scholarly journals The Nonmevalonate Pathway of Isoprenoid Biosynthesis Supports Anaerobic Growth of Listeria monocytogenes

2019 ◽  
Vol 88 (2) ◽  
Author(s):  
Eric D. Lee ◽  
Kathleen I. Navas ◽  
Daniel A. Portnoy
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Doubling Time ◽  
Mevalonate Pathway ◽  
Anaerobic Growth ◽  
Clinical Isolates ◽  
Content Type ◽  
Nonmevalonate Pathway ◽  
Common Precursor ◽  
The Difference

ABSTRACT Isoprenoids are an essential and diverse class of molecules, present in all forms of life, that are synthesized from an essential common precursor derived from either the mevalonate pathway or the nonmevalonate pathway. Most bacteria have one pathway or the other, but the Gram-positive, facultative intracellular pathogen Listeria monocytogenes is unusual because it carries all the genes for both pathways. While the mevalonate pathway has previously been reported to be essential, here we demonstrate that the nonmevalonate pathway can support growth of strains 10403S and EGD-e, but only anaerobically. L. monocytogenes lacking the gene hmgR, encoding the rate-limiting enzyme of the mevalonate pathway, had a doubling time of 4 h under anaerobic conditions, in contrast to the 45 min doubling time of the wild type. In contrast, deleting hmgR in two clinical isolates resulted in mutants that grew significantly faster, doubling in approximately 2 h anaerobically, although they still failed to grow under aerobic conditions without mevalonate. The difference in anaerobic growth rate was traced to three amino acid changes in the nonmevalonate pathway enzyme GcpE, and these changes were sufficient to increase the growth rate of 10403S to the rate observed in the clinical isolates. Despite an increased growth rate, virulence was still dependent on the mevalonate pathway in 10403S strains expressing the more active GcpE allele.

scholarly journals Enhancement of chicken primordial germ cell in vitro maintenance using an automated cell image analyser

2018 ◽  
Vol 66 (4) ◽  
pp. 518-529 ◽  
Author(s):  
Mahek Anand ◽  
Bence Lázár ◽  
Roland Tóth ◽  
Emőke Páll ◽  
Eszter Patakiné Várkonyi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Doubling Time ◽  
Primordial Germ Cells ◽  
Genotypic Variation ◽  
Primordial Germ Cell ◽  
Significant Difference ◽  
The Difference ◽  
In Vitro Maintenance

Primordial germ cells (PGCs) were isolated from blood samples of chicken embryos. We established four PGC lines: two males (FS-ZZ-101, GFP-ZZ-4ZP) and two females (FS-ZW-111, GFP-ZW-5ZP). We could not detect a significant difference in the marker expression profile, but there was a remarkable difference between the proliferation rates of these PGC lines. We monitored the number of PGCs throughout a three-day period using a high-content screening cell imaging and analysing system (HCS). We compared three different initial cell concentrations in the wells: ~1000 cells (1×, ~4000 (4× and ~8000 (8×. For the GFPZW- 5ZP, FS-ZZ-101 and FS-ZW-111 PGC lines the lowest doubling time was observed at 4× concentration, while for GFP-ZZ-4ZP we found the lowest doubling time at 1× concentration. At 8× initial concentration, the growth rate was high during the first two days for all cell lines, but this was followed by the appearance of cell aggregates decreasing the cell growth rate. We could conclude that the difference in proliferation rate could mainly be attributed to genotypic variation in the established PGC lines, but external factors such as cell concentration and quality of the culture medium also affect the growth rate of PGCs.

scholarly journals In VitroProperties of a Listeria monocytogenes Bacteriophage-Resistant Mutant Predict Its Efficacy as a Live Oral Vaccine Strain

2011 ◽  
Vol 79 (12) ◽  
pp. 5001-5009 ◽  
Author(s):  
Patricia A. Spears ◽  
M. Mitsu Suyemoto ◽  
Terri S. Hamrick ◽  
Rebecca L. Wolf ◽  
Edward A. Havell ◽  
...  
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Time Course ◽  
Oral Vaccine ◽  
Fold Increase ◽  
Resistant Mutant ◽  
Oral Immunization ◽  
Intracellular Growth ◽  
Content Type ◽  
Live Oral Vaccine

ABSTRACTAListeria monocytogenesglcVmutation precludes the binding of certain listerial phages and produces a profound attenuation characterized by the absence of detectable mutants in the livers and spleens of orally inoculated mice.Invitro, we found that the mutant formed plaques on mouse enterocyte monolayers as efficiently as the parent but the plaques formed were smaller. Intracellular growth rate determinations and examination of infected enterocytes by light and fluorescence microscopy established that the mutant was impaired not in intracellular growth rate but in cell-to-cell spreading. Because this property is shared by other immunogenic mutants (e.g.,actAmutants), ourglcVmutant was tested for vaccine efficacy. Oral immunization with the mutant and subsequent oral challenge (22 days postvaccination) with the parent revealed a ca. 10,000-fold increase in protection afforded by the mutant compared to sham-vaccinated controls. TheglcVmutant did not stimulate innate immunity under the dose and route employed for vaccination, and an infectivity index time course experiment revealed pronounced mutant persistence in Peyer's patches. The immunogenicity of theglcVmutant compared to an isogenicactAmutant reference strain was next tested in an experiment with a challenge given 52 days postvaccination. Both mutant strains showed scant vital organ infectivity and high levels of protection similar to those seen using theglcVmutant in the 22-day postvaccination challenge. Our results indicate that oral administration of a profoundly attenuated listerial mutant can safely elicit solid protective immunity.

scholarly journals Anaerobic Growth of Listeria monocytogenes on Rhamnose Is Stimulated by Vitamin B 12 and Bacterial Microcompartment-Dependent 1,2-Propanediol Utilization

mSphere ◽  
2021 ◽  
Author(s):  
Zhe Zeng ◽  
Siming Li ◽  
Sjef Boeren ◽  
Eddy J. Smid ◽  
Richard A. Notebaart ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Mechanisms ◽  
Foodborne Pathogen ◽  
Anaerobic Growth ◽  
Severe Illness ◽  
Vitamin B ◽  
Anaerobic Conditions ◽  
Content Type ◽  
Bacterial Microcompartment ◽  
Vitamin B 12

Listeria monocytogenes is a foodborne pathogen causing severe illness and, as such, it is crucial to understand the molecular mechanisms contributing to its survival strategy and pathogenicity. Rhamnose is a deoxyhexose sugar abundant in a range of environments, including the human intestine, and can be degraded in anaerobic conditions into 1,2-propanediol.

scholarly journals Daptomycin Activity against Uncommonly Isolated Streptococcal and Other Gram-Positive Species Groups

2013 ◽  
Vol 57 (12) ◽  
pp. 6378-6380 ◽  
Author(s):  
Helio S. Sader ◽  
Robert K. Flamm ◽  
David J. Farrell ◽  
Ronald N. Jones
Keyword(s):  
Listeria Monocytogenes ◽  
Clinical Isolates ◽  
Streptococcus Bovis ◽  
Broth Microdilution ◽  
Streptococcus Dysgalactiae ◽  
Streptococcus Mitis ◽  
Content Type ◽  
Streptococcus Oralis ◽  
Species Groups ◽  
Viridans Group Streptococci

ABSTRACTA total of 1,356 clinical isolates were tested against daptomycin by broth microdilution methods. Daptomycin was active against seven groups of viridans group streptococci (MIC50and MIC90values ranging from ≤0.06 and ≤0.06 μg/ml [Streptococcus bovisandStreptococcus dysgalactiae] to 0.5 and 1 μg/ml [Streptococcus mitis,Streptococcus oralis, andStreptococcus parasanguinis], respectively), beta-hemolytic streptococci serogroups C, F, and G (MIC50and MIC90, ≤0.06 to 0.25 and 0.12 to 0.25 μg/ml, respectively),Corynebacteriumspp. (MIC50and MIC90, ≤0.06 and 0.12 μg/ml, respectively), andMicrococcusspp. (MIC50and MIC90, ≤0.06 and 0.25 μg/ml, respectively).Listeria monocytogenesexhibited higher daptomycin MICs (MIC50and MIC90, 2 and 4 μg/ml, respectively) than other tested organisms.

scholarly journals Atypical Listeria monocytogenes Serotype 4b Strains Harboring a Lineage II-Specific Gene Cassette

2011 ◽  
Vol 78 (3) ◽  
pp. 660-667 ◽  
Author(s):  
Sangmi Lee ◽  
Todd J. Ward ◽  
Lewis M. Graves ◽  
Leslie A. Wolf ◽  
Kate Sperry ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Regional Distribution ◽  
Gene Cassette ◽  
The United States ◽  
Clinical Isolates ◽  
Specific Gene ◽  
Content Type ◽  
Hybridization Data ◽  
Group 3 ◽  
Serotype 4B

ABSTRACTListeria monocytogenesis the etiological agent of listeriosis, a severe food-borne illness. The population ofL. monocytogenesis divided into four lineages (I to IV), and serotype 4b in lineage I has been involved in numerous outbreaks. Several serotype 4b epidemic-associated clonal groups (ECI, -II, and -Ia) have been identified. In this study, we characterized a panel of strains of serotype 4b that produced atypical results with a serotype-specific multiplex PCR and possessed thelmo0734tolmo0739gene cassette that had been thought to be specific to lineage II. The cassette was harbored in a genomically syntenic locus in these isolates and in lineage II strains. Three distinct clonal groups (groups 1 to 3) were identified among these isolates based on single-nucleotide polymorphism-based multilocus genotyping (MLGT) and DNA hybridization data. Groups 1 and 2 had MLGT haplotypes previously encountered among clinical isolates and were composed of clinical isolates from multiple states in the United States. In contrast, group 3 consisted of clinical and environmental isolates solely from North Carolina and exhibited a novel haplotype. In addition, all group 3 isolates had DNA that was resistant to MboI, suggesting methylation of adenines at GATC sites. Sequence analysis of thelmo0734tolmo0739gene cassette from two strains (group 1 and group 3) revealed that the genes were highly conserved (>99% identity). The data suggest relatively recent horizontal gene transfer from lineage IIL. monocytogenesintoL. monocytogenesserotype 4b and subsequent dissemination among at least three distinct clonal groups ofL. monocytogenesserotype 4b, one of which exhibits restrictions in regional distribution.

Micro/macro fatigue crack growth rate model for 2024-T3 aluminum panel

2015 ◽  
Vol 6 (4) ◽  
pp. 522-540
Author(s):  
George Sih
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Structural Components ◽  
Content Type ◽  
Short Cracks ◽  
The Difference ◽  
Dual Scale

Purpose – Fatigue crack growth rate data for 2024-T3 aluminum are found using three parameters d*, σ* and μ* for short and long cracks for Regions I-III in conventional fatigue. Asymptotic solution of a line crack with a micro-tip is found to yield a singular stress behavior of order 0.75 in contrast to the 0.50 order known for the macrocrack. The difference is due to the micro-macro interaction effects. The three parameters account for the combined effects of load, material and geometry via the tip region. Data for short and long cracks lie on a straight with a slope of about 3.9-4.8 for R values of 0.286-0.565. The results were based on an initial crack a1 mm where a is the half length for a central crack panel. The paper aims to discuss these issues. Design/methodology/approach – The belief that specimen fatigue data could assist the design of structural components was upended when FAA discovered that the NASGRO FCGD are not valid for short cracks that are tight and may even be closed. The regular ΔK vs da/dN model was limited to long cracks. The issue become critical for short cracks connecting the long ones of a few mm to cm or even m according to da/dN for the same crack history. The danger of short/long fatigue crack growth (SLFCG) prompted FAA to introduce an added test known as Limit of Validity (LOV), a way of setting empirical limits for structural components. The dual scale SLFCG data from ΔK micro/macro provide support for the LOV tests. Findings – Data for short and long cracks lie on a straight with a slope of about 3.9-4.8 for R values of 0.286-0.565. The single dual scale relation on ΔK micro/macro can switch from microscopic to macroscopic or vice and versa. The difference is fundamental. Order other than 0.75 can be obtained for simulating different microstructure effects as well as different materials and test conditions. Originality/value – Scale shifting from short to long fatigue cracks for 2024-T3 aluminum is new. The crack driving force is found to depend on the crack tightness. The sigmoidal curve based on the regular ΔK plot disappeared. The data from ΔK micro/macro for short cracks may supplement the FAA LOV tests for setting more reliable fatigue safe limits.

scholarly journals The Serratia marcescens Siderophore Serratiochelin Is Necessary for Full Virulence during Bloodstream Infection

2020 ◽  
Vol 88 (8) ◽  
Author(s):  
Danelle R. Weakland ◽  
Sara N. Smith ◽  
Bailey Bell ◽  
Ashootosh Tripathi ◽  
Harry L. T. Mobley
Keyword(s):  
Serratia Marcescens ◽  
Bloodstream Infection ◽  
Iron Acquisition ◽  
Gene Clusters ◽  
Clinical Isolates ◽  
Wild Type ◽  
Serratia Plymuthica ◽  
Content Type ◽  
Cas Assay ◽  
Essential Nutrient

ABSTRACT Serratia marcescens is a bacterium frequently found in the environment, but over the last several decades it has evolved into a concerning clinical pathogen, causing fatal bacteremia. To establish such infections, pathogens require specific nutrients; one very limited but essential nutrient is iron. We sought to characterize the iron acquisition systems in S. marcescens isolate UMH9, which was recovered from a clinical bloodstream infection. Using RNA sequencing (RNA-seq), we identified two predicted siderophore gene clusters (cbs and sch) that were regulated by iron. Mutants were constructed to delete each iron acquisition locus individually and in conjunction, generating both single and double mutants for the putative siderophore systems. Mutants lacking the sch gene cluster lost their iron-chelating ability as quantified by the chrome azurol S (CAS) assay, whereas the cbs mutant retained wild-type activity. Mass spectrometry-based analysis identified the chelating siderophore to be serratiochelin, a siderophore previously identified in Serratia plymuthica. Serratiochelin-producing mutants also displayed a decreased growth rate under iron-limited conditions created by dipyridyl added to LB medium. Additionally, mutants lacking serratiochelin were significantly outcompeted during cochallenge with wild-type UMH9 in the kidneys and spleen after inoculation via the tail vein in a bacteremia mouse model. This result was further confirmed by an independent challenge, suggesting that serratiochelin is required for full S. marcescens pathogenesis in the bloodstream. Nine other clinical isolates have at least 90% protein identity to the UMH9 serratiochelin system; therefore, our results are broadly applicable to emerging clinical isolates of S. marcescens causing bacteremia.

What makes the difference? Employee social media brand engagement

2019 ◽  
Vol 34 (7) ◽  
pp. 1459-1467 ◽  
Author(s):  
Sherese Y. Duncan ◽  
Raeesah Chohan ◽  
João José Ferreira
Keyword(s):  
Social Media ◽  
Brand Equity ◽  
Positive Emotions ◽  
Content Type ◽  
Word Use ◽  
Brand Engagement ◽  
Analytical Thinking ◽  
Industry Competition ◽  
The Difference ◽  
Business To Business

Purpose This paper aims to explore, using the employee lens of business-to-business firms, word use through brand engagement and social media interaction to understand the difference between employees who rate their employer brands highly on social media and those who don't. Design/methodology/approach We conducted a textual content analysis of posts published on the social media job evaluation site glassdoor.com. LIWC software package was used to analyze 30 of the top 200 business-to-business brands listed on Brandwatch using four variables, namely, analytical thinking, clout, authenticity and emotional tone. Findings The results show that employees who rate their employer’s brand low use significantly more words, are significantly less analytic and write with significantly more clout because they focus more on others than themselves. Employees who rate their employer’s brand highly, write with significantly more authenticity, exhibit a significantly higher tone and display far more positive emotions in their reviews. Practical implications Brand managers should treat social media data disseminated by individual stakeholders, like the variables used in this study (tone, word count, frequency), as a valuable tool for brand insight on their industry, competition and their own brand equity, now and especially over time. Originality/value This study provides acknowledgement that social media is a significant source of marketing intelligence that may improve brand equity by better understanding and managing brand engagement.

scholarly journals Retrospective Molecular Analysis of DIM-1 Metallo-β-Lactamase Discovered in Pseudomonas stutzeri from India in 2000

2013 ◽  
Vol 58 (1) ◽  
pp. 596-598 ◽  
Author(s):  
Lalitagauri M. Deshpande ◽  
Ronald N. Jones ◽  
Leah N. Woosley ◽  
Mariana Castanheira
Keyword(s):  
Molecular Analysis ◽  
Pseudomonas Stutzeri ◽  
Clinical Isolates ◽  
Gram Negative ◽  
Content Type ◽  
Environmental Source ◽  
Lactamase Gene ◽  
Encoding Genes

ABSTRACTAmong 220 clinical isolates of Gram-negative bacilli collected in India during 2000, 22 strains showing elevated imipenem MICs were evaluated for carbapenemase production. One DIM-1-producingPseudomonas stutzeriisolate was detected, and no other carbapenemase-encoding genes were identified. This detection of a DIM-1-producingP. stutzeriisolate from India predating the finding of this gene in the index Dutch strain and the very recent detection of DIM-1 in Africa suggest an unidentified environmental source of this metallo-β-lactamase gene.

A Model of Wheat Grain Growth and Its Applications to Different Temperature and Carbon Dioxide Levels

1995 ◽  
Vol 22 (5) ◽  
pp. 843 ◽  
Author(s):  
YP Wang ◽  
RM Gifford
Keyword(s):  
Growth Rate ◽  
Grain Growth ◽  
Temperature Response ◽  
Rate Sensitivity ◽  
Temperature Sensitive ◽  
Potential Growth ◽  
Carbon Supply ◽  
The Difference ◽  
Carbon Dioxide Levels ◽  
Kernel Growth

Kernel growth after anthesis is simulated as a function of the potential kernel growth rate, current photosynthate production and mobilisation of stored reserves. The potential growth rate of the kernel is simulated as two temperature-sensitive processes, cell production and cell growth. The difference between the potential and actual growth rates of the kernel depends on the carbon supply to the free space of the kernel endosperm, while the carbon supply is itself affected by the actual kernel growth rate. Sensitivity analysis showed that the growth rate of the grain per plant is most sensitive to the potential growth rate of the kernel and number of kernels per plant. This model is able to simulate the observed rates of grain growth and leaf senescence from anthesis to physiological maturity for wheat plants grown in two CO2 concentrations. The simulated temperature response of grain growth agrees well with the experimenal observations.

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