RESUMEN
Misconceptions, also known as alternate conceptions, about key concepts often hinder the ability of students to learn new knowledge. Concept inventories (CIs) are designed to assess students' understanding of key concepts, especially those prone to misconceptions. Two-tiered CIs include prompts that ask students to explain the logic behind their answer choice. Such two-tiered CIs afford an opportunity for faculty to explore the student thinking behind the common misconceptions represented by their choice of a distractor. In this study, we specifically sought to probe the misconceptions that students hold prior to beginning an introductory microbiology course (i.e., preconceptions). Faculty-learning communities at two research-intensive universities used the validated Host-Pathogen Interaction Concept Inventory (HPI-CI) to reveal student preconceptions. Our method of deep analysis involved communal review and discussion of students' explanations for their CI answer choice. This approach provided insight valuable for curriculum development. Here the process is illustrated using one question from the HPI-CI related to the important topic of antibiotic resistance. The frequencies with which students chose particular multiple-choice responses for this question were highly correlated between institutions, implying common underlying misconceptions. Examination of student explanations using our analysis approach, coupled with group discussions within and between institutions, revealed patterns in student thinking to the participating faculty. Similar application of a two-tiered concept inventory by general microbiology instructors, either individually or in groups, at other institutions will allow them to better understand student thinking related to key concepts in their curriculum.
RESUMEN
To assess the importance of two separate antioxidant activities in Helicobacter pylori, we tested the abilities of strains with mutations in either tpx (encoding thiolperoxidase) or ahpC (encoding alkyl hydroperoxide reductase [AhpC]) to colonize the stomachs of mice. The tpx strain was clearly more sensitive than the parent strain to both oxygen and cumene hydroperoxide. The strain colonized only 5% of the inoculated mice. Two different classes of oxygen-sensitive ahpC mutants in the type strain (ATCC 43504) were recently described (A. A. Olczak, J. W. Olson, and R. J. Maier, J. Bacteriol. 184:3186-3193, 2002). The same two classes of mutants were recovered upon ahpC mutagenesis of the mouse-adapted strain, SS1. Neither of these mutants was able to colonize mouse stomachs, whereas 78% of the mice inoculated with the parent strain became H. pylori positive.
