scholarly journals Specific Osmolyte Transporters Mediate Bile Tolerance in Listeria monocytogenes

2009 ◽  
Vol 77 (11) ◽  
pp. 4895-4904 ◽  
Author(s):  
Debbie Watson ◽  
Roy D. Sleator ◽  
Pat G. Casey ◽  
Colin Hill ◽  
Cormac G. M. Gahan
Keyword(s):  
Listeria Monocytogenes ◽  
Oral Infection ◽  
Infection Model ◽  
Minor Role ◽  
Uptake System ◽  
Systematic Analysis ◽  
Bile Tolerance ◽  
Genes Encoding ◽  
A Minor

ABSTRACT The food-borne pathogenic bacterium Listeria monocytogenes has the potential to adapt to an array of suboptimal growth environments encountered within the host. The pathogen is relatively bile tolerant and has the capacity to survive and grow within both the small intestine and the gallbladder in murine models of oral infection. We have previously demonstrated a role for the principal carnitine transport system of L. monocytogenes (OpuC) in gastrointestinal survival of the pathogen (R. Sleator, J. Wouters, C. G. M. Gahan, T. Abee, and C. Hill, Appl. Environ. Microbiol. 67:2692-2698, 2001). However, the mechanisms by which OpuC, or indeed carnitine, protects the pathogen in this environment are unclear. In the current study, systematic analysis of strains with mutations in osmolyte transporters revealed a role for OpuC in resisting the acute toxicity of bile, with a minor role also played by BetL, a secondary betaine uptake system which also exhibits a low affinity for carnitine. In addition, the toxic effects of bile on wild-type L. monocytogenes cells were ameliorated when carnitine (but not betaine) was added to the medium. lux-promoter fusions to the promoters of the genes encoding the principal osmolyte uptake systems Gbu, BetL, and OpuC and the known bile tolerance system BilE were constructed. Promoter activity for all systems was significantly induced in the presence of bile, with the opuC and bilE promoters exhibiting the highest levels of bile-dependent expression in vitro and the betL and bilE promoters showing the highest expression levels in the intestines of orally inoculated mice. A direct comparison of all osmolyte transporter mutants in a murine oral infection model confirmed a major role for OpuC in intestinal persistence and systemic invasion and a minor role for the BetL transporter in fecal carriage. This study therefore demonstrates a previously unrecognized function for osmolyte uptake systems in bile tolerance in L. monocytogenes.

scholarly journals Designing P. aeruginosa synthetic phages with reduced genomes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Diana P. Pires ◽  
Rodrigo Monteiro ◽  
Dalila Mil-Homens ◽  
Arsénio Fialho ◽  
Timothy K. Lu ◽  
...  
Keyword(s):  
Galleria Mellonella ◽  
Antibacterial Properties ◽  
Genetically Engineered ◽  
In Vivo Studies ◽  
Infection Model ◽  
Promising Therapeutic Approach ◽  
Genes Encoding ◽  
First Time

AbstractIn the era where antibiotic resistance is considered one of the major worldwide concerns, bacteriophages have emerged as a promising therapeutic approach to deal with this problem. Genetically engineered bacteriophages can enable enhanced anti-bacterial functionalities, but require cloning additional genes into the phage genomes, which might be challenging due to the DNA encapsulation capacity of a phage. To tackle this issue, we designed and assembled for the first time synthetic phages with smaller genomes by knocking out up to 48% of the genes encoding hypothetical proteins from the genome of the newly isolated Pseudomonas aeruginosa phage vB_PaeP_PE3. The antibacterial efficacy of the wild-type and the synthetic phages was assessed in vitro as well as in vivo using a Galleria mellonella infection model. Overall, both in vitro and in vivo studies revealed that the knock-outs made in phage genome do not impair the antibacterial properties of the synthetic phages, indicating that this could be a good strategy to clear space from phage genomes in order to enable the introduction of other genes of interest that can potentiate the future treatment of P. aeruginosa infections.

scholarly journals 40S ribosome profiling reveals distinct roles for Tma20/Tma22 (MCT-1/DENR) and Tma64 (eIF2D) in 40S subunit recycling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David J. Young ◽  
Sezen Meydan ◽  
Nicholas R. Guydosh
Keyword(s):  
Protein Synthesis ◽  
Neurological Disease ◽  
Ribosome Profiling ◽  
Minor Role ◽  
Stop Codons ◽  
Genes Encoding ◽  
Ribosome Footprinting ◽  
A Minor ◽  
And Control ◽  
In Cells

AbstractThe recycling of ribosomes at stop codons for use in further rounds of translation is critical for efficient protein synthesis. Removal of the 60S subunit is catalyzed by the ATPase Rli1 (ABCE1) while removal of the 40S is thought to require Tma64 (eIF2D), Tma20 (MCT-1), and Tma22 (DENR). However, it remains unclear how these Tma proteins cause 40S removal and control reinitiation of downstream translation. Here we used a 40S ribosome footprinting strategy to directly observe intermediate steps of ribosome recycling in cells. Deletion of the genes encoding these Tma proteins resulted in broad accumulation of unrecycled 40S subunits at stop codons, directly establishing their role in 40S recycling. Furthermore, the Tma20/Tma22 heterodimer was responsible for a majority of 40S recycling events while Tma64 played a minor role. Introduction of an autism-associated mutation into TMA22 resulted in a loss of 40S recycling activity, linking ribosome recycling and neurological disease.

scholarly journals Listeria Monocytogenes: A Model Pathogen Continues to Refine Our Knowledge of the CD8 T Cell Response

Pathogens ◽  
2018 ◽  
Vol 7 (2) ◽  
pp. 55 ◽  
Author(s):  
Zhijuan Qiu ◽  
Camille Khairallah ◽  
Brian Sheridan
Keyword(s):  
Listeria Monocytogenes ◽  
T Cell ◽  
Cell Response ◽  
Protective Immunity ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
Oral Infection ◽  
T Cell Response ◽  
Infection Model ◽  
Cell Responses

Listeria monocytogenes (Lm) infection induces robust CD8 T cell responses, which play a critical role in resolving Lm during primary infection and provide protective immunity to re-infections. Comprehensive studies have been conducted to delineate the CD8 T cell response after Lm infection. In this review, the generation of the CD8 T cell response to Lm infection will be discussed. The role of dendritic cell subsets in acquiring and presenting Lm antigens to CD8 T cells and the events that occur during T cell priming and activation will be addressed. CD8 T cell expansion, differentiation and contraction as well as the signals that regulate these processes during Lm infection will be explored. Finally, the formation of memory CD8 T cell subsets in the circulation and in the intestine will be analyzed. Recently, the study of CD8 T cell responses to Lm infection has begun to shift focus from the intravenous infection model to a natural oral infection model as the humanized mouse and murinized Lm have become readily available. Recent findings in the generation of CD8 T cell responses to oral infection using murinized Lm will be explored throughout the review. Finally, CD8 T cell-mediated protective immunity against Lm infection and the use of Lm as a vaccine vector for cancer immunotherapy will be highlighted. Overall, this review will provide detailed knowledge on the biology of CD8 T cell responses after Lm infection that may shed light on improving rational vaccine design.

scholarly journals Interleukin-15 May Be Responsible for Early Activation of Intestinal Intraepithelial Lymphocytes after Oral Infection with Listeria monocytogenes in Rats

1998 ◽  
Vol 66 (12) ◽  
pp. 5677-5683 ◽  
Author(s):  
Kenji Hirose ◽  
Hirohiko Suzuki ◽  
Hitoshi Nishimura ◽  
Akio Mitani ◽  
Junji Washizu ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Cell Receptor ◽  
Intraepithelial Lymphocytes ◽  
Oral Infection ◽  
Epithelial Cell Line ◽  
Intestinal Intraepithelial Lymphocytes ◽  
Interleukin 15 ◽  
Ifn Γ

ABSTRACT Exogenous interleukin-15 (IL-15) stimulates intestinal intraepithelial lymphocytes (i-IEL) from mice to proliferate and produce gamma interferon (IFN-γ) in vitro. To determine whether endogenous IL-15 is involved in activation of i-IEL during intestinal infection, we examined IL-15 synthesis by intestinal epithelial cells (i-EC) after infection with Listeria monocytogenes in rats. In in vitro experiments, invasion of L. monocytogenes into IEC-6 cells, a rat small intestine epithelial cell line, evidently induced IL-15 mRNA expression coincident with nuclear factor κB (NF-κB) activation, which is essential for IL-15 gene expression. IL-15 synthesis was detected in rat i-EC on day 1 after an oral inoculation of L. monocytogenes in vivo. The numbers of T-cell receptor (TCR) γδ+ T cells, NKR.P1+cells, and CD3+ CD8+ αα cells in i-IEL were significantly increased on day 1 after oral infection. The i-IEL from infected rats produced larger amounts of IFN-γ upon stimulation with immobilized anti-TCR γδ or anti-NKR.P1 monoclonal antibodies. These results suggest that IL-15 produced by i-EC may stimulate significant fractions of i-IEL to produce IFN-γ at an early phase of oral infection with L. monocytogenes.

scholarly journals An iron-regulated LysR-type element mediates antimicrobial peptide resistance and virulence in Yersinia pseudotuberculosis

Microbiology ◽  
2009 ◽  
Vol 155 (7) ◽  
pp. 2168-2181 ◽  
Author(s):  
Sonia Arafah ◽  
Marie-Laure Rosso ◽  
Linda Rehaume ◽  
Robert E. W. Hancock ◽  
Michel Simonet ◽  
...  
Keyword(s):  
Antimicrobial Peptide ◽  
Yersinia Pseudotuberculosis ◽  
Polymyxin B ◽  
Uptake System ◽  
Mesenteric Lymph Nodes ◽  
Iron Starvation ◽  
Iron Deprivation ◽  
Genes Encoding ◽  
Antimicrobial Peptide Resistance

During the course of its infection of the mammalian digestive tract, the entero-invasive, Gram-negative bacterium Yersinia pseudotuberculosis must overcome various hostile living conditions (notably, iron starvation and the presence of antimicrobial compounds produced in situ). We have previously reported that in vitro bacterial growth during iron deprivation raises resistance to the antimicrobial peptide polymyxin B; here, we show that this phenotype is mediated by a chromosomal gene (YPTB0333) encoding a transcriptional regulator from the LysR family. We determined that the product of YPTB0333 is a pleiotropic regulator which controls (in addition to its own expression) genes encoding the Yfe iron-uptake system and polymyxin B resistance. Lastly, by using a mouse model of oral infection, we demonstrated that YPTB0333 is required for colonization of Peyer's patches and mesenteric lymph nodes by Y. pseudotuberculosis.

scholarly journals Diversity, Epidemiology, and Genetics of Class D β-Lactamases

2009 ◽  
Vol 54 (1) ◽  
pp. 24-38 ◽  
Author(s):  
Laurent Poirel ◽  
Thierry Naas ◽  
Patrice Nordmann
Keyword(s):  
Natural Resistance ◽  
Minor Role ◽  
Insertion Sequences ◽  
Class 1 Integron ◽  
Gram Negative ◽  
Class D ◽  
Class 1 ◽  
Great Heterogeneity ◽  
Genes Encoding ◽  
A Minor

ABSTRACT Class D β-lactamase-mediated resistance to β-lactams has been increasingly reported during the last decade. Those enzymes also known as oxacillinases or OXAs are widely distributed among Gram negatives. Genes encoding class D β-lactamases are known to be intrinsic in many Gram-negative rods, including Acinetobacter baumannii and Pseudomonas aeruginosa, but play a minor role in natural resistance phenotypes. The OXAs (ca. 150 variants reported so far) are characterized by an important genetic diversity and a great heterogeneity in terms of β-lactam hydrolysis spectrum. The acquired OXAs possess either a narrow spectrum or an expanded spectrum of hydrolysis, including carbapenems in several instances. Acquired class D β-lactamase genes are mostly associated to class 1 integron or to insertion sequences.

scholarly journals In Vitro and In Vivo Biology of Recombinant Adenovirus Vectors with E1, E1/E2A, or E1/E4 Deleted

1998 ◽  
Vol 72 (3) ◽  
pp. 2022-2032 ◽  
Author(s):  
M. Lusky ◽  
M. Christ ◽  
K. Rittner ◽  
A. Dieterle ◽  
D. Dreyer ◽  
...  
Keyword(s):  
Recombinant Adenovirus ◽  
Virus Genome ◽  
Minor Role ◽  
Immunodeficient Mice ◽  
Viral Genomes ◽  
Viral Genes ◽  
Adenovirus Vectors ◽  
A Minor

ABSTRACT Isogenic, E3-deleted adenovirus vectors defective in E1, E1 and E2A, or E1 and E4 were generated in complementation cell lines expressing E1, E1 and E2A, or E1 and E4 and characterized in vitro and in vivo. In the absence of complementation, deletion of both E1 and E2A completely abolished expression of early and late viral genes, while deletion of E1 and E4 impaired expression of viral genes, although at a lower level than the E1/E2A deletion. The in vivo persistence of these three types of vectors was monitored in selected strains of mice with viral genomes devoid of transgenes to exclude any interference by immunogenic transgene-encoded products. Our studies showed no significant differences among the vectors in the short-term maintenance and long-term (4-month) persistence of viral DNA in liver and lung cells of immunocompetent and immunodeficient mice. Furthermore, all vectors induced similar antibody responses and comparable levels of adenovirus-specific cytotoxic T lymphocytes. These results suggest that in the absence of transgenes, the progressive deletion of the adenovirus genome does not extend the in vivo persistence of the transduced cells and does not reduce the antivirus immune response. In addition, our data confirm that, in the absence of transgene expression, mouse cellular immunity to viral antigens plays a minor role in the progressive elimination of the virus genome.

Ethanol metabolism by the rat heart and alcohol dehydrogenase activity

1976 ◽  
Vol 54 (6) ◽  
pp. 539-545 ◽  
Author(s):  
G. W. Forsyth ◽  
H. T. Nagasawa ◽  
C. S. Alexander
Keyword(s):  
Alcohol Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Rat Heart ◽  
Specific Activity ◽  
Ph Dependence ◽  
Ethanol Metabolism ◽  
Minor Role ◽  
Alcohol Dehydrogenase Activity ◽  
A Minor

Rat hearts perfused with oxygenated buffer containing [1-14C]ethanol metabolized small amounts of the ethanol to carbon dioxide. Very sensitive techniques are required to separate the resulting 14CO2 from the ethanol. This metabolism is not inhibited by levels of pyrazole which markedly inhibit NAD dependent liver alcohol dehydrogenase (EC 1.1.1.1). In vitro studies suggest that NADP functions as a cofactor for the rat heart alcohol dehydrogenase activity of crude heart homogenates. The kinetic parameters, the specific activity, and the pH dependence of the enzyme activity measured in these experiments suggest that it may have a minor role in ethanol metabolism by the rat.

scholarly journals High-Frequency RecA-Dependent and -Independent Mechanisms of Congo Red Binding Mutations in Yersinia pestis

1999 ◽  
Vol 181 (16) ◽  
pp. 4896-4904 ◽  
Author(s):  
Janelle M. Hare ◽  
Kathleen A. McDonough
Keyword(s):  
Yersinia Pestis ◽  
Congo Red ◽  
High Frequency ◽  
Yersinia Pseudotuberculosis ◽  
Resistance Mutation ◽  
Laboratory Culture ◽  
Uptake System ◽  
Deletion Event ◽  
Genes Encoding

ABSTRACT Yersinia pestis, which causes bubonic and pneumonic plague, forms pigmented red colonies on Congo red (CR) dye agar. ThehmsHFRS genes required for CR binding (Crb+) are genetically linked to virulence-associated genes encoding a siderophore uptake system. These genes are contained in a 102-kb chromosomal pgm locus that is lost in a high-frequency deletion event, resulting in loss of the Crb+ phenotype. We constructed a recA mutant strain of Y. pestisKIM10+ (YPRA) to test whether the high frequency Crb mutants result from a RecA-mediated deletion of the IS100-flankedpgm locus. Two Pgm-associated phenotypes (Crb+and pesticin sensitivity [Psts]) were used as markers for the presence of the pgm locus in the RecA+KIM10+ and RecA− YPRA strains. In KIM10+, both phenotypes were lost at a very high (2 × 10−3) frequency, due to the deletion of the entire pgm locus. In YPRA, the Crb+ phenotype was still lost at a high frequency (4.5 × 10−5), although the loss of the Pstsphenotype occurred at spontaneous antibiotic resistance mutation frequencies (2 × 10−7). These RecA-independent Crb− mutants were caused by mutations in both thehmsHFRS locus and in a newly identified gene,hmsT. Nonpigmented Yersinia pseudotuberculosisand Escherichia coli strains transformed with bothhmsT and hmsHFRS became Crb+. This study demonstrates that in a laboratory culture, the Crb+phenotype is unstable, independent of the pgm locus deletion. We propose that a lack of selection for the CR-binding ability of Y. pestis in vitro may contribute to the mutation frequencies observed at the hmsHFRS andhmsT loci.

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