Antiprotozoal Avermectins

Avermectins are a group of secondary metabolites produced by Streptomyces avermitilis, which act on invertebrates. They activate glutamate-gated chloride channels in their nerves and muscles which in turn disrupt pharyngeal function and locomotion. Avermectin ingested insects are paralyzed and starve to death. Ten isolates identified as avermectin producers were characterized by morphological, colony characters and biochemical tests. Secondary screening leads to the identification of four isolates PM2; PM4; PM7 and PM10 which produced 10, 8.4, 3.8 and 6.9mg respectively as identified by HPTLC. Bio-autography illustrated their anti-nematodal and antiprotozoal activity; the zone of clearance (turbid) was recorded 43, 24, 32 and 37 mm respectively for PM2 through PM10.