FATE OF BACTERIA AND ON SET OF IMMUNE RESPONSE IN SILKWORM, BOMBYX MORI L

ABSTRACT Dynamics of immune responses in five cross breeds of mulberry silkworm, Bombyx mori was assessed by following through pattern of bacterial colonization in vivo. The colony forming units (cfu/ml) were measuring at specified time intervals at 0h, 6h, 12h, 24h, 30h, 36h and 48h after inoculations of non-pathogenic bacteria, Escherichia coli (Kanamycin resistant) @ 106 cfu/ml into larvae of silkworm breeds during third, fourth and fifth stages. The colonization pattern shows that there was a surge in colony counts at 6h post immunization followed by a sharp decline. At 48h post immunization, bulk of the ingested bacteria was cleared off in most of the breeds. Comparison of the pattern of E. coli colonization in different breeds during third, fourth and fifth instars revealed that the rate of clearance of ingested bacteria was in the order of fifth instar > fourth instar > third instars. Among the breeds APM2 x APS12 and APM3 x APS12 recorded faster clearance of bacteria as depicted by 40-50% reduction in colony forming units at around 12– 24 h. Significant differences in clearance of ingested marker bacteria E. coli shows that some of the cross breeds like APM2 x APS12 and APM3 x APS12 are more immune to invasions of bacteria than popular cross breed like PM x CSR2.