Phenotypic characterization of an indigenous Bacillus thuringiensis strain (B.T. LDC 501) expressing cancer cell killing protein

Abstract

Screening of coastal soil samples from Ramnad district, Tamil Nadu, South India, revealed the presence of a novel non-haemolytic and non-insecticidal Bacillus thuringiensis strain that contained spherical inclusion body and exerted cytotoxic action on cultured human cancer cells. When protoplasmic extract of the B.t. LDC 501 isolate digest with proteinase K exerted significant toxicity on cell lines such as U-937, HL-60 and primary leukemic cells. It also had mild influence on Jurkat (T cell lymphoma) but nontoxic to normal human leukocytes. Majority of the biochemical tests of the strain revealed similar characteristics like that of insecticidal strain B. thuringiensis (BGSC-4Q2) with slight variation. Moreover, antibiotic sensitivity assay discriminated the strain from B. anthracis due to its ability to resist ampicillin. Phylogenetic analysis revealed the distinctive nature of the strain as it forms a separate clade from other Bacillus strains.