Characterization of parasporin gene harboring Indian isolates of Bacillus thuringiensis

Abstract

Bacillus thuringiensis (Bt) is popularly known as insecticidal bacterium. However, non-insecticidal Bt strains are more extensively available in natural environment than the insecticidal ones. Parasporin (PS) is a collection of genealogically heterogeneous Cry proteins synthesized in non-insecticidal isolates of Bt. An important character generally related with PS proteins is their strong cytocidal activity preferentially on human cancer cells of various origins. Identification and characterization of novel parasporin protein which are non-hemolytic and non-insecticidal but having selective anticancer activity raise the possibility of a novel application of Bt in medical field. In the present study, seven new indigenous isolates (T6, T37, T68, T98, T165, T186, and T461) of Bt showed variation in colony morphology, crystal characters and protein profiles with each other. Out of the seven new isolates screened for parasporin (ps) and cry genes, two of the new indigenous isolates (T98 and T186) of Bt showed the presence of ps4 gene. Partial ps4 gene was cloned from the two new isolates and the sequence of partial ps4 gene showed high homology with its holotype ps4Aa1. These two isolates were characterized based on the proteolytic processing of the inclusion proteins and the proteolytic products were found to be comparable to the PS4 reference strain A1470. The two isolates of Bt did not show toxicity toward Spodoptera litura and Helicoverpa armigera. Based on the results of this study, it can be concluded that the isolates T98 and T186 are parasporin producers.

The Replacement of five Consecutive Amino Acids in the Cyt1A Protein of Bacillus thuringiensis Enhances its Cytotoxic Activity against Lung Epithelial Cancer Cells

“…PCR with whole DNA extract from all the Qatari Bti-like isolates and the reference failed to amplify any of the parasporin genes. This was expected as the insecticidal activity due to endotoxins and the anticancer property due to parasporins are known to be mutually exclusive among the Bt strains [ 24 , 25 ]. However, the lack of parasporin genes warranted further investigation of the cyt1A gene.…”

The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells

“…Time later, it was accepted that non-hemolytic but insecticidal activity could also be part of this classification [96]. Bt strains that produce PS have been isolated from soils of various ecosystems in several countries such as Japan [95,, Vietnam [121,122], India [94,123], Malaysia [124], China [125], Iran [126], and Saudi Arabia [127]. Canada [128] and Caribbean [129] have contributed with new parasporins.…”

Overexpression and Cytocidal Activity of Parasporin-1 from Bacillus thuringiensis against Human Cancer Cell Lines

“…PS4Aa1 exhibits no homology to the three-domain Cry proteins and is lacking any of the five conserved blocks of the Cry proteins (including PS1Aa1 and PS3Aa1). Moreover, PS4Aa1 shares very low amino acid sequence homology (<30%) to the existing Cry and Cyt proteins of B. thuringiensis [18][19][20].…”