Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.

Bacillus thuringiensis (Bt) and its insecticidal toxins are widely exploited in microbial biopesticides and genetically modified crops. Its population biology is, however, poorly understood. Important issues for the safe, sustainable exploitation of Bt include understanding how selection maintains e...

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Autores principales:	Ben Raymond, Kelly L Wyres, Samuel K Sheppard, Richard J Ellis, Michael B Bonsall
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2010
Materias:	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/a33884e201b7441897790e10a1c2f639
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spelling	oai:doaj.org-article:a33884e201b7441897790e10a1c2f6392021-12-02T20:00:39ZEnvironmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.1553-73661553-737410.1371/journal.ppat.1000905https://doaj.org/article/a33884e201b7441897790e10a1c2f6392010-05-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/20502683/?tool=EBIhttps://doaj.org/toc/1553-7366https://doaj.org/toc/1553-7374Bacillus thuringiensis (Bt) and its insecticidal toxins are widely exploited in microbial biopesticides and genetically modified crops. Its population biology is, however, poorly understood. Important issues for the safe, sustainable exploitation of Bt include understanding how selection maintains expression of insecticidal toxins in nature, whether entomopathogenic Bt is ecologically distinct from related human pathogens in the Bacillus cereus group, and how the use of microbial pesticides alters natural bacterial populations. We addressed these questions with a MLST scheme applied to a field experiment in which we excluded/added insect hosts and microbial pesticides in a factorial design. The presence of insects increased the density of Bt/B. cereus in the soil and the proportion of strains expressing insecticidal toxins. We found a near-epidemic population structure dominated by a single entomopathogenic genotype (ST8) in sprayed and unsprayed enclosures. Biopesticidal ST8 proliferated in hosts after spraying but was also found naturally associated with leaves more than any other genotype. In an independent experiment several ST8 isolates proved better than a range of non-pathogenic STs at endophytic and epiphytic colonization of seedlings from soil. This is the first experimental demonstration of Bt behaving as a specialized insect pathogen in the field. These data provide a basis for understanding both Bt ecology and the influence of anthropogenic factors on Bt populations. This natural population of Bt showed habitat associations and a population structure that differed markedly from previous MLST studies of less ecologically coherent B. cereus sample collections. The host-specific adaptations of ST8, its close association with its toxin plasmid and its high prevalence within its clade are analogous to the biology of Bacillus anthracis. This prevalence also suggests that selection for resistance to the insecticidal toxins of ST8 will have been stronger than for other toxin classes.Ben RaymondKelly L WyresSamuel K SheppardRichard J EllisMichael B BonsallPublic Library of Science (PLoS)articleImmunologic diseases. AllergyRC581-607Biology (General)QH301-705.5ENPLoS Pathogens, Vol 6, Iss 5, p e1000905 (2010)
institution	DOAJ
collection	DOAJ
language	EN
topic	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5
spellingShingle	Immunologic diseases. Allergy RC581-607 Biology (General) QH301-705.5 Ben Raymond Kelly L Wyres Samuel K Sheppard Richard J Ellis Michael B Bonsall Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
description	Bacillus thuringiensis (Bt) and its insecticidal toxins are widely exploited in microbial biopesticides and genetically modified crops. Its population biology is, however, poorly understood. Important issues for the safe, sustainable exploitation of Bt include understanding how selection maintains expression of insecticidal toxins in nature, whether entomopathogenic Bt is ecologically distinct from related human pathogens in the Bacillus cereus group, and how the use of microbial pesticides alters natural bacterial populations. We addressed these questions with a MLST scheme applied to a field experiment in which we excluded/added insect hosts and microbial pesticides in a factorial design. The presence of insects increased the density of Bt/B. cereus in the soil and the proportion of strains expressing insecticidal toxins. We found a near-epidemic population structure dominated by a single entomopathogenic genotype (ST8) in sprayed and unsprayed enclosures. Biopesticidal ST8 proliferated in hosts after spraying but was also found naturally associated with leaves more than any other genotype. In an independent experiment several ST8 isolates proved better than a range of non-pathogenic STs at endophytic and epiphytic colonization of seedlings from soil. This is the first experimental demonstration of Bt behaving as a specialized insect pathogen in the field. These data provide a basis for understanding both Bt ecology and the influence of anthropogenic factors on Bt populations. This natural population of Bt showed habitat associations and a population structure that differed markedly from previous MLST studies of less ecologically coherent B. cereus sample collections. The host-specific adaptations of ST8, its close association with its toxin plasmid and its high prevalence within its clade are analogous to the biology of Bacillus anthracis. This prevalence also suggests that selection for resistance to the insecticidal toxins of ST8 will have been stronger than for other toxin classes.
format	article
author	Ben Raymond Kelly L Wyres Samuel K Sheppard Richard J Ellis Michael B Bonsall
author_facet	Ben Raymond Kelly L Wyres Samuel K Sheppard Richard J Ellis Michael B Bonsall
author_sort	Ben Raymond
title	Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
title_short	Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
title_full	Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
title_fullStr	Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
title_full_unstemmed	Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.
title_sort	environmental factors determining the epidemiology and population genetic structure of the bacillus cereus group in the field.
publisher	Public Library of Science (PLoS)
publishDate	2010
url	https://doaj.org/article/a33884e201b7441897790e10a1c2f639
work_keys_str_mv	AT benraymond environmentalfactorsdeterminingtheepidemiologyandpopulationgeneticstructureofthebacilluscereusgroupinthefield AT kellylwyres environmentalfactorsdeterminingtheepidemiologyandpopulationgeneticstructureofthebacilluscereusgroupinthefield AT samuelksheppard environmentalfactorsdeterminingtheepidemiologyandpopulationgeneticstructureofthebacilluscereusgroupinthefield AT richardjellis environmentalfactorsdeterminingtheepidemiologyandpopulationgeneticstructureofthebacilluscereusgroupinthefield AT michaelbbonsall environmentalfactorsdeterminingtheepidemiologyandpopulationgeneticstructureofthebacilluscereusgroupinthefield
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Environmental factors determining the epidemiology and population genetic structure of the Bacillus cereus group in the field.

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