Characterization of native Bacillus thuringiensis strains by PCR-RAPD based fingerprinting

Genetic fingerprint and diversity evaluation of halophilic Bacillus species by RAPD-PCR

Random amplified polymorphic DNA-PCR (RAPD-PCR) is a technique successfully used to generate characteristic fingerprints of different bacteria. Bacillus is a genus that includes heterogeneous species, thus a combination of different techniques is essential for their identification. Here we used RAPD-PCR methodology to distinguish among genetically similar strains and to evaluate the genetic diversity of Bacillus species from the Salar del Hombre Muerto, in the Northwest of Argentina. The RAPD-PCR used allowed obtaining different amplification profiles for each Bacillus species and strains. By comparing the fingerprint profiles, we could observe that some of the salt flat isolates showed similar profiles than identified strains. As expected, the bacilli group isolated revealed a wide heterogeneity. RAPD-PCR was found to be a quick and reliable technique to evaluate the diversity of Bacillus strain and was successfully applied to characterize the genetic diversity present in the Salar del Hombre Muerto.

Study on the Identification Methods for Effective Microorganisms in Commercially Available Organic Agriculture Materials

The identification of microorganisms in closely related groups is challenging. The present work focused on the different molecular methodology for the accurate microbial identification in the five commercially available organic agriculture materials enriched with effective microorganisms. From the tested five organic agricultural materials, a total of seven distinct bacterial colonies (A-1, B-1, C-1, D-1, E-1, E-2, and E-3) were isolated and processed for sequential identification utilizing HiCrome™ Bacillus agar, biochemical tests with API CHB50, 16S rRNA gene analysis, random amplified polymorphic DNA (RAPD), and species-specific PCR analysis. All the isolated microorganisms were Gram-positive rods and spore former belonging to Bacillus group and appeared as a differential characteristic feature on HiCrome™ Bacillus agar. All isolates showed high-percentage similarities with the different members of Bacillus species in biochemical testing and 16S rRNA gene analysis. The collective identification results revealed isolates, A-1, B-1, and C-1, close to B. velezensis. Further RAPD-PCR and species-specific PCR discriminated and provided confirmatory evidence for D-1 as B. thuringiensis and E-1, E-2, and E-3 as B. licheniformis, respectively. In addition, presence of B. thuringiensis was also confirmed by toxin crystal protein staining. In conclusion, the species-specific primers could be used as a rapid and accurate identification tool to discriminate closely related Bacillus species such as B. subtilis, B. licheniformis, and B. thuringiensis.

The correlation of the presence and expression levels of cry genes with the insecticidal activities against Plutella xylostella for Bacillus thuringiensis strains

The use of Bacillusthuringiensis (Bt) strains with high insecticidal activity is essential for the preparation of bioinsecticide. In this study, for 60 Bt strains isolated in Taiwan, their genotypes and the correlation of some cry genes as well as the expression levels of cry1 genes, with their insecticidal activities against Plutella xylostella, were investigated. Pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) results revealed that the genotypes of these Bt strains are highly diversified. Also, a considerable number of the Bt strains isolated in Taiwan were found to have high insecticidal activities. Since strains that showed individual combined patterns of PFGE and RAPD exhibited distinct insecticidal activities against P. xylostella, thus, these genotypes may be useful for the identification of the new Bt strains and those which have been used in bioinsecticides. In addition, although the presence of cry2Aa1 may have a greater effect on the insecticidal activity of Bt strains in bioassay than other cry genes, only high expression level of cry1 genes plays a key role to determine the insecticidal activity of Bt strains. In conclusion, both RAPD and PFGE are effective in the differentiation of Bt strains. The presence of cry2Aa1 and, especially, the expression level of cry1 genes are useful for the prediction of the insecticidal activities of Bt strains against P. xylostella.

Molecular typing of native Bacillus thuringiensis isolates from diverse habitats in India using REP-PCR and ERIC-PCR analysis

Bacillus thuringiensis is a bacterium of great agronomic and scientific interest. The subspecies of this bacterium colonize and kill a large variety of host insects and even nematodes, but each strain does so with a high degree of specificity. Therefore molecular typing and diversity analysis of B. thuringiensis has enormous importance for discrimination of strains isolated from different sources. In this study, 113 native B. thuringiensis isolates collected from diverse habitats and locations in India and 27 B. thuringiensis type strains obtained from the Bacillus Genetic Stock Centre (BGSC), Ohio State University, USA and used as reference, were analyzed for molecular typing. Genotypic data of 140 B. thuringiensis isolates and type strains was generated by using REP-PCR and ERIC-PCR primers and unweighted pair group method with arithmetic mean (UPGMA) analysis using NTSYSpc2.2 and grouped into 4 main clusters. All the groups have isolates from diverse origins. No group was found to represent any specific origin or location. The observed patterns of REP-PCR and ERIC-PCR pattern were discriminatory enough to reveal differences in the B. thuringiensis isolates and reference strains. The resolution power and marker index of the ERIC-PCR (RP 9.39, MI 6.34) was found to be higher than that of the REP-PCR (RP 6.20, MI 4.48). The REP-PCR and ERIC-PCR markers have been found to be useful for discrimination of B. thuringiensis isolates and reference strains. ERIC-PCR was the more informative of the two techniques. This study showed that the B. thuringiensis isolates collected from diverse habitats in India had a high degree of genetic diversity.