Rapid optically based measurements of diameter and length for spherical or rod-shaped bacteria in vivo

Detection and photothermal inactivation of Gram-positive and Gram-negative bloodstream bacteria using photonic crystal biosensor and plasmonic core-shell

Plasmonics and core-shell nanomaterials hold great potential to develop pharmaceuticals and medical equipment due to their eco-friendly and cost effective fabrication procedures. Despite these advancements, combating drug-resistant bacterial infections remains a global challenge. Therefore, this study aims to introduce a tailored theoretical framework for a one-dimensional (1D) photonic crystal biosensor (PCB) composed of (ZrO2/GaN)N/defect layer/(ZrO2/GaN)N, designed to detect Gram-positive and Gram-negative bloodstream bacteria employing the transfer matrix method (TMM). In addition, using the finite difference methods (FDM), the photothermal inactivation of bloodstream bacteria with plasmonic core-shell structures (FeO@AuBiS2) was explored using key factors such as light absorption, heat generation, and thermal diffusion. By incorporating six dielectric layers and contaminated blood into the proposed PCB, a maximum sensitivity of 562 nm per RIU was recorded, and using rod-shaped plasmonic core-shell structures, 5.8 nm-1 light absorption capacity and 152 K change in temperature were achieved. The maximum detection sensitivity, light absorption, heat conduction and heat convection capacity of the proposed 1D PCB and plasmonic core-shell show an effective approach to combating drug-resistant bacteria.

A Method to Reduce the Occurrence of Egg Translucency and Its Effect on Bacterial Invasion

Translucent egg consumption is low due to consumer acceptance and quality concerns, which is a problem that egg producers need to address. This study was performed to evaluate the reasons for the high occurrence of egg translucency in summer, as well as whether the addition of mono-dicalcium phosphate (MDCP) to the diet can relieve eggshell translucency and whether eggshell translucency is associated with the risk of bacterial invasion. A total of 72 laying hens that were 36 weeks old were randomly divided into control (CON) and MDCP groups and fed in the same environment. Results showed that the number of translucent eggs increases in July and August as the temperature and humidity increase. Compared with the CON group, in July, August, and October, the translucent egg grade (TEG) of the MDCP group was lower than that of the CON group (p < 0.05). TEG was correlated with mastoid space height (MSH), width (MSW), and area (MSA) (correlation coefficients 0.63, 0.59, and 0.68, respectively, p ≤ 0.05). There was no significant difference in the invasion rate of E. coli between translucent and non-translucent egg groups (47.2% vs. 39.33%), and translucent area and non-translucent area (13.49% vs. 15.08%). In conclusion, our results show that dietary MDCP may alleviate eggshell translucency and that eggshell translucency would not increase the probability of E. coli cross-shell penetration rate.

Spreading of biologically relevant liquids over the laser textured surfaces

HYPOTHESIS

The distribution of biological objects upon the spreading of biologically relevant dispersions over laser textured surfaces is affected by the dispersion composition and substrate chemistry and roughness.

EXPERIMENTS

To examine the role of the substrate texture in biologically relevant liquid spreading, the dynamic behavior of droplets of water and dispersions of bacterial cells and viruses and dynamic behavior of droplet/air surface tension were addressed. A new procedure to simultaneously distinguish three different spreading fronts was developed.

FINDINGS

The study of spreading of water and the biologically relevant liquids over the laser textured substrate indicate the development of three spreading fronts associated with the movement of bulk droplet base, the flow along the microchannels, and the nanotexture impregnation. The anisotropy of spreading for all types of liquid fronts was found. Despite the expected difference in the rheological behavior of water and the biologically relevant liquids, the spreading of all tested liquids was successfully described by power-law fits. The droplet base spreading for all tested liquids followed the Tanner law. The advancing of water and dispersions in the microchannels along both fast and slow axes was described by Washburn type behavior. The impregnation of the nanotexture by water and biologically relevant liquids demonstrated universality in power fit description with an exponent n = 0.23.

Sensitivity study on the contribution of scattering by randomly oriented nonspherical hydrosols to linear polarization in clear to semi-turbid shallow waters

The influence of hydrosol nonsphericity on the polarization characteristics of light under water is investigated by combining accurate single-scattering models for randomly oriented spheroidal scatterers with a radiative transfer model that employs Stokes formalism and considers refraction of direct unpolarized solar radiation and 100% linearly polarized radiation at the air-water interface followed by single scattering. Variations in what we call the "linear polarization phase function" (the degree of linear polarization as a function of scattering angle and the angle of linear polarization as a function of scattering angle) are examined for a wide range of spheroid aspect ratios and complex refractive indices of hydrosols. Implications for polarization-sensitive marine organisms and for remote sensing of the marine environment are discussed.

Modeling of heavy nitrate corrosion in anaerobe aquifer injection water biofilm: a case study in a flow rig

Heavy carbon steel corrosion developed during nitrate mitigation of a flow rig connected to a water injection pipeline flowing anaerobe saline aquifer water. Genera-specific QPCR primers quantified 74% of the microbial biofilm community, and further 87% of the community of the nonamended parallel rig. The nonamended biofilm hosted 6.3 × 10(6) SRB cells/cm(2) and the S(35)-sulfate-reduction rate was 1.1 μmol SO4(2-)/cm(2)/day, being congruent with the estimated SRB biomass formation and the sulfate areal flux. Nitrate amendment caused an 18-fold smaller SRB population, but up to 44 times higher sulfate reduction rates. This H2S formation was insufficient to form the observed Fe3S4 layer. Additional H2S was provided by microbial disproportionation of sulfur, also explaining the increased accessibility of sulfate. The reduced nitrate specie nitrite inhibited the dominating H2-scavenging Desulfovibrio population, and sustained the formation of polysulfide and Fe3S4, herby also dissolved sulfur. This terminated the availability of acetate in the inner biofilm and caused cell starvation that initiated growth upon metallic electrons, probably by the sulfur-reducing Desulfuromonas population. On the basis of these observations we propose a model of heavy nitrate corrosion where three microbiological processes of nitrate reduction, disproportionation of sulfur, and metallic electron growth are nicely woven into each other.

Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering

Two-dimensional angle-resolved light scattering maps of individual rod-shaped bacteria are measured at the single-cell level. Using quantitative phase imaging and Fourier transform light scattering techniques, the light scattering patterns of individual bacteria in four rod-shaped species (Bacillus subtilis, Lactobacillus casei, Synechococcus elongatus, and Escherichia coli) are measured with unprecedented sensitivity in a broad angular range from −70° to 70°. The measured light scattering patterns are analyzed along the two principal axes of rod-shaped bacteria in order to systematically investigate the species-specific characteristics of anisotropic light scattering. In addition, the cellular dry mass of individual bacteria is calculated and used to demonstrate that the cell-to-cell variations in light scattering within bacterial species is related to the cellular dry mass and growth.

Three-dimensional depth-resolved and extended-resolution micro-particle characterization by holographic light scattering spectroscopy

Fourier-holographic light scattering spectroscopy is applied to record complex angular scattering spectra of two- and three-dimensional samples over a wide field of view. We introduce a computational depth sectioning technique and, for the first time, demonstrate that a single-exposure hologram can generate a quantitative, three-dimensional map of particle sizes and locations over several cubic millimeters with micrometer resolution. Such spatially resolved maps of particle sizes are generated by Mie-inversion and could not be ascertained from the directly reconstructed intensity-distribution images. We also demonstrate synthesis of multiple angular scattering intensity spectra to increase the angular range and improve size detection sensitivity.

Light scattering calculations exploring sensitivity of depolarization ratio to shape changes. II. Single rod-shaped vegetative bacteria in air

In article I of this series, calculations and graphs of the depolarization ratio, D(Theta,lambda)=1-<S22>/<S11>, for light scattered from an ensemble of single-aerosolized Bacillus spores using the discrete dipole approximation (DDA) (sometimes also called the coupled dipole approximation) were presented. The Sij in these papers denote the appropriate Mueller matrix elements. We compare graphs for different size parameters for both D(Theta,lambda) and the ratio R34(Theta,lambda)=<S34>/<S11>. The ratio R34(Theta,lambda) was shown previously to be sensitive to diameters of rod-shaped and spherical bacteria suspended in liquids. The present paper isolates the effect of length changes and shows that R34(Theta,lambda) is not very sensitive to these changes, but D(Theta,lambda) is sensitive to length changes when the aspect ratio becomes small enough. In the present article, we extend our analysis to vegetative bacteria which, because of their high percentage of water, generally have a substantially lower index of refraction than spores. The parameters used for the calculations were chosen to simulate values previously measured for log-phase Escherichia coli. Each individual E. coli bacterium appears microscopically approximately like a right-circular cylinder, capped smoothly at each end by a hemisphere of the same diameter. With the present model we focus particular attention on determining the effect, if any, of length changes on the graphs of D(Theta,lambda) and R34(Theta,lambda). We study what happens to these two functions when the diameters of the bacteria remain constant and their basic shape remains that of a capped cylinder, but with total length changed by reducing the length of the cylindrical part of each cell. This approach also allows a test of the model, since the limiting case as the length of the cylindrical part approaches zero is exactly a sphere, which is known to give a value identically equal to zero for D(Theta,lambda) but not for R34(Theta,lambda).

Light scattering calculations exploring sensitivity of depolarization ratio to shape changes. I. Single spores in air

Calculations of the depolarization ratio, D(Theta, lambda) = 1 - (S22)/(S11), for light scattered from an ensemble or cloud of single aerosolized spores in air were studied using the discrete dipole approximation (DDA), sometimes also called the coupled-dipole approximation. Here S(ij) is the appropriate Mueller matrix element for scattering angle Theta and wavelength lambda. The effect of modest shape changes on D(Theta, lambda) was determined. The shapes compared were prolate ellipsoids versus right circular cylinders joined smoothly to end caps consisting of hemispheres of the same diameter as the cylinder. Using the same models, the graphs of (S34)/(S11) versus angle were compared with those for D(Theta, lambda). The latter shows sensitivity to length in some cases we examined, while (S34)/(S11) does not. Size parameters and optical constants suggested by measurements of Bacillus cereus endospores were used. An ensemble of spores was modeled with prolate spheroids. The results of this model were compared with results of a model using the same size and optical parameters, but for capped cylinders. The two models produced distinguishably different results for the same parameters. In calculations for all the graphs shown, averaging over random orientations was performed. Averaging over size distributions similar to those from experimental measurements was performed where indicated. The results show that measurements of D(Theta, lambda) could be quite useful in characterizing the shape of particles in an unknown aerosol and for distinguishing between two likely shapes, but not to reconstruct the shapes from the graphs alone without additional information.

Microscopic particle discrimination using spatially-resolved Fourier-holographic light scattering angular spectroscopy

We utilize Fourier-holographic light scattering angular spectroscopy to record the spatially resolved complex angular scattering spectra of samples over wide fields of view in a single or few image captures. Without resolving individual scatterers, we are able to generate spatially-resolved particle size maps for samples composed of spherical scatterers, by comparing generated spectra with Mie-theory predictions. We present a theoretical discussion of the fundamental principles of our technique and, in addition to the sphere samples, apply it experimentally to a biological sample which comprises red blood cells. Our method could possibly represent an efficient alternative to the time-consuming and laborious conventional procedure in light microscopy of image tiling and inspection, for the characterization of microscopic morphology over wide fields of view.

AqpZ-mediated water permeability in Escherichia coli measured by stopped-flow spectroscopy

We report that the water permeability of wild-type Escherichia coli during exponential growth is comparable to that of an aqpZ disruption mutant. In contrast, an increase in permeability is observed for the wild type at the onset of the stationary stage with no significant corresponding change in the permeability of the mutant.