scholarly journals Inactivation of Lgt Allows Systematic Characterization of Lipoproteins from Listeria monocytogenes

2006 ◽  
Vol 189 (2) ◽  
pp. 313-324 ◽  
Author(s):  
Maja Baumgärtner ◽  
Uwe Kärst ◽  
Birgit Gerstel ◽  
Martin Loessner ◽  
Jürgen Wehland ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Wild Type Strain ◽  
Culture Supernatant ◽  
Eukaryotic Cell ◽  
Signal Peptidase ◽  
Wild Type ◽  
Intracellular Growth ◽  
Extracellular Proteome ◽  
Insight Into

ABSTRACT Lipoprotein anchoring in bacteria is mediated by the prolipoprotein diacylglyceryl transferase (Lgt), which catalyzes the transfer of a diacylglyceryl moiety to the prospective N-terminal cysteine of the mature lipoprotein. Deletion of the lgt gene in the gram-positive pathogen Listeria monocytogenes (i) impairs intracellular growth of the bacterium in different eukaryotic cell lines and (ii) leads to increased release of lipoproteins into the culture supernatant. Comparative extracellular proteome analyses of the EGDe wild-type strain and the Δlgt mutant provided systematic insight into the relative expression of lipoproteins. Twenty-six of the 68 predicted lipoproteins were specifically released into the extracellular proteome of the Δlgt strain, and this proved that deletion of lgt is an excellent approach for experimental verification of listerial lipoproteins. Consequently, we generated Δlgt ΔprfA double mutants to detect lipoproteins belonging to the main virulence regulon that is controlled by PrfA. Overall, we identified three lipoproteins whose extracellular levels are regulated and one lipoprotein that is posttranslationally modified depending on PrfA. It is noteworthy that in contrast to previous studies of Escherichia coli, we unambiguously demonstrated that lipidation by Lgt is not a prerequisite for activity of the lipoprotein-specific signal peptidase II (Lsp) in Listeria.

The major PEP-phosphotransferase systems (PTSs) for glucose, mannose and cellobiose of Listeria monocytogenes, and their significance for extra- and intracellular growth

Microbiology ◽  
2010 ◽  
Vol 156 (4) ◽  
pp. 1069-1083 ◽  
Author(s):  
Regina Stoll ◽  
Werner Goebel
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Epithelial Cells ◽  
Type Strain ◽  
Minimal Medium ◽  
Wild Type Strain ◽  
Wild Type ◽  
Intracellular Growth ◽  
Sugar Alcohols ◽  
Genes Encoding

In this report we examine the PEP-dependent phosphotransferase systems (PTSs) of Listeria monocytogenes EGD-e, especially those involved in glucose and cellobiose transport. This L. monocytogenes strain possesses in total 86 pts genes, encoding 29 complete PTSs for the transport of carbohydrates and sugar alcohols, and several single PTS components, possibly supporting transport of these compounds. By a systematic deletion analysis we identified the major PTSs involved in glucose, mannose and cellobiose transport, when L. monocytogenes grows in a defined minimal medium in the presence of these carbohydrates. Whereas all four PTS permeases belonging to the PTSMan family may be involved in mannose transport, only two of these (PTSMan-2 and PTSMan-3), and in addition at least one (PTSGlc-1) of the five PTS permeases belonging to the PTSGlc family, are able to transport glucose, albeit with different efficiencies. Cellobiose is transported mainly by one (PTSLac-4) of the six members belonging to the PTSLac family. In addition, PTSGlc-1 appears to be also able to transport cellobiose. The transcription of the operons encoding PTSMan-2 and PTSLac-4 (but not that of the operon for PTSMan-3) is regulated by LevR-homologous PTS regulation domain (PRD) activators. Whereas the growth rate of the mutant lacking PTSMan-2, PTSMan-3 and PTSGlc-1 is drastically reduced (compared with the wild-type strain) in the presence of glucose, and that of the mutant lacking PTSLac-4 and PTSGlc-1 in the presence of cellobiose, replication of both mutants within epithelial cells or macrophages is as efficient as that of the wild-type strain.

Volatile Anesthetics Affect Nutrient Availability in Yeast

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 563-574
Author(s):  
Laura K Palmer ◽  
Darren Wolfe ◽  
Jessica L Keeley ◽  
Ralph L Keil
Keyword(s):  
Amino Acids ◽  
Nutrient Availability ◽  
Wild Type Strain ◽  
Volatile Anesthetic ◽  
Volatile Anesthetics ◽  
Wild Type ◽  
Anesthetic Exposure ◽  
Sites Of Action ◽  
Insight Into ◽  
Lines Of Evidence

Abstract Volatile anesthetics affect all cells and tissues tested, but their mechanisms and sites of action remain unknown. To gain insight into the cellular activities of anesthetics, we have isolated genes that, when overexpressed, render Saccharomyces cerevisiae resistant to the volatile anesthetic isoflurane. One of these genes, WAK3/TAT1, encodes a permease that transports amino acids including leucine and tryptophan, for which our wild-type strain is auxotrophic. This suggests that availability of amino acids may play a key role in anesthetic response. Multiple lines of evidence support this proposal: (i) Deletion or overexpression of permeases that transport leucine and/or tryptophan alters anesthetic response; (ii) prototrophic strains are anesthetic resistant; (iii) altered concentrations of leucine and tryptophan in the medium affect anesthetic response; and (iv) uptake of leucine and tryptophan is inhibited during anesthetic exposure. Not all amino acids are critical for this response since we find that overexpression of the lysine permease does not affect anesthetic sensitivity. These findings are consistent with models in which anesthetics have a physiologically important effect on availability of specific amino acids by altering function of their permeases. In addition, we show that there is a relationship between nutrient availability and ubiquitin metabolism in this response.

Characterization of Enterococcus faecium mutants resistant to mundticin KS, a class IIa bacteriocin

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2901-2908 ◽  
Author(s):  
Youko Sakayori ◽  
Mizuho Muramatsu ◽  
Satoshi Hanada ◽  
Yoichi Kamagata ◽  
Shinichi Kawamoto ◽  
...  
Keyword(s):  
Enterococcus Faecium ◽  
Antimicrobial Agents ◽  
Wild Type Strain ◽  
Unsaturated Fatty Acids ◽  
Class I ◽  
Wild Type ◽  
Food Preservatives ◽  
In The Wild ◽  
Resistant Mutants

The emergence and spread of mutants resistant to bacteriocins would threaten the safety of using bacteriocins as food preservatives. To determine the physiological characteristics of resistant mutants, mutants of Enterococcus faecium resistant to mundticin KS, a class IIa bacteriocin, were isolated. Two types of mutant were found that had different sensitivities to other antimicrobial agents such as nisin (class I) and kanamycin. Both mutants were resistant to mundticin KS even in the absence of Mg2+ ions. The composition of unsaturated fatty acids in the resistant mutants was significantly increased in the presence of mundticin KS. The composition of the phospholipids in the two resistant mutants also differed from those in the wild-type strain. The putative zwitterionic amino-containing phospholipid in both mutants significantly increased, whereas amounts of phosphatidylglycerol and cardiolipin decreased. These changes in membrane structure may influence resistance of enterococci to class IIa and class I bacteriocins.

scholarly journals Construction and Characterization of aMycobacterium tuberculosis Mutant Lacking the Alternate Sigma Factor Gene, sigF

2000 ◽  
Vol 68 (10) ◽  
pp. 5575-5580 ◽  
Author(s):  
Ping Chen ◽  
Rafael E. Ruiz ◽  
Qing Li ◽  
Richard F. Silver ◽  
William R. Bishai
Keyword(s):  
Stationary Phase ◽  
Sigma Factor ◽  
Type Strain ◽  
Wild Type Strain ◽  
Axenic Culture ◽  
Wild Type ◽  
Intracellular Growth ◽  
Factor Gene ◽  
Time To Death

ABSTRACT The alternate RNA polymerase sigma factor gene, sigF, which is expressed in stationary phase and under stress conditions in vitro, has been deleted in the virulent CDC1551 strain ofMycobacterium tuberculosis. The growth rate of the ΔsigF mutant was identical to that of the isogenic wild-type strain in exponential phase, although in stationary phase the mutant achieved a higher density than the wild type. The mutant showed increased susceptibility to rifampin and rifapentine. Additionally, the ΔsigF mutant displayed diminished uptake of chenodeoxycholate, and this effect was reversed by complementation with a wild-type sigF gene. No differences in short-term intracellular growth between mutant and wild-type organisms within human monocytes were observed. Similarly, the organisms did not differ in their susceptibilities to lymphocyte-mediated inhibition of intracellular growth. However, mice infected with the ΔsigF mutant showed a median time to death of 246 days compared with 161 days for wild-type strain-infected animals (P < 0.001). These data indicate that M. tuberculosis sigF is a nonessential alternate sigma factor both in axenic culture and for survival in macrophages in vitro. While the ΔsigF mutant produces a lethal infection of mice, it is less virulent than its wild-type counterpart by time-to-death analysis.

scholarly journals Influence of Chemotaxis and Swimming Patterns on the Virulence of the Coral PathogenVibrio coralliilyticus

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Blake Ushijima ◽  
Claudia C. Häse
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Colonization ◽  
Valuable Insight ◽  
Wild Type ◽  
Coral Mucus ◽  
Content Type ◽  
Swimming Pattern ◽  
Vibrio Coralliilyticus ◽  
Insight Into

ABSTRACTChemotaxis, the directed movement toward or away from a chemical signal, can be essential to bacterial pathogens for locating hosts or avoiding hostile environments. The coral pathogenVibrio coralliilyticuschemotaxes toward coral mucus; however, chemotaxis has not been experimentally demonstrated to be important for virulence. To further examine this, in-frame mutations were constructed in genes predicted to be important forV. coralliilyticuschemotaxis. MostVibriogenomes contain multiple homologs of various chemotaxis-related genes, and two paralogs of each forcheB,cheR, andcheAwere identified. Based on single mutant analyses, the paralogscheB2,cheR2, andcheA1were essential for chemotaxis in laboratory assays. As predicted, the ΔcheA1and ΔcheR2strains had a smooth-swimming pattern, while the ΔcheB2strain displayed a zigzag pattern when observed under light microscopy. However, these mutants, unlike the parent strain, were unable to chemotax toward the known attractants coral mucus, dimethylsulfoniopropionate, andN-acetyl-d-glucosamine. The ΔcheB2strain and an aflagellate ΔfliG1strain were avirulent to coral, while the ΔcheA1and ΔcheR2strains were hypervirulent (90 to 100% infection within 14 h on average) compared to the wild-type strain (66% infection within 36 h on average). Additionally, the ΔcheA1and ΔcheR2strains appeared to better colonize coral fragments than the wild-type strain. These results suggest that although chemotaxis may be involved with infection (the ΔcheB2strain was avirulent), a smooth-swimming phenotype is important for bacterial colonization and infection. This study provides valuable insight into understandingV. coralliilyticuspathogenesis and how this pathogen may be transmitted between hosts.IMPORTANCECorals are responsible for creating the immense structures that are essential to reef ecosystems; unfortunately, pathogens like the bacteriumVibrio coralliilyticuscan cause fatal infections of reef-building coral species. However, compared to related human pathogens, the mechanisms by whichV. coralliilyticusinitiates infections and locates new coral hosts are poorly understood. This study investigated the effects of chemotaxis, the directional swimming in response to chemical signals, and bacterial swimming patterns on infection of the coralMontipora capitata. Infection experiments with different mutant strains suggested that a smooth-swimming pattern resulted in hypervirulence. These results demonstrate that the role of chemotaxis in coral infection may not be as straightforward as previously hypothesized and provide valuable insight intoV. coralliilyticuspathogenesis.

Inactivation of the Crp/Fnr Family of Regulatory Genes in Listeria monocytogenes Strain F2365 Does Not Alter Its Heat Resistance at 60°C†

2006 ◽  
Vol 69 (11) ◽  
pp. 2758-2760 ◽  
Author(s):  
DARRELL O. BAYLES ◽  
GAYLEN A. UHLICH
Keyword(s):  
Listeria Monocytogenes ◽  
Heat Resistance ◽  
Thermal Tolerance ◽  
Type Strain ◽  
Transcriptional Control ◽  
Wild Type Strain ◽  
Gene Cassette ◽  
Wild Type ◽  
Mutant Strains ◽  
Virulence Regulator

A surprising facet of the Listeria monocytogenes genome is the presence of 15 genes that code for regulators in the Crp/Fnr family and include the virulence regulator PrfA. The genes under the transcriptional control of these regulators are currently undetermined, with the exception of some genes controlled by the major virulence regulator PrfA. Using 12 strains of L. monocytogenes, each with an inserted gene cassette that interrupts and renders nonfunctional a different L. monocytogenes strain F2365 Crp/Fnr regulator, we heat challenged each strain at 60°C with an immersed-coil heating apparatus, modeled the survivor data to calculate the underlying mean and mode of the heat resistance distribution for each strain, and compared the thermal tolerance of each mutant to the wild-type strain to determine if any of the Crp/Fnr mutants demonstrated altered heat tolerance. All 12 of the Crp/Fnr mutant strains tested had heat resistance characteristics similar to the wild-type strain (P &gt; 0.05), indicating that mutations in these Crp/Fnr genes neither increased nor decreased the sensitivity of L. monocytogenes strain F2365 to mild heat.

scholarly journals Avoidance of Autophagy Mediated by PlcA or ActA Is Required for Listeria monocytogenes Growth in Macrophages

2015 ◽  
Vol 83 (5) ◽  
pp. 2175-2184 ◽  
Author(s):  
Gabriel Mitchell ◽  
Liang Ge ◽  
Qiongying Huang ◽  
Chen Chen ◽  
Sara Kianian ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Wild Type Strain ◽  
Fold Increase ◽  
Host Cells ◽  
Listeriolysin O ◽  
Wild Type ◽  
Conjugation System ◽  
Content Type ◽  
A Cell ◽  
Gain Access

Listeria monocytogenesis a facultative intracellular pathogen that escapes from phagosomes and grows in the cytosol of infected host cells. Most of the determinants that govern its intracellular life cycle are controlled by the transcription factor PrfA, including the pore-forming cytolysin listeriolysin O (LLO), two phospholipases C (PlcA and PlcB), and ActA. We constructed a strain that lacked PrfA but expressed LLO from a PrfA-independent promoter, thereby allowing the bacteria to gain access to the host cytosol. This strain did not grow efficiently in wild-type macrophages but grew normally in macrophages that lacked ATG5, a component of the autophagy LC3 conjugation system. This strain colocalized more with the autophagy marker LC3 (42% ± 7%) at 2 h postinfection, which constituted a 5-fold increase over the colocalization exhibited by the wild-type strain (8% ± 6%). While mutants lacking the PrfA-dependent virulence factor PlcA, PlcB, or ActA grew normally, a double mutant lacking both PlcA and ActA failed to grow in wild-type macrophages and colocalized more with LC3 (38% ± 5%). Coexpression of LLO and PlcA in a PrfA-negative strain was sufficient to restore intracellular growth and decrease the colocalization of the bacteria with LC3. In a cell-free assay, purified PlcA protein blocked LC3 lipidation, a key step in early autophagosome biogenesis, presumably by preventing the formation of phosphatidylinositol 3-phosphate (PI3P). The results of this study showed that avoidance of autophagy byL. monocytogenesprimarily involves PlcA and ActA and that either one of these factors must be present forL. monocytogenesgrowth in macrophages.

Comparison of the PR mutant with the wild-type strain of Proteus mirabilis brings insight into peroxide resistance factors and regulation of catalase expression

2001 ◽  
Vol 47 (2) ◽  
pp. 130-138 ◽  
Author(s):  
Pierre Andreoletti ◽  
Bruno Franzetti ◽  
Laurent Nussaume ◽  
Jean-Pierre Andrieu ◽  
Jean Gagnon ◽  
...  
Keyword(s):  
Proteus Mirabilis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Resistance Factors ◽  
Insight Into

scholarly journals Recovery of Fusarium oxysporum Fo47 Mutants Affected in Their Biocontrol Activity After Transposition of the Fot1 Element

2002 ◽  
Vol 92 (9) ◽  
pp. 936-945 ◽  
Author(s):  
Sophie Trouvelot ◽  
Chantal Olivain ◽  
Ghislaine Recorbet ◽  
Quirico Migheli ◽  
Claude Alabouvette
Keyword(s):  
Fusarium Oxysporum ◽  
Insertional Mutagenesis ◽  
Wild Type Strain ◽  
Growth Habit ◽  
Antagonistic Activity ◽  
Phenotypic Characterization ◽  
Wild Type ◽  
Biocontrol Activity

To investigate the biocontrol mechanisms by which the antagonistic Fusarium oxysporum strain Fo47 is active against Fusarium wilt, a Fot1 transposon-mediated insertional mutagenesis approach was adopted to generate mutants affected in their antagonistic activity. Ninety strains in which an active Fot1 copy had transposed were identified with a phenotypic assay for excision and tested for their biocontrol activity against F. oxysporum f. sp. lini on flax in greenhouse experiments. Sixteen strains were affected in their capacity to protect flax plants, either positively (more antagonistic than Fo47) or negatively (less antagonistic). The molecular characterization of these mutants confirms the excision of Fot1 and its reinsertion in most of the cases. Moreover, we demonstrate that other transposable elements such as Fot2, impala, and Hop have no transposition activity in the mutant genomes. The phenotypic characterization of these mutants shows that they are affected neither in their in vitro growth habit nor in their competitiveness in soil compared with wild-type strain Fo47. These results show that mutants are not impaired in their saprophytic phase and suggest that the altered biocontrol phenotype should likely be expressed during the interaction with the host plant.

scholarly journals Characterization of a Legionella pneumophila relA Insertion Mutant and Roles of RelA and RpoS in Virulence Gene Expression

2002 ◽  
Vol 184 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Tal Zusman ◽  
Ohad Gal-Mor ◽  
Gil Segal
Keyword(s):  
Gene Expression ◽  
Stationary Phase ◽  
Gene Product ◽  
Legionella Pneumophila ◽  
Type Strain ◽  
Wild Type Strain ◽  
Insertion Mutant ◽  
Wild Type ◽  
Intracellular Growth ◽  
Virulence Gene Expression

ABSTRACT To investigate the involvement of RelA in the regulation of Legionella pneumophila virulence, a deletion substitution was constructed in the relA gene. The relA knockout resulted in an undetectable level of ppGpp in the cells during the stationary phase, but the original level was restored when the relA gene product was supplied on a plasmid. The effect of the relA mutation was examined with two systems that are known to be expressed during the stationary phase in L. pneumophila. Pigment production was found to be dependent on the relA gene product, and only one-half as much pigment was produced by the relA mutant as by the wild-type strain. Flagellum gene expression was also found to be dependent on the relA gene product, as determined with a flaA::lacZ fusion. However, the relA gene product was found to be dispensable for intracellular growth both in HL-60-derived human macrophages and in the protozoan host Acanthamoeba castellanii. To determine the involvement of the relA gene product in expression of L. pneumophila genes required for intracellular growth (icm/dot genes), nine icm::lacZ fusions were constructed, and expression of these fusions in the wild-type strain was compared with their expression in relA mutant strains. Expression of only one of the icm::lacZ fusions was moderately reduced in the relA mutant strain. Expression of the nine icm::lacZ fusions was also examined in a strain containing an insertion in the gene that codes for the stationary-phase sigma factor RpoS, and similar results were obtained. We concluded that RelA is dispensable for intracellular growth of L. pneumophila in the two hosts examined and that both RelA and RpoS play minor roles in L. pneumophila icm/dot gene expression.

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