Project Details
Projekt
How cannibalism shapes and functionalizes biofilm tissue in Bacillus subtilis
Applicants
Dr. Daniel Dar, Ph.D.; Professor Dr. Thorsten Mascher
Subject Area
Metabolism, Biochemistry and Genetics of Microorganisms
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 504017689
Bacillus subtilis is a Gram-positive model organism that is able to differentiate into highly structured colony biofilms on solid agar surfaces. This differentiation strategy involves a spatiotemporally controlled diversification of the multicellular community into a number of phenotypically different subpopulations that provide the colony biofilm with an overall selective advantage in fluctuating and competitive environments. Ultimately, prolonged phases of starvation will result in the formation of highly resilient endospores, which are formed by cells at the tip of fruiting bodies within the colony. Cannibalism is a bacterial form of programmed cell death that involves the production of three cannibalism toxins, the sporulation killing factor (SKF), the sporulation delay protein (SDP), and the epipeptide (EPE). As producers, the cannibalistic cells are autoimmune against the self-produced toxins while non-producing sibling cells are not. It was originally postulated that this subpopulation is sacrificed through toxin-dependent lysis, thereby releasing nutrients that can be taken up by the cannibalistic cells to overcome starvation and thereby delay endospore formation, which is an irreversible and energy-demanding process. Understanding the biological significance of cannibalism is an ongoing project and the primary goal of this proposal. Results from the first funding period challenge the original picture of cannibalism as a last-exit survival strategy that involves ‘altruistic killing’ of a subpopulation. Our preliminary data indicate that cannibalism toxins are not primarily killing agents, at least in the context of differentiated colonies. Instead, they structure and functionalize biofilms. We propose that cannibalism balances colony spreading and wrinkling and that the resulting cannibalism-dependent structures THEN determine the functions within them, including the rate of sporulation and cell death. Investigating this hypothesis is the main focus of this joint proposal. To unravel the role of cannibalism toxins for shaping and functionalizing biofilm tissue in B. subtilis development, we will analyze, modify and correlate the relevant differentiation strategies and phenotypes in biofilms by two highly complementary approaches: Spatial transcriptomics will allow studying microcolony differentiation in 2D with single cell resolution, while cryo-thin sectioning of macrocolonies will provide a 3D picture of cannibalism action at a fully differentiated bacterial biofilm. Together, these approaches will provide a comprehensive, spatiotemporally resolved understanding of how cannibalism affects the structure and function of biofilm differentiation across four orders of magnitude, from the micrometer range of individual cells to the cm range of a mature and highly structured colony.
DFG Programme
Priority Programmes
International Connection
Israel
