10.22376/ijpbs.2019.10.1.p1-12 Volume 2 Issue 4 2011 (October - December) Seven different species of bacteria were isolated from the midgut of infected Silkworm lessThan i greaterThan Bombyx mori lessThan /i greaterThan in the 4 lessThan sup greaterThan th lessThan /sup greaterThan instar stage. Out of seven four strains were observed as lethal to host. These isolates were undergone for identification by physico-chemical characterization identified as Gram-negative, facultative anaerobic bacilli proteobacteria  lessThan i greaterThan Vibrio sp. lessThan /i greaterThan lessThan i greaterThan Vibrio lessThan /i greaterThan strains are pathogenic or opportunistic pathogens. So this particular strain was termed to using Sodium Dodecyl Sulfate (SDS) polyacrylamide gel electrophoresis as per Laemmli method. The result had shown the presence of 61kDa (kilo Dalton) and 18kDa proteins in the protein band. Purification and characterization of protein profile revealed that the silkworm-killing activity was due to the presence of 61kDa and 18kDa protein, because of this the particular molecular weighted proteins are having the tendency to secret extracellular toxin and kill the host namely Knottins (small inhibitors, toxins, lectins) folded omega toxin like protein. Finally this particular species were undergone for 16s rRNA sequence to the clear understanding of phylogenetic relationship. Pradhap. M. And Selvisabhanayakam Facultative, Opportunistic pathogen, SDS, Extracellular toxin, Phylogeny 29-37