Einzelzellanalyse der MazF-abhängigen Stressantwort

Bacteria adapt to adverse environmental conditions by altering gene expression patterns. Recently, a novel stress adaptation mechanism has been described that allows Escherichia coli to alter gene expression at the post-transcriptional level. The endoribonuclease MazF (the toxin component of the toxin-antitoxin module MazEF) is one of the key players responsible for the stress-induced production of leaderless mRNAs, which lack the ribosome binding site. MazF concomitantly modifies the ribosomes, making them selective for the translation of leaderless mRNAs. Intriguingly, the activation of MazF and other toxin-antitoxin systems has been implicated in the persistence phenotype in E. coli. Persistence is a prime example of phenotypic heterogeneity that arises in populations of genetically identical cells independently of genetic or environmental differences. Persister cells represent only a minor fraction of a clonal population that grows much slower than the majority of cells and can endure antibiotic treatments.
However, the function of MazF in bacterial cells that persist antibiotic treatment or nutrient starvation still remains elusive. Thus, my main interest is to study the MazF-mediated post-transcriptional stress response from the single-cell perspective. Since only a small fraction of a bacterial population is able to express the persistence phenotype, I will address the question whether all cells or only a fraction of cells within a clonal population induce MazF under antibiotic stress or nutrient starvation. I hypothesize that the potential heterogeneous production and translation of leaderless mRNAs provide benefits for bacterial populations. Consequently, the cells with active MazF would selectively survive stress and thereby represent the subpopulation that will resume growth after the stress is removed. To tackle these questions, I will use flow cytometry combined with biochemical techniques as well as fluorescence time-lapse microscopy and microfluidics.
This research project is anticipated to assess the physiological importance of the newly discovered MazF-dependent stress adaptation mechanism in single bacterial cells with respect to survival of the population. Hence, the expected results will provide novel insights into the molecular basis of phenotypic heterogeneity in the bacterial stress response and will contribute to a better understanding how bacterial populations endure antibiotic treatments and starvation upon host infection. Collectively, this is an important step towards development of strategies for the eradication of persister cells, which is currently one of the most challenging problems in medical microbiology.