Dissolved Inorganic Carbon-Accumulating Complexes from Autotrophic Bacteria from Extreme Environments.

In nature, concentrations of dissolved inorganic carbon (DIC; CO2 + HCO3- + CO32-) can be low, and autotrophic organisms adapt with a variety of mechanisms to elevate intracellular DIC concentrations to enhance CO2 fixation. Such mechanisms have been well studied in Cyanobacteria, but much remains to be learned about their activity in other phyla. Novel multisubunit membrane-spanning complexes capable of elevating intracellular DIC were recently described in three species of bacteria. Homologs of these complexes are distributed among 17 phyla in Bacteria and Archaea and are predicted to consist of one, two, or three subunits. To determine whether DIC accumulation is a shared feature of these diverse complexes, seven of them, representative of organisms from four phyla, from a variety of habitats, and with three different subunit configurations, were chosen for study. A high-CO2-requiring, carbonic anhydrase-deficient (ΔyadF ΔcynT) strain of Escherichia coli Lemo21(DE3), which could be rescued via elevated intracellular DIC concentrations, was created for heterologous expression and characterization of the complexes. Expression of all seven complexes rescued the ability of E. coli Lemo21(DE3) ΔyadF ΔcynT to grow under low-CO2 conditions, and six of the seven generated measurably elevated intracellular DIC concentrations when their expression was induced. For complexes consisting of two or three subunits, all subunits were necessary for DIC accumulation. Isotopic disequilibrium experiments clarified that CO2 was the substrate for these complexes. In addition, the presence of an ionophore prevented the accumulation of intracellular DIC, suggesting that these complexes may couple proton potential to DIC accumulation. IMPORTANCE To facilitate the synthesis of biomass from CO2, autotrophic organisms use a variety of mechanisms to increase intracellular DIC concentrations. A novel type of multisubunit complex has recently been described, which has been shown to generate measurably elevated intracellular DIC concentrations in three species of bacteria, raising the question of whether these complexes share this capability across the 17 phyla of Bacteria and Archaea where they are found. This study shows that DIC accumulation is a trait shared by complexes with various subunit structures, from organisms with diverse physiologies and taxonomies, suggesting that this trait is universal among them. Successful expression in E. coli suggests the possibility of their expression in engineered organisms synthesizing compounds of industrial importance from CO2.

The Arkansas River Valley Rural Health Cooperative: building a three-pronged approach to improved health and health care.

This paper describes the Arkansas River Valley Rural Health Cooperative (ARVRHC), one of the Arkansas networks jump-started with support from the Southern Rural Access Program (SRAP). The initial goal of the network was to develop a subsidized health insurance program to provide affordable medical services for the uninsured population (23%) in the 3-county service area. When planning efforts called for the network to address broader needs, the ARVRHC crafted a more comprehensive 3-pronged program model consisting of 3 interrelated programs: (1) the Health Care Access Program (HCAP), (2) the Health Education and Disease Management Program (HE&DMP), and 3) the Information and Assistance Program (I&AP). The HCAP is designed to address the financial barriers to access through a community-based health plan. The HE&DMP focuses on improving the health of individuals through education, counseling, and preventive care. The I&AP links low-income families to existing public assistance programs (e.g., Medicaid) and social support services. The Prescription Drug Assistance Program is one of the I&AP programs that helps individuals without prescription coverage obtain drugs at no cost. A key lesson learned is the importance of combining technical assistance with funding. The ARVRHC has been successful in leveraging funding, having received over $1.7 million in grant funds since 1999. A critical challenge facing the network today is the need for ongoing subsidy funding. Proposed legislation for a federal demonstration of the HCAP and similar programs would enable full implementation and evaluation of this model.