Minor Keywords of Political Theory: Migration as a Critical Standpoint. A collaborative project of collective writing

Coordinated and Edited by: N De Genova, M Tazzioli Co-Authored by: Claudia Aradau, Brenna Bhandar, Manuela Bojadzijev, Josue David Cisneros, N De Genova, Julia Eckert, Elena Fontanari, Tanya Golash-Boza, Jef Huysmans, Shahram Khosravi, Clara Lecadet, Patrisia Macías-Rojas, Federica Mazzara, Anne McNevin, Peter Nyers, Stephan Scheel, Nandita Sharma, Maurice Stierl, Vicki Squire, M Tazzioli, Huub van Baar and William Walter

Molecular basis for group-specific activation of the virulence regulator PlcR by PapR heptapeptides

The transcriptional regulator PlcR and its cognate cell–cell signalling peptide PapR form a quorum-sensing system that controls the expression of extra-cellular virulence factors in various species of the Bacillus cereus group. PlcR and PapR alleles are clustered into four groups defining four pherotypes. However, the molecular basis for group specificity remains elusive, largely because the biologically relevant PapR form is not known. Here, we show that the in vivo active form of PapR is the C-terminal heptapeptide of the precursor, and not the pentapeptide, as previously suggested. Combining genetic complementation, anisotropy assays and structural analysis we provide a detailed functional and structural explanation for the group specificity of the PlcR–PapR quorum-sensing system. We further show that the C-terminal helix of the PlcR regulatory domain, specifically the 278 residue, in conjunction with the N-terminal residues of the PapR heptapeptide determines this system specificity. Variability in the specificity-encoding regions of plcR and papR genes suggests that selection and evolution of quorum-sensing systems play a major role in adaptation and ecology of Bacilli

Necrotrophism Is a Quorum-Sensing-Regulated Lifestyle in Bacillus thuringiensis

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

Immunological and Metabolomic Impacts of Administration of Cry1Ab Protein and MON 810 Maize in Mouse

We have investigated the immunological and metabolomic impacts of Cry1Ab administration to mice, either as a purified protein or as the Cry1Ab-expressing genetically modified (GM) MON810 maize. Humoral and cellular specific immune responses induced in BALB/cJ mice after intra-gastric (i.g.) or intra-peritoneal (i.p.) administration of purified Cry1Ab were analyzed and compared with those induced by proteins of various immunogenic and allergic potencies. Possible unintended effects of the genetic modification on the pattern of expression of maize natural allergens were studied using IgE-immunoblot and sera from maize-allergic patients. Mice were experimentally sensitized (i.g. or i.p. route) with protein extracts from GM or non-GM maize, and then anti-maize proteins and anti-Cry1Ab–induced immune responses were analyzed. In parallel, longitudinal metabolomic studies were performed on the urine of mice treated via the i.g. route. Weak immune responses were observed after i.g. administration of the different proteins. Using the i.p. route, a clear Th2 response was observed with the known allergenic proteins, whereas a mixed Th1/Th2 immune response was observed with immunogenic protein not known to be allergenic and with Cry1Ab. This then reflects protein immunogenicity in the BALB/c Th2-biased mouse strain rather than allergenicity. No difference in natural maize allergen profiles was evidenced between MON810 and its non-GM comparator. Immune responses against maize proteins were quantitatively equivalent in mice treated with MON810 vs the non-GM counterpart and no anti-Cry1Ab–specific immune response was detected in mice that received MON810. Metabolomic studies showed a slight “cultivar” effect, which represented less than 1% of the initial metabolic information. Our results confirm the immunogenicity of purified Cry1Ab without evidence of allergenic potential. Immunological and metabolomic studies revealed slight differences in mouse metabolic profiles after i.g. administration of MON810 vs its non-GM counterpart, but no significant unintended effect of the genetic modification on immune responses was seen

Bacterial Cooperation Causes Systematic Errors in Pathogen Risk Assessment due to the Failure of the Independent Action Hypothesis

The Independent Action Hypothesis (IAH) states that pathogenic individuals (cells, spores, virus particles etc.) behave independently of each other, so that each has an independent probability of causing systemic infection or death. The IAH is not just of basic scientific interest; it forms the basis of our current estimates of infectious disease risk in humans. Despite the important role of the IAH in managing disease interventions for food and water-borne pathogens, experimental support for the IAH in bacterial pathogens is indirect at best. Moreover since the IAH was first proposed, cooperative behaviors have been discovered in a wide range of microorganisms, including many pathogens. A fundamental principle of cooperation is that the fitness of individuals is affected by the presence and behaviors of others, which is contrary to the assumption of independent action. In this paper, we test the IAH in Bacillus thuringiensis (B.t), a widely occurring insect pathogen that releases toxins that benefit others in the inoculum, infecting the diamondback moth, Plutella xylostella. By experimentally separating B.t. spores from their toxins, we demonstrate that the IAH fails because there is an interaction between toxin and spore effects on mortality, where the toxin effect is synergistic and cannot be accommodated by independence assumptions. Finally, we show that applying recommended IAH dose-response models to high dose data leads to systematic overestimation of mortality risks at low doses, due to the presence of synergistic pathogen interactions. Our results show that cooperative secretions can easily invalidate the IAH, and that such mechanistic details should be incorporated into pathogen risk analysis

Isolation of a DNA sequence related to several plasmids from Bacillus thuringiensis after a mating involving the Streptococcus faecalis plasmid pAM beta 1

The transmissible plasmid pAM beta 1, which codes for resistance to erythromycin and lincomycin, was transferred from Streptococcus faecalis to several strains of Bacillus thuringiensis by a filter-mating process. Introduction of pAM beta 1 into the Emr transconjugant strains of B. thuringiensis was confirmed by Southern hybridisation using the 32P-labelled pAM beta 1 as a probe. In the B. thuringiensis transconjugant strains, used as donors, the beta plasmid conserved its ability to be transferred during intraspecific mating, with a frequency of 10(-4) per recipient cell. In addition, the transconjugant clones acted as donors of the erythromycin resistance marker and permitted the transfer of cryptic plasmids present in the B. thuringiensis (beta) strains used as donors. From a transconjugant clone of B. thuringiensis a hybrid plasmid resulting from an in vivo insertion into pAM beta 1 of a 3 Md DNA sequence was isolated. This 3 Md DNA molecule originated from a 54 Md plasmid of a kurstaki strain and is related to several plasmids found in different serotypes of B. thuringiensis