scholarly journals Sulfide ProtectsStaphylococcus aureusfrom Aminoglycoside Antibiotics but Cannot Be Regarded as a General Defense Mechanism against Antibiotics

2018 ◽  
Vol 62 (10) ◽  
Author(s):  
Julia Weikum ◽  
Niklas Ritzmann ◽  
Nils Jelden ◽  
Anna Klöckner ◽  
Sebastian Herkersdorf ◽  
...  
Keyword(s):  
Defense Mechanism ◽  
Model Organism ◽  
Inhibitory Effect ◽  
Aminoglycoside Antibiotics ◽  
Drug Uptake ◽  
Protective Mechanism ◽  
Bacterial Cells ◽  
Content Type ◽  
Sulfide Production ◽  
The Impact

ABSTRACTSulfide production has been proposed to be a universal defense mechanism against antibiotics in bacteria (K. Shatalin, E. Shatalina, A. Mironov, and E. Nudler, Science 334:986–990, 2011, doi:10.1126/science.1209855). To gain insight into the mechanism underlying sulfide protection, we systematically and comparatively addressed the interference of sulfide with antibiotic activity againstStaphylococcus aureus, as a model organism. The impact of sulfide and sulfide precursors on the antibiotic susceptibility ofS. aureusto the most important classes of antibiotics was analyzed using modified disk diffusion assays, killing kinetic assays, and drug uptake studies. In addition, sulfide production and the impact of exogenously added sulfide on the physiology ofS. aureuswere analyzed. Sulfide protection was found to be limited to aminoglycoside antibiotics, which are known to be taken up by bacterial cells in an energy-dependent process. The protective mechanism was found to rely on an inhibitory effect of sulfide on the bacterial respiratory chain, leading to reduced drug uptake.S. aureuswas found to be incapable of producing substantial amounts of sulfide. We propose that bacterial sulfide production should not be regarded as a general defense mechanism against antibiotics, since (i) it is limited to aminoglycosides and (ii) production levels vary considerably among species and, as forS. aureus, may be too low for protection.

scholarly journals A Comprehensive Coexpression Network Analysis in Vibrio cholerae

mSystems ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Cory D. DuPai ◽  
Claus O. Wilke ◽  
Bryan W. Davies
Keyword(s):  
Network Analysis ◽  
Vibrio Cholerae ◽  
Rna Sequencing ◽  
High Throughput Sequencing ◽  
Model Organism ◽  
Coexpression Network ◽  
Sequencing Data ◽  
Content Type ◽  
The Impact ◽  
Coexpression Network Analysis

ABSTRACT Research into the evolution and pathogenesis of Vibrio cholerae has benefited greatly from the generation of high-throughput sequencing data to drive molecular analyses. The steady accumulation of these data sets now provides a unique opportunity for in silico hypothesis generation via coexpression analysis. Here, we leverage all published V. cholerae RNA sequencing data, in combination with select data from other platforms, to generate a gene coexpression network that validates known gene interactions and identifies novel genetic partners across the entire V. cholerae genome. This network provides direct insights into genes influencing pathogenicity, metabolism, and transcriptional regulation, further clarifies results from previous sequencing experiments in V. cholerae (e.g., transposon insertion sequencing [Tn-seq] and chromatin immunoprecipitation sequencing [ChIP-seq]), and expands upon microarray-based findings in related Gram-negative bacteria. IMPORTANCE Cholera is a devastating illness that kills tens of thousands of people annually. Vibrio cholerae, the causative agent of cholera, is an important model organism to investigate both bacterial pathogenesis and the impact of horizontal gene transfer on the emergence and dissemination of new virulent strains. Despite the importance of this pathogen, roughly one-third of V. cholerae genes are functionally unannotated, leaving large gaps in our understanding of this microbe. Through coexpression network analysis of existing RNA sequencing data, this work develops an approach to uncover novel gene-gene relationships and contextualize genes with no known function, which will advance our understanding of V. cholerae virulence and evolution.

scholarly journals Impact of Ralstonia eutropha's Poly(3-Hydroxybutyrate) (PHB) Depolymerases and Phasins on PHB Storage in Recombinant Escherichia coli

2014 ◽  
Vol 80 (24) ◽  
pp. 7702-7709 ◽  
Author(s):  
Jessica Eggers ◽  
Alexander Steinbüchel
Keyword(s):  
Escherichia Coli ◽  
Ralstonia Eutropha ◽  
Model Organism ◽  
Dry Weight ◽  
Growth Behavior ◽  
Carbon Limitation ◽  
Content Type ◽  
Phb Depolymerase ◽  
E Coli ◽  
The Impact

ABSTRACTThe model organism for polyhydroxybutyrate (PHB) biosynthesis,Ralstonia eutrophaH16, possesses multiple isoenzymes of granules coating phasins as well as of PHB depolymerases, which degrade accumulated PHB under conditions of carbon limitation. In this study, recombinantEscherichia coliBL21(DE3) strains were used to study the impact of selected PHB depolymerases ofR. eutrophaH16 on the growth behavior and on the amount of accumulated PHB in the absence or presence of phasins. For this purpose, 20 recombinantE. coliBL21(DE3) strains were constructed, which harbored a plasmid carrying thephaCABoperon fromR. eutrophaH16 to ensure PHB synthesis and a second plasmid carrying different combinations of the genes encoding a phasin and a PHB depolymerase fromR. eutrophaH16. It is shown in this study that the growth behavior of the respective recombinantE. colistrains was barely affected by the overexpression of the phasin and PHB depolymerase genes. However, the impact on the PHB contents was significantly greater. The strains expressing the genes of the PHB depolymerases PhaZ1, PhaZ2, PhaZ3, and PhaZ7 showed 35% to 94% lower PHB contents after 30 h of cultivation than the control strain. The strain harboringphaZ7reached by far the lowest content of accumulated PHB (only 2.0% [wt/wt] PHB of cell dry weight). Furthermore, coexpression of phasins in addition to the PHB depolymerases influenced the amount of PHB stored in cells of the respective strains. It was shown that the phasins PhaP1, PhaP2, and PhaP4 are not substitutable without an impact on the amount of stored PHB. In particular, the phasins PhaP2 and PhaP4 seemed to limit the degradation of PHB by the PHB depolymerases PhaZ2, PhaZ3, and PhaZ7, whereas almost no influence of the different phasins was observed ifphaZ1was coexpressed. This study represents an extensive analysis of the impact of PHB depolymerases and phasins on PHB accumulation and provides a deeper insight into the complex interplay of these enzymes.

scholarly journals A Matter of Timing: Contrasting Effects of Hydrogen Sulfide on Oxidative Stress Response in Shewanella oneidensis

2015 ◽  
Vol 197 (22) ◽  
pp. 3563-3572 ◽  
Author(s):  
Genfu Wu ◽  
Fen Wan ◽  
Huihui Fu ◽  
Ning Li ◽  
Haichun Gao
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Sulfide ◽  
Shewanella Oneidensis ◽  
Inhibitory Effect ◽  
Time Dependent ◽  
Bacterial Cells ◽  
Bacterial Survival ◽  
Intracellular Iron ◽  
Content Type ◽  
Stress Responding

ABSTRACTHydrogen sulfide (H2S), well known for its toxic properties, has recently become a research focus in bacteria, in part because it has been found to prevent oxidative stress caused by treatment with some antibiotics. H2S has the ability to scavenge reactive oxygen species (ROS), thus preventing oxidative stress, but it is also toxic, leading to conflicting reports of its effects in different organisms. Here, withShewanella oneidensisas a model, we report that the effects of H2S on the response to oxidative stress are time dependent. When added simultaneously with H2O2, H2S promoted H2O2toxicity by inactivating catalase, KatB, a heme-containing enzyme involved in H2O2degradation. Such an inhibitory effect may apply to other heme-containing proteins, such as cytochromecbb3oxidase. When H2O2was supplied 20 min or later after the addition of H2S, the oxidative-stress-responding regulator OxyR was activated, resulting in increased resistance to H2O2. The activation of OxyR was likely triggered by the influx of iron, a response to lowered intracellular iron due to the iron-sequestering property of H2S. Given thatShewanellabacteria thrive in redox-stratified environments that have abundant sulfur and iron species, our results imply that H2S is more important for bacterial survival in such environmental niches than previously believed.IMPORTANCEPrevious studies have demonstrated that H2S is either detrimental or beneficial to bacterial cells. While it can act as a growth-inhibiting molecule by damaging DNA and denaturing proteins, it helps cells to combat oxidative stress. Here we report that H2S indeed has these contrasting biological functions and that its effects are time dependent. Immediately after H2S treatment, there is growth inhibition due to damage of heme-containing proteins, at least to catalase and cytochromecoxidase. In contrast, when added a certain time later, H2S confers an enhanced ability to combat oxidative stress by activating the H2O2-responding regulator OxyR. Our data reconcile conflicting observations about the functions of H2S.

scholarly journals Serratia marcescens Quinoprotein Glucose Dehydrogenase Activity Mediates Medium Acidification and Inhibition of Prodigiosin Production by Glucose

2012 ◽  
Vol 78 (17) ◽  
pp. 6225-6235 ◽  
Author(s):  
James E. Fender ◽  
Cody M. Bender ◽  
Nicholas A. Stella ◽  
Roni M. Lahr ◽  
Eric J. Kalivoda ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Serratia Marcescens ◽  
Large Scale ◽  
Transcriptional Control ◽  
Glucose Dehydrogenase ◽  
Model Organism ◽  
Inhibitory Effect ◽  
Biologically Active ◽  
Scale Production ◽  
Content Type

ABSTRACTSerratia marcescensis a model organism for the study of secondary metabolites. The biologically active pigment prodigiosin (2-methyl-3-pentyl-6-methoxyprodiginine), like many other secondary metabolites, is inhibited by growth in glucose-rich medium. Whereas previous studies indicated that this inhibitory effect was pH dependent and did not require cyclic AMP (cAMP), there is no information on the genes involved in mediating this phenomenon. Here we used transposon mutagenesis to identify genes involved in the inhibition of prodigiosin by glucose. Multiple genetic loci involved in quinoprotein glucose dehydrogenase (GDH) activity were found to be required for glucose inhibition of prodigiosin production, including pyrroloquinoline quinone and ubiquinone biosynthetic genes. Upon assessing whether the enzymatic products of GDH activity were involved in the inhibitory effect, we observed thatd-glucono-1,5-lactone andd-gluconic acid, but notd-gluconate, were able to inhibit prodigiosin production. These data support a model in which the oxidation ofd-glucose by quinoprotein GDH initiates a reduction in pH that inhibits prodigiosin production through transcriptional control of the prodigiosin biosynthetic operon, providing new insight into the genetic pathways that control prodigiosin production. Strains generated in this report may be useful in large-scale production of secondary metabolites.

scholarly journals Excreted Cytoplasmic Proteins Contribute to Pathogenicity in Staphylococcus aureus

2016 ◽  
Vol 84 (6) ◽  
pp. 1672-1681 ◽  
Author(s):  
Patrick Ebner ◽  
Janina Rinker ◽  
Minh Thu Nguyen ◽  
Peter Popella ◽  
Mulugeta Nega ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Host Cell ◽  
Host Cells ◽  
Infection Model ◽  
Bacterial Cells ◽  
Host Matrix ◽  
Content Type ◽  
Cell Internalization ◽  
Cytoplasmic Proteins ◽  
The Impact

Excretion of cytoplasmic proteins in pro- and eukaryotes, also referred to as “nonclassical protein export,” is a well-known phenomenon. However, comparatively little is known about the role of the excreted proteins in relation to pathogenicity. Here, the impact of two excreted glycolytic enzymes, aldolase (FbaA) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), on pathogenicity was investigated inStaphylococcus aureus. Both enzymes bound to certain host matrix proteins and enhanced adherence of the bacterial cells to host cells but caused a decrease in host cell invasion. FbaA and GAPDH also bound to the cell surfaces of staphylococcal cells by interaction with the major autolysin, Atl, that is involved in host cell internalization. Surprisingly, FbaA showed high cytotoxicity to both MonoMac 6 (MM6) and HaCaT cells, while GAPDH was cytotoxic only for MM6 cells. Finally, the contribution of external FbaA and GAPDH toS. aureuspathogenicity was confirmed in an insect infection model.

scholarly journals Lack of Antimicrobial Bactericidal Activity in Mycobacterium abscessus

2014 ◽  
Vol 58 (7) ◽  
pp. 3828-3836 ◽  
Author(s):  
Florian P. Maurer ◽  
Vera L. Bruderer ◽  
Claudia Ritter ◽  
Claudio Castelberg ◽  
Guido V. Bloemberg ◽  
...  
Keyword(s):  
Bactericidal Activity ◽  
Mode Of Action ◽  
Model Organism ◽  
Mycobacterium Abscessus ◽  
Therapeutic Outcome ◽  
Natural Resistance ◽  
Content Type ◽  
The Poor ◽  
Poor Therapeutic Outcome ◽  
The Impact

ABSTRACTAntibiotic therapy of infections caused by the emerging pathogenMycobacterium abscessusis challenging due to the organism's natural resistance toward most clinically available antimicrobials. We investigated the bactericidal activity of antibiotics commonly administered inM. abscessusinfections in order to better understand the poor therapeutic outcome. Time-kill curves were generated for clinicalM. abscessusisolates,Mycobacterium smegmatis, andEscherichia coliby using antibiotics commonly categorized as bactericidal (amikacin and moxifloxacin) or bacteriostatic (tigecycline and linezolid). In addition, the impact of aminoglycoside-modifying enzymes on the mode of action of substrate and nonsubstrate aminoglycosides was studied by usingM. smegmatisas a model organism. While amikacin and moxifloxacin were bactericidal againstE. coli, none of the tested compounds showed bactericidal activity againstM. abscessus. Further mechanistic investigations of the mode of action of aminoglycosides inM. smegmatisrevealed that the bactericidal activity of tobramycin and gentamicin was restored by disruption of the chromosomalaac(2′) gene in the mycobacterial genome. The lack of bactericidal antibiotics in currently recommended treatment regimens provides a reasonable explanation for the poor therapeutic outcome inM. abscessusinfection. Our findings suggest that chromosomally encoded drug-modifying enzymes play an important role in the lack of aminoglycoside bactericidal activity against rapidly growing mycobacteria.

scholarly journals Parallel Genomics Uncover Novel Enterococcal-Bacteriophage Interactions

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Anushila Chatterjee ◽  
Julia L. E. Willett ◽  
Uyen Thy Nguyen ◽  
Brendan Monogue ◽  
Kelli L. Palmer ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Response Regulator ◽  
Burst Size ◽  
Bacterial Community Composition ◽  
Model Organism ◽  
Phage Infection ◽  
Bacterial Cells ◽  
Transcriptomic Profiling ◽  
Bacterial Gene ◽  
Content Type

ABSTRACT Bacteriophages (phages) have been proposed as alternative therapeutics for the treatment of multidrug-resistant bacterial infections. However, there are major gaps in our understanding of the molecular events in bacterial cells that control how bacteria respond to phage predation. Using the model organism Enterococcus faecalis, we used two distinct genomic approaches, namely, transposon library screening and RNA sequencing, to investigate the interaction of E. faecalis with a virulent phage. We discovered that a transcription factor encoding a LytR family response regulator controls the expression of enterococcal polysaccharide antigen (epa) genes that are involved in phage infection and bacterial fitness. In addition, we discovered that DNA mismatch repair mutants rapidly evolve phage adsorption deficiencies, underpinning a molecular basis for epa mutation during phage infection. Transcriptomic profiling of phage-infected E. faecalis revealed broad transcriptional changes influencing viral replication and progeny burst size. We also demonstrate that phage infection alters the expression of bacterial genes associated with intra- and interbacterial interactions, including genes involved in quorum sensing and polymicrobial competition. Together, our results suggest that phage predation has the potential to influence complex microbial behavior and may dictate how bacteria respond to external environmental stimuli. These responses could have collateral effects (positive or negative) on microbial communities, such as the host microbiota, during phage therapy. IMPORTANCE We lack fundamental understanding of how phage infection influences bacterial gene expression and, consequently, how bacterial responses to phage infection affect the assembly of polymicrobial communities. Using parallel genomic approaches, we have discovered novel transcriptional regulators and metabolic genes that influence phage infection. The integration of whole-genome transcriptomic profiling during phage infection has revealed the differential regulation of genes important for group behaviors and polymicrobial interactions. Our work suggests that therapeutic phages could more broadly influence bacterial community composition outside their intended host targets.

scholarly journals The Effect of Cellular Redox Status on the Evolvability of New Catabolic Pathways

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Maia Kivisaar
Keyword(s):  
Metabolic Pathways ◽  
Mutagenic Effect ◽  
Redox Status ◽  
Biochemical Network ◽  
Bacterial Cells ◽  
Catabolic Pathways ◽  
Cellular Redox ◽  
Content Type ◽  
Environmental Bacteria ◽  
The Impact

ABSTRACTOxidation of aromatic compounds can be mutagenic due to the accumulation of reactive oxygen species (ROS) in bacterial cells and thereby facilitate evolution of corresponding catabolic pathways. To examine the effect of the background biochemical network on the evolvability of environmental bacteria hosting a new catabolic pathway, Akkaya and colleagues (mBio 9:e01512-18, 2018,https://doi.org/10.1128/mBio.01512-18) introduced the still-evolving 2,4-dinitrotoluene (2,4-DNT) pathway genes from the original environmentalBurkholderiasp. isolate into the genome ofPseudomonas putidaKT2440. They show that the mutagenic effect of 2,4-DNT oxidation, which is associated with the accumulation of ROS and oxidative damage on DNA, can be avoided by preserving high NADPH levels inP. putida. The observations of this study highlight the impact of the cellular redox status of bacteria on the evolvability of new metabolic pathways.

scholarly journals Unprotonated Short-Chain Alkylamines Inhibit Staphylolytic Activity of Lysostaphin in a Wall Teichoic Acid-Dependent Manner

2018 ◽  
Vol 84 (14) ◽  
Author(s):  
Xia Wu ◽  
Seok Joon Kwon ◽  
Domyoung Kim ◽  
Jian Zha ◽  
Mauricio Mora-Pale ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Respiratory Infections ◽  
Teichoic Acid ◽  
Inhibitory Effect ◽  
Short Chain ◽  
Dependent Manner ◽  
Cell Binding ◽  
Wall Teichoic Acid ◽  
Content Type ◽  
The Impact

ABSTRACTLysostaphin (Lst) is a potent bacteriolytic enzyme that killsStaphylococcus aureus, a common bacterial pathogen of humans and animals. With high activity against both planktonic cells and biofilms, Lst has the potential to be used in industrial products, such as commercial cleansers, for decontamination. However, Lst is inhibited in the presence of monoethanolamine (MEA), a chemical widely used in cleaning solutions and pharmaceuticals, and the underlying mechanism of inhibition remains unknown. In this study, we examined the cell binding and killing capabilities of Lst againstS. aureusATCC 6538 in buffered salt solution with MEA at different pH values (7.5 to 10.5) and discovered that only the unprotonated form of MEA inhibited Lst binding to the cell surface, leading to low Lst activity, despite retention of its secondary structure. This reduced enzyme activity could be largely recovered via a reduction in wall teichoic acid (WTA) biosynthesis through tunicamycin treatment, indicating that the suppression of Lst activity was dependent on the presence and amount of WTA. We propose that the decreased cell binding and killing capabilities of Lst are associated with the influence of uncharged MEA on the conformation of WTA. A similar effect was confirmed with other short-chain alkylamines. This study offers new insight into the impact of short-chain alkylamines on both Lst and WTA structure and function and provides guidance for the application of Lst in harsh environments.IMPORTANCELysostaphin (Lst) effectively and selectively killsStaphylococcus aureus, the bacterial culprit of many hospital- and community-acquired skin and respiratory infections and food poisoning. Lst has been investigated in animal models and clinical trials, industrial formulations, and environmental settings. Here, we studied the mechanistic basis of the inhibitory effect of alkylamines, such as monoethanolamine (MEA), a widely used chemical in commercial detergents, on Lst activity, for the potential incorporation of Lst in disinfectant solutions. We have found that protonated MEA has little influence on Lst activity, while unprotonated MEA prevents Lst from binding toS. aureuscells and hence dramatically decreases the enzyme's bacteriolytic efficacy. Following partial removal of the wall teichoic acid, an important component of the bacterial cell envelope, the inhibitory effect of unprotonated MEA on Lst is reduced. This phenomenon can be extended to other short-chain alkylamines. This mechanistic report of the impact of alkylamines on Lst functionality will help guide future applications of Lst in disinfection and decontamination of health-related commercial products.

scholarly journals Partitiviruses Infecting Drosophila melanogaster and Aedes aegypti Exhibit Efficient Biparental Vertical Transmission

2020 ◽  
Vol 94 (20) ◽  
Author(s):  
Shaun T. Cross ◽  
Bernadette L. Maertens ◽  
Tillie J. Dunham ◽  
Case P. Rodgers ◽  
Ali L. Brehm ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Virus Infection ◽  
Aedes Aegypti ◽  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Model Organism ◽  
Model Organisms ◽  
Wild Populations ◽  
Content Type ◽  
The Impact

ABSTRACT Partitiviruses are segmented, multipartite double-stranded RNA (dsRNA) viruses that until recently were only known to infect fungi, plants, and protozoans. Metagenomic surveys have revealed that partitivirus-like sequences are also commonly associated with arthropods. One arthropod-associated partitivirus, galbut virus, is common in wild populations of Drosophila melanogaster. To begin to understand the processes that underlie this virus’s high global prevalence, we established colonies of wild-caught infected flies. Infection remained at stably high levels over 3 years, with between 63 and 100% of individual flies infected. Galbut virus infects fly cells and replicates in tissues throughout infected adults, including reproductive tissues and the gut epithelium. We detected no evidence of horizontal transmission via ingestion, but vertical transmission from either infected females or infected males was ∼100% efficient. Vertical transmission of a related partitivirus, verdadero virus, that we discovered in a laboratory colony of Aedes aegypti mosquitoes was similarly efficient. This suggests that efficient biparental vertical transmission may be a feature of at least a subset of insect-infecting partitiviruses. To study the impact of galbut virus infection free from the confounding effect of other viruses, we generated an inbred line of flies with galbut virus as the only detectable virus infection. We were able to transmit infection experimentally via microinjection of homogenate from these galbut-only flies. This sets the stage for experiments to understand the biological impact and possible utility of partitiviruses infecting model organisms and disease vectors. IMPORTANCE Galbut virus is a recently discovered partitivirus that is extraordinarily common in wild populations of the model organism Drosophila melanogaster. Like for most viruses discovered through metagenomics, most of the basic biological questions about this virus remain unanswered. We found that galbut virus, along with a closely related partitivirus found in Aedes aegypti mosquitoes, is transmitted from infected females or males to offspring with ∼100% efficiency and can be maintained in laboratory colonies over years. This efficient transmission mechanism likely underlies the successful spread of these viruses through insect populations. We created Drosophila lines that contained galbut virus as the only virus infection and showed that these flies can be used as a source for experimental infections. This provides insight into how arthropod-infecting partitiviruses may be maintained in nature and sets the stage for exploration of their biology and potential utility.

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