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Genome sequence analysis and insecticidal characterization of Bacillus thuringiensis Bt-UNVM_94, a strain showing dual insecticidal activity against lepidopteran and coleopteran pests.
1 , 2 , 2 , 2 , 3 , 4, 5 , 4, 5 , 6 , 7 , * 1, 8
1  Centro de Investigaciones y Transferencia de Villa María (CIT-VM), Universidad Nacional de Villa María, 5900 Villa María, Córdoba, Argentina.
2  Instituto Nacional de Tecnología Agropecuaria (INTA), Instituto de Microbiología y Zoología Agrícola, 1636 Hurlingham, Buenos Aires, Argentina.
3  Department of Biology, Institute of Microbiology, Bialystok University, 15097 Bialystok, Poland.
4  Institute for Multidisciplinary Research in Applied Biology, Universidad Pública de Navarra, 31006 Pamplona, Navarra, Spain.
5  Departamento de Investigación y Desarrollo, Bioinsectis SL, Polígono Industrial Mocholi Plaza CEIN 5, Nave A14, 31110 Noáin, Navarra, Spain.
6  Cardiff School of Biosciences, Cardiff University, Park Place, Cardiff, CF10 3AX, UK
7  ICiagro Litoral, Universidad Nacional del Litoral, CONICET, Facultad de Ciencias Agrarias.
8  Instituto de Ciencias Básicas y Aplicadas (IAPCByA), Universidad Nacional de Villa María (UNVM), 5900 Villa María, Córdoba, Argentina.


Bacillus thuringiensis is a gram-positive and spore-forming bacterium that synthesizes a wide diversity of proteins with insecticidal activity and which has demonstrated its potential and safety as a biocontrol agent for more than four decades. However, several susceptible insect species have been reported for evolving resistance, which demands screening for strains exhibiting novel insecticidal properties. In this work, we performed the genome sequence analysis and the insecticidal characterization of B. thuringiensis strain Bt-UNVM_94 isolated from Argentina. This strain produced quasi symmetric bipyramidal parasporal crystals as shown using Scanning Electron Microscopy. Its genomic sequence harbours one coding sequence showing homology to the crystal toxin Cry7Ga2 and another, with similarity to the Mpp2Aa3 (Mtx2) toxin. Known Cry7A and Cry7B are known to be active against some coleopteran and lepidopteran larvae, respectively. However, bioassays performed with spore-crystal mixtures of strain Bt-UNVM_94 exhibited dual toxicity with 50% and 91% mortality against Cydia pomonella (Lepidoptera: Tortricidae) and Anthonomus grandis (Coleoptera: Curculionidae), respectively. No toxicity was detected against the free-living nematode Panagrellus redivivus (Rhabditidae: Panagrolaimidae). This strain also showed no PCR amplification of the type I b-exotoxin thuE gene, consistent with the absence of mortality in b-exotoxin bioassays with Musca domestica (Diptera: Muscidae). Screenings of novel B. thuringiensis strains may provide toxins with novel insecticidal properties that can be used to suppress insect resistance to the most used B. thuringiensis-crops in the field.

Keywords: Bacillus thuringiensis; Cry toxins; Biological control; Insect pests