Pathology Commons^™

An Intravenous Pancreatic Cancer Therapeutic: Characterization Of Crispr/Cas9n-Modified Clostridium Novyi-Non Toxic, Kaitlin M. Dailey, James M. Small, Jessica E. Pullan, Seth Winfree, Krysten E. Vance, Megan Orr, Sanku Mallik, Kenneth W. Bayles, Michael A. Hollingsworth, Amanda E Brooks

Journal Articles: Pathology and Microbiology

Clostridium novyi has demonstrated selective efficacy against solid tumors largely due to the microenvironment contained within dense tumor cores. The core of a solid tumor is typically hypoxic, acidic, and necrotic-impeding the penetration of current therapeutics. C. novyi is attracted to the tumor microenvironment and once there, can both lyse and proliferate while simultaneously re-activating the suppressed immune system. C. novyi systemic toxicity is easily mitigated by knocking out the phage DNA plasmid encoded alpha toxin resulting in C. novyi-NT; but, after intravenous injection spores are quickly cleared by phagocytosis before accomplishing significant tumor localization. C. novyi-NT could be designed …

A Central Role For Carbon-Overflow Pathways In The Modulation Of Bacterial Cell Death., Vinai Chittezham Thomas, Marat Sadykov, Sujata S. Chaudhari, Joselyn Jones, Jennifer L. Endres, Todd J. Widhelm, Jong-Sam Ahn, Randeep S. Jawa, Matthew C. Zimmerman, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

Similar to developmental programs in eukaryotes, the death of a subpopulation of cells is thought to benefit bacterial biofilm development. However mechanisms that mediate a tight control over cell death are not clearly understood at the population level. Here we reveal that CidR dependent pyruvate oxidase (CidC) and α-acetolactate synthase/decarboxylase (AlsSD) overflow metabolic pathways, which are active during staphylococcal biofilm development, modulate cell death to achieve optimal biofilm biomass. Whereas acetate derived from CidC activity potentiates cell death in cells by a mechanism dependent on intracellular acidification and respiratory inhibition, AlsSD activity effectively counters CidC action by diverting carbon flux …

Ccpa Regulates Arginine Biosynthesis In Staphylococcus Aureus Through Repression Of Proline Catabolism., Austin S. Nuxoll, Steven M. Halouska, Marat Sadykov, Mark L. Hanke, Kenneth W. Bayles, Tammy Kielian, Robert Powers, Paul D. Fey

Journal Articles: Pathology and Microbiology

Staphylococcus aureus is a leading cause of community-associated and nosocomial infections. Imperative to the success of S. aureus is the ability to adapt and utilize nutrients that are readily available. Genomic sequencing suggests that S. aureus has the genes required for synthesis of all twenty amino acids. However, in vitro experimentation demonstrates that staphylococci have multiple amino acid auxotrophies, including arginine. Although S. aureus possesses the highly conserved anabolic pathway that synthesizes arginine via glutamate, we demonstrate here that inactivation of ccpA facilitates the synthesis of arginine via the urea cycle utilizing proline as a substrate. Mutations within putA, rocD, …

Low Levels Of Β-Lactam Antibiotics Induce Extracellular Dna Release And Biofilm Formation In Staphylococcus Aureus., Jeffrey B. Kaplan, Era A. Izano, Prerna Gopal, Michael T. Karwacki, Sangho Kim, Jeffrey L. Bose, Kenneth W. Bayles, Alexander R. Horswill

Journal Articles: Pathology and Microbiology

UNLABELLED: Subminimal inhibitory concentrations of antibiotics have been shown to induce bacterial biofilm formation. Few studies have investigated antibiotic-induced biofilm formation in Staphylococcus aureus, an important human pathogen. Our goal was to measure S. aureus biofilm formation in the presence of low levels of β-lactam antibiotics. Fifteen phylogenetically diverse methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains were employed. Methicillin, ampicillin, amoxicillin, and cloxacillin were added to cultures at concentrations ranging from 0× to 1× MIC. Biofilm formation was measured in 96-well microtiter plates using a crystal violet binding assay. Autoaggregation was measured using a visual test tube …

Contribution Of The Staphylococcus Aureus Atl Am And Gl Murein Hydrolase Activities In Cell Division, Autolysis, And Biofilm Formation., Jeffrey L. Bose, Mckenzie K. Lehman, Paul D. Fey, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

The most prominent murein hydrolase of Staphylococcus aureus, AtlA, is a bifunctional enzyme that undergoes proteolytic cleavage to yield two catalytically active proteins, an amidase (AM) and a glucosaminidase (GL). Although the bifunctional nature of AtlA has long been recognized, most studies have focused on the combined functions of this protein in cell wall metabolism and biofilm development. In this study, we generated mutant derivatives of the clinical S. aureus isolate, UAMS-1, in which one or both of the AM and GL domains of AtlA have been deleted. Examination of these strains revealed that each mutant exhibited growth rates comparable …

Epistatic Relationships Between Sara And Agr In Staphylococcus Aureus Biofilm Formation., Karen E. Beenken, Lara N. Mrak, Linda M. Griffin, Agnieszka K. Zielinska, Lindsey N. Shaw, Kelly C. Rice, Alexander R. Horswill, Kenneth W. Bayles, Mark S. Smeltzer

Journal Articles: Pathology and Microbiology

BACKGROUND: The accessory gene regulator (agr) and staphylococcal accessory regulator (sarA) play opposing roles in Staphylococcus aureus biofilm formation. There is mounting evidence to suggest that these opposing roles are therapeutically relevant in that mutation of agr results in increased biofilm formation and decreased antibiotic susceptibility while mutation of sarA has the opposite effect. To the extent that induction of agr or inhibition of sarA could potentially be used to limit biofilm formation, this makes it important to understand the epistatic relationships between these two loci.

METHODOLOGY/PRINCIPAL FINDINGS: We generated isogenic sarA and agr mutants in clinical isolates of S. …

Modulation Of Edna Release And Degradation Affects Staphylococcus Aureus Biofilm Maturation., Ethan E. Mann, Kelly C. Rice, Blaise R. Boles, Jennifer L. Endres, Dev Ranjit, Lakshmi Chandramohan, Laura H. Tsang, Mark S. Smeltzer, Alexander R. Horswill, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

Recent studies have demonstrated a role for Staphylococcus aureus cidA-mediated cell lysis and genomic DNA release in biofilm adherence. The current study extends these findings by examining both temporal and additional genetic factors involved in the control of genomic DNA release and degradation during biofilm maturation. Cell lysis and DNA release were found to be critical for biofilm attachment during the initial stages of development and the released DNA (eDNA) remained an important matrix component during biofilm maturation. This study also revealed that an lrgAB mutant exhibits increased biofilm adherence and matrix-associated eDNA consistent with its proposed role as an …

Assembly And Development Of The Pseudomonas Aeruginosa Biofilm Matrix., Luyan Ma, Matthew Conover, Haiping Lu, Matthew R. Parsek, Kenneth W. Bayles, Daniel J. Wozniak

Journal Articles: Pathology and Microbiology

Virtually all cells living in multicellular structures such as tissues and organs are encased in an extracellular matrix. One of the most important features of a biofilm is the extracellular polymeric substance that functions as a matrix, holding bacterial cells together. Yet very little is known about how the matrix forms or how matrix components encase bacteria during biofilm development. Pseudomonas aeruginosa forms environmentally and clinically relevant biofilms and is a paradigm organism for the study of biofilms. The extracellular polymeric substance of P. aeruginosa biofilms is an ill-defined mix of polysaccharides, nucleic acids, and proteins. Here, we directly visualize …