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Chloroplast function is orchestrated by the organelle's intricate architecture. By combining cryo-focused ion beam milling of vitreous Chlamydomonas cells with cryo-electron tomography, we acquired three-dimensional structures of the chloroplast in its native state within the cell. Chloroplast envelope inner membrane invaginations were frequently found in close association with thylakoid tips, and the tips of multiple thylakoid stacks converged at dynamic sites on the chloroplast envelope, implicating lipid transport in thylakoid biogenesis. Subtomogram averaging and nearest neighbor analysis revealed that RuBisCO complexes were hexagonally packed within the pyrenoid, with similar to 15 nm between their centers. Thylakoid stacks and the pyrenoid were connected by cylindrical pyrenoid tubules, physically bridging the sites of light-dependent photosynthesis and light-independent carbon fixation. Multiple parallel minitubules were bundled within each pyrenoid tubule, possibly serving as conduits for the targeted one-dimensional diffusion of small molecules such as ATP and sugars between the chloroplast stroma and the pyrenoid matrix

ORAL HEALTH CURRICULUM IN ACCREDITED DIETETICS PROGRAMS

The Accreditation Council for Education in Nutrition and Dietetics (ACEND) Accreditation Standards for Didactic Programs in Dietetics (DPD) outlines the required curricular topics and student knowledge competencies for accredited programs. Subjects that must be covered in DPD programs include medical nutrition therapy and the Nutrition Care Process; principles of food science, food safety, and food service management; and the roles of environment, food, nutrition, and lifestyle choices in health promotion and disease prevention.1 There is no current requirement to specifically cover oral health in DPD programs; however, programs are given discretion to integrate relevant topics into their curriculum above and beyond the subjects required in the standards. A survey was designed to learn more about the curriculum dietetics students receive and to understand whether, when, and how oral health and hygiene concepts are addressed in ACEND accredited dietetics programs. The survey was emailed to dietetics educators, preceptors, support staff, and program directors of ACEND accredited programs and remained open for a period of two weeks. More than half of the respondents reported that they currently cover oral health topics in their curriculum and that nearly ninety percent feel that it is important for future dietetics professionals to be knowledgeable about oral health and hygiene topics. I argue that oral health and hygiene are vital topics that all nutrition students should be knowledgeable about and should be implemented in the knowledge competencies for ACEND accredited DPD programs

Membrane Curvature Induced by Aggregates of LH2s and Monomeric LH1s

The photosynthetic apparatus of purple bacteria is contained within organelles called chromatophores, which form as extensions of the cytoplasmic membrane. The shape of these chromatophores can be spherical (as in Rhodobacter sphaeroides), lamellar (as in Rhodopseudomonas acidophila and Phaeospirillum molischianum), or tubular (as in certain Rb. sphaeroides mutants). Chromatophore shape is thought to be influenced by the integral membrane proteins Light Harvesting Complexes I and II (LH1 and LH2), which pack tightly together in the chromatophore. It has been suggested that the shape of LH2, together with its close packing in the membrane, induces membrane curvature. The mechanism of LH2-induced curvature is explored via molecular dynamics simulations of multiple LH2 complexes in a membrane patch. LH2s from three species—Rb. sphaeroides, Rps. acidophila, and Phsp. molischianum—were simulated in different packing arrangements. In each case, the LH2s pack together and tilt with respect to neighboring LH2s in a way that produces an overall curvature. This curvature appears to be driven by a combination of LH2's shape and electrostatic forces that are modulated by the presence of well-conserved cytoplasmic charged residues, the removal of which inhibits LH2 curvature. The interaction of LH2s and an LH1 monomer is also explored, and it suggests that curvature is diminished by the presence of LH1 monomers. The implications of our results for chromatophore shape are discussed