Biology subjects

Kraigher, B.

Publications and source records attributed to Kraigher, B..

4 recordsLinked to original sources

bioRxiv2025

An ERF transcription factor StPTI5, a novel regulator of endophyte community maintenance in potato

We have recently identified ERF transcription factor PTI5 as a susceptibility factor, negatively regulating immune response to diverse pathogens. Here we investigated the processes involved in colonisation of potato with beneficial organisms. RNAseq showed that at the time of Bacillus subtilis biofilm establishment, immune responses in interacting roots were attenuated, and complex transcriptional network was triggered, with ethylene signalling being a central module and PTI5 strongly induced. Interestingly, the response is intensified if plants are inoculated by two antagonistic B. subtilis strains. While PTI5 is not involved in the establishment of biofilm on roots, we show that bacterial abundance increases in PTI5-silenced plants. Remarkably, root colonization by the arbuscular mycorrhizal fungus Rhizophagus irregularis was also higher in the PTI5-silenced plants. PTI5 is thus involved both in blocking defence against harmful and blocking colonisation with beneficial microbes. Such mechanistic understanding of plant-microbe interaction paves the way for sustainable crop management.

plant biology↗

bioRxiv2024

The rise of cheats during experimental evolution is restricted by non-kin interactions between Bacillus subtilis soil isolates

Cooperative behaviors in human, animal, and even microbial societies are vulnerable to exploitation. Kin discrimination (KD) has been hypothesized to help stabilize cooperation. However, the mechanisms that sustain cooperative behavior remain poorly understood. We here investigate the role of KD in limiting the rise of cheats during surfactant dependent cooperative swarming over surfaces by bacterium Bacillus subtilis as a model organism. We show that mixing surfactant secreting cooperators and cheats that do not produce surfactants leads to cooperation collapse. However, when such mixed swarms transiently encounter non-kin B. subtilis swarms, the frequency of the surfactant nonproducers decreases, suggesting that kinship dependent interactions may limit cheats advantage. To further validate this hypothesis, we subjected wild-type co-operators to transient encounters with kin and non-kin swarms over 20 cycles of experimental evolution. Evolved populations exposed to non-kin swarms exhibited lower occurrences of genotypes with defective swarming phenotypes compared to those encountering kin swarms. These results provide compelling support for the prediction that the evolution of cheats in bacterial populations is impeded by kin discrimination providing experimental proof of its role in stabilizing cooperative behavior.

microbiology↗

bioRxiv2021

Kin discrimination modifies fitness, spatial segregation and matrix sharing between strains with low relatedness in Bacillus subtilis biofilms

Microorganisms in nature form multicellular groups called biofilms. In biofilms bacteria embedded in a matrix of extracellular polymeric substances (EPS) interact intensely, due to their proximity to each other. Most studies have investigated genetically homogeneous biofilms, leaving a gap in knowledge on genetically heterogeneous biofilms. Recent insights show that a Gram-positive model bacterium, Bacillus subtilis, discriminates between strains of high (kin) and low (non-kin) phylogenetic relatedness, reflected in merging (kin) and boundaries (non-kin) between swarms. However, it is not clear how kinship between interacting strains affects their fitness, the genotype distribution, and the EPS sharing in floating biofilms (pellicles). To address this gap in knowledge we cultivate B. subtilis strains as mixtures of kin and non-kin strains in static cultures, allowing them to form pellicles. We show here that in non-kin pellicles only one strains fitness was reduced; at the same time, strains segregated into larger patches and exhibited decreased matrix sharing, as compared to kin and isogenic pellicles, in which both strains had comparable colony forming units (CFU) counts and more homogenous cell mixing. Overall, our results emphasize kin discrimination (KD) as a social behavior that shapes fitness, spatial segregation and sharing of the extracellular matrix in genetically heterogenous biofilms of B. subtilis. IMPORTANCEBiofilm communities have both beneficial and harmful effects on human societies in natural, medical and industrial environments. Bacillus subtilis, a Gram-positive and biotechnologically important bacterium, serves as a model for studying biofilms. Recent studies have shown that this species engages in kin discriminatory behavior during swarming, which may have implications for community assembly, thus being of fundamental importance. Effects of KD on fitness, genotype segregation and matrix sharing in biofilms is not well understood. By using environmental strains with determined kin types and integrated fluorescent reporters we provide evidence that KD involves antagonism of the dominant strain against non-kin, which has important implications for genotype segregation and sharing of matrix polysaccharides between producers and non-producers. Our results reveal novel consequences of KD and are important for advancing our fundamental understanding of microbial sociality, and its role in the assembly of multicellular groups and in the shaping of microbial diversity.

ecology↗

bioRxiv2019

Intra-species DNA exchange: Bacillus subtilis prefers sex with less related strains

B. subtilis is a surface-dwelling bacterium that is competent for natural transformation. Genetically distinct B. subtilis swarms form a boundary upon encounter, mediated by a fast-evolving molecular kin discrimination (KD) system. We here demonstrate that KD-mediated swarm antagonisms in B. subtilis promote transformation-mediated horizontal gene transfer between strains of low relatedness. Gene transfer is largely uni-directional and the result of the induction of competence of the recipient strain by the donor strain is linked to a sigW-mediated stress response. More closely related strains, which in theory would experience more efficient recombination due to increased sequence homology, did not upregulate transformation upon encounter, demonstrating that social interactions can override mechanistic barriers to horizontal gene transfer. KD-mediated competence in response to the encounter of distinct neighbouring strains could maximize the probability of efficient incorporation of novel alleles and genes that have proved to function in a genomically and ecologically similar context.

microbiology↗