Action of Chlorhexidine Digluconate against Yeast and Filamentous Forms in an Early-Stage Candida albicans Biofilm

ABSTRACT An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded onto the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.

Download Full-text

GROWTH OF OXIDE LAYER ON GERMANIUM (011) SUBSTRATE UNDER DRY AND WET ATMOSPHERES

Surface Review and Letters ◽

10.1142/s0218625x99001141 ◽

1999 ◽

Vol 06 (06) ◽

pp. 1053-1060 ◽

Cited By ~ 11

Author(s):

N. TABET ◽

J. AL-SADAH ◽

M. SALIM

Keyword(s):

Simple Model ◽

Oxide Film ◽

Growth Kinetics ◽

Photoelectron Spectroscopy ◽

Early Stage ◽

X Ray ◽

Apparent Thickness ◽

Different Temperatures ◽

Kinetics Of

X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the oxidation of (011) Ge substrates. The sample surfaces were CP4-etched, then annealed in situ, at different temperatures, for various durations. Dry and wet atmospheres were used. The oxidation rate during the early stage was increased by the presence of moisture in the atmosphere. A simple model was used to define and determine an apparent thickness of the oxide film from XPS measurements. The time dependence of the apparent thickness is consistent with a partial coverage of the surface by oxide islands. The growth kinetics of the oxide islands obeys a nearly cubic law.

Download Full-text

Effect of Casting Condition on Density and Hardness Gradients of Al-Al2Cu Alloy FGM Fabricated by Centrifugal In Situ Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.631-632.449 ◽

2009 ◽

Vol 631-632 ◽

pp. 449-454 ◽

Cited By ~ 1

Author(s):

Kenichi Tabushi ◽

Hisashi Sato ◽

Yoshimi Watanabe

Keyword(s):

Density Gradient ◽

Master Alloy ◽

Early Stage ◽

Functionally Graded ◽

Processing Temperature ◽

Casting Condition ◽

Cu Alloy ◽

In Situ Method ◽

Master Alloys

Functionally graded material (FGM) is a combined material that has a component gradient from one material at one surface to another material at the opposite surface. 　As one of the fabrication processes of FGM, centrifugal in-situ method has been proposed. Centrifugal in-situ method is a casting that centrifugal force is applied during solidification to both the primary crystal and the matrix. In a previous study, the density and hardness gradients of Al-3mass%Cu FGM ring fabricated by centrifugal in-situ method have been investigated. According to the study, Cu concentration within the FGM ring monolithically increases towards the ring's inner position, and its density also increases toward inner region. This is because the density of the primary -Al crystal is larger than that of the molten Al-Cu alloy in the early stage of solidification. Based on this solidification process, it is considered that the casting condition and the initial Cu concentration of Al-Cu master alloy affect on the density and hardness gradients in the Al-Cu FGM ring. In this study, effects of the casting condition on the density and hardness gradients of Al-Al2Cu FGM rings fabricated by the centrifugal in-situ method were investigated. It was found that density gradient of the Al-Al2Cu FGM rings increases with increasing Cu concentration of Al-Cu master alloys. Also, processing temperature for Al-Cu master alloy can control density gradient of Al-Al2Cu FGM rings. These phenomena were explained by variation of the densities of primary -Al and the molten Al matrix during the solidification.

Download Full-text

Phase Formation and Growth Kinetics of an Interface Layer in Ni/SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.600-603.631 ◽

2008 ◽

Vol 600-603 ◽

pp. 631-634

Author(s):

Kenichiro Terui ◽

Atsuko Sekiguchi ◽

Hiroshi Yoshizaki ◽

Junichi Koike

Keyword(s):

Growth Rate ◽

Late Stage ◽

Growth Kinetic ◽

Early Stage ◽

Interface Reaction ◽

Interface Layer ◽

Nickel Silicide ◽

Composition And Structure ◽

The Difference ◽

Kinetics Of

The reaction behavior and growth kinetic of reaction layer were investigated in the Ni contact to n-type 6H-SiC. Annealing was performed at temperature in the range between 800 and 1000 °C for 1 to 240 minutes in Ar atmosphere. The interface reaction of Ni/SiC starts with Ni diffusion into SiC. Ni3Si is initially precipitated and subsequently forms the continuous layer of d-Ni2Si. Kirkendall voids are formed at the reaction front. Carbon is segregated in the interface layer of nickel silicide. The growth rate of the interface layer follows a parabolic law, meaning that the growth rate is controlled by diffusion. The growth occurs in two steps at all examined temperatures: a fast growth is followed by a slow growth. In addition, in the late stage, the growth rate changes dramatically below and above 850°C. The observed growth kinetic can be explained by the difference of Ni diffusivity and the required concentration change for phase transition depending on the phase composition and structure. The d-Ni2Si is formed in the early stage, while the e-Ni3Si2 and q-Ni2Si are formed in the late stage below and above 850°C, respectively.

Download Full-text

Genome-Wide Transcription Profiling of the Early Phase of Biofilm Formation by Candida albicans

Eukaryotic Cell ◽

10.1128/ec.4.9.1562-1573.2005 ◽

2005 ◽

Vol 4 (9) ◽

pp. 1562-1573 ◽

Cited By ~ 106

Author(s):

Luis A. Murillo ◽

George Newport ◽

Chung-Yu Lan ◽

Stefan Habelitz ◽

Jan Dungan ◽

...

Keyword(s):

Candida Albicans ◽

Biofilm Formation ◽

Early Stage ◽

Sulfur Metabolism ◽

Single Cells ◽

Alternative Pathway ◽

Opportunistic Pathogen ◽

Abiotic Surfaces ◽

Expression Of Genes ◽

Structure Changes

ABSTRACT The ability to adhere to surfaces and develop as a multicellular community is an adaptation used by most microorganisms to survive in changing environments. Biofilm formation proceeds through distinct developmental phases and impacts not only medicine but also industry and evolution. In organisms such as the opportunistic pathogen Candida albicans, the ability to grow as biofilms is also an important mechanism for persistence, facilitating its growth on different tissues and a broad range of abiotic surfaces used in medical devices. The early stage of C. albicans biofilm is characterized by the adhesion of single cells to the substratum, followed by the formation of an intricate network of hyphae and the beginning of a dense structure. Changes in the transcriptome begin within 30 min of contact with the substrate and include expression of genes related to sulfur metabolism, in particular MET3, and the equivalent gene homologues of the Ribi regulon in Saccharomyces cerevisiae. Some of these changes are initiated early and maintained throughout the process; others are restricted to the earliest stages of biofilm formation. We identify here a potential alternative pathway for cysteine metabolism and the biofilm-associated expression of genes involved in glutathione production in C. albicans.

Download Full-text

Spectra Library: An Assumption-Free In Situ Method to Access the Kinetics of Catechols Binding to Colloidal ZnO Quantum Dots

Angewandte Chemie ◽

10.1002/ange.201508252 ◽

2015 ◽

Vol 128 (3) ◽

pp. 944-947 ◽

Cited By ~ 5

Author(s):

Wei Lin ◽

Michael Haderlein ◽

Johannes Walter ◽

Wolfgang Peukert ◽

Doris Segets

Keyword(s):

Quantum Dots ◽

In Situ Method ◽

Zno Quantum Dots ◽

Kinetics Of

Download Full-text

An in situ method on kinetics of gas hydrates

Review of Scientific Instruments ◽

10.1063/1.5082333 ◽

2019 ◽

Vol 90 (3) ◽

pp. 035111 ◽

Cited By ~ 1

Author(s):

Ali Masoudi ◽

Parham Jafari ◽

Masoumeh Nazari ◽

Varun Kashyap ◽

Bahareh Eslami ◽

...

Keyword(s):

Gas Hydrates ◽

In Situ Method ◽

Kinetics Of

Download Full-text

Kinetics of Void Drift in Copper Interconnects

MRS Proceedings ◽

10.1557/proc-0914-f08-03 ◽

2006 ◽

Vol 914 ◽

Cited By ~ 4

Author(s):

Zung-Sun Choi ◽

Reiner Mönig ◽

Carl V. Thompson ◽

Michael Burns

Keyword(s):

Grain Boundaries ◽

Void Nucleation ◽

Copper Interconnects ◽

Time Behavior ◽

Electrical Failure ◽

Grain Orientations ◽

The Difference ◽

Kinetics Of ◽

Electron Back Scattered Diffraction

AbstractWe have observed the real-time behavior of electomigration-induced voids in both passivated and unpassivated copper interconnects in a Scanning Electron Microscope (SEM), and correlated void nucleation, growth, drift and stagnation with post-electromigration crystallographic microanalyses carried out using Electron Back-Scattered Diffraction (EBSD) analysis. Voids that nucleate at various locations along the interconnects often drift toward the cathode, where they grow, coalesce, and eventually cause electrical failure. In-situ SEM observations allowed for the tracking of void shapes and drift rates over long (multi-grain) distances. Changes in the size and the velocity of the voids were observed when the voids passed through different grains. These changes are attributed to the difference in diffusivity for different grain orientations. In passivated lines, voids were often trapped at individual grain boundaries, where they grew to cause failure, or de-trapped to continue to drift toward the cathode. In unpassivated lines, voids did not drift, but instead always nucleated and grew and grain boundaries. Locations at which voids grew in unpassivated lines, or at which voids were trapped and grew in passivated lines, were correlated with the crystallographic orientations of “upwind” and “downwind” grains. From these analyses, we find that the average electromigration interface diffusivities (z*D) as a function of grain orientation are ordered according to {100} > {111} > {110}. Quantitative analysis of void dynamics, correlated with crystallographic microanalyses, provides important data for modeling of electromigration-induced failure, and for process-optimization for improved reliability.

Download Full-text

Inhibition of Candida albicans Biofilm Formation by Farnesol, a Quorum-Sensing Molecule

Applied and Environmental Microbiology ◽

10.1128/aem.68.11.5459-5463.2002 ◽

2002 ◽

Vol 68 (11) ◽

pp. 5459-5463 ◽

Cited By ~ 441

Author(s):

Gordon Ramage ◽

Stephen P. Saville ◽

Brian L. Wickes ◽

José L. López-Ribot

Keyword(s):

Candida Albicans ◽

Quorum Sensing ◽

Biofilm Formation ◽

Northern Blot Analysis ◽

Adherent Cell ◽

Naturally Occurring ◽

Biofilm Development ◽

Further Development ◽

Quorum Sensing Molecule

ABSTRACT Farnesol is a quorum-sensing molecule that inhibits filamentation in Candida albicans. Both filamentation and quorum sensing are deemed to be important factors in C. albicans biofilm development. Here we examined the effect of farnesol on C. albicans biofilm formation. C. albicans adherent cell populations (after 0, 1, 2, and 4 h of adherence) and preformed biofilms (24 h) were treated with various concentrations of farnesol (0, 3, 30, and 300 μM) and incubated at 37°C for 24 h. The extent and characteristics of biofilm formation were then assessed microscopically and with a semiquantitative colorimetric technique based on the use of 2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide. The results indicated that the effect of farnesol was dependent on the concentration of this compound and the initial adherence time, and preincubation with 300 μM farnesol completely inhibited biofilm formation. Supernatant media recovered from mature biofilms inhibited the ability of planktonic C. albicans to form filaments, indicating that a morphogenetic autoregulatory compound is produced in situ in biofilms. Northern blot analysis of RNA extracted from cells in biofilms indicated that the levels of expression of HWP1, encoding a hypha-specific wall protein, were decreased in farnesol-treated biofilms compared to the levels in controls. Our results indicate that farnesol acts as a naturally occurring quorum-sensing molecule which inhibits biofilm formation, and we discuss its potential for further development and use as a novel therapeutic agent.

Download Full-text