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Pathogenic Microbiology Commons

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Full-Text Articles in Pathogenic Microbiology

Comparative Genomics, Transcriptomics, And Physiology Distinguish Symbiotic From Free-Living Chlorella Strains, Cristian F. Quispe, Olivia Sonderman, Maya Khasin, Wayne R. Riekhof, James L. Van Etten, Kenneth Nickerson Jul 2016

Comparative Genomics, Transcriptomics, And Physiology Distinguish Symbiotic From Free-Living Chlorella Strains, Cristian F. Quispe, Olivia Sonderman, Maya Khasin, Wayne R. Riekhof, James L. Van Etten, Kenneth Nickerson

Kenneth Nickerson Papers

Most animal–microbe symbiotic interactions must be advantageous to the host and provide nutritional benefits to the endosymbiont. When the host provides nutrients, it can gain the capacity to control the interaction, promote self-growth, and increase its fitness. Chlorella-like green algae engage in symbiotic relationships with certain protozoans, a partnership that significantly impacts the physiology of both organisms. Consequently, it is often challenging to grow axenic Chlorella cultures after isolation from the host because they are nutrient fastidious and often susceptible to virus infection. We hypothesize that the establishment of a symbiotic relationship resulted in natural selection for nutritional and ...


Killer Toxin From Several Food-Derived Debaryomyces Hansenii Strains Effective Against Pathogenic Candida Yeasts, Nabaraj Banjara, Kenneth Nickerson, Mallory J. Suhr, Heather E. Hallen-Adams Jan 2016

Killer Toxin From Several Food-Derived Debaryomyces Hansenii Strains Effective Against Pathogenic Candida Yeasts, Nabaraj Banjara, Kenneth Nickerson, Mallory J. Suhr, Heather E. Hallen-Adams

Kenneth Nickerson Papers

Candida yeasts are the dominant fungi in the healthy human microbiome, but are well-known for causing disease following a variety of perturbations. Evaluation of fungal populations from the healthy human gut revealed a significant negative correlation between the foodborne yeast, Debaryomyces hansenii, and Candida species. D. hansenii is reported to produce killer toxins (mycocins) effective against other yeast species. In order to better understand this phenomenon, a collection of 42 D. hansenii isolates was obtained from 22 cheeses and evaluated for killer activity against Candida albicans and Candida tropicalis over a range of temperatures and pH values. Twenty three strains ...


Proteomic Adaptations To Starvation Prepare Escherichia Coli For Disinfection Tolerance, Zhe Du, Renu Nandakumar, Kenneth W. Nickerson, Xu Li Jan 2015

Proteomic Adaptations To Starvation Prepare Escherichia Coli For Disinfection Tolerance, Zhe Du, Renu Nandakumar, Kenneth W. Nickerson, Xu Li

Kenneth Nickerson Papers

Despite the low nutrient level and constant presence of secondary disinfectants, bacterial re-growth still occurs in drinking water distribution systems. The molecular mechanisms that starved bacteria use to survive low-level chlorine-based disinfectants are not well understood. The objective of this study is to investigate these molecular mechanisms at the protein level that prepare starved cells for disinfection tolerance. Two commonly used secondary disinfectants chlorine and monochloramine, both at 1 mg/L, were used in this study. The proteomes of normal and starved Escherichia coli (K12 MG1655) cells were studied using quantitative proteomics. Over 60-min disinfection, starved cells showed significantly higher ...


Candida Albicans Quorum Sensing Molecules Stimulate Mouse Macrophage Migration, Jessica C. Hargarten, Tyler C. Moore, Thomas M. Petro, Kenneth W. Nickerson, Audrey L. Atkin Jan 2015

Candida Albicans Quorum Sensing Molecules Stimulate Mouse Macrophage Migration, Jessica C. Hargarten, Tyler C. Moore, Thomas M. Petro, Kenneth W. Nickerson, Audrey L. Atkin

Kenneth Nickerson Papers

The polymorphic commensal fungus Candida albicans causes life-threatening disease via bloodstream and intra-abdominal infections in immunocompromised and transplant patients. Although host immune evasion is a common strategy used by successful human fungal pathogens, C. albicans provokes recognition by host immune cells less capable of destroying it. To accomplish this, C. albicans white cells secrete a low-molecular-weight chemoattractive stimulant(s) of macrophages, a phagocyte that they are able to survive within and eventually escape from. C. albicans opaque cells do not secrete this chemoattractive stimulant( s). We report here a physiological mechanism that contributes to the differences in the interaction of ...


A Glutathione-Independent Glyoxalase Of The Dj-1 Superfamily Plays An Important Role In Managing Metabolically Generated Methylglyoxal In Candida Albicans, Sahar Hasim, Nur Ahmad Hussin, Fadhel Alomar, Keshore R. Bidasee, Kenneth W. Nickerson, Mark A. Wilson Jan 2014

A Glutathione-Independent Glyoxalase Of The Dj-1 Superfamily Plays An Important Role In Managing Metabolically Generated Methylglyoxal In Candida Albicans, Sahar Hasim, Nur Ahmad Hussin, Fadhel Alomar, Keshore R. Bidasee, Kenneth W. Nickerson, Mark A. Wilson

Kenneth Nickerson Papers

Methylglyoxal is a cytotoxic reactive carbonyl compound produced by central metabolism. Dedicated glyoxalases convert methylglyoxal to D-lactate using multiple catalytic strategies. In this study, the DJ-1 superfamily member ORF 19.251/GLX3 from Candida albicans is shown to possess glyoxalase activity, making this the first demonstrated glutathione-independent glyoxalase in fungi. The crystal structure of Glx3p indicates that the protein is a monomer containing the catalytic triad Cys136- His137-Glu168. Purified Glx3p has an in vitro methylglyoxalase activity (Km = 5.5 mM andkcat = 7.8 s-1) that is significantly greater than that of more distantly ...


Histone Biotinylation In Candida Albicans, Sahar Hasim, Swetha Tati, Nandakumar Madayiputhiya, Renu Nandakumar, Kenneth W. Nickerson Jan 2013

Histone Biotinylation In Candida Albicans, Sahar Hasim, Swetha Tati, Nandakumar Madayiputhiya, Renu Nandakumar, Kenneth W. Nickerson

Kenneth Nickerson Papers

Candida albicans is an opportunistic fungal pathogen in humans. It is a polymorphic fungus: it can live as yeasts, hyphae, or pseudohyphae. Biotin is required for cell growth and fatty acid metabolism because it is used as a cofactor for carboxylases such as acetyl-CoA carboxylase, and pyruvate carboxylase. In addition, we have discovered that biotin is used to modify histones in C. albicans. Biotinylation was detected by Western blots using a monoclonal antibiotin HRP-conjugated antibody as well as with qTOF and LC/MS/MS mass spectrometry. As a precaution, the antibiotin antibody was dialyzed against neutravidin prior to use. During ...


Candida Albicans Czf1 And Efg1 Coordinate The Response To Farnesol During Quorum Sensing, White-Opaque Thermal Dimorphism, And Cell Death, Melanie L. Langford, Jessica C. Hargarten, Krista D. Patefield, Elizabeth Marta, Jill R. Blankenship, Saranna Fanning, Kenneth W. Nickerson, Audrey L. Atkin Jan 2013

Candida Albicans Czf1 And Efg1 Coordinate The Response To Farnesol During Quorum Sensing, White-Opaque Thermal Dimorphism, And Cell Death, Melanie L. Langford, Jessica C. Hargarten, Krista D. Patefield, Elizabeth Marta, Jill R. Blankenship, Saranna Fanning, Kenneth W. Nickerson, Audrey L. Atkin

Kenneth Nickerson Papers

Quorum sensing by farnesol in Candida albicans inhibits filamentation and may be directly related to its ability to cause both mucosal and systemic diseases. The Ras1-cyclic AMP signaling pathway is a target for farnesol inhibition. However, a clear understanding of the downstream effectors of the morphological farnesol response has yet to be unraveled. To address this issue, we screened a library for mutants that fail to respond to farnesol. Six mutants were identified, and the czf1/czf1 mutant was selected for further characterization. Czf1 is a transcription factor that regulates filamentation in embedded agar and also whiteto- opaque switching. We ...


Quorum Sensing And Other Aspects Of The Biology Of Candida Albicans, Kenneth W. Nickerson Aug 2012

Quorum Sensing And Other Aspects Of The Biology Of Candida Albicans, Kenneth W. Nickerson

Kenneth Nickerson Papers

Most dimorphic fungi exhibit cell density dependent effects in that they grow as yeasts when inoculated at > 106 cells per ml and as mycelia when inoculated at < 106 cells per ml. For Candida albicans, we discovered (2001) that this phenomenon (quorum sensing) is due to the production and secretion of the C15 isoprenoid trans-trans farnesol. Since then, we found that C. albicans cells treated with sublethal levels of zaragozic acid (2003) or fluconazole (2004) produced 10-40X more farnesol and that these fluconazole treated cells were ca. 5X more toxic to mice following tail vein injection. This suggestion that ...


Quorum Sensing Activity In Ophiostoma Ulmi: Effects Of Fusel Oils And Branched Chain Amino Acids On Yeast-Mycelial Dimorphism, A. Berrocal, J. Navarrete, C. Oviedo, K. W. Nickerson Jan 2012

Quorum Sensing Activity In Ophiostoma Ulmi: Effects Of Fusel Oils And Branched Chain Amino Acids On Yeast-Mycelial Dimorphism, A. Berrocal, J. Navarrete, C. Oviedo, K. W. Nickerson

Kenneth Nickerson Papers

Aims: For Ophiostoma (Ceratocystis) ulmi, the ability to undergo morphological change is a crucial factor for its virulence. To gain an understanding of quorum- sensing activity in O. ulmi as it relates to yeast-mycelium dimorphism control, this study examines the effects of branched-chain amino acids as well as their fusel alcohols and fusel acids as quorum sensing molecules.

Methods and Results: In a defined medium containing glucose, proline and salts, O. ulmi grew as yeasts when the culture was inoculated with a high density of spores (2-107 CFU ml-1) and as mycelia when inoculated with a low spore ...


Zap1 Control Of Cell-Cell Signaling In Candida Albicans Biofilms, Shantanu Ganguly, Andrew C. Bishop, Wenjie Xu, Suman Ghosh, Kenneth W. Nickerson, Frederick Lanni, Jana Patton-Vogt, Aaron P. Mitchell Nov 2011

Zap1 Control Of Cell-Cell Signaling In Candida Albicans Biofilms, Shantanu Ganguly, Andrew C. Bishop, Wenjie Xu, Suman Ghosh, Kenneth W. Nickerson, Frederick Lanni, Jana Patton-Vogt, Aaron P. Mitchell

Kenneth Nickerson Papers

Biofilms of Candida albicans include both yeast cells and hyphae. Prior studies indicated that a zap1/ mutant, defective in zinc regulator Zap1, has increased accumulation of yeast cells in biofilms. This altered yeast-hypha balance may arise from internal regulatory alterations or from an effect on the production of diffusible quorum-sensing (QS) molecules. Here, we develop biosensor reporter strains that express yeastspecific YWP1-RFP or hypha-specific HWP1-RFP, along with a constitutive TDH3-GFP normalization standard. Seeding these biosensor strains into biofilms allows a biological activity assay of the surrounding biofilm milieu. A zap1/ biofilm induces the yeast-specific YWP1-RFP reporter in a wild-type biosensor ...


Dur3 Is The Major Urea Transporter In Candida Albicans And Is Co-Regulated With The Urea Amidolyase Dur1,2, Dhammika H. M. L. P Navarathna, Aditi Das, Joachim Morschhauser, Kenneth W. Nickerson, David D. Roberts Jan 2011

Dur3 Is The Major Urea Transporter In Candida Albicans And Is Co-Regulated With The Urea Amidolyase Dur1,2, Dhammika H. M. L. P Navarathna, Aditi Das, Joachim Morschhauser, Kenneth W. Nickerson, David D. Roberts

Kenneth Nickerson Papers

Hemiascomycetes, including the pathogen Candida albicans, acquire nitrogen from urea using the urea amidolyase Dur1,2, whereas all other higher fungi use primarily the nickel-containing urease. Urea metabolism via Dur1,2 is important for resistance to innate host immunity in C. albicans infections. To further characterize urea metabolism in C. albicans we examined the function of seven putative urea transporters. Gene disruption established that Dur3, encoded by orf 19.781, is the predominant transporter. [14C]Urea uptake was energy-dependent and decreased approximately sevenfold in a dur3D mutant. DUR1,2 and DUR3 expression was strongly induced by urea, whereas the ...


Candida Albicans Cellwall Components And Farnesol Stimulate The Expression Of Both Inflammatory And Regulatory Cytokines In The Murine Raw264.7 Macrophage Cell Line, Suman Ghosh, Nina Howe, Katie Volk, Swetha Tati, Kenneth W. Nickerson, Thomas M. Petro Jan 2010

Candida Albicans Cellwall Components And Farnesol Stimulate The Expression Of Both Inflammatory And Regulatory Cytokines In The Murine Raw264.7 Macrophage Cell Line, Suman Ghosh, Nina Howe, Katie Volk, Swetha Tati, Kenneth W. Nickerson, Thomas M. Petro

Kenneth Nickerson Papers

Candida albicans causes candidiasis, secretes farnesol, and switches from yeast to hyphae to escape from macrophages after phagocytosis. However, before escape, macrophages may respond to C. albicans’ pathogen-associated molecular patterns (PAMPs) through toll-like receptor 2 (TLR2) and dectin-1 receptors by expressing cytokines involved in adaptive immunity, inflammation, and immune regulation. Therefore, macrophages and the RAW264.7 macrophage line were challenged with C. albicans preparations of live wild-type cells, heat-killed cells, a live mutant defective in hyphae formation, a live mutant producing less farnesol, or an isolate producing farnesoic acid instead of farnesol. Interleukin-6 (IL-6), and IL-1b, IL- 10, and tumor ...


Evolutionary Aspects Of Urea Utilization By Fungi, Dhammika H. M. L. P Navarathna, Steven D. Harris, David D. Roberts, Kenneth W. Nickerson Jan 2010

Evolutionary Aspects Of Urea Utilization By Fungi, Dhammika H. M. L. P Navarathna, Steven D. Harris, David D. Roberts, Kenneth W. Nickerson

Kenneth Nickerson Papers

The higher fungi exhibit a dichotomy with regard to urea utilization. The hemiascomycetes use urea amidolyase (DUR1,2), whereas all other higher fungi use the nickel-containing urease. Urea amidolyase is an energy-dependent biotincontaining enzyme. It likely arose before the Euascomycete/Hemiascomycete divergence c. 350 million years ago by insertion of an unknown gene into one copy of a duplicated methylcrotonyl CoA carboxylase (MccA). The dichotomy between urease and urea amidolyase coincides precisely with that for the Ni/Co transporter (Nic1p), which is present in the higher fungi that use urease and is absent in those that do not. We suggest ...


Escherichia Coli O157:H7 And Other E. Coli Strains Share Physiological Properties Associated With Intestinal Colonization, Lisa Jacobsen, Lisa Durso, Tyrell Conway, Kenneth W. Nickerson Jul 2009

Escherichia Coli O157:H7 And Other E. Coli Strains Share Physiological Properties Associated With Intestinal Colonization, Lisa Jacobsen, Lisa Durso, Tyrell Conway, Kenneth W. Nickerson

Kenneth Nickerson Papers

Escherichia coli isolates (72 commensal and 10 O157:H7 isolates) were compared with regard to physiological and growth parameters related to their ability to survive and persist in the gastrointestinal tract and found to be similar. We propose that nonhuman hosts in E. coli O157:H7 strains function similarly to other E. coli strains in regard to attributes relevant to gastrointestinal colonization.


Candida Albicans Tup1 Is Involved In Farnesol-Mediated Inhibition Of Filamentous-Growth Induction, Bessie W. Kebaara, Melanie L. Langford, Dhammika H. M. L. P. Navarathna, Raluca Dumitru, Kenneth W. Nickerson, Audrey L. Atkin Jun 2008

Candida Albicans Tup1 Is Involved In Farnesol-Mediated Inhibition Of Filamentous-Growth Induction, Bessie W. Kebaara, Melanie L. Langford, Dhammika H. M. L. P. Navarathna, Raluca Dumitru, Kenneth W. Nickerson, Audrey L. Atkin

Kenneth Nickerson Papers

Candida albicans is a dimorphic fungus that can interconvert between yeast and filamentous forms. Its ability to regulate morphogenesis is strongly correlated with virulence. Tup1, a transcriptional repressor, and the signaling molecule farnesol are both capable of negatively regulating the yeast to filamentous conversion. Based on this overlap in function, we tested the hypothesis that the cellular response to farnesol involves, in part, the activation of Tup1. Tup1 functions with the DNA binding proteins Nrg1 and Rfg1 as a transcription regulator to repress the expression of hypha-specific genes. The tup1/tup1 and nrg1/nrg1 mutants, but not the rfg1/rfg1 ...