title: An in-depth characterization of the entomopathogenic strain Bacillus pumilus 15.1 reveals that it produces inclusion bodies similar to the parasporal crystals of Bacillus thuringiensis.
abstract: In the present work, the local isolate Bacillus pumilus 15.1 has been morphologically and biochemically characterized in order to gain a better understanding of this novel entomopathogenic strain active against Ceratitis capitata. This strain could represent an interesting biothechnological tool for the control of this pest. Here, we report on its nutrient preferences, extracellular enzyme production, motility mechanism, biofilm production, antibiotic suceptibility, natural resistance to chemical and physical insults, and morphology of the vegetative cells and spores. The pathogen was found to be β-hemolytic and susceptible to penicillin, ampicillin, chloramphenicol, gentamicin, kanamycin, rifampicin, tetracycline, and streptomycin. We also report a series of biocide, thermal, and UV treatments that reduce the viability of B. pumilus 15.1 by several orders of magnitude. Heat and chemical treatments kill at least 99.9 % of vegetative cells, but spores were much more resistant. Bleach was the only chemical that was able to completely eliminate B. pumilus 15.1 spores. Compared to the B. subtilis 168 spores, B. pumilus 15.1 spores were between 2.67 and 350 times more resistant to UV radiation while the vegetative cells of B. pumilus 15.1 were almost up to 3 orders of magnitude more resistant than the model strain. We performed electron microscopy for morphological characterization, and we observed geometric structures resembling the parasporal crystal inclusions synthesized by Bacillus thuringiensis. Some of the results obtained here such as the parasporal inclusion bodies produced by B. pumilus 15.1 could potentially represent virulence factors of this novel and potentially interesting strain.
authors.affiliation: Institute of Biotechnology, Campus Fuentenueva s/n, University of Granada, 18071, Granada, Spain.
authors.forename: Diana C
authors.initials: DC
authors.lastname: Garcia-Ramon
authors.affiliation: Institute of Biotechnology, Campus Fuentenueva s/n, University of Granada, 18071, Granada, Spain.|Present Address: International Center for Zoonosis (CIZ), Faculty of Veterinary Medicine and Zootechnic, Central University of Ecuador, Quito, Ecuador.
authors.forename: C Alfonso
authors.initials: CA
authors.lastname: Molina
authors.affiliation: Institute of Biotechnology, Campus Fuentenueva s/n, University of Granada, 18071, Granada, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Osuna
authors.affiliation: Institute of Biotechnology, Campus Fuentenueva s/n, University of Granada, 18071, Granada, Spain. svt@ugr.es.|Department of Biochemistry and Molecular Biology I, Campus Fuentenueva s/n, University of Granada, 18071, Granada, Spain. svt@ugr.es.
authors.forename: Susana
authors.initials: S
authors.lastname: Vílchez
mesh_terms: D000818:Animals; D000069979:Bacillus pumilus / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D001413:Bacillus thuringiensis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D033622:Ceratitis capitata / Q000382:microbiology*; D002479:Inclusion Bodies / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D013171:Spores, Bacterial / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D014466:Ultraviolet Rays
keywords: Bacillus pumilus; Crystal inclusions; Entomopathogenic bacteria; UV resistance