The field of microbiology has traditionally been concerned with and focused on studies at the population level. Information on how cells respond to their environment, interact with each other, or undergo complex processes such as cellular differentiation or gene expression has been obtained mostly by inference from population-level data. Individual microorganisms, even those in supposedly “clonal” populations, may differ widely from each other in terms of their genetic composition, physiology, biochemistry, or behavior. This genetic and phenotypic heterogeneity has important practical consequences for a number of human interests, including antibiotic or biocide resistance, the productivity and stability of industrial fermentations, the efficacy of food preservatives, and the potential of pathogens to cause disease. New appreciation of the importance of cellular heterogeneity, coupled with recent advances in technology, has driven the development of new tools and techniques for the study of individual microbial cells. Because observations made at the single-cell level are not subject to the “averaging” effects characteristic of bulk-phase, population-level methods, they offer the unique capacity to observe discrete microbiological phenomena unavailable using traditional approaches. As a result, scientists have been able to characterize microorganisms, their activities, and their interactions at unprecedented levels of detail

The sesquiterpenoids nerolidol, farnesol, bisabolol, and apritone were investigated for their abilities to enhance bacterial permeability and susceptibility to exogenous antimicrobial compounds. Initially, it was observed by flow cytometry that these sesquiterpenoids promoted the intracellular accumulation of the membrane-impermeant nucleic acid stain ethidium bromide by live cells of Lactobacillus fermentum, suggesting that enhanced permeability resulted from disruption of the cytoplasmic membrane. The ability of these sesquiterpenoids to increase bacterial susceptibility to a number of clinically important antibiotics was then investigated. In disk diffusion assays, treatment with low concentrations (0.5 to 2 mM) of nerolidol, bisabolol, or apritone enhanced the susceptibility of Staphylococcus aureus to ciprofloxacin, clindamycin, erythromycin, gentamicin, tetracycline, and vancomycin. Nerolidol and farnesol also sensitized Escherichia coli to polymyxin B. Our results indicate the practical utility of sensitizing bacteria to antimicrobials with sesquiterpenoids that have traditionally been used as flavorants and aroma compounds in the food and perfume industries.

Advances in molecular technologies and automated instrumentation have provided many opportunities for improved detection and identification of microorganisms; however, the upstream sample preparation steps needed to apply these advances to foods have not been adequately researched or developed. Thus, the extent to which these advances have improved food microbiology has been limited. The purpose of this review is to present the current state of sample preparation, to identify knowledge gaps and opportunities for improvement, and to recognize the need to support greater research and development efforts on preparative methods in food microbiology. The discussion focuses on the need to push technological developments toward methods that do not rely on enrichment culture. Among the four functional components of microbiological analysis (i.e., sampling, separation, concentration, detection), the separation and concentration components need to be researched more extensively to achieve rapid, direct, and quantitative methods. The usefulness of borrowing concepts of separation and concentration from other disciplines and the need to regard the microorganism as a physicochemical analyte that may be directly extracted from the food matrix are discussed. The development of next-generation systems that holistically integrate sample preparation with rapid, automated detection will require interdisciplinary collaboration and substantially increased funding. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Protection, Vol. 72, No. 8, 2009, Pages 1774-1789 ABSTRACT Advances in molecular technologies and automated instrumentation have provided many opportunities for improved detection and identification of microorganisms; however, the upstream sample preparation steps needed to apply these advances to foods have not been adequately researched or developed. Thus, the extent to which these advances have improved food microbiology has been limited. The purpose of this review is to present the current state of sample preparation, to identify knowledge gaps and opportunities for improvement, and to recognize the need to support greater research and development efforts on preparative methods in food microbiology. The discussion focuses on the need to push technological developments toward methods that do not rely on enrichment culture. Among the four functional components of microbiological analysis (i.e., sampling, separation, concentration, detection), the separation and concentration components need to be researched more extensively to achieve rapid, direct, and quantitative methods. The usefulness of borrowing concepts of separation and concentration from other disciplines and the need to regard the microorganism as a physicochemical analyte that may be directly extracted from the food matrix are discussed. The development of next-generation systems that holistically integrate sample preparation ...

Antibacterial soybean-oil-based cationic polyurethane (PU) coatings have been successfully prepared from five different amino polyols. The structure and hydroxyl functionality of these amino polyols affects the particle morphology, mechanical properties, thermal stability, and antibacterial properties of the resulting coatings. An increase in the hydroxyl functionality of the amino polyols increases the cross-link density, resulting in an increased glass transition temperature and improved mechanical properties. Both the cross-link density and the amount of ammonium cations incorporated into the PU backbone affect the thermal stability of PU films. PUs with the lowest ammonium cation content and highest cross-link density exhibit the best thermal stability. With some strain-specific exceptions, these PUs show good antibacterial properties toward a panel of bacterial pathogens comprised of Listeria monocytogenes NADC 2045, Salmonella typhimurium ATCC 13311 and Salmonella minnesota (S. minnesota) R613. S. minnesota R613 is a "deep rough" mutant lacking a full outer membrane (OM) layer, an important barrier structure in gram-negative bacteria. With wild-type strains, the PU coatings exhibit better antibacterial properties toward the gram-positive Listeria monocytogenes than the gram-negative S. minnesota. However, the coatings have excellent activity against S. minnesota R613, suggesting a protective role for an intact OM against the action of these PUs.

We surveyed a panel of 13 metal nanoparticle (NP) catalysts for their antifungal activities against Candida albicans ATCC 90028. Initial characterization using scanning electron microscopy (SEM) suggested that our ability to detect NP binding to Candida surfaces with this method was impeded by preparation artifacts. As an alternative method for visualizing NP binding, we used an enhanced dark field illumination system (CytoViva) attached to a standard light microscope. When viewed using this system, all NP produced intense optical signals due to resonant light scattering. To assay binding, NP were allowed to interact with C. albicans hyphae and cells in spent RPMI broth for 15 min with gentle inversion, followed by viewing with the CytoViva system. The antifungal efficacy of NP preparations was determined separately using a 24-h broth microdilution test. For single-metal NP, observations of binding at 15 min made via CytoViva corresponded to antifungal efficacy at 24 h, with the most antifungal NP yielding complete coverage of hyphal surfaces. Our work suggests the utility of visual screening using the CytoViva system for rapid, simple and artifact-free viewing of NP-cell interactions in support of antimicrobial screening efforts. This approach provides a quick and accessible alternative to SEM for imaging of NP-cell interactions.