scholarly journals Supplementation of Intracellular XylR Leads to Coutilization of Hemicellulose Sugars

2012 ◽  
Vol 78 (7) ◽  
pp. 2221-2229 ◽  
Author(s):  
Dan Groff ◽  
Peter I. Benke ◽  
Tanveer S. Batth ◽  
Gregory Bokinsky ◽  
Christopher J. Petzold ◽  
...  
Keyword(s):  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
Gene Insertion ◽  
Starting Point ◽  
Different Types ◽  
Important Challenge ◽  
Biomass Sugars ◽  
Hemicellulosic Sugars ◽  
Type Strains

ABSTRACTEscherichia colihas the potential to be a powerful biocatalyst for the conversion of lignocellulosic biomass into useful materials such as biofuels and polymers. One important challenge in usingE. colifor the transformation of biomass sugars is diauxie, or sequential utilization of different types of sugars. We demonstrate that, by increasing the intracellular levels of the transcription factor XylR, the preferential consumption of arabinose before xylose can be eliminated. In addition, XylR augmentation must be finely tuned for robust coutilization of these two hemicellulosic sugars. Using a novel technique for scarless gene insertion, an additional copy ofxylRwas inserted into thearaBADoperon. The resulting strain was superior at cometabolizing mixtures of arabinose and xylose and was able to produce at least 36% more ethanol than wild-type strains. This strain is a useful starting point for the development of anE. colibiocatalyst that can simultaneously convert all biomass sugars.

scholarly journals Minicells as a Damage Disposal Mechanism inEscherichia coli

mSphere ◽  
2018 ◽  
Vol 3 (5) ◽  
Author(s):  
Camilla U. Rang ◽  
Audrey Proenca ◽  
Christen Buetz ◽  
Chao Shi ◽  
Lin Chao
Keyword(s):  
Wild Type ◽  
Chromosomal Dna ◽  
Cell Level ◽  
Content Type ◽  
E Coli ◽  
Survival And Growth ◽  
First Time ◽  
Antibiotic Level ◽  
Type Strains ◽  
Sister Cells

ABSTRACTMany bacteria produce small, spherical minicells that lack chromosomal DNA and therefore are unable to proliferate. Although minicells have been used extensively by researchers as a molecular tool, nothing is known about why bacteria produce them. Here, we show that minicells helpEscherichia colicells to rid themselves of damaged proteins induced by antibiotic stress. By comparing the survival and growth rates of wild-type strains with theE. coliΔminCmutant, which produces excess minicells, we found that the mutant was more resistant to streptomycin. To determine the effects of producing minicells at the single-cell level, we also tracked the growth ofΔminClineages by microscopy. We were able to show that the mutant increased the production of minicells in response to a higher level of the antibiotic. When we compared two sister cells, in which one produced minicells and the other did not, the daughters of the former had a shorter doubling time at this higher antibiotic level. Additionally, we found that minicells were more likely produced at the mother’s old pole, which is known to accumulate more aggregates. More importantly, by using a fluorescent IbpA chaperone to tag damage aggregates, we found that polar aggregates were contained by and ejected with the minicells produced by the mother bacterium. These results demonstrate for the first time the benefit to bacteria for producing minicells.IMPORTANCEBacteria have the ability to produce minicells, or small spherical versions of themselves that lack chromosomal DNA and are unable to replicate. A minicell can constitute as much as 20% of the cell’s volume. Although molecular biology and biotechnology have used minicells as laboratory tools for several decades, it is still puzzling that bacteria should produce such costly but potentially nonfunctional structures. Here, we show that bacteria gain a benefit by producing minicells and using them as a mechanism to eliminate damaged or oxidated proteins. The elimination allows the bacteria to tolerate higher levels of stress, such as increasing levels of streptomycin. If this mechanism extends from streptomycin to other antibiotics, minicell production could be an overlooked pathway that bacteria are using to resist antimicrobials.

scholarly journals Effects of Norspermidine and Spermidine on Biofilm Formation by Potentially Pathogenic Escherichia coli and Salmonella enterica Wild-Type Strains

2015 ◽  
Vol 81 (6) ◽  
pp. 2226-2232 ◽  
Author(s):  
Live L. Nesse ◽  
Kristin Berg ◽  
Lene K. Vestby
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Biofilm Formation ◽  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
Pathogenic Escherichia Coli ◽  
Serovar Typhimurium ◽  
And Control ◽  
Type Strains

ABSTRACTPolyamines are present in all living cells. In bacteria, polyamines are involved in a variety of functions, including biofilm formation, thus indicating that polyamines may have potential in the control of unwanted biofilm. In the present study, the effects of the polyamines norspermidine and spermidine on biofilms of 10 potentially pathogenic wild-type strains ofEscherichia coliserotype O103:H2,Salmonella entericasubsp.entericaserovar Typhimurium, andS. entericaserovar Agona were investigated. We found that exogenously supplied norspermidine and spermidine did not mediate disassembly of preformed biofilm of any of theE. coliandS. entericastrains. However, the polyamines did affect biofilm production. Interestingly, the two species reacted differently to the polyamines. Both polyamines reduced the amount of biofilm formed byE. colibut tended to increase biofilm formation byS. enterica. Whether the effects observed were due to the polyamines specifically targeting biofilm formation, being toxic for the cells, or maybe a combination of the two, is not known. However, there were no indications that the effect was mediated through binding to exopolysaccharides, as earlier suggested forE. coli. Our results indicate that norspermidine and spermidine do not have potential as inhibitors ofS. entericabiofilm. Furthermore, we found that the commercial polyamines used contributed to the higher pH of the test medium. Failure to acknowledge and control this important phenomenon may lead to misinterpretation of the results.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals A new sex factor ofPseudomonas aeruginosa

1973 ◽  
Vol 21 (3) ◽  
pp. 263-272 ◽  
Author(s):  
J. M. Pemberton ◽  
B. W. Holloway
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Structural Gene ◽  
Suppressor Gene ◽  
Genetic Determinant ◽  
Sex Factors ◽  
Wild Type ◽  
Leucine Biosynthesis ◽  
Different Types ◽  
A Site ◽  
Type Strains

SUMMARYOf 150 wild-type strains ofPseudomonas aeruginosaexamined, 48 formed recombinants when mated toP. aeruginosastrain PAO FP−and hence presumably possess sex factors. Three different types of sex factor were distinguished by the pattern of transfer of particular markers in different regions of the chromosome and by the ability to confer resistance to mercury in strain PAO. One new sex factor, FP39, was studied in detail, and while similar to the previously studied FP2 in terms of transfer kinetics, natural stability and resistance to curing by acridines, it differed from FP2 in promoting chromosome transfer from a site 10 min to the left of the FP2 origin and in showing apparently aberrant entry kinetics for a leucine marker situated 48 min from the FP2 origin. This was due to FP39 having a genetic determinant either for a structural gene of leucine biosynthesis or a specific suppressor gene for this locus. PAO strains carrying both FP2 and FP39 were unstable for both sex factors, suggesting a relationship between them.

Trust, risk and transaction intention in consumer-to-consumer e-marketplaces

2019 ◽  
Vol 119 (2) ◽  
pp. 331-350 ◽  
Author(s):  
Kangning Wei ◽  
Yuzhu Li ◽  
Yong Zha ◽  
Jing Ma
Keyword(s):  
Qualitative Study ◽  
Perceived Risk ◽  
Design Methodology ◽  
Future Research ◽  
Trust Building ◽  
Content Type ◽  
Online Transactions ◽  
Starting Point ◽  
Different Types ◽  
Practical Implications

Purpose The purpose of this paper is to compare the relative impacts of trust and risk on individual’s transaction intention in consumer-to-consumer (C2C) e-marketplaces from both the buyers’ and the sellers’ perspectives. Design/methodology/approach Two surveys were used to collect data regarding buyers’ and sellers’ perceptions and transaction intentions at a typical C2C e-marketplace. Partial least squares was used to analyze the data. A complementary qualitative study was conducted to triangulate the results from the quantitative study. Findings Institution-based trust (IBT) exerts a stronger influence on transaction intentions for buyers than for sellers. Sellers perceive a stronger impact of trust in intermediary (TII) than buyers on transaction intentions. The impacts of perceived risk in transactions are not different between buyers and sellers. Furthermore, IBT mediates the impacts of TII and perceived risk on transaction intentions for buyers. Research limitations/implications The results indicate that the impacts of trust and risk on transaction intention in e-marketplaces do differ between buyers and sellers. This suggests a need to further investigate the buyer–seller difference in online transactions. Practical implications Intermediaries need to focus on different types of trust-building mechanisms when attracting buyers and sellers to make transactions in the e-marketplace. Originality/value C2C e-marketplaces cannot survive without participation from both buyers and sellers. Most prior research is conducted from the buyers’ perspective. This research sets a starting point for future research to further explore the differences between buyers’ and sellers’ behavior in C2C e-commerce environments.

scholarly journals Molecular Analysis of Resistance and Detection of Non-Wild-Type Strains Using Etest Epidemiological Cutoff Values for Amphotericin B and Echinocandins for Bloodstream Candida Infections from a Tertiary Hospital in Qatar

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
Saad J. Taj-Aldeen ◽  
Husam Salah ◽  
Winder B. Perez ◽  
Muna Almaslamani ◽  
Mary Motyl ◽  
...  
Keyword(s):  
Amphotericin B ◽  
Hot Spot ◽  
Antifungal Susceptibility ◽  
Tertiary Hospital ◽  
Wild Type ◽  
Content Type ◽  
Cutoff Values ◽  
Echinocandin Resistance ◽  
Candida Infections ◽  
Type Strains

ABSTRACT A total of 301 Candida bloodstream isolates collected from 289 patients over 5 years at a tertiary hospital in Qatar were evaluated. Out of all Candida infections, 53% were diagnosed in patients admitted to the intensive care units. Steady increases in non-albicans Candida species were reported from 2009 to 2014 (30.2% for Candida albicans versus 69.8% for the other Candida species). Etest antifungal susceptibility testing was performed on all recovered clinical isolates to determine echinocandin (micafungin and anidulafungin) and amphotericin B susceptibilities and assess non-wild-type (non-WT) strains (strains for which MICs were above the epidemiological cutoff values). DNA sequence analysis was performed on all isolates to assess the presence of FKS mutations, which confer echinocandin resistance in Candida species. A total of 3.9% of isolates (12/301) among strains of C. albicans and C. orthopsilosis contained FKS hot spot mutations, including heterozygous mutations in FKS1. For C. tropicalis, the Etest appeared to overestimate strains non-WT for micafungin, anidulafungin, and amphotericin B, as 14%, 11%, and 35% of strains, respectively, had values above the epidemiological cutoff value. However, no FKS mutations were identified in this species. For all other species, micafungin best reported the echinocandin non-WT strains relative to the FKS genotype, as anidulafungin tended to overestimate non-wild-type strains. Besides C. tropicalis, few strains were classified as non-WT for amphotericin B.

scholarly journals Loss of Trefoil Factor 2 Sensitizes Rat Pups to Systemic Infection with the Neonatal PathogenEscherichia coliK1

2019 ◽  
Vol 87 (5) ◽  
Author(s):  
Alex J. McCarthy ◽  
George M. H. Birchenough ◽  
Peter W. Taylor
Keyword(s):  
Small Intestine ◽  
Neonatal Rat ◽  
Mucus Layer ◽  
Trefoil Factor ◽  
Wild Type ◽  
Content Type ◽  
Distal Small Intestine ◽  
E Coli ◽  
Rat Pups ◽  
Trefoil Factor 2

ABSTRACTGastrointestinal (GI) colonization of 2-day-old (P2) rat pups withEscherichia coliK1 results in translocation of the colonizing bacteria across the small intestine, bacteremia, and invasion of the meninges, with animals frequently succumbing to lethal infection. Infection, but not colonization, is strongly age dependent; pups become progressively less susceptible to infection over the P2-to-P9 period. Colonization leads to strong downregulation of the gene encoding trefoil factor 2 (Tff2), preventing maturation of the protective mucus barrier in the small intestine. Trefoil factors promote mucosal homeostasis. We investigated the contribution of Tff2 to protection of the neonatal rat fromE. coliK1 bacteremia and tissue invasion. Deletion oftff2, using clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9, sensitized P9 pups toE. coliK1 bacteremia. There were no differences betweentff2−/−homozygotes and the wild type with regard to the dynamics of GI colonization. Loss of the capacity to elaborate Tff2 did not impact GI tract integrity or the thickness of the small-intestinal mucus layer but, in contrast to P9 wild-type pups, enabledE. coliK1 bacteria to gain access to epithelial surfaces in the distal region of the small intestine and exploit an intracellular route across the epithelial monolayer to enter the blood circulation via the mesenteric lymphatic system. Although primarily associated with the mammalian gastric mucosa, we conclude that loss of Tff2 in the developing neonatal small intestine enables the opportunistic neonatal pathogenE. coliK1 to enter the compromised mucus layer in the distal small intestine prior to systemic invasion and infection.

scholarly journals Differential Gene Expression of Three Mastitis-Causing Escherichia coli Strains Grown under Planktonic, Swimming, and Swarming Culture Conditions

mSystems ◽  
2016 ◽  
Vol 1 (4) ◽  
Author(s):  
John D. Lippolis ◽  
Brian W. Brunelle ◽  
Timothy A. Reinhardt ◽  
Randy E. Sacco ◽  
Tyler C. Thacker ◽  
...  
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Bacterial Motility ◽  
Differentially Expressed ◽  
Iron Regulation ◽  
Content Type ◽  
E Coli ◽  
Different Types ◽  
Compare Gene Expression ◽  
Gene Expression Levels

ABSTRACT Bacteria can exhibit various types of motility. It is known that different types of motilities can be associated with virulence. In this work, we compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E. coli motility. Better understanding of the mechanisms of how bacteria can cause an infection is an important first step to better diagnostics and therapeutics. Bacterial motility is thought to play an important role in virulence. We have previously shown that proficient bacterial swimming and swarming in vitro is correlated with the persistent intramammary infection phenotype observed in cattle. However, little is known about the gene regulation differences important for different motility phenotypes in Escherichia coli. In this work, three E. coli strains that cause persistent bovine mastitis infections were grown in three media that promote different types of motility (planktonic, swimming, and swarming). Using whole-transcriptome RNA sequencing, we identified a total of 935 genes (~21% of the total genome) that were differentially expressed in comparisons of the various motility-promoting conditions. We found that approximately 7% of the differentially expressed genes were associated with iron regulation. We show that motility assays using iron or iron chelators confirmed the importance of iron regulation to the observed motility phenotypes. Because of the observation that E. coli strains that cause persistent infections are more motile, we contend that better understanding of the genes that are differentially expressed due to the type of motility will yield important information about how bacteria can become established within a host. Elucidating the mechanisms that regulate bacterial motility may provide new approaches in the development of intervention strategies as well as facilitate the discovery of novel diagnostics and therapeutics. IMPORTANCE Bacteria can exhibit various types of motility. It is known that different types of motilities can be associated with virulence. In this work, we compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E. coli motility. Better understanding of the mechanisms of how bacteria can cause an infection is an important first step to better diagnostics and therapeutics.

scholarly journals RpoS Contributes to Phagocyte Oxidase-Mediated Stress Resistance during Urinary Tract Infection by Escherichia coli CFT073

mBio ◽  
2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Andrew J. Hryckowian ◽  
Rodney A. Welch
Keyword(s):  
Oxidative Stress ◽  
Urinary Tract ◽  
Wild Type ◽  
Upec Strain ◽  
Content Type ◽  
General Stress Response ◽  
E Coli ◽  
Phagocyte Oxidase ◽  
Strain Cft073 ◽  
K 12

ABSTRACTUropathogenicEscherichia coli(UPEC) is the most common causative agent of community-acquired urinary tract infection (UTI). In order to cause UTI, UPEC must endure stresses ranging from nutrient limitation to host immune components. RpoS (σS), the general stress response sigma factor, directs gene expression under a variety of inhibitory conditions. Our study ofrpoSin UPEC strain CFT073 began after we discovered anrpoS-frameshift mutation in one of our laboratory stocks of “wild-type” CFT073. We demonstrate that anrpoS-deletion mutation in CFT073 leads to a colonization defect during UTI of CBA/J mice at 48 hours postinfection (hpi). There is no difference between the growth rates of CFT073 and CFT073rpoSin urine. This indicates thatrpoSis needed for replication and survival in the host rather than being needed to address limitations imposed by urine nutrients. Consistent with previous observations inE. coliK-12, CFT073rpoSis more sensitive to oxidative stress than the wild type. We demonstrate that peroxide levels are elevated in voided urine from CFT073-infected mice compared to urine from mock-infected mice, which supports the notion that oxidative stress is generated by the host in response to UPEC. In mice that lack phagocyte oxidase, the enzyme complex expressed by phagocytes that produces superoxide, the competitive defect of CFT073rpoSin bladder colonization is lost. These results demonstrate that σSis important for UPEC survival under conditions of phagocyte oxidase-generated stress during UTI. Though σSaffects the pathogenesis of other bacterial species, this is the first work that directly implicates σSas important for UPEC pathogenesis.IMPORTANCEUPEC must cope with a variety of stressful conditions in the urinary tract during infection. RpoS (σS), the general stress response sigma factor, is known to direct the expression of many genes under a variety of stressful conditions in laboratory-adaptedE. coliK-12. Here, we show that σSis needed by the model UPEC strain CFT073 to cope with oxidative stress provided by phagocytes during infection. These findings represent the first report that implicates σSin the fitness of UPEC during infection and support the idea of the need for a better understanding of the effects of this global regulator of gene expression during UTI.

scholarly journals Nisin Resistance of Listeria monocytogenes Is Increased by Exposure to Salt Stress and Is Mediated via LiaR

2013 ◽  
Vol 79 (18) ◽  
pp. 5682-5688 ◽  
Author(s):  
Teresa M. Bergholz ◽  
Silin Tang ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Salt Stress ◽  
Listeria Monocytogenes ◽  
Safety Concern ◽  
Response Regulator ◽  
Brain Heart Infusion ◽  
Control Measures ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
Type Strains

ABSTRACTGrowth ofListeria monocytogeneson refrigerated, ready-to-eat food is a significant food safety concern. Natural antimicrobials, such as nisin, can be used to control this pathogen on food, but little is known about how other food-related stresses may impact how the pathogen responds to these compounds. Prior work demonstrated that exposure ofL. monocytogenesto salt stress at 7°C led to increased expression of genes involved in nisin resistance, including the response regulatorliaR. We hypothesized that exposure to salt stress would increase subsequent resistance to nisin and that LiaR would contribute to increased nisin resistance. Isogenic deletion mutations inliaRwere constructed in 7 strains ofL. monocytogenes, and strains were exposed to 6% NaCl in brain heart infusion broth and then tested for resistance to nisin (2 mg/ml Nisaplin) at 7°C. For the wild-type strains, exposure to salt significantly increased subsequent nisin resistance (P< 0.0001) over innate levels of resistance. Compared to the salt-induced nisin resistance of wild-type strains, ΔliaRstrains were significantly more sensitive to nisin (P< 0.001), indicating that induction of LiaFSR led to cross-protection ofL. monocytogenesagainst subsequent inactivation by nisin. Transcript levels of LiaR-regulated genes were induced by salt stress, and lmo1746 andtelAwere found to contribute to LiaR-mediated salt-induced nisin resistance. These data suggest that environmental stresses similar to those on foods can influence the resistance ofL. monocytogenesto antimicrobials such as nisin, and potential cross-protective effects should be considered when selecting and applying control measures for this pathogen on ready-to-eat foods.

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