Molecular Biology and Physiology
Research Article | Molecular Biology and PhysiologyMolecular Basis and Ecological Relevance of Caulobacter Cell Filamentation in Freshwater HabitatsMany bacteria drastically change their cell size and morphology in response to changing environmental conditions. Here, we demonstrate that the freshwater bacterium Caulobacter crescentus and related species transform into filamentous cells in response to conditions that commonly occur in their natural habitat as a result of algal blooms during the warm summer months...
Research Article | Molecular Biology and PhysiologyCombining Mutations That Inhibit Two Distinct Steps of the ATP Hydrolysis Cycle Restores Wild-Type Function in the Lipopolysaccharide Transporter and Shows that ATP Binding Triggers TransportGram-negative bacteria are naturally resistant to many antibiotics because their surface is covered by the glycolipid LPS. Newly synthesized LPS is transported across the cell envelope by the multiprotein Lpt machinery, which includes LptB2FGC, an unusual ABC transporter that extracts LPS from the inner membrane. Like in other ABC transporters, the LptB2FGC transport cycle is driven by the cyclical conformational...
Research Article | Molecular Biology and PhysiologyMetabolomics Analysis Identifies Sphingolipids as Key Signaling Moieties in Appressorium Morphogenesis and Function in Magnaporthe oryzaeOur untargeted analysis of metabolomics throughout the course of pathogenic development gave us an unprecedented high-resolution view of major shifts in metabolism that occur in the topmost fungal pathogen that infects rice, wheat, barley, and millet. Guided by these metabolic insights, we demonstrated their practical application by using two different small-molecule inhibitors of sphingolipid biosynthesis enzymes to successfully block...
Research Article | Molecular Biology and PhysiologyRole of Flagellin-Homologous Proteins in Biofilm Formation by Pathogenic Vibrio SpeciesFlagellar filaments of the pathogenic Vibrio species, including V. vulnificus, V. parahaemolyticus, and V. cholerae, are composed of multiple flagellin subunits. In their genomes, however, there are higher numbers of the...
Research Article | Molecular Biology and PhysiologyMolecular Mimicry of SecA and Signal Recognition Particle Binding to the Bacterial RibosomeBacterial protein transport via the conserved SecYEG translocon is generally classified as either cotranslational, i.e., when transport is coupled to translation, or posttranslational, when translation and transport are separated. We show here that the ATPase SecA, which is considered to bind its substrates posttranslationally, already scans the ribosomal tunnel for potential substrates. In the presence of a nascent chain, SecA retracts...
Research Article | Molecular Biology and PhysiologyAggregation of Nontuberculous Mycobacteria Is Regulated by Carbon-Nitrogen BalanceFree-living bacteria can assemble into multicellular structures called biofilms. Biofilms help bacteria tolerate multiple stresses, including antibiotics and the host immune system. Nontuberculous mycobacteria are a group of emerging opportunistic pathogens that utilize biofilms to adhere to household plumbing and showerheads and to avoid phagocytosis by host immune cells. Typically, bacteria regulate biofilm formation by controlling...
Research Article | Molecular Biology and PhysiologyStructural Basis for the Differential Regulatory Roles of the PDZ Domain in C-Terminal Processing ProteasesPrc, also known previously as Tsp, is the founding member of the carboxyl-terminal processing protease (CTP) family of PDZ domain-containing proteases that include CtpA and CtpB. The substrate-binding PDZ domain is responsible for regulating the protease activity of CTP proteases; however, the regulatory role of PDZ domain is stimulatory in Prc but inhibitory in CtpA/B. By determining a series of crystal structures of Prc in the...
Research Article | Molecular Biology and PhysiologyA Functional Polymorphism-Mediated Disruption of EGR1/ADAM10 Pathway Confers the Risk of Sepsis ProgressionSepsis is characterized as life-threatening organ dysfunction, with unacceptably high mortality. Evidence has indicated that functional SNPs within inflammatory genes are associated with susceptibility, progression, and prognosis of sepsis. These mechanisms on which these susceptible sites depended often suggest the key pathogenesis and potential targets in sepsis. In the present study, we confirmed that a functional variant acts as an...
Research Article | Molecular Biology and PhysiologyRegulation of Iron Storage by CsrA Supports Exponential Growth of Escherichia coliIron is an essential micronutrient for nearly all living organisms but is toxic in excess. Consequently, the maintenance of iron homeostasis is a critical biological process, and the genes involved in this function are tightly regulated. Here, we explored a new role for the bacterial RNA binding protein CsrA in the regulation of iron homeostasis. CsrA was shown to be a key regulator of iron storage genes in...
Research Article | Molecular Biology and PhysiologyFinding of Agr Phase Variants in Staphylococcus aureusStaphylococcus aureus is responsible for a broad range of infections. This pathogen has a vast arsenal of virulence factors at its disposal, but avirulent strains are frequently isolated as the cause of clinical infections. These isolates have a mutated agr locus and have been believed to have no evolutionary future. Here we show that a fraction of Agr-...