title: Necrotrophism is a quorum-sensing-regulated lifestyle in Bacillus thuringiensis.
abstract: How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading.
authors.affiliation: INRA, UMR1319 Micalis, La Minière, Guyancourt, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dubois
authors.forename: Karoline
authors.initials: K
authors.lastname: Faegri
authors.forename: Stéphane
authors.initials: S
authors.lastname: Perchat
authors.forename: Christelle
authors.initials: C
authors.lastname: Lemy
authors.forename: Christophe
authors.initials: C
authors.lastname: Buisson
authors.forename: Christina
authors.initials: C
authors.lastname: Nielsen-LeRoux
authors.forename: Michel
authors.initials: M
authors.lastname: Gohar
authors.forename: Philippe
authors.initials: P
authors.lastname: Jacques
authors.forename: Nalini
authors.initials: N
authors.lastname: Ramarao
authors.forename: Anne-Brit
authors.initials: AB
authors.lastname: Kolstø
authors.forename: Didier
authors.initials: D
authors.lastname: Lereclus
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D007313:Insecta / Q000382:microbiology*; D009154:Mutation; D053038:Quorum Sensing / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins