Subcellular Localization of Enzymes of Carbon and Nitrogen Metabolism in Nodules of Medicago sativa

Alfalfa (Medicago sativa L. cv. Vernal) nodules were separatedinto host plant fractions and fractions of rhizobial originby differential centrifugation and sedimentation equilibriumcentrifugation. Both NAD- and NADP-linked isocitrate dehydrogenase(70%, 90%) and glutamate dehydrogenase activities (90%, 83%)were located primarily (percent total nodule activity) in thefractions of plant origin and their specific activities werehighest in the fractions of plant origin. More than 50% of thenodules' total activity of both glutamine synthetase and NAD-glutamatesynthase and greater than 90% of the total glutamate oxaloacetatetransaminase activity was located in plant fractions. However,the fractions of rhizobial origin had the highest specific activitiesof glutamine synthetase and glutamate synthase. (Received September 5, 1981; Accepted December 7, 1981)     

The Escherichia coli dnaW mutation is an allele of the adk gene

Summary A dnaW mutant, isolated on the basis of inability to effect conjugal DNA transfer at high temperature, has been shown by complementation and enzyme assay to be defective in the adk (adenylate kinase; EC 2.7.4.3) locus. The adk mutant, known to have reduced ATP concentration at the nonpermissive temperature (Cousin and Belaich 1966), was used to demonstrate a donor energy requirement for stable aggregate formation and for chromosome transfer in conjugation.     

Inspiratory pressure generation: comparison of subjects with COPD and age-matched normals

We continuously monitored esophageal (Pes) and gastric (Pga) pressures and used these measurements in a three-component model to estimate instantaneous diaphragmatic (DIA), inspiratory accessory muscle (IAM), and postexpiratory recoil (PER) pressures at various times during inspiration. We validated our model both by volume-pressure relationships of the respiratory system (Vrc-Pga and Vab-Pga, where Vrc and Vab are the rib cage and abdominal volumes, respectively) as well as electromyography of the respiratory muscles. Measurements were carried out at rest and during graded treadmill exercise in 11 subjects with chronic obstructive pulmonary disease (COPDs) and 8 age-matched normal subjects (AMNs). AMNs were 59 +/- 2 (SE) yr and had a forced expiratory volume at 1 s (FEV1.0) of 3.6 +/- 0.2 liters; COPDs were 66 +/- 2 yr and had a FEV1.0 of 1.0 +/- 0.1 liters. We noted the following. At rest, both AMNs and COPDs exhibited an increasing DIA pressure (PDIA) across inspiratory time (TI) at rest. As expired minute ventilation increased with exercise intensity, AMNs continued to maintain this PDIA ramp across inspiration; in contrast, COPDs exhibited higher values of PDIA during the first half of TI than during the second half. At all intensities of exercise, COPDs exhibited higher IAM and PER pressures than the AMNs.     

IgE-induced release of a platelet-activating factor from rabbit lung.

Sensitized rabbit lung fragments release a platelet-activating factor (PAFL) after challenge with specific antigen or monospecific antibody to rabbit IgE. This release requires calcium and is less evident in lungs from rabbits producing IgG as well as IgE antibody. The PAFL released from lung stimulates the secretion of serotonin from washed rabbit platelets. PAFL is distinguishable from ADP or thrombin and has properties similar to PAF derived from basophils (PAFB). It is not, however, identical to PAFB since rabbit platelets specifically desenitized to PAF still respond by releasing serotonin if stimulated with PAFL.     

In Silico Metabolic Design of Two‐Strain Biofilm Systems Predicts Enhanced Biomass Production and Biochemical Synthesis

Engineered biofilm consortia have the potential to solve important biotechnological problems that have proved difficult for monoculture biofilms and planktonic consortia, such as conversion of lignocellulosic material to useful biochemicals. While considerable experimental progress has been reported for engineering and characterizing biofilm consortia, the field still lacks in silico tools for simulation, design, and optimization of stable, robust, and productive designed consortia. We developed biofilm consortia metabolic models for two coculture systems centered around the ecological design motif of a primary cell type that utilizes a supplied electron donor and secretes acetate as a byproduct and a secondary cell type that consumes the acetate, relieving byproduct inhibition on the primary cell type and enhancing overall system biomass. The models presented in this paper predict that distinct metabolic niches for the two cell types could be established by supplying electron donors and acceptors at opposite ends of the biofilm and that acetate consumption by the secondary cell type could increase total biomass accumulation and the synthesis of valuable biochemicals, such as isobutanol, by the primary cell type. System tunability is enhanced when each cell type is supplied with a unique terminal electron acceptor at opposite ends of the biofilm rather than competing for a common electron acceptor. Our model provides good qualitative agreement with data for a synthetic Escherichia coli coculture system, suggesting that the proposed design rules may have wide applicability to engineered biofilm consortia.