Not understanding is central to scientific work: what scientists do is learn about the natural world, which involves seeking out what they do not know. In classrooms, however, the position of not‐understanding is generally a liability; confusion is an unfortunate condition to resolve as quickly as possible, or to conceal. In this article, we argue that students' public displays of uncertainty or confusion can be pivotal contributions to the classroom dynamics in initiating and sustaining a class's science inquiry. We present this as a central finding from a cross‐case analysis of eight episodes of students' scientific engagement, drawing on literature on framing to show how participants positioned themselves as not‐understanding and how that was consequential for the class's scientific engagement. We show how participants enacted this positioning by asking questions or expressing uncertainty around a phenomenon or model. We then analyze how participants' displays of not‐understanding shaped the conceptual, epistemic, and social aspects of classroom activity. We present two cases in detail: one in which a student's positioning helped initiate the class's scientific engagement and another in which it helped sustain it. We argue that this work motivates considering how to help students learn to embrace and value the role of expressing one's confusion in science.

The work of physics learners at all levels revolves around problems. Physics education research has inspired attention to the forms of these problems, whether conceptual or algorithmic, closed or open response, well or ill structured. Meanwhile, it has been the work of curriculum developers and instructors to develop these problems. Physics education research has supported these efforts with studies of students problem solving and the effects of different kinds of problems on learning. In this article we argue, first, that developing problems is central to the discipline of physics. It involves noticing a gap of understanding, identifying and articulating its precise nature, and motivating a community of its existence and significance. We refer to this activity as problematizing, and we show its importance by drawing from writings in physics and philosophy of science. Second, we argue that students, from elementary age to adults, can problematize as part of their engaging in scientific inquiry. We present four cases, drawing from episodes vetted by a panel of collaborating faculty in science departments as clear instances of students doing science. Although neither we nor the scientists had problematizing in mind when screening cases, we found it across the episodes. We close with implications for instruction, including the value of helping students recognize and manage the situation of being confused but not yet having a clear question, and implications for research, including the need to build problematizing into our models of learning.

Despite recent advances in our understanding of how Helicobacter pylori causes disease, the factors that allow this pathogen to persist in the stomach have not yet been fully characterized. To identify new virulence factors in H. pylori, we generated low-infectivity variants of a mouse-colonizing H. pylori strain using the classical technique of in vitro attenuation. The resulting variants and their highly infectious progenitor bacteria were then analyzed by global gene expression profiling. The gene expression levels of five open reading frames (ORFs) were significantly reduced in low-infectivity variants, with the most significant changes observed for ORFs HP1583 and HP1582. These ORFs were annotated as encoding homologs of the Escherichia coli vitamin B6 biosynthesis enzymes PdxA and PdxJ. Functional complementation studies with E. coli confirmed H. pylori PdxA and PdxJ to be bona fide homologs of vitamin B6 biosynthesis enzymes. Importantly, H. pylori PdxA was required for optimal growth in vitro and was shown to be essential for chronic colonization in mice. In addition to having a well-known metabolic role, vitamin B6 is necessary for the synthesis of glycosylated flagella and for flagellum-based motility in H. pylori. Thus, for the first time, we identify vitamin B6 biosynthesis enzymes as novel virulence factors in bacteria. Interestingly, pdxA and pdxJ orthologs are present in a number of human pathogens, but not in mammalian cells. We therefore propose that PdxA/J enzymes may represent ideal candidates for therapeutic targets against bacterial pathogens.

The Next Generation Science Standards states that “science begins with a question.” (NGSS Lead States [2013] Next generation science standards: For states, by states. Washington, DC: National Academies Press). Yet scientific inquiry among students and scientists alike often begins without a clear question. In this article, we describe problematizing as the intellectual work to identify, articulate, and motivate a gap or inconsistency in a community's or one's own current understanding. We describe problematizing in professional science to show how it is central to disciplinary practices of science. We then present an episode of fifth‐grade students’ problematizing, as a detailed illustration of the construct and as an example of evidence that students can engage in this work. Through these two approaches, we show problematizing is central to the disciplinary practice of science and that it is a part of students’ engagement. We further show that it is missing from the description of practices in the Next Generation Science Standards. Lastly, we make recommendations for research on student problematizing, for revisions to the Standards, and for instruction.

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