Ursinus College Bulletin Vol. 8, No. 2

A digitized copy of the November 1891 Ursinus College Bulletin.https://digitalcommons.ursinus.edu/ucbulletin/1069/thumbnail.jp

Ursinus College Bulletin Vol. 8, No. 1

A digitized copy of the October 1891 Ursinus College Bulletin.https://digitalcommons.ursinus.edu/ucbulletin/1068/thumbnail.jp

Nanopods: A New Bacterial Structure and Mechanism for Deployment of Outer Membrane Vesicles

Background: Bacterial outer membrane vesicles (OMV) are packets of periplasmic material that, via the proteins and other molecules they contain, project metabolic function into the environment. While OMV production is widespread in proteobacteria, they have been extensively studied only in pathogens, which inhabit fully hydrated environments. However, many (arguably most) bacterial habitats, such as soil, are only partially hydrated. In the latter, water is characteristically distributed as films on soil particles that are, on average thinner, than are typical OMV (ca. ≤10 nm water film vs. 20 to >200 nm OMV;). Methodology/Principal Findings: We have identified a new bacterial surface structure, termed a "nanopod", that is a conduit for projecting OMV significant distances (e.g., ≥6 µm) from the cell. Electron cryotomography was used to determine nanopod three-dimensional structure, which revealed chains of vesicles within an undulating, tubular element. By using immunoelectron microscopy, proteomics, heterologous expression and mutagenesis, the tubes were determined to be an assembly of a surface layer protein (NpdA), and the interior structures identified as OMV. Specific metabolic function(s) for nanopods produced by Delftia sp. Cs1-4 are not yet known. However, a connection with phenanthrene degradation is a possibility since nanopod formation was induced by growth on phenanthrene. Orthologs of NpdA were identified in three other genera of the Comamonadaceae family, and all were experimentally verified to form nanopods. Conclusions/Significance: Nanopods are new bacterial organelles, and establish a new paradigm in the mechanisms by which bacteria effect long-distance interactions with their environment. Specifically, they create a pathway through which cells can effectively deploy OMV, and the biological activity these transmit, in a diffusion-independent manner. Nanopods would thus allow environmental bacteria to expand their metabolic sphere of influence in a manner previously unknown for these organisms

Model Systems to Study the Chronic, Polymicrobial Infections in Cystic Fibrosis: Current Approaches and Exploring Future Directions

A recent workshop titled “Developing Models to Study Polymicrobial Infections,” sponsored by the Dartmouth Cystic Fibrosis Center (DartCF), explored the development of new models to study the polymicrobial infections associated with the airways of persons with cystic fibrosis (CF). The workshop gathered 351 investigators over two virtual sessions. Here, we present the findings of this workshop, summarize some of the challenges involved with developing such models, and suggest three frameworks to tackle this complex problem. The frameworks proposed here, we believe, could be generally useful in developing new model systems for other infectious diseases. Developing and validating new approaches to study the complex polymicrobial communities in the CF airway could open windows to new therapeutics to treat these recalcitrant infections, as well as uncovering organizing principles applicable to chronic polymicrobial infections more generally

Disagreement as a Measure of Uncertainty.

This paper presents evidence from the Livingston survey of inflation forecasts that forecaster disagreement provides a useful measure of forecast uncertainty. The evidence is analogous to the evidence for ARCH effects. Disagreement at the time of the forecast has as large positive effect on the conditional variance of the subsequent forecast error. As a conditioning variable, forecaster disagreement dominates ARCH for both survey errors and the error terms in Robert Engle's quarterly model of inflation. As measured by the resulting conditional variances, disagreement indicates larger and more variable levels of uncertainty for the 1946-94 period. Copyright 1996 by Ohio State University Press.

Inflation and Relative Price Variability: Parks' Study Reexamined.

The authors show that Richard W. Parks' (1978) widely cited evidence on the correlation between the rate of inflation and the variability of relative prices in the United States during 1948-75 depends on one observation, 1974. When the sample period is extended through 1989, the correlation depends on the observations for 1974 and 1980. Since both are years of large oil price shocks, the authors make the case that causation is likely to run from these shocks to relative price variability and inflation with accommodating monetary policy playing a role. Copyright 1993 by Ohio State University Press.