Microevolution of Anthrax from a Young Ancestor (M.A.Y.A.) Suggests a Soil-Borne Life Cycle of Bacillus anthracis.
During an anthrax outbreak at the Pollino National Park (Basilicata, Italy) in 2004, diseased cattle were buried and from these anthrax-foci Bacillus anthracis endospores still diffuse to the surface resulting in local accumulations. Recent data suggest that B. anthracis multiplies in soil outside the animal-host body. This notion is supported by the frequent isolation of B. anthracis from soil lacking one or both virulence plasmids. Such strains represent an evolutionary dead end, as they are likely no longer able to successfully infect new hosts. This loss of virulence plasmids is explained most simply by postulating a soil-borne life cycle of the pathogen. To test this hypothesis we investigated possible microevolution at two natural anthrax foci from the 2004 outbreak. If valid, then genotypes of strains isolated from near the surface at these foci should be on a different evolutionary trajectory from those below residing in deeper-laying horizons close to the carcass. Thus, the genetic diversity of B. anthracis isolates was compared conducting Progressive Hierarchical Resolving Assays using Nucleic Acids (PHRANA) and next generation Whole Genome Sequencing (WGS). PHRANA was not discriminatory enough to resolve the fine genetic relationships between the isolates. Conversely, WGS of nine isolates from near-surface and nine from near-carcass revealed five isolate specific SNPs, four of which were found only in different near-surface isolates. In support of our hypothesis, one surface-isolate lacked plasmid pXO1 and also harbored one of the unique SNPs. Taken together, our results suggest a limited soil-borne life cycle of B. anthracis.
Bundeswehr Institute of Microbiology, Munich, Germany; Technische Universität München, Wissenschaftszentrum Weihenstephan, Chair for Soil Ecology, Freising, Germany.
Peter
P
Braun
Bundeswehr Institute of Microbiology, Munich, Germany.
Gregor
G
Grass
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Angela
A
Aceti
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Luigina
L
Serrecchia
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Alessia
A
Affuso
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Leonardo
L
Marino
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Stefania
S
Grimaldi
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Stefania
S
Pagano
Bundeswehr Institute of Microbiology, Munich, Germany.
Matthias
M
Hanczaruk
Bundeswehr Institute of Microbiology, Munich, Germany.
Enrico
E
Georgi
Bundeswehr Institute of Microbiology, Munich, Germany; Ludwig Maximilians Universität München, Institute for Laboratory Medicine, Munich, Germany.
Bernd
B
Northoff
German Research Center for Environmental Health, Research Unit for Environmental Genomics, Neuherberg, Germany.
Anne
A
Schöler
Technische Universität München, Wissenschaftszentrum Weihenstephan, Chair for Soil Ecology, Freising, Germany; German Research Center for Environmental Health, Research Unit for Environmental Genomics, Neuherberg, Germany.
Michael
M
Schloter
Bundeswehr Institute of Microbiology, Munich, Germany.
Markus
M
Antwerpen
Istituto Zooprofilattico Sperimentale of Puglia and Basilicata, Anthrax Reference Institute of Italy, Foggia, Italy.
Antonio
A
Fasanella
D000818:Animals; D000881:Anthrax / Q000382:microbiology* / Q000662:veterinary; D001408:Bacillus anthracis / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity; D002417:Cattle; D004196:Disease Outbreaks; D019143:Evolution, Molecular; D064349:Genome, Microbial; D008018:Life Cycle Stages; D020641:Polymorphism, Single Nucleotide; D012988:Soil Microbiology