Medical Microbiology Commons^™

Differential Sensitivity Of Leukocyte Populations To Staphylococcus Aureus Biofilm, Nichole D. Brandquist, Tammy Kielian

Journal Articles: Pathology and Microbiology

Staphylococcus aureus is a leading cause of prosthetic joint infection (PJI) typified by biofilm formation. Anti-inflammatory granulocytic myeloid-derived suppressor cells (G-MDSCs) represent the main leukocyte population in a mouse model of S. aureus PJI, followed by neutrophils (PMNs), and macrophages (Mφs), which is also seen during human PJI. Defining how each leukocyte population responds to S. aureus biofilm vs planktonic bacteria could have important implications for how S. aureus evades immune detection to facilitate biofilm persistence. This study compared the kinetics of leukocyte death and relationship to mitochondrial ROS (mtROS) production following exposure to planktonic S. aureus or biofilm. Mφs …

Mitochondrial Transfer To Granulocytic Myeloid-Derived Suppressor Cells Augments Immunosuppressive Activity, Prabhakar Arumugam, Cortney E. Heim, Rachel W. Fallet, Dhananjay Shinde, Vinai Chittezham Thomas, Rafael J. Argüello, Tammy Kielian

Journal Articles: Pathology and Microbiology

The anti-inflammatory properties of granulocytic myeloid-derived suppressor cells (G-MDSCs) promote Staphylococcus aureus (S. aureus) biofilm persistence. Evidence suggests that G-MDSC activity is shaped not only by S. aureus products but also by intrinsic metabolic programs. This study explores whether G-MDSC activity can be modulated by increasing mitochondrial abundance using a co-culture paradigm with macrophages as a mitochondrial donor. Macrophages transfer mitochondria directly to G-MDSCs via tunneling nanotubes, enhancing G-MDSC respiration, as reflected by increased basal, maximal, and spare respiratory capacity. Augmenting mitochondrial abundance in G-MDSCs enhances T cell-suppressive activity and reduces tumor necrosis factor (TNF) and interleukin 6 (IL-6) production. …

Quaternized Chitosan Derivatives Inhibit Growth And Affect Biofilm Formation Of Staphylococcus Aureus, Alex Miranda, Nichole D. Brandquist, Kristen Johnson, Elena Muldiiarova, Aleksandr Fadeev, Mahboubeh Ghanbari, Jennifer L. Endres, Kenneth W. Bayles, Jason N. Mactaggart, Denis Svechkarev, Marat Sadykov, Yury Salkovskiy

Journal Articles: Pathology and Microbiology

Antimicrobial resistance (AMR) poses a global health threat, severely impeding the effective treatment of bacterial infections and jeopardizing the safety of routine medical procedures. Methicillin-resistant Staphylococcus aureus (MRSA) is particularly problematic because of its resistance to beta-lactams and the ability to form resilient biofilms. Conventional antibiotics, including last-resort options, have serious side effects and may contribute to further resistance. Chitosan, a natural biopolymer, offers a promising alternative due to its biocompatibility and antimicrobial properties, though its effectiveness against biofilms is limited. Recent studies suggest that increasing the positive charge density and adding hydrophobic moieties to chitosan, can enhance its antimicrobial …

Extracellular Adherence Proteins Reduce Matrix Porosity And Enhance Staphylococcus Aureus Biofilm Survival During Prosthetic Joint Infection, Mohini Bhattacharya, Tyler D. Scherr, Jessica Lister, Tammy Kielian, Alexander R. Horswill

Journal Articles: Pathology and Microbiology

Biofilms are a cause of chronic, non-healing infections. Staphylococcus aureus is a proficient biofilm-forming pathogen commonly isolated from prosthetic joint infections that develop following primary arthroplasty. Extracellular adherence protein (Eap), previously characterized in planktonic or non-biofilm populations as being an adhesin and immune evasion factor, was recently identified in the exoproteome of S. aureus biofilms. This work demonstrates that Eap and its two functionally orphaned homologs EapH1 and EapH2 contribute to biofilm structure and prevent macrophage invasion and phagocytosis in these communities. Biofilms unable to express Eap proteins demonstrated increased porosity and reduced biomass. We describe the role of Eap …

The Rise, Fall, And Resurgence Of Phage Therapy For Urinary Tract Infection, Jacob J Zulk, Kathryn A Patras, Anthony W Maresso

Faculty, Staff and Students Publications

In the face of rising antimicrobial resistance, bacteriophage therapy, also known as phage therapy, is seeing a resurgence as a potential treatment for bacterial infections including urinary tract infection (UTI). Primarily caused by uropathogenic Escherichia coli, the 400 million UTI cases annually are major global healthcare burdens and a primary cause of antibiotic prescriptions in the outpatient setting. Phage therapy has several potential advantages over antibiotics including the ability to disrupt bacterial biofilms and synergize with antimicrobial treatments with minimal side effects or impacts on the microbiota. Phage therapy for UTI treatment has shown generally favorable results in recent …

Optimization Of The Antifungal Properties Of The Bacterial Peptide Entv By Variant Analysis, Shantanu Guha, Shane A Cristy, Giuseppe Buda De Cesare, Melissa R Cruz, Michael C Lorenz, Danielle A Garsin

Faculty, Staff and Student Publications

Fungal resistance to commonly used medicines is a growing public health threat, and there is a dire need to develop new classes of antifungals. We previously described a peptide produced by Enterococcus faecalis, EntV, that restricts Candida albicans to a benign form rather than having direct fungicidal activity. Moreover, we showed that one 12-amino acid (aa) alpha helix of this peptide retained full activity, with partial activity down to the 10aa alpha helix. Using these peptides as a starting point, the current investigation sought to identify the critical features necessary for antifungal activity and to screen for new variants …

Granulocytic Myeloid-Derived Suppressor Cell Activity During Biofilm Infection Is Regulated By A Glycolysis/Hif1a Axis, Christopher M. Horn, Prabhakar Arumugam, Zachary Van Roy, Cortney E. Heim, Rachel W. Fallet, Blake P. Bertrand, Dhananjay Shinde, Vinai Chittezham Thomas, Svetlana Romanova, Tatiana K. Bronich, Curtis Hartman, Kevin Garvin, Tammy Kielian

Journal Articles: Pathology and Microbiology

Staphylococcus aureus is a leading cause of biofilm-associated prosthetic joint infection (PJI). A primary contributor to infection chronicity is an expansion of granulocytic myeloid-derived suppressor cells (G-MDSCs), which are critical for orchestrating the antiinflammatory biofilm milieu. Single-cell sequencing and bioinformatic metabolic algorithms were used to explore the link between G-MDSC metabolism and S. aureus PJI outcome. Glycolysis and the hypoxia response through HIF1a were significantly enriched in G-MDSCs. Interfering with both pathways in vivo, using a 2-deoxyglucose nanopreparation and granulocyte-targeted Hif1a conditional KO mice, respectively, attenuated G-MDSC-mediated immunosuppression and reduced bacterial burden in a mouse model of S. aureus PJI. …

Metabolism Shapes Immune Responses To Staphylococcus Aureus., Prabhakar Arumugam, Tammy Kielian

Journal Articles: Pathology and Microbiology

BACKGROUND: Staphylococcus aureus (S. aureus) is a common cause of hospital- and community-acquired infections that can result in various clinical manifestations ranging from mild to severe disease. The bacterium utilizes different combinations of virulence factors and biofilm formation to establish a successful infection, and the emergence of methicillin- and vancomycin-resistant strains introduces additional challenges for infection management and treatment.

SUMMARY: Metabolic programming of immune cells regulates the balance of energy requirements for activation and dictates pro- versus anti-inflammatory function. Recent investigations into metabolic adaptations of leukocytes and S. aureus during infection indicate that metabolic crosstalk plays a crucial role in …

Elucidating Granulocytic Myeloid-Derived Suppressor Cell Heterogeneity During Staphylococcus Aureus Biofilm Infection, Blake P. Bertrand, Cortney E. Heim, Scott A. Koepsell, Tammy Kielian

Journal Articles: Pathology and Microbiology

Myeloid-derived suppressor cells (MDSCs) are pathologically activated immature myeloid cells with immunosuppressive activity that expand during chronic inflammation, such as cancer and prosthetic joint infection (PJI). Myeloid-derived suppressor cells can be broadly separated into 2 populations based on surface marker expression and function: monocytic myeloid-derived suppressor cells (M-MDSCs) and granulocytic myeloid-derived suppressor cells (G-MDSCs). Granulocytic myeloid-derived suppressor cells are the most abundant leukocyte infiltrate during PJI; however, how this population is maintained in vivo and cellular heterogeneity is currently unknown. In this study, we identified a previously unknown population of Ly6G+Ly6C+F4/80+MHCII+ MDSCs during PJI that displayed immunosuppressive properties ex vivo. …

Bacterial Single-Cell Rna Sequencing Captures Biofilm Transcriptional Heterogeneity And Differential Responses To Immune Pressure, Lee E. Korshoj, Tammy Kielian

Journal Articles: Pathology and Microbiology

Biofilm formation is an important mechanism of survival and persistence for many bacterial pathogens. These multicellular communities contain subpopulations of cells that display metabolic and transcriptional diversity along with recalcitrance to antibiotics and host immune defenses. Here, we present an optimized bacterial single-cell RNA sequencing method, BaSSSh-seq, to study Staphylococcus aureus diversity during biofilm growth and transcriptional adaptations following immune cell exposure. BaSSSh-seq captures extensive transcriptional heterogeneity during biofilm compared to planktonic growth. We quantify and visualize transcriptional regulatory networks across heterogeneous biofilm subpopulations and identify gene sets that are associated with a trajectory from planktonic to biofilm growth. BaSSSh-seq …

Metabolic Diversity Of Human Macrophages: Potential Influence On Staphylococcus Aureus Intracellular Survival, Blake P. Bertrand, Dhananjay Shinde, Vinai C. Thomas, Marvin Whiteley, Carolyn B. Ibberson, Tammy Kielian

Journal Articles: Pathology and Microbiology

Staphylococcus aureus is a leading cause of medical device-associated biofilm infections. This is influenced by the ability of S. aureus biofilm to evade the host immune response, which is partially driven by the anti-inflammatory cytokine interleukin-10 (IL-10). Here, we show that treatment of human monocyte-derived macrophages (HMDMs) with IL-10 enhanced biofilm formation, suggesting that macrophage anti-inflammatory programming likely plays an important role during the transition from planktonic to biofilm growth. To identify S. aureus genes that were important for intracellular survival in HMDMs and how this was affected by IL-10, transposon sequencing was performed. The size of the S. aureus …

Tetracycline And Oxacillin Act Synergistically On Biofilms And Display Increased Efficacy In Vivo Against Staphylococcus Aureus, Amy K. Tooke, Rebecca E. Hodges, Josie F. Pyrah, Kenneth W. Bayles, Stephen A. Renshaw, Simon J. Foster

Journal Articles: Pathology and Microbiology

Oxacillin (bactericidal) and tetracycline (bacteriostatic) are clinically relevant antibiotics that are routinely prescribed to treat Staphylococcus aureus infections but not conventionally used in combination. There is an urgent need for treatment regimens that can act upon biofilms during infection, associated with chronic infections on indwelling devices, as well as acute planktonic (systemic) infection. Here we show that in an in vitro model oxacillin and tetracycline act synergistically against S. aureus UAMS-1 biofilms, reducing the concentration of both antibiotics necessary to eradicate an established biofilm. Using an in vivo zebrafish larval infection model with S. aureus NewHG, they display improved bacterial …

Catalase Produced By Candida Albicans Protects Streptococcus Mutans From H2o2 Stress-One More Piece In The Cross-Kingdom Synergism Puzzle, Callahan Katrak, Bruna A Garcia, Louise M Dornelas-Figueira, Mary Nguyen, Robert B Williams, Michael C Lorenz, Jacqueline Abranches

Faculty, Staff and Student Publications

Co-infection with Streptococcus mutans and Candida albicans is associated with dental caries, and their co-cultivation results in enhanced biofilm matrix production that contributes to increased virulence and caries risk. Moreover, the catalase-negative S. mutans demonstrates increased oxidative stress tolerance when co-cultivated in biofilms with C. albicans, a catalase-producing yeast. Here, we sought to obtain mechanistic insights into the increased H2O2 tolerance of S. mutans when co-cultivated with clinical isolates of Candida glabrata, Candida tropicalis, and C. albicans. Additionally, the C. albicans SC5314 laboratory strain, its catalase mutant (SC5314Δcat1), and S. mutans UA159 and its glucosyltransferase B/C …

Effect Of Various Types Of Extracellular Dna On V Hyugaensis Biofilm Formation, Carmen Gu Liu, Anthony W Maresso

Faculty, Staff and Students Publications

Marine bacteria face a constant influx of new extracellular DNA (exDNA) due to the massive viral lysis that occurs in the ocean on a daily basis. Generally, biofilms have shown to be induced by self-secreted exDNA. However, the effect of various types of exDNA with varying lengths, self vs non-self, as well as guanine-cytosine content (GC) content on biofilm formation has not been explored, despite being a critical component of the extracellular polymeric substance. To test the effect of such exDNA on biofilms, a marine bioluminescent bacterium (Vibrio hyugaensis) was isolated from the Sippewissett Salt Marsh, USA, and …

Impacts Of A Duf2207 Family Protein On Streptococcus Mutans Stress Tolerance Responses And Biofilm Formation, Xiaochang Huang, Camile G. Laird, Paul P. Riley, Zezhang Tom Wen

School of Dentistry Faculty Publications

Locus SMU.243 in Streptococcus mutans was annotated as a member of the DUF2207 family proteins highly conserved in all bacteria but with unknown function. To investigate its role in S. mutans physiology, a SMU.243-deficient mutant was constructed using allelic exchange mutagenesis, and the impacts of SMU.243 deletion on bacterial growth, stress tolerance response, and biofilm formation were analyzed. Compared to the wild-type UA159, S. mutans lacking SMU.243 displayed a reduced growth rate and a reduced overnight culture density (p < 0.01) when grown at low pH and in the presence of methyl viologen. Relative to the parent strain, the deficient mutant also had a reduced survival rate following incubation in a buffer of pH 2.8 (p < 0.01) and in a buffer containing hydrogen peroxide at 58 mM after 60 min (p < 0.001) and had a reduced capacity in biofilm formation especially in the presence of sucrose (p < 0.01). To study any ensuing functional/phenotypical links between SMU.243 and uppP, which is located immediately downstream of SMU.243 and encodes an undecaprenyl pyrophosphate phosphatase involved in recycling of carrier lipid undecaprenyl phosphate, a uppP deficient mutant was generated using allelic exchange mutagenesis. Unlike the SMU.243 mutant, deletion of uppP affected cell envelope biogenesis and caused major increases in susceptibility to bacitracin. In addition, two variant morphological mutants, one forming rough colonies and the other forming mucoid, smooth colonies, also emerged following the deletion of uppP. The results suggest that the SMU.243-encoded protein of the DUF2207 family in S. mutans plays an important role in stress tolerance response and biofilm formation, but unlike the downstream uppP, does not seem to be involved in cell envelope biogenesis, although the exact roles in S. mutans’ physiology awaits further investigation.

Biofilms: Formation, Research Models, Potential Targets, And Methods For Prevention And Treatment, Yajuan Su, Jaime T. Yrastorza, Mitchell Matis, Jenna Cusick, Siwei Zhao, Guangshun Wang, Jingwei Xie

Journal Articles: Pathology and Microbiology

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment …

Development Of Phage Cocktails To Treat E Coli Catheter-Associated Urinary Tract Infection And Associated Biofilms, Belkys C Sanchez, Emmaline R Heckmann, Sabrina I Green, Justin R Clark, Heidi B Kaplan, Robert F Ramig, Casey Hines-Munson, Felicia Skelton, Barbara W Trautner, Anthony W Maresso

Faculty, Staff and Students Publications

High rates of antimicrobial resistance and formation of biofilms makes treatment of Escherichia coli catheter-associated urinary tract infections (CAUTI) particularly challenging. CAUTI affect 1 million patients per year in the United States and are associated with morbidity and mortality, particularly as an etiology for sepsis. Phage have been proposed as a potential therapeutic option. Here, we report the development of phage cocktails that lyse contemporary E. coli strains isolated from the urine of patients with spinal cord injury (SCI) and display strong biofilm-forming properties. We characterized E. coli phage against biofilms in two in vitro CAUTI models. Biofilm viability was …

Development Of Phage Cocktails To Treate Coli Catheter-Associated Urinary Tract Infection And Associated Biofilms, Belkys C Sanchez, Emmaline R Heckmann, Sabrina I Green, Justin R Clark, Heidi B Kaplan, Robert F Ramig, Casey Hines-Munson, Felicia Skelton, Barbara W Trautner, Anthony W Maresso

Faculty, Staff and Students Publications

High rates of antimicrobial resistance and formation of biofilms makes treatment of Escherichia coli catheter-associated urinary tract infections (CAUTI) particularly challenging. CAUTI affect 1 million patients per year in the United States and are associated with morbidity and mortality, particularly as an etiology for sepsis. Phage have been proposed as a potential therapeutic option. Here, we report the development of phage cocktails that lyse contemporary E. coli strains isolated from the urine of patients with spinal cord injury (SCI) and display strong biofilm-forming properties. We characterized E. coli phage against biofilms in two in vitro CAUTI models. Biofilm viability was …

Structure And Activity Of A Selective Antibiofilm Peptide Sk-24 Derived From The Nmr Structure Of Human Cathelicidin Ll-37, Yingxia Zhang, Jayaram Lakshmaiah Narayana, Qianhui Wu, Xiangli Dang, Guangshun Wang

Journal Articles: Pathology and Microbiology

The deployment of the innate immune system in humans is essential to protect us from infection. Human cathelicidin LL-37 is a linear host defense peptide with both antimicrobial and immune modulatory properties. Despite years of studies of numerous peptides, SK-24, corresponding to the long hydrophobic domain (residues 9–32) in the anionic lipid-bound NMR structure of LL-37, has not been investigated. This study reports the structure and activity of SK-24. Interestingly, SK-24 is entirely helical (~100%) in phosphate buffer (PBS), more than LL-37 (84%), GI-20 (75%), and GF-17 (33%), while RI-10 and 17BIPHE2 are essentially randomly coiled (helix%: 7–10%). These results …

Stochastic Expression Of Sae-Dependent Virulence Genes During Staphylococcus Aureus Biofilm Development Is Dependent On Saes, Elizabeth A. Delmain, Derek E. Moormeier, Jennifer L. Endres, Rebecca E. Hodges, Marat R. Sadykov, Alexander R. Horswill, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

The intricate process of biofilm formation in the human pathogen Staphylococcus aureus involves distinct stages during which a complex mixture of matrix molecules is produced and modified throughout the developmental cycle. Early in biofilm development, a subpopulation of cells detaches from its substrate in an event termed “exodus” that is mediated by SaePQRS-dependent stochastic expression of a secreted staphylococcal nuclease, which degrades extracellular DNA within the matrix, causing the release of cells and subsequently allowing for the formation of metabolically heterogenous microcolonies. Since the SaePQRS regulatory system is involved in the transcriptional control of multiple S. aureus virulence factors, the …

Identification Of Extracellular Dna-Binding Proteins In The Biofilm Matrix., Jeffrey S. Kavanaugh, Caralyn E. Flack, Jessica Lister, Erica B. Ricker, Carolyn B. Ibberson, Christian Jenul, Derek E. Moormeier, Elizabeth A. Delmain, Kenneth W. Bayles, Alexander R. Horswill

Journal Articles: Pathology and Microbiology

We developed a new approach that couples Southwestern blotting and mass spectrometry to discover proteins that bind extracellular DNA (eDNA) in bacterial biofilms. Using Staphylococcus aureus as a model pathogen, we identified proteins with known DNA-binding activity and uncovered a series of lipoproteins with previously unrecognized DNA-binding activity. We demonstrated that expression of these lipoproteins results in an eDNA-dependent biofilm enhancement. Additionally, we found that while deletion of lipoproteins had a minimal impact on biofilm accumulation, these lipoprotein mutations increased biofilm porosity, suggesting that lipoproteins and their associated interactions contribute to biofilm structure. For one of the lipoproteins, SaeP, we …

Observations Of Shear Stress Effects On Staphylococcus Aureus Biofilm Formation, Erica Sherman, Kenneth W. Bayles, Derek E. Moormeier, Jennifer L. Endres, Timothy Wei

Journal Articles: Pathology and Microbiology

Staphylococcus aureus bacteria form biofilms and distinctive microcolony or "tower" structures that facilitate their ability to tolerate antibiotic treatment and to spread within the human body. The formation of microcolonies, which break off, get carried downstream, and serve to initiate biofilms in other parts of the body, is of particular interest here. It is known that flow conditions play a role in the development, dispersion, and propagation of biofilms in general. The influence of flow on microcolony formation and, ultimately, what factors lead to microcolony development are, however, not well understood. The hypothesis being examined is that microcolony structures form …

Requirements For Pseudomonas Aeruginosa Type I-F Crispr-Cas Adaptation Determined Using A Biofilm Enrichment Assay, Gary E. Heussler, Jon L. Miller, Courtney E. Price, Alan J. Collins

Dartmouth Scholarship

CRISPR (clustered regularly interspaced short palindromic repeat)-Cas (CRISPR-associated protein) systems are diverse and found in many archaea and bacteria. These systems have mainly been characterized as adaptive immune systems able to protect against invading mobile genetic elements, including viruses. The first step in this protection is acquisition of spacer sequences from the invader DNA and incorporation of those sequences into the CRISPR array, termed CRISPR adaptation. Progress in understanding the mechanisms and requirements of CRISPR adaptation has largely been accomplished using overexpression of cas genes or plasmid loss assays; little work has focused on endogenous CRISPR-acquired immunity from viral predation. …

The Pseudomonas Aeruginosa Efflux Pump Mexghi-Opmd Transports A Natural Phenazine That Controls Gene Expression And Biofilm Development, Hassan Sakhtah, Leslie Koyama, Yihan Zhang, Diana K. Morales, Blanche Fields, Alexa Price-Whelan, Deborah Hogan

Dartmouth Scholarship

Redox-cycling compounds, including endogenously produced phenazine antibiotics, induce expression of the efflux pump MexGHI-OpmD in the opportunistic pathogen Pseudomonas aeruginosa Previous studies of P. aeruginosa virulence, physiology, and biofilm development have focused on the blue phenazine pyocyanin and the yellow phenazine-1-carboxylic acid (PCA). In P. aeruginosa phenazine biosynthesis, conversion of PCA to pyocyanin is presumed to proceed through the intermediate 5-methylphenazine-1-carboxylate (5-Me-PCA), a reactive compound that has eluded detection in most laboratory samples. Here, we apply electrochemical methods to directly detect 5-Me-PCA and find that it is transported by MexGHI-OpmD in P. aeruginosa strain PA14 planktonic and biofilm cells. We …

Staphylococcus Aureus Biofilms Induce Macrophage Dysfunction Through Leukocidin Ab And Alpha-Toxin., Tyler D. Scherr, Mark L. Hanke, Ouwen Huang, David B.A. James, Alexander R. Horswill, Kenneth W. Bayles, Paul D. Fey, Victor J. Torres, Tammy Kielian

Journal Articles: Pathology and Microbiology

UNLABELLED: The macrophage response to planktonic Staphylococcus aureus involves the induction of proinflammatory microbicidal activity. However, S. aureus biofilms can interfere with these responses in part by polarizing macrophages toward an anti-inflammatory profibrotic phenotype. Here we demonstrate that conditioned medium from mature S. aureus biofilms inhibited macrophage phagocytosis and induced cytotoxicity, suggesting the involvement of a secreted factor(s). Iterative testing found the active factor(s) to be proteinaceous and partially agr-dependent. Quantitative mass spectrometry identified alpha-toxin (Hla) and leukocidin AB (LukAB) as critical molecules secreted by S. aureus biofilms that inhibit murine macrophage phagocytosis and promote cytotoxicity. A role for Hla …

Links Between Anr And Quorum Sensing In Pseudomonas Aeruginosa Biofilms, John H. Hammond, Emily F. Dolben, T. Jarrod Smith, Sabin Bhuju, Deborah Hogan

Dartmouth Scholarship

In Pseudomonas aeruginosa, the transcription factor Anr controls the cellular response to low oxygen or anoxia. Anr activity is high in oxygen-limited environments, including biofilms and populations associated with chronic infections, and Anr is necessary for persistence in a model of pulmonary infection. In this study, we characterized the Anr regulon in biofilm-grown cells at 1% oxygen in the laboratory strain PAO1 and in a quorum sensing (QS)-deficient clinical isolate, J215. As expected, transcripts related to denitrification, arginine fermentation, high-affinity cytochrome oxidases, and CupA fimbriae were lower in the Δanr derivatives. In addition, we observed that transcripts associated with quorum …

Clustered Regularly Interspaced Short Palindromic Repeat-Dependent, Biofilm-Specific Death Of Pseudomonas Aeruginosa Mediated By Increased Expression Of Phage-Related Genes, Gary E. E. Heussler, Kyle C. Cady, Katja Koeppen, Sabin Bhuju, Bruce A. Stanton, George A. O’Toole

Dartmouth Scholarship

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (CRISPR/Cas) system is an adaptive immune system present in many archaea and bacteria. CRISPR/Cas systems are incredibly diverse, and there is increasing evidence of CRISPR/Cas systems playing a role in cellular functions distinct from phage immunity. Previously, our laboratory reported one such alternate function in which the type 1-F CRISPR/Cas system of the opportunistic pathogen Pseudomonas aeruginosa strain UCBPP-PA14 (abbreviated as P. aeruginosa PA14) inhibits both biofilm formation and swarming motility when the bacterium is lysogenized by the bacteriophage DMS3. In this study, we demonstrated that the presence of just the DMS3 …

Antimicrobial Peptides In 2014., Guangshun Wang, Biswajit Mishra, Kyle Lau, Tamara Lushnikova, Radha Golla, Xiuqing Wang

Journal Articles: Pathology and Microbiology

This article highlights new members, novel mechanisms of action, new functions, and interesting applications of antimicrobial peptides reported in 2014. As of December 2014, over 100 new peptides were registered into the Antimicrobial Peptide Database, increasing the total number of entries to 2493. Unique antimicrobial peptides have been identified from marine bacteria, fungi, and plants. Environmental conditions clearly influence peptide activity or function. Human α-defensin HD-6 is only antimicrobial under reduced conditions. The pH-dependent oligomerization of human cathelicidin LL-37 is linked to double-stranded RNA delivery to endosomes, where the acidic pH triggers the dissociation of the peptide aggregate to release …

Temporal And Stochastic Control Of Staphylococcus Aureus Biofilm Development., Derek E. Moormeier, Jeffrey L. Bose, Alexander R. Horswill, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

Biofilm communities contain distinct microniches that result in metabolic heterogeneity and variability in gene expression. Previously, these niches were visualized within Staphylococcus aureus biofilms by observing differential expression of the cid and lrg operons during tower formation. In the present study, we examined early biofilm development and identified two new stages (designated "multiplication" and "exodus") that were associated with changes in matrix composition and a distinct reorganization of the cells as the biofilm matured. The initial attachment and multiplication stages were shown to be protease sensitive but independent of most cell surface-associated proteins. Interestingly, after 6 h of growth, an …

Analysis Of Candida Albicans Mutants Defective In The Cdk8 Module Of Mediator Reveal Links Between Metabolism And Biofilm Formation, Allia K. Lindsay, Diana K. Morales, Zhongle Liu, Nora Grahl, Anda Zhang, Sven D. Willger, Lawrence C. Myers, Deborah A. Hogan

Dartmouth Scholarship

Candida albicans biofilm formation is a key virulence trait that involves hyphal growth and adhesin expression. Pyocyanin (PYO), a phenazine secreted by Pseudomonas aeruginosa, inhibits both C. albicans biofilm formation and development of wrinkled colonies. Using a genetic screen, we identified two mutants, ssn3Δ/Δ and ssn8Δ/Δ, which continued to wrinkle in the presence of PYO. Ssn8 is a cyclin-like protein and Ssn3 is similar to cyclin-dependent kinases; both proteins are part of the heterotetrameric Cdk8 module that forms a complex with the transcriptional co-regulator, Mediator. Ssn3 kinase activity was also required for PYO sensitivity as a kinase dead mutant maintained …