A novel class of mosquitocidal delta-endotoxin, Cry19B, encoded by a Bacillus thuringiensis serovar higo gene

Mosquitocidal toxin-like islands in Bacillus thuringiensis S2160-1 revealed by complete-genome sequence and MS proteomic analysis

Here, we present the whole genome sequence of Bt S2160-1, a potential alternative to the mosquitocidal model strain, Bti. One chromosome genome and four mega-plasmids were contained in Bt S2160-1, and 13 predicted genes encoding predicted insecticidal crystal proteins were identified clustered on one plasmid pS2160-1p2 containing two pathogenic islands (PAIs) designed as PAI-1 (Cry54Ba, Cry30Ea4, Cry69Aa-like, Cry50Ba2-like, Cry4Ca1-like, Cry30Ga2, Cry71Aa-like, Cry72Aa-like, Cry70Aa-like, Cyt1Da2-like and Vpb4C1-like) and PAI-2 (Cyt1Aa-like, and Tpp80Aa1-like). The clusters appear to represent mosquitocidal toxin islands similar to pathogenicity islands. Transcription/translation of 10 of the 13 predicted genes was confirmed by whole-proteome analysis using LTQ-Orbitrap LC-MS/MS. In summary, the present study identified the existence of a mosquitocidal toxin island in Bacillus thuringiensis, and provides important genomic information for understanding the insecticidal mechanism of B. thuringiensis.

Potential for Bacillus thuringiensis and Other Bacterial Toxins as Biological Control Agents to Combat Dipteran Pests of Medical and Agronomic Importance

The control of dipteran pests is highly relevant to humans due to their involvement in the transmission of serious diseases including malaria, dengue fever, Chikungunya, yellow fever, zika, and filariasis; as well as their agronomic impact on numerous crops. Many bacteria are able to produce proteins that are active against insect species. These bacteria include Bacillus thuringiensis, the most widely-studied pesticidal bacterium, which synthesizes proteins that accumulate in crystals with insecticidal properties and which has been widely used in the biological control of insects from different orders, including Lepidoptera, Coleoptera, and Diptera. In this review, we summarize all the bacterial proteins, from B. thuringiensis and other entomopathogenic bacteria, which have described insecticidal activity against dipteran pests, including species of medical and agronomic importance.

Bacillus thuringiensis serovar mogi (flagellar serotype 3a3b3d), a novel serogroup with a mosquitocidal activity

The flagellated vegetative cells of the Bacillus thuringiensis strain K4 were agglutinated with the H3 reference antiserum and further, agglutinated with 3b and 3d monospecific factor sera but non-reactive for 3c and 3e factor sera. This creates a new serogroup with flagellar antigenic structure of 3a3b3d: B. thuringiensis serovar mogi. The strain K4 showed high activity against dipteran larvae, Anopheles sinensis and Culex pipienspallens while no lepidopteran toxicity. It produced ovoidal parasporal inclusions (crystals) whose SDS-PAGE protein profile consisted of several bands ranging from 75 to 30kDa. Through the protein identification by nano-LC-ESI-IT MS analysis, the putative peptides of Cry19Ba, Cry40ORF2, Cry27Aa and Cry20Aa were detected.

Bacillus thuringiensis serovar shandongiensis strain 89-T-34-22 produces multiple cytotoxic proteins with similar molecular masses against human cancer cells

AIMS

To prove that Bacillus thuringiensis serovar shandongiensis strain 89-T-34-22 produces several novel cytotoxic proteins against human leukaemic T cells.

METHODS AND RESULTS

Parasporal inclusion protein was solubilized and processed by proteinase K and was separated by anion-exchange chromatography. Cytopathic effects of each fraction against MOLT-4 and Jurkat cells were monitored.

CONCLUSIONS

Existence of at least two novel cytotoxic proteins was suggested and N-terminal sequences of the newly identified proteins were determined to be QSTTDVIREY and X (Y or I) (P or I) NLANELA (X indicates uncertain amino acids). Molecular masses of the two proteins were approx. 27-28 kDa.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, we demonstrated that the strain 89-T-34-22 produces at least two novel cytotoxic proteins with similar molecular masses against human cancer cells. This is the first strain of B. thuringiensis which produces multiple cytotoxic proteins against human cancer cells.

Characterization of a mosquitocidal Bacillus thuringiensis serovar sotto strain isolated from Okinawa, Japan

AIMS

To characterize the mosquitocidal activity of parasporal inclusions of the Bacillus thuringiensis serovar sotto strain 96-OK-85-24, for comparison with two well-characterized mosquitocidal strains.

METHODS AND RESULTS

The strain 96-OK-85-24 significantly differed from the existing mosquitocidal B. thuringiensis strains in: (1) lacking the larvicidal activity against Culex pipiens molestus and haemolytic activity, and (2) SDS-PAGE profiles, immunological properties and N-terminal amino acid sequences of parasporal inclusion proteins.

CONCLUSIONS

It is clear from the results that the strain 96-OK-85-24 synthesizes a novel mosquitocidal Cry protein with a unique toxicity spectrum.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of the occurrence of a mosquitocidal B. thuringiensis strain with an unusual toxicity spectrum, lacking the activity against the culicine mosquito.

Parasporin, a human leukemic cell-recognizing parasporal protein of Bacillus thuringiensis

An unusual property, human leukemic cell-recognizing activity, associated with parasporal inclusions of a noninsecticidal Bacillus thuringiensis soil isolate was investigated, and a protein (named parasporin in this study) responsible for the activity was cloned. The parasporin, encoded by a gene 2,169 bp long, was a polypeptide of 723 amino acid residues with a predicted molecular weight of 81, 045. The sequence of parasporin contained the five conserved blocks commonly found in B. thuringiensis Cry proteins; however, only very low homologies (<25%) between parasporin and the existing classes of Cry and Cyt proteins were detected. Parasporin exhibited cytocidal activity only when degraded by proteases into smaller molecules of 40 to 60 kDa. Trypsin and proteinase K activated parasporin, while chymotrypsin did not. The activated parasporin showed strong cytocidal activity against human leukemic T cells (MOLT-4) and human uterus cervix cancer cells (HeLa) but not against normal T cells.

Cloning and characterization of a Bacillus thuringiensis serovar higo gene encoding a novel class of the delta-endotoxin protein, Cry27A, specifically active on the Anopheles mosquito

A novel gene encoding a 98-kDa mosquitocidal delta-endotoxin protein, designated Cry27A, was cloned from a Bacillus thuringiensis serovar higo strain. The Cry27A protein contained the five sequence blocks of amino acids commonly conserved in most B. thuringiensis Cry proteins. Relatively high homologies, ranging from 43.0% to 84.4%, existed between the Cry27A protein and several established classes of mosquitocidal Cry proteins (Cry4A, Cry10A, Cry19A, Cry19B, and Cry20A) in the sequence of 51 N-terminal amino acids. The complete sequence of this protein, however, showed low levels (<40%) of amino acid identity to those of the known Cry proteins. Although the expression level of the cry27A gene was low in the transformants under the control of its own promoter, the use of the cyt1A promoter resulted in high-level expression of the gene, leading to the formation of inclusions. The expressed Cry27A protein showed larvicidal activity highly specific for Anopheles stephensi, but lacked the toxicity against Culex pipiens molestus and Aedes aegypti. The results suggest that the Cry27A protein is responsible for the Anopheles-preferential toxicity of the B. thuringiensis serovar higo strain.