scholarly journals Phage-Antibiotic Synergy via Delayed Lysis

2018 ◽  
Vol 84 (22) ◽  
Author(s):  
Minjin Kim ◽  
Yunyeol Jo ◽  
Yoon Jung Hwang ◽  
Hye Won Hong ◽  
Sung Sik Hong ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Underlying Mechanism ◽  
Host Cells ◽  
Oxygen Species ◽  
Particle Assembly ◽  
Content Type ◽  
Host Membrane ◽  
Quinolone Antibiotics ◽  
Phage Production

ABSTRACTWhen phages infect bacteria cultured in the presence of sublethal doses of antibiotics, the sizes of the phage plaques are significantly increased. This phenomenon is known as phage-antibiotic synergy (PAS). In this study, the observation of PAS was extended to a wide variety of bacterium-phage pairs using different classes of antibiotics. PAS was shown in both Gram-positive and Gram-negative bacteria. Cells stressed with β-lactam antibiotics filamented or swelled extensively, resulting in an increase in phage production. PAS was also sometimes observed in the presence of other classes of antibiotics with or without bacterial filamentation. The addition of antibiotics inducedrecAexpression in various bacteria, but arecAdeletion mutant strain ofEscherichia colialso showed filamentation and PAS in the presence of quinolone antibiotics. The phage adsorption efficiency did not change in the presence of the antibiotics when the cell surfaces were enlarged as they filamented. Increases in the production of phage DNA and mRNAs encoding phage proteins were observed in these cells, with only a limited increase in protein production. The data suggest that PAS is the product of a prolonged period of particle assembly due to delayed lysis. The increase in the cell surface area far exceeded the increase in phage holin production in the filamented host cells, leading to a relatively limited availability of intracellular holins for aggregating and forming holes in the host membrane. Reactive oxygen species (ROS) stress also led to an increased production of phages, while heat stress resulted in only a limited increase in phage production.IMPORTANCEPhage-antibiotic synergy (PAS) has been reported for a decade, but the underlying mechanism has never been vigorously investigated. This study shows the presence of PAS from a variety of phage-bacterium-antibiotic pairings. We show that increased phage production resulted directly from a lysis delay caused by the relative shortage of holin in filamented bacterial hosts in the presence of sublethal concentrations of stress-inducing substances, such as antibiotics and reactive oxygen species (ROS).

scholarly journals The Helicobacter pylori CZB Cytoplasmic Chemoreceptor TlpD Forms an Autonomous Polar Chemotaxis Signaling Complex That Mediates a Tactic Response to Oxidative Stress

2016 ◽  
Vol 198 (11) ◽  
pp. 1563-1575 ◽  
Author(s):  
Kieran D. Collins ◽  
Tessa M. Andermann ◽  
Jenny Draper ◽  
Lisa Sanders ◽  
Susan M. Williams ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Helicobacter Pylori ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Host Cells ◽  
Oxygen Species ◽  
Content Type ◽  
Signaling Complex ◽  
H Pylori

ABSTRACTCytoplasmic chemoreceptors are widespread among prokaryotes but are far less understood than transmembrane chemoreceptors, despite being implicated in many processes. One such cytoplasmic chemoreceptor isHelicobacter pyloriTlpD, which is required for stomach colonization and drives a chemotaxis response to cellular energy levels. Neither the signals sensed by TlpD nor its molecular mechanisms of action are known. We report here that TlpD functions independently of the other chemoreceptors. When TlpD is the sole chemoreceptor, it is able to localize to the pole and recruits CheW, CheA, and at least two CheV proteins to this location. It loses the normal membrane association that appears to be driven by interactions with other chemoreceptors and with CheW, CheV1, and CheA. These results suggest that TlpD can form an autonomous signaling unit. We further determined that TlpD mediates a repellent chemotaxis response to conditions that promote oxidative stress, including being in the presence of iron, hydrogen peroxide, paraquat, and metronidazole. Last, we found that all testedH. pyloristrains express TlpD, whereas other chemoreceptors were present to various degrees. Our data suggest a model in which TlpD coordinates a signaling complex that responds to oxidative stress and may allowH. pylorito avoid areas of the stomach with high concentrations of reactive oxygen species.IMPORTANCEHelicobacter pylorisenses its environment with proteins called chemoreceptors. Chemoreceptors integrate this sensory information to affect flagellum-based motility in a process called chemotaxis. Chemotaxis is employed during infection and presumably aidsH. pyloriin encountering and colonizing preferred niches. A cytoplasmic chemoreceptor named TlpD is particularly important in this process, and we report here that this chemoreceptor is able to operate independently of other chemoreceptors to organize a chemotaxis signaling complex and mediate a repellent response to oxidative stress conditions.H. pyloriencounters and must cope with oxidative stress during infection due to oxygen and reactive oxygen species produced by host cells. TlpD's repellent response may allow the bacteria to escape niches experiencing inflammation and elevated reactive oxygen species (ROS) production.

scholarly journals Maintenance of Mitochondrial Morphology inCryptococcus neoformansIs Critical for Stress Resistance and Virulence

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Andrew L. Chang ◽  
Tamara L. Doering
Keyword(s):  
Reactive Oxygen Species ◽  
Mitochondrial Function ◽  
Reactive Oxygen ◽  
Mitochondrial Fusion ◽  
Host Cells ◽  
Mitochondrial Morphology ◽  
Oxygen Species ◽  
Content Type ◽  
Cellular Processes ◽  
Increased Susceptibility

ABSTRACTMitochondria are essential organelles that act in pathways including ATP production, β-oxidation, and clearance of reactive oxygen species. They occur as a complex reticular network that constantly undergoes fusion and fission, mediated by dynamin-related proteins (DRPs). DRPs include Fzo1, which mediates fusion, and Dnm1, Mdv1, and Fis1, which mediate fission. Mitochondrial morphology has been implicated in virulence in multiple fungi, as with the association between virulence and increased mitochondrial fusion inCryptococcus gattii. This relationship, however, has not been studied inCryptococcus neoformans, a related opportunistic pathogen.C. neoformansis an environmental yeast that can adapt to the human host environment, overcome the innate immune system, and eventually disseminate and cause lethal meningoencephalitis. We used gene deletion of key DRPs to study their role in mitochondrial morphology and pathogenesis of this yeast. Interestingly, increasing mitochondrial fusion did not increase resistance to oxidative stress, unlike in model yeast. Blocking mitochondrial fusion, however, yielded increased susceptibility to oxidative and nitrosative stresses as well as complete avirulence. This lack of virulence was not mediated by any effects of altered mitochondrial function on two major virulence factors, capsule and melanin. Instead, it was due to decreased survival within macrophages, which in turn was a consequence of increased susceptibility to oxidative and nitrosative stress. Supporting this conclusion, reactive oxygen species (ROS) scavengers rescued the ability of fusion mutants to survive intracellularly. These findings increase our understanding of cryptococcal biology and virulence and shed light on an important group of proteins and cellular processes in this pathogen.IMPORTANCEC. neoformansis a yeast that causes fatal brain infection in close to 200,000 people worldwide every year, mainly afflicting individuals with AIDS or others who are severely immunocompromised. One feature of this microbe that helps it cause disease is that it is able to withstand toxic molecules it encounters when host cells engulf it in their efforts to control the infection. Mitochondria are important organelles responsible for energy production and other key cellular processes. They typically exist in a complex network that changes morphology by fusing and dividing; these alterations also influence mitochondrial function. Using genetic approaches, we found that changes in mitochondrial morphology dramatically influence cryptococcal virulence. We showed that this occurs because the altered mitochondria are less able to eliminate the harmful molecules that host cells produce to kill invading microbes. These findings are important because they elucidate fundamental biology and virulence and may suggest avenues for therapy.

scholarly journals Ehrlichia chaffeensis Uses an Invasin To Suppress Reactive Oxygen Species Generation by Macrophages via CD147-Dependent Inhibition of Vav1 To Block Rac1 Activation

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Omid Teymournejad ◽  
Yasuko Rikihisa
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Host Cells ◽  
Cell Surface Receptor ◽  
Ros Generation ◽  
Ehrlichia Chaffeensis ◽  
Oxygen Species ◽  
Content Type ◽  
Monocytes And Macrophages ◽  
Surface Receptor

ABSTRACT The obligatory intracellular pathogen Ehrlichia chaffeensis lacks most factors that could respond to oxidative stress (a host cell defense mechanism). We previously found that the C terminus of Ehrlichia surface invasin, entry-triggering protein of Ehrlichia (EtpE; EtpE-C) directly binds mammalian DNase X, a glycosylphosphatidylinositol-anchored cell surface receptor and that binding is required to induce bacterial entry and simultaneously to block the generation of reactive oxygen species (ROS) by host monocytes and macrophages. However, how the EtpE-C−DNase X complex mediates the ROS blockade was unknown. A mammalian transmembrane glycoprotein CD147 (basigin) binds to the EtpE-DNase X complex and is required for Ehrlichia entry and infection of host cells. Here, we found that bone marrow-derived macrophages (BMDM) from myeloid cell lineage-selective CD147-null mice had significantly reduced Ehrlichia-induced or EtpE-C-induced blockade of ROS generation in response to phorbol myristate acetate. In BMDM from CD147-null mice, nucleofection with CD147 partially restored the Ehrlichia-mediated inhibition of ROS generation. Indeed, CD147-null mice as well as their BMDM were resistant to Ehrlichia infection. Moreover, in human monocytes, anti-CD147 partially abrogated EtpE-C-induced blockade of ROS generation. Both Ehrlichia and EtpE-C could block activation of the small GTPase Rac1 (which in turn activates phagocyte NADPH oxidase) and suppress activation of Vav1, a hematopoietic-specific Rho/Rac guanine nucleotide exchange factor by phorbol myristate acetate. Vav1 suppression by Ehrlichia was CD147 dependent. E. chaffeensis is the first example of pathogens that block Rac1 activation to colonize macrophages. Furthermore, Ehrlichia uses EtpE to hijack the unique host DNase X-CD147-Vav1 signaling to block Rac1 activation. IMPORTANCE Ehrlichia chaffeensis is an obligatory intracellular bacterium with the capability of causing an emerging infectious disease called human monocytic ehrlichiosis. E. chaffeensis preferentially infects monocytes and macrophages, professional phagocytes, equipped with an arsenal of antimicrobial mechanisms, including rapid reactive oxygen species (ROS) generation upon encountering bacteria. As Ehrlichia isolated from host cells are readily killed upon exposure to ROS, Ehrlichia must have evolved a unique mechanism to safely enter phagocytes. We discovered that binding of the Ehrlichia surface invasin to the host cell surface receptor not only triggers Ehrlichia entry but also blocks ROS generation by the host cells by mobilizing a novel intracellular signaling pathway. Knowledge of the mechanisms by which ROS production is inhibited may lead to the development of therapeutics for ehrlichiosis as well as other ROS-related pathologies.

scholarly journals The Na/K-ATPase Signaling: From Specific Ligands to General Reactive Oxygen Species

2018 ◽  
Vol 19 (9) ◽  
pp. 2600 ◽  
Author(s):  
Rebecca Pratt ◽  
Cameron Brickman ◽  
Cameron Cottrill ◽  
Joseph Shapiro ◽  
Jiang Liu
Keyword(s):  
Reactive Oxygen Species ◽  
Positive Feedback ◽  
Reactive Oxygen ◽  
Underlying Mechanism ◽  
Short Review ◽  
Oxygen Species ◽  
Signaling Function ◽  
Amplification Loop

The signaling function of the Na/K-ATPase has been established for 20 years and is widely accepted in the field, with many excellent reports and reviews not cited here. Even though there is debate about the underlying mechanism, the signaling function is unquestioned. This short review looks back at the evolution of Na/K-ATPase signaling, from stimulation by cardiotonic steroids (also known as digitalis-like substances) as specific ligands to stimulation by reactive oxygen species (ROS) in general. The interplay of cardiotonic steroids and ROS in Na/K-ATPase signaling forms a positive-feedback oxidant amplification loop that has been implicated in some pathophysiological conditions.

scholarly journals Oxidative Stressors Modify the Response of Streptococcus mutans to Its Competence Signal Peptides

2017 ◽  
Vol 83 (22) ◽  
Author(s):  
Matthew De Furio ◽  
Sang Joon Ahn ◽  
Robert A. Burne ◽  
Stephen J. Hagen
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Dental Caries ◽  
Signaling Pathway ◽  
Streptococcus Mutans ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Oral Biofilm ◽  
Genetic Competence ◽  
Content Type

ABSTRACTThe dental caries pathogenStreptococcus mutansis continually exposed to several types of stress in the oral biofilm environment. Oxidative stress generated by reactive oxygen species has a major impact on the establishment, persistence, and virulence ofS. mutans. Here, we combined fluorescent reporter-promoter fusions with single-cell imaging to study the effects of reactive oxygen species on activation of genetic competence inS. mutans. Exposure to paraquat, which generates superoxide anion, produced a qualitatively different effect on activation of expression of the gene for the master competence regulator, ComX, than did treatment with hydrogen peroxide (H2O2), which can yield hydroxyl radical. Paraquat suppressed peptide-mediated induction ofcomXin a progressive and cumulative fashion, whereas the response to H2O2displayed a strong threshold behavior. Low concentrations of H2O2had little effect on induction ofcomXor the bacteriocin genecipB, but expression of these genes declined sharply if extracellular H2O2exceeded a threshold concentration. These effects were not due to decreased reporter gene fluorescence. Two different threshold concentrations were observed in the response to H2O2, depending on the gene promoter that was analyzed and the pathway by which the competence regulon was stimulated. The results show that paraquat and H2O2affect theS. mutanscompetence signaling pathway differently, and that some portions of the competence signaling pathway are more sensitive to oxidative stress than others.IMPORTANCEStreptococcus mutansinhabits the oral biofilm, where it plays an important role in the development of dental caries. Environmental stresses such as oxidative stress influence the growth ofS. mutansand its important virulence-associated behaviors, such as genetic competence.S. mutanscompetence development is a complex behavior that involves two different signaling peptides and can exhibit cell-to-cell heterogeneity. Although oxidative stress is known to influenceS. mutanscompetence, it is not understood how oxidative stress interacts with the peptide signaling or affects heterogeneity. In this study, we used fluorescent reporters to probe the effect of reactive oxygen species on competence signaling at the single-cell level. Our data show that different reactive oxygen species have different effects onS. mutanscompetence, and that some portions of the signaling pathway are more acutely sensitive to oxidative stress than others.

scholarly journals Drosophila hemocytes recognize lymph gland tumors of mxc mutants and activate the Toll pathway in reactive oxygen species-dependent manner

2021 ◽  
Author(s):  
Suzuko Kinoshita ◽  
Kazuki Takarada ◽  
Yoshihiro H. Inoue
Keyword(s):  
Reactive Oxygen Species ◽  
Fat Body ◽  
Ectopic Expression ◽  
Reactive Oxygen ◽  
Underlying Mechanism ◽  
Innate Immune ◽  
Dependent Manner ◽  
Oxygen Species ◽  
Matrix Metalloproteinase 1 ◽  
Membrane Components

Mechanisms of cancer cell recognition and elimination by the innate immune system remains unclear. Circulating hemocytes are associated with the hematopoietic tumors in Drosophila mxcmbn1 mutant larvae. The innate immune signalling pathways are activated in the fat body to suppress the tumor growth by inducing antimicrobial peptides (AMP). Here, we investigated the regulatory mechanism underlying the activation in the mutant. Reactive oxygen species accumulated in the hemocytes due to induction of dual oxidase and its activator. The hemocytes were also localized on the fat body. These were essential for transmitting the information on tumors toward the fat body to induce AMP expression. Regarding to the tumor recognition, we found that matrix metalloproteinase 1 (MMP1) and MMP2 were highly expressed in the tumors. Ectopic expression of MMP2 was associated with AMP induction in the mutants. Furthermore, the basement membrane components in the tumors were reduced and ultimately lost. The hemocytes may recognize the disassembly in the tumors. Our findings highlight the underlying mechanism via which macrophage-like hemocytes recognize tumor cells and relay the information toward the fat body to induce AMPs. and contribute to uncover the immune system's roles against cancer.

scholarly journals Selective Activation of Endoplasmic Reticulum Stress by Reactive-Oxygen-Species-Mediated Ochratoxin A-Induced Apoptosis in Tubular Epithelial Cells

2021 ◽  
Vol 22 (20) ◽  
pp. 10951
Author(s):  
Chong-Sun Khoi ◽  
Yu-Wen Lin ◽  
Jia-Huang Chen ◽  
Biing-Hui Liu ◽  
Tzu-Yu Lin ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Ochratoxin A ◽  
Reactive Oxygen ◽  
Underlying Mechanism ◽  
Oxygen Species ◽  
Food And Feed ◽  
Renal Proximal Tubular Cells ◽  
Induced Apoptosis

Ochratoxin A (OTA), one of the major food-borne mycotoxins, impacts the health of humans and livestock by contaminating food and feed. However, the underlying mechanism of OTA nephrotoxicity remains unknown. This study demonstrated that OTA induced apoptosis through selective endoplasmic reticulum (ER) stress activation in human renal proximal tubular cells (HK-2). OTA increased ER-stress-related JNK and precursor caspase-4 cleavage apoptotic pathways. Further study revealed that OTA increased reactive oxygen species (ROS) levels, and N-acetyl cysteine (NAC) could reduce OTA-induced JNK-related apoptosis and ROS levels in HK-2 cells. Our results demonstrate that OTA induced ER stress-related apoptosis through an ROS-mediated pathway. This study provides new evidence to clarify the mechanism of OTA-induced nephrotoxicity.

scholarly journals The Dynll1-Cox4i1 Complex Regulates Intracellular Pathogen Clearance via Release of Mitochondrial Reactive Oxygen Species

2020 ◽  
Vol 88 (4) ◽  
Author(s):  
Jiangbei Yuan ◽  
Zihan Zheng ◽  
Liting Wang ◽  
Haiying Ran ◽  
Xiangyu Tang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Listeria Monocytogenes ◽  
Membrane Proteins ◽  
Defense Mechanisms ◽  
Reactive Oxygen ◽  
Cellular Membrane ◽  
Oxygen Species ◽  
Dynein Light Chain ◽  
Mitochondrial Reactive Oxygen Species ◽  
Content Type

ABSTRACT Cellular membrane proteins are a critical part of the host defense mechanisms against infection and intracellular survival of Listeria monocytogenes. The complex spatiotemporal regulation of bacterial infection by various membrane proteins has been challenging to study. Here, using mass spectrometry analyses, we depicted the dynamic expression landscape of membrane proteins upon L. monocytogenes infection in dendritic cells. We showed that Dynein light chain 1 (Dynll1) formed a persistent complex with the mitochondrial cytochrome oxidase Cox4i1, which is disturbed by pathogen insult. We discovered that the dissociation of the Dynll1-Cox4i1 complex is required for the release of mitochondrial reactive oxygen species and serves as a regulator of intracellular proliferation of Listeria monocytogenes. Our study shows that Dynll1 is an inhibitor of mitochondrial reactive oxygen species and can serve as a potential molecular drug target for antibacterial treatment.

scholarly journals Ascorbate-Dependent Peroxidase (APX) from Leishmania amazonensis Is a Reactive Oxygen Species-Induced Essential Enzyme That Regulates Virulence

2019 ◽  
Vol 87 (12) ◽  
Author(s):  
Lucia Xiang ◽  
Maria Fernanda Laranjeira-Silva ◽  
Fernando Y. Maeda ◽  
Jason Hauzel ◽  
Norma W. Andrews ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Macrophage Infection ◽  
Cutaneous Lesions ◽  
Signaling Mechanism ◽  
Content Type ◽  
Temporal Regulation ◽  
Metacyclic Promastigotes

ABSTRACT The molecular mechanisms underlying biological differences between two Leishmania species that cause cutaneous disease, L. major and L. amazonensis, are poorly understood. In L. amazonensis, reactive oxygen species (ROS) signaling drives differentiation of nonvirulent promastigotes into forms capable of infecting host macrophages. Tight spatial and temporal regulation of H2O2 is key to this signaling mechanism, suggesting a role for ascorbate-dependent peroxidase (APX), which degrades mitochondrial H2O2. Earlier studies showed that APX-null L. major parasites are viable, accumulate higher levels of H2O2, generate a greater yield of infective metacyclic promastigotes, and have increased virulence. In contrast, we found that in L. amazonensis, the ROS-inducible APX is essential for survival of all life cycle stages. APX-null promastigotes could not be generated, and parasites carrying a single APX allele were impaired in their ability to infect macrophages and induce cutaneous lesions in mice. Similar to what was reported for L. major, APX depletion in L. amazonensis enhanced differentiation of metacyclic promastigotes and amastigotes, but the parasites failed to replicate after infecting macrophages. APX expression restored APX single-knockout infectivity, while expression of catalytically inactive APX drastically reduced virulence. APX overexpression in wild-type promastigotes reduced metacyclogenesis, but enhanced intracellular survival following macrophage infection or inoculation into mice. Collectively, our data support a role for APX-regulated mitochondrial H2O2 in promoting differentiation of virulent forms in both L. major and L. amazonensis. Our results also uncover a unique requirement for APX-mediated control of ROS levels for survival and successful intracellular replication of L. amazonensis.

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