ABSTRACT Biofilms are associated with a wide variety of bacterial infections and pose serious problem in clinical medicine due to their inherent resilience antibiotic treatment. Within biofilms, persister cells comprise small subpopulation that exhibits multidrug tolerance antibiotics without undergoing genetic change. The low frequency cell formation makes it difficult isolate study persisters, persistence is often attributed quiescent metabolic state induced by toxins regulated through...

Antigenic or mitogenic stimulation of T cells induces the secretion an array protein hormones that regulate immune responses. Molecular cloning has contributed strongly to our present understanding nature this regulation. A complementary DNA (cDNA) library prepared from a cloned concanavalin A-activated mouse T-helper cell line was screened for abundant and induction-specific cDNA's. One such randomly chosen cDNA found encode preproenkephalin messenger RNA (mRNA). Preproenkephalin mRNA...

Since persister cells cause chronic infections and since Escherichia coli toxin MqsR increases persisters, we used protein engineering to increase the toxicity of gain insights into cell formation. Through two amino acid replacements that increased stability MqsR, persistence were increased. A whole-transcriptome study revealed variant by repressing genes for resistance, multidrug resistance osmotic resistance. Corroborating these microarray results, deletion rpoS, as well master stress...

The nitrilases are enzymes that convert nitriles to the corresponding acid and ammonia. They members of a superfamily, which includes amidases occur in both prokaryotes eukaryotes. superfamily is characterized by having homodimeric building block with alpha beta alpha-alpha sandwich fold an active site containing four positionally conserved residues: cys, glu, glu lys. Their high chemical specificity frequent enantioselectivity makes them attractive biocatalysts for production fine chemicals...

For toxin/antitoxin (TA) systems, no toxin has been identified that functions by cleaving DNA. Here, we demonstrate RalR and RalA of the cryptic prophage rac form a type I TA pair in which antitoxin RNA is trans-encoded small with 16 nucleotides complementarity to mRNA. We suggest newly discovered gene be named ralA for antitoxin. Toxin as non-specific endonuclease cleaves methylated unmethylated The chaperone Hfq required activity appears stabilize RalA. Also, RalR/RalA beneficial...

Summary Toxin endoribonucleases of toxin/antitoxin ( TA ) systems regulate protein production by selectively degrading mRNAs but have never been shown to control other systems. Here we demonstrate that toxin MqsR the / MqsA system enriches ghoT mRNA in vivo and vitro , since this transcript lacks primary cleavage site 5′‐ GCU . GhoT is a membrane causes ghost cell phenotype, part type V with antitoxin GhoS cleaves specifically Introduction sites into reduces death likely due increased...

Persister cells survive antibiotic and other environmental stresses by slowing metabolism. Since toxins of toxin/antitoxin (TA) systems have been postulated to be responsible for persister cell formation, we investigated the influence toxin YafQ YafQ/DinJ Escherichia coli TA system on formation. Under stress, alters metabolism cleaving transcripts with in-frame 5'-AAA-G/A-3' sites. Production increased formation multiple antibiotics, investigating changes in protein expression, found that...

Persisters are bacteria that highly tolerant to antibiotics due their dormant state and of clinical significance owing role in infections. Given the population persisters increases biofilms cyclic diguanylate (c-di-GMP) is an intracellular signal biofilm formation, we sought determine whether c-di-GMP has a bacterial persistence. By examining effect 30 genes from Escherichia coli, including cyclases synthesize phosphodiesterases breakdown c-di-GMP, determined DosP (direct oxygen sensing...

Toxin/antitoxin (TA) systems perhaps enable cells to reduce their metabolism weather environmental challenges although there is little evidence support this hypothesis. Escherichia coli GhoT/GhoS a TA system in which toxin GhoT expression reduced by cleavage of its messenger RNA (mRNA) antitoxin GhoS, and MqsR/MqsA controls through differential mRNA decay. However, the physiological role has not been determined. We show here transmission electron microscopy, confocal microscopy fluorescent...

Summary Antitoxins are becoming recognized as proteins that regulate more than their own synthesis; for example, we found previously antitoxin MqsA of the Escherichia coli toxin/antitoxin (TA) pair MqsR/MqsA directly represses gene encoding stationary‐phase sigma factor RpoS. Here, investigated physiological role DinJ YafQ/DinJ TA and also affects general stress response by decreasing RpoS levels. Corroborating reduced levels upon producing DinJ, RpoS‐regulated phenotypes catalase activity,...

Persistence, the stress-tolerant state, is arguably most vital phenotype since nearly all cells experience nutrient stress, which causes a sub-population to become dormant. However, how persister wake reconstitute infections not understood well. Here, using single-cell observations, we determined that Escherichia coli resuscitate primarily when presented with specific carbon sources, rather than spontaneously. In addition, found mechanism of cell waking through sensing nutrients by...

Arguably, the greatest threat to bacteria is phages. It often assumed that those escape phage infection have mutated or utilized phage-defence systems; however, another possibility a subpopulation forms dormant persister state in manner similar demonstrated for bacterial cells undergoing nutritive, oxidative, and antibiotic stress. Persister do not undergo mutation survive lethal conditions by ceasing growth transiently. Slower dormancy play key physiological role as they allow host defence...

We report the crystal structure of alanine racemase from Mycobacterium tuberculosis (AlrMtb) at 1.9 Å resolution. In our structure, AlrMtb is found to be a dimer formed by two crystallographically different monomers, each comprising 384 residues. The domain makeup monomer similar that Bacillus and Pseudomonas racemases includes both an α/β-barrel N-terminus C-terminus primarily made β-strands. hinge angle between these domains unique for AlrMtb, but active site geometry conserved. PLP...

Serratia marcescens, a gram-negative enteric bacterium, is capable of secreting number proteins extracellularly. The types activity found in the growth media include proteases, chitinases, nuclease, and lipase. Genetic studies have been undertaken to investigate mechanisms used for extracellular secretion these exoproteins by S. marcescens. Many independent mutations affecting enzymes were isolated after chemical transposon mutagenesis. Using indicator media, we identified loci involved...

Layer-by-layer (LbL) assembly, a technique that alternately deposites cationic and anionic materials, has proven to be powerful for assembling thin films with variety of properties applications. The present work incorporates the antimicrobial agent cetyltrimethylammonium bromide (CTAB) in layer uses poly(acrylic acid) (PAA) as layer. When are exposed humid environment, these agents diffuse out film, inhibiting bacterial growth neighboring regions. Film growth, microstructure, efficacy...

Toxin/antitoxin (TA) systems are ubiquitous within bacterial genomes, and the mechanisms of many TA well characterized. As such, several roles for have been proposed, such as phage inhibition, gene regulation persister cell formation. However, significance these is nebulous due to subtle influence from individual systems. For example, a single system has only minor contribution Hence, there lack defining physiological In this study, phenotype assays were used determine that MqsR/MqsA type II...

When grown at acidic pH, Escherichia coli cells secrete cadaverine, a polyamine known to inhibit porin-mediated outer membrane permeability. In order understand the physiological significance of cadaverine excretion and inhibition porins, we isolated an OmpC mutant that showed resistance spermine during growth polyamine-resistant fluxes. Here, show addition exogenous allows wild-type survive 30-min exposure pH 3.6 better than expressing cadaverine-insensitive porin. Competition experiments...

Summary When a liquid culture of Serratia spp. reaches the last part logarithmic phase growth it induces synthesis several extracellular hydrolytic enzymes. In this communication we show that and secretion phospholipase is coupled to expression flagella. Expression flagella demonstrated follow growth‐phase‐dependent pattern. Cloning, complementation studies DNA‐sequencing analysis has identified genetic region in liquefaciens which exhibits extensive homology Escherichia coli flhD flagellar...