7 research outputs found
A Shift in Central Metabolism Accompanies Virulence Activation in Pseudomonas aeruginosa.
The availability of energy has significant impact on cell physiology. However, the role of cellular metabolism in bacterial pathogenesis is not understood. We investigated the dynamics of central metabolism during virulence induction by surface sensing and quorum sensing in early-stage biofilms of the multidrug-resistant bacterium Pseudomonas aeruginosa We established a metabolic profile for P. aeruginosa using fluorescence lifetime imaging microscopy (FLIM), which reports the activity of NADH in live cells. We identified a critical growth transition period during which virulence is activated. We performed FLIM measurements and direct measurements of NADH and NAD+ concentrations during this period. Here, planktonic (low-virulence) and surface-attached (virulence-activated) populations diverged into distinct metabolic states, with the surface-attached population exhibiting FLIM lifetimes that were associated with lower levels of enzyme-bound NADH and decreasing total NAD(H) production. We inhibited virulence by perturbing central metabolism using citrate and pyruvate, which further decreased the enzyme-bound NADH fraction and total NAD(H) production and suggested the involvement of the glyoxylate pathway in virulence activation in surface-attached populations. In addition, we induced virulence at an earlier time using the electron transport chain oxidase inhibitor antimycin A. Our results demonstrate the use of FLIM to noninvasively measure NADH dynamics in biofilms and suggest a model in which a metabolic rearrangement accompanies the virulence activation period.IMPORTANCE The rise of antibiotic resistance requires the development of new strategies to combat bacterial infection and pathogenesis. A major direction has been the development of drugs that broadly target virulence. However, few targets have been identified due to the species-specific nature of many virulence regulators. The lack of a virulence regulator that is conserved across species has presented a further challenge to the development of therapeutics. Here, we identify that NADH activity has an important role in the induction of virulence in the pathogen P. aeruginosa This finding, coupled with the ubiquity of NADH in bacterial pathogens, opens up the possibility of targeting enzymes that process NADH as a potential broad antivirulence approach
Coalescence of bubbles and drops in an outer fluid
When two liquid drops touch, a microscopic connecting liquid bridge forms and rapidly grows as the two drops merge into one. Whereas coalescence has been thoroughly studied when drops coalesce in vacuum or air, many important situations involve coalescence in a dense surrounding fluid, such as oil coalescence in brine. Here we study the merging of gas bubbles and liquid drops in an external fluid. Our data indicate that the flows occur over much larger length scales in the outer fluid than inside the drops themselves. Thus, we find that the asymptotic early regime is always dominated by the viscosity of the drops, independent of the external fluid. A phase diagram showing the crossovers into the different possible late-time dynamics identifies a dimensionless number that signifies when the external viscosity can be important
Recommended from our members
Wetting Transition of Water on Crystalline Surfaces
In this report I investigate the properties of water interfacing with various crystalline surfaces, by studying its adhesivity as a function of temperature. Through direct visualization of the liquid-solid interface, I report the wetting behavior of water on silicon carbide, oxygen, hydrogen and fluorine terminated CVD diamond, and epitaxial monolayer graphene along the liquid-vapor coexistence curve by varying the temperature from room temperature to ∼ 550 K. Wetting transitions were identified by both vanishing contact angles (SiC, graphene) and drop-wise to film-wise condensation (all samples). Both methods yield similar wetting temperatures, which are 489±9 K, 480±10 K, 530±10 K, 505±2 K and 509±6 K for SiC, o-diamond, h-diamond, f-diamond and graphene respectively. Where applicable, we compare our data to predictions from a simple theoretical model and molecular dynamics simulations of the liquid-solid interactions. We also compare our data with previously reported experimental results. Further, with regard to recent experimental data our evidence suggests that monolayer graphene is not transparent to wetting, but instead exhibits ‘translucency’.This study appends new - and updates existing - information about the interfacial properties of water on technologically relevant substrates. It reviews the underlying science behind the wetting phenomenon and interfacial interactions, and surveys contemporary experimental data regarding these properties for several substrates.Finally, this study hopes to aid in the design and development of novel medical, optoelectronic, micro- and nano-fluidic devices
Wetting Transition of Water on Crystalline Surfaces
In this report I investigate the properties of water interfacing with various crystalline surfaces, by studying its adhesivity as a function of temperature. Through direct visualization of the liquid-solid interface, I report the wetting behavior of water on silicon carbide, oxygen, hydrogen and fluorine terminated CVD diamond, and epitaxial monolayer graphene along the liquid-vapor coexistence curve by varying the temperature from room temperature to ∼ 550 K. Wetting transitions were identified by both vanishing contact angles (SiC, graphene) and drop-wise to film-wise condensation (all samples). Both methods yield similar wetting temperatures, which are 489±9 K, 480±10 K, 530±10 K, 505±2 K and 509±6 K for SiC, o-diamond, h-diamond, f-diamond and graphene respectively. Where applicable, we compare our data to predictions from a simple theoretical model and molecular dynamics simulations of the liquid-solid interactions. We also compare our data with previously reported experimental results. Further, with regard to recent experimental data our evidence suggests that monolayer graphene is not transparent to wetting, but instead exhibits ‘translucency’.This study appends new - and updates existing - information about the interfacial properties of water on technologically relevant substrates. It reviews the underlying science behind the wetting phenomenon and interfacial interactions, and surveys contemporary experimental data regarding these properties for several substrates.Finally, this study hopes to aid in the design and development of novel medical, optoelectronic, micro- and nano-fluidic devices
Recommended from our members
Dynamic switching enables efficient bacterial colonization in flow
Bacteria colonize environments that contain networks of moving fluids, including digestive pathways, blood vasculature in animals, and the xylem and phloem networks in plants. In these flow networks, bacteria form distinct biofilm structures that have an important role in pathogenesis. The physical mechanisms that determine the spatial organization of bacteria in flow are not understood. Here, we show that the bacterium P. aeruginosa colonizes flow networks using a cyclical process that consists of surface attachment, upstream movement, detachment, movement with the bulk flow, and surface reattachment. This process, which we have termed dynamic switching, distributes bacterial subpopulations upstream and downstream in flow through two phases: movement on surfaces and cellular movement via the bulk. The model equations that describe dynamic switching are identical to those that describe dynamic instability, a process that enables microtubules in eukaryotic cells to search space efficiently to capture chromosomes. Our results show that dynamic switching enables bacteria to explore flow networks efficiently, which maximizes dispersal and colonization and establishes the organizational structure of biofilms. A number of eukaryotic and mammalian cells also exhibit movement in two phases in flow, which suggests that dynamic switching is a modality that enables efficient dispersal for a broad range of cell types
Recommended from our members
A Shift in Central Metabolism Accompanies Virulence Activation in Pseudomonas aeruginosa.
The availability of energy has significant impact on cell physiology. However, the role of cellular metabolism in bacterial pathogenesis is not understood. We investigated the dynamics of central metabolism during virulence induction by surface sensing and quorum sensing in early-stage biofilms of the multidrug-resistant bacterium Pseudomonas aeruginosa We established a metabolic profile for P. aeruginosa using fluorescence lifetime imaging microscopy (FLIM), which reports the activity of NADH in live cells. We identified a critical growth transition period during which virulence is activated. We performed FLIM measurements and direct measurements of NADH and NAD+ concentrations during this period. Here, planktonic (low-virulence) and surface-attached (virulence-activated) populations diverged into distinct metabolic states, with the surface-attached population exhibiting FLIM lifetimes that were associated with lower levels of enzyme-bound NADH and decreasing total NAD(H) production. We inhibited virulence by perturbing central metabolism using citrate and pyruvate, which further decreased the enzyme-bound NADH fraction and total NAD(H) production and suggested the involvement of the glyoxylate pathway in virulence activation in surface-attached populations. In addition, we induced virulence at an earlier time using the electron transport chain oxidase inhibitor antimycin A. Our results demonstrate the use of FLIM to noninvasively measure NADH dynamics in biofilms and suggest a model in which a metabolic rearrangement accompanies the virulence activation period.IMPORTANCE The rise of antibiotic resistance requires the development of new strategies to combat bacterial infection and pathogenesis. A major direction has been the development of drugs that broadly target virulence. However, few targets have been identified due to the species-specific nature of many virulence regulators. The lack of a virulence regulator that is conserved across species has presented a further challenge to the development of therapeutics. Here, we identify that NADH activity has an important role in the induction of virulence in the pathogen P. aeruginosa This finding, coupled with the ubiquity of NADH in bacterial pathogens, opens up the possibility of targeting enzymes that process NADH as a potential broad antivirulence approach
A Shift in Central Metabolism Accompanies Virulence Activation in Pseudomonas aeruginosa
The rise of antibiotic resistance requires the development of new strategies to combat bacterial infection and pathogenesis. A major direction has been the development of drugs that broadly target virulence. However, few targets have been identified due to the species-specific nature of many virulence regulators. The lack of a virulence regulator that is conserved across species has presented a further challenge to the development of therapeutics. Here, we identify that NADH activity has an important role in the induction of virulence in the pathogen P. aeruginosa. This finding, coupled with the ubiquity of NADH in bacterial pathogens, opens up the possibility of targeting enzymes that process NADH as a potential broad antivirulence approach.The availability of energy has significant impact on cell physiology. However, the role of cellular metabolism in bacterial pathogenesis is not understood. We investigated the dynamics of central metabolism during virulence induction by surface sensing and quorum sensing in early-stage biofilms of the multidrug-resistant bacterium Pseudomonas aeruginosa. We established a metabolic profile for P. aeruginosa using fluorescence lifetime imaging microscopy (FLIM), which reports the activity of NADH in live cells. We identified a critical growth transition period during which virulence is activated. We performed FLIM measurements and direct measurements of NADH and NAD+ concentrations during this period. Here, planktonic (low-virulence) and surface-attached (virulence-activated) populations diverged into distinct metabolic states, with the surface-attached population exhibiting FLIM lifetimes that were associated with lower levels of enzyme-bound NADH and decreasing total NAD(H) production. We inhibited virulence by perturbing central metabolism using citrate and pyruvate, which further decreased the enzyme-bound NADH fraction and total NAD(H) production and suggested the involvement of the glyoxylate pathway in virulence activation in surface-attached populations. In addition, we induced virulence at an earlier time using the electron transport chain oxidase inhibitor antimycin A. Our results demonstrate the use of FLIM to noninvasively measure NADH dynamics in biofilms and suggest a model in which a metabolic rearrangement accompanies the virulence activation period