title: Identification of distinct Bacillus thuringiensis 4A4 nematicidal factors using the model nematodes Pristionchus pacificus and Caenorhabditis elegans.
abstract: Bacillus thuringiensis has been extensively used for the biological control of insect pests. Nematicidal B. thuringiensis strains have also been identified; however, virulence factors of such strains are poorly investigated. Here, we describe virulence factors of the nematicidal B. thuringiensis 4A4 strain, using the model nematodes Pristionchus pacificus and Caenorhabditis elegans. We show that B. thuringiensis 4A4 kills both nematodes via intestinal damage. Whole genome sequencing of B. thuringiensis 4A4 identified Cry21Ha, Cry1Ba, Vip1/Vip2 and β-exotoxin as potential nematicidal factors. Only Cry21Ha showed toxicity to C. elegans, while neither Cry nor Vip toxins were active against P. pacificus, when expressed in E. coli. Purified crystals also failed to intoxicate P. pacificus, while autoclaved spore-crystal mixture of B. thuringiensis 4A4 retained toxicity, suggesting that primary β-exotoxin is responsible for P. pacificus killing. In support of this, we found that a β-exotoxin-deficient variant of B. thuringiensis 4A4, generated by plasmid curing lost virulence to the nematodes. Thus, using two model nematodes we revealed virulence factors of the nematicidal strain B. thuringiensis 4A4 and showed the multifactorial nature of its virulence.
authors.affiliation: Department for Evolutionary Biology, Max-Planck Institute for Developmental Biology, Spemannstrasse 37, 72076 Tuebingen, Germany. igor.iatsenko@tuebingen.mpg.de.
authors.forename: Igor
authors.initials: I
authors.lastname: Iatsenko
authors.affiliation: Institute for Chemistry and Biochemistry, Free University of Berlin, Thielallee 63, 14195 Berlin, Germany. angelnikolov17@yahoo.com.
authors.forename: Angel
authors.initials: A
authors.lastname: Nikolov
authors.affiliation: Department for Evolutionary Biology, Max-Planck Institute for Developmental Biology, Spemannstrasse 37, 72076 Tuebingen, Germany. ralf.sommer@tuebingen.mpg.de.
authors.forename: Ralf J
authors.initials: RJ
authors.lastname: Sommer
mesh_terms: D000818:Animals; D000969:Antinematodal Agents / Q000633:toxicity*; D001413:Bacillus thuringiensis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000633:toxicity*; D001427:Bacterial Toxins / Q000235:genetics / Q000633:toxicity*; D002633:Chemotaxis / Q000187:drug effects; D007422:Intestines / Q000187:drug effects / Q000473:pathology; D009348:Nematoda / Q000187:drug effects* / Q000502:physiology; D037521:Virulence Factors / Q000235:genetics / Q000633:toxicity*
chemical_list: D000969:Antinematodal Agents; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D037521:Virulence Factors