Project description:Sulfonamides are traditional synthetic antimicrobial agents used in clinical and veterinary medical settings. Their long-term excessive overuse has resulted in widespread microbial resistance, limiting their application for medical interventions. Resistance to sulfonamides is primarily conferred by the alternative genes sul1, sul2, and sul3 encoding dihydropteroate synthase in bacteria. Studying the potential fitness cost of these sul genes is crucial for understanding the evolution and transmission of sulfonamide-resistant bacteria. In vitro studies have been conducted on the fitness cost of sul genes in bacteria. In this study, we provide critical insights into bacterial adaptation and transmission using an in vivo approach.
Project description:We evolved Escherichia coli cells over 500 generations under five environments that include four abiotic stressors: osmotic, acidic, oxidative, n-butanol, and control The goal of the experiment: Bacterial populations have a remarkable capacity to cope with extreme environmental fluctuations in their natural environments. In certain cases, adaptation to one stressful environment provides a fitness advantage when cells are exposed to a second stressor, a phenomenon that has been coined as cross-stress protection. A tantalizing question in bacterial physiology is how the cross-stress behavior emerges during adaptation and what the genetic basis of acquired stress resistance is.
Project description:Adenosine-to-inosine A-to-I mRNA editing alters genetic information post-transcriptionally and can impact protein sequence and function, yet its regulation in bacteria remains unclear. Here, we profiled A-to-I editing in Escherichia coli across nutrient-rich LB and minimal M9 media and different growth phases. Our analysis expanded the repertoire of TadA-dependent A-to-I edited mRNAs to 27, including 12 novel sites, and revealed that editing levels were dynamic and markedly increased at stationary phase in LB but not in M9. Editing levels were independent of mRNA expression yet correlated with tRNA-Arg2 downregulation, and overexpressing tRNA-Arg2 reduced mRNA editing, demonstrating substrate competition for TadA, the sole bacterial tRNA adenosine deaminase. Mutants with TadA-deficient editing or reduced tRNA-Arg2 expression displayed similar LB-specific growth defects. Moreover, tRNA-Arg2 expression, tRNA-Arg2-dependent codon usage, and tRNA-Arg2 editing were all elevated in LB compared to M9. These findings establish regulatory principles for bacterial RNA editing, implicate tRNA editing in nutrient-responsive fitness, and provide a framework to explore the physiological roles of mRNA editing
Project description:Transfer RNAs (tRNAs) are essential components of the translation machinery and carry numerous post‑transcriptional modifications that contribute to decoding accuracy, efficiency and cellular fitness. In Escherichia coli K‑12, all tRNA modification pathways have been identified, yet the functional interactions between these pathways remain largely unexplored. Here, we systematically analyses genetic interactions between 29 non‑essential tRNA modification genes using a pairwise synthetic lethal screen based on P1 transduction. Most combinations of tRNA modification gene deletions are tolerated during growth in rich medium; however, we identify five synthetically lethal pairs and fifteen additional combinations that display negative genetic interactions. Deletions of truA, which encodes the pseudouridine synthase responsible for modifications at positions 38–40 of multiple tRNAs, show the highest frequency of negative epistasis. Synthetic lethality associated with truA can be complemented by expression of truA in trans and, in specific cases, partially suppressed by overexpression of its tRNA substrates, indicating substrate‑specific functional dependencies. Analysis of tRNA abundance by northern blotting and AQRNA‑seq demonstrates that loss of individual tRNA modification enzymes does not generally lead to widespread tRNA destabilization. Instead, further phenotypic characterization of viable double mutants reveals condition‑dependent growth defects influenced by carbon source, temperature and metabolic stress, as well as toxicity associated with overexpression of specific tRNAs. Together, these results reveal a limited but distinct set of genetic interactions among bacterial tRNA modification pathways and highlight the importance of physiological context in uncovering their cellular roles.
Project description:We evolved Escherichia coli cells over 500 generations under five environments that include four abiotic stressors: osmotic, acidic, oxidative, n-butanol, and control The goal of the experiment: Bacterial populations have a remarkable capacity to cope with extreme environmental fluctuations in their natural environments. In certain cases, adaptation to one stressful environment provides a fitness advantage when cells are exposed to a second stressor, a phenomenon that has been coined as cross-stress protection. A tantalizing question in bacterial physiology is how the cross-stress behavior emerges during adaptation and what the genetic basis of acquired stress resistance is. RNA profiles were obtained for six E. coli strains evolved for 500 generations under abiotic stressors; two technical replicates for each strain where sequenced by Illumina GAII analyzer
Project description:DNA damage induces the mutations that drive bacterial adaption, evolution, and antibiotic escape. Both mutagenic and non-mutagenic DNA damage repair is coordinated by the SOS response, but despite extensive work, the functions of some SOS-induced genes remain obscure. Here, we clarify the function of Escherichia coli SbmC (GyrI). Despite its proposed function as a gyrase inhibitor, cells either lacking or overexpressing SbmC instead exhibit phenotypes consistent with a role in limiting DNA damage and cellular variation. Importantly, SbmC levels inversely correlate with E. coli mutation rate. Excess SbmC limits mutation whereas loss of SbmC increases mutation, possibly because ∆sbmC cells variably induce the SOS response, including mutagenic DNA Pol V. We additionally show that SbmC is dispensable for survival in the presence of double-strand break inducing drugs but is required to limit their mutational effects. Finally, evolutionary analysis indicates that bacterial SbmC homologs maintain their small molecule-binding domain but not the gyrase interacting residues identified in E. coli. Together, our findings suggest that SbmC-like proteins may bind to a yet-unknown cofactor to limit DNA damage and organismal evolution.
Project description:We used microarrays to study the changes in whole-genome expression profiles accompanying the evolution of one bacterial population propagated in glucose minimal medium for 20,000 generations.
Project description:Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription. Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription.
Project description:Type IV secretion systems (T4SSs) are central to bacterial pathogenesis due to their versatile functions. While traditionally known for their role in DNA transfer via conjugation and secretion of effector proteins, T4SSs have been shown to mediate biofilm formation in various bacteria. These biofilms are critical for the fitness of adherent-invasive strains of Escherichia coli (AIEC), which are commonly isolated from Crohn’s disease patients and are known for propelling gut inflammation. Many AIEC strains carry F-like plasmids encoding the IncF subgroup of T4SSs. Unlike minimized systems that comprise 12 core components, the IncF family has evolved into an expanded T4SS through the acquisition of additional genes that enhance conjugation. Here, we show that a biofilm-forming AIEC strain harbors an unusual IncF plasmid that lacks two conserved components otherwise considered essential for T4SS functionality. We demonstrate that this strain forms a natural hybrid T4SS, where the two components missing in the plasmid are supplied by a co-residing chromosomal T4SS present on an integrative and conjugative element (ICE). Using biochemical assays, we show that this functional machine is a mosaic of IncF and ICE-encoded proteins that co-operatively drive pilin polymerization and biofilm formation on epithelial cells. Furthermore, we show that a subpopulation of bacteria expresses the IncF and ICE-encoded genes in response to host cells, leading to the assembly of biofilms that promote AIEC fitness in the gut. Together, these findings uncover a crosstalk between two co-residing and evolutionary distant mobile genetic elements to form a hybrid T4SS that mediates biofilm biogenesis by a Crohn’s disease-associated pathogen.