Diverse bacterial species possess the ability to produce the auxin phytohormone indole-3-acetic acid (IAA). Different biosynthesis pathways have been identified and redundancy for IAA biosynthesis is widespread among plant-associated bacteria. Interactions between IAA-producing bacteria and plants lead to diverse outcomes on the plant side, varying from pathogenesis to phytostimulation. Reviewing the role of bacterial IAA in different microorganism–plant interactions highlights the fact that bacteria use this phytohormone to interact with plants as part of their colonization strategy, including phytostimulation and circumvention of basal plant defense mechanisms. Moreover, several recent reports indicate that IAA can also be a signaling molecule in bacteria and therefore can have a direct effect on bacterial physiology. This review discusses past and recent data, and emerging views on IAA, a well-known phytohormone, as a microbial metabolic and signaling molecule.

Indole-3-acetic acid in microbial and microorganism-plant signaling.

The known facts about nucleation phenomena in liquid metals are interpreted satisfactorily on the basis of the critical size and interfacial energy concepts. In large continuous masses nucleation is almost always catalyzed by extraneous interfaces. However, in very small droplets the probability that a catalytic inclusion is present is so much less that their minimum nucleation frequencies are reproducible and form a consistent set of values.Interfacial energies, σ, between crystal nuclei and the corresponding liquids have been calculated from nucleation frequencies of small droplets on the basis of the theory of homogeneous nucleation. Energies of interfaces, σg, one atom thick and containing N atoms were calculated from the σ's. The ratio of σg to the gram atomic heat of fusion, ΔHf, was approximately 0.45 for most metals but ∼0.32 for H2O, Bi, Sb, and Ge.The effect of relative complexity of crystal structure upon the supercooling behavior of pure metals apparently is a reflection of its effect upon ΔHf.

Formation of Crystal Nuclei in Liquid Metals

The variation of surface tension of solutions with time has in some cases, where the change is over within a few seconds or less, been explained on the basis of diffusion. This paper attempts a rigorous mathematical analysis of the role that diffusion might play in such time‐effects. The limitations of diffusion theories which have been proposed previously are discussed. A general theory of diffusion to the surface is derived, which allows for back‐diffusion and which makes no special assumptions of a physical nature. It is possible to use Fick's equation to calculate the total amount of solute which diffuses from a semi‐infinite bulk solution into the surface if the concentration immediately under the surface is known at various times throughout the process. It is shown how the latter information may be deduced from the variation of surface tension with time together with final equilibrium values of surface tension. The methods of this theory are applied to analyze recent data on time‐effects of short duration. It is concluded that even in cases where the variation of the surface tension is over in less than a second the rate‐determining process is not diffusion. Even for these very rapid changes one is therefore led to assume the existence of an activation barrier which determines the rate of adsorption.

Time‐Dependence of Boundary Tensions of Solutions I. The Role of Diffusion in Time‐Effects

This chapter highlights a variety of techniques that are commonly used to measure contact angles, including the conventional telescope-goniometer method, the Wilhelmy balance method, and the more recently developed drop-shape analysis methods. The various applications and limitations of these techniques are described. Notably, studies of ultrasmall droplets on solid surfaces allow wetting theories to be tested down to the nanometer scale, bringing new insight to contact angle phenomena and wetting behavior.

https://www.springer.com/cda/content/document/cda_downloaddocument/9783642342424-c1.pdf?SGWID=0-0-45-1368817-p174704744

Contact Angle and Wetting Properties

The design of advanced, nanostructured materials at the molecular level is of tremendous interest for the scientific and engineering communities because of the broad application of these materials in the biomedical field. Among the available techniques, the layer-by-layer assembly method introduced by Decher and co-workers in 1992 has attracted extensive attention because it possesses extraordinary advantages for biomedical applications: ease of preparation, versatility, capability of incorporating high loadings of different types of biomolecules in the films, fine control over the materials’ structure, and robustness of the products under ambient and physiological conditions. In this context, a systematic review of current research on biomedical applications of layer-by-layer assembly is presented. The structure and bioactivity of biomolecules in thin films fabricated by layer-by-layer assembly are introduced. The applications of layer-bylayer assembly in biomimetics, biosensors, drug delivery, protein and cell adhesion, mediation of cellular functions, and implantable materials are addressed. Future developments in the field of biomedical applications of layer-by-layer assembly are also discussed.

/pdf/biomedical-applications-of-layer-by-layer-assembly-from-1i20r8iian.pdf

Vincent J. Schaefer

Papers

Activities of Urease and Pepsin Monolayers

The Effect of Dissolved Salts on Insoluble Monolayers

The Production of Ice Crystals in a Cloud of Supercooled Water Droplets

Rates of evaporation of water through compressed monolayers on water

Composition of Fatty Acid Films on Water Containing Calcium or Barium Salts