Differential depolymerization mechanisms of pectate lyases secreted by Erwinia chrysanthemi EC16.

The four pectate lyases (EC 4.2.2.2) secreted by Erwinia chrysanthemi EC16 have been individually produced as recombinant enzymes in Escherichia coli. Oligogalacturonates formed from polygalacturonic acid during reactions catalyzed by each enzyme have been determined by high-performance liquid chromatography analysis. PLa catalyzes the formation of a series of oligomers ranging from dimer to dodecamer through a random endolytic depolarization mechanism. PLb and PLc are trimer- and tetramer-generating enzymes with an identical combination of endolytic and exolytic mechanisms. PLe catalyzes a nonrandom endolytic depolymerization with the formation of dimer as the predominant product. The pectate lyases secreted by E. chrysanthemi EC16 represent a battery of enzymes with three distinct approaches to the depolymerization of plant cell walls.     

Efficient fermentation of Pinus sp. acid hydrolysates by an ethanologenic strain of Escherichia coli.

Process conditions for the acid hydrolysis of pine hemicellulose and cellulose have been described which provide a biocompatible sugar solution. By using an improved strain of recombinant Escherichia coli, strain KO11, hydrolysates supplemented with yeast extract and tryptone nutrients were converted to ethanol with an efficiency of 85% to over 100% on the basis of monomer sugar content (approximately 72 g/liter) and with the production of 35 g of ethanol per liter in 48 h. In the process described, approximately 347 liters of ethanol could be produced per dry metric ton of lignocellulose.     

Controlled trial of supervised exercise training in chronic bronchitis.

In a controlled trial of exercise retraining in patients with severe chronic bronchitis, 33 subjects were followed for a mean period of 10.3 months. The exercise programme was supervised once a week, and daily training comprised a 12-minute walk and simple stair climbing exercises. The subjects in the exercise group showed a highly significant improvement in their walking distance, attaining a maximum increase of 24% after eight to 12 months. There was also considerable subjective improvement. The control group did not improve. No significant changes in cardiorespiratory function or muscle strength were seen. Simple exercise rehabilitation is of benefit to patients with disabling obstructive lung disease.     

Factors controlling phytoplankton primary productivity in Byram Lake,Mt. Kisco,N.Y., summer 1977

Phytoplankton productivity was measured in Byram Lake Reservoir during summer 1977. Depth integrated productivity (0–5 gC m^{– 2} d^–1) increased with station depth, which together with visibility measurements indicated that light did not limit deep station productivity (C1 and S2). Macrophytes at station C5 (shallow) reduced the euphotic zone to 0 in June.On a unit depth basis, C5 was the most productive station. Apparently changes in macrophyte growth, regulated by light and temperature, controlled phytoplankton production. At C1, productivity was related to levels of different nutrients at different depths, the thermocline influencing nutrient availability at mid-depth. At S2, NH₃-N controlled mid-depth productivity. Surface and mid-depth productivity appeared influenced by factors not measured in this study.     

Inhibition of unsaturated fatty acid synthesis in escherichia coli by the antibiotic cerulenin.

Low concentrations of cerulenin inhibit the growth of Escherichia coli by selectively blocking unsaturated fatty acid synthesis. This inhibition was relieved by unsaturated fatty acid supplements alone but not by saturated fatty acid supplements. The utilization of exogenous unsaturated fatty acids to sustain growth in the presence of cerulenin was confirmed by the analysis of bulk lipid composition. The effects of cerulenin on fatty acid synthesis were examined in vivo by pulse labeling with [14C]acetate and in vitro using [14C]malonyl-coenzyme A. In both cases, unsaturated fatty acid synthesis was inhibited by low concentrations of cerulenin with a stimulation of saturated fatty acid synthesis. Using mutant strains deficient in fatty acid synthesis, the effects of cerulenin on beta-ketoacyl-[acyl-carrier-protein] synthetases I and II were examined. Our results indicate that beta-ketoacyl-[acyl-carrier-protein] synthetase I is more sensitive to inhibition by cerulenin than beta-ketoacyl-[acyl-carrier-protein] synthetase II.     

The immune response of brown trout (Salmo trutta L.) to injection with soluble antigens.

The immune response of brown trout (Salmo trutta) to horse serum and keyhole limpet haemocyanin was studied. Intraperitoneal and intramuscular injections were used, with and without adjuvant, in 209 fish. Complement-fixing antibodies (CFA) and precipitins were produced to both antigens. CFA were detected after 8 days to haemocyanin and after 13 days to horse serum. Maximum CFA titres to a single intraperitoneal injection of horse serum or haemocyanin were reached at 44 and 43-46 days respectively. Precipitins to a single injection of haemocyanin given intraperitoneally were detected after 19 days using gel diffusion. Similarly using the intramuscular route they were detected after 22 days. However, using counter-current electrophoresis, precipitins were detected after 8 days by the intraperitoneal route and after 9 days by the intramuscular. Precipitins to horse serum given intraperitoneally were demonstrated after 22 days by both gel diffusion and counter-current electrophoresis. Fish given 2 intraperitoneal injections of haemocyanin in adjuvant reached maximum CFA titres after 55 days; a 3rd injection on day 56 did not produce a marked increase in titre. Fish given intramuscular injections of haemocyanin in adjuvant showed maximum CFA titres at day 43. After a 3rd injection on day 56, maximum CFA titres were reached between days 92 and 106. Intramuscular injections gave significantly higher titres than those given by the intraperitoneal route. Some fish which showed no precipitins by gel diffusion were positive by counter-current electrophoresis. Precipitating antibodies to haemocyanin migrating in the beta2-gamma1 region were detected by immuno-electrophoresis.     

Globin synthesis in fibroblasts fused with erythroblasts. I. Avian fibroblasts.

Heterokaryons of chick embryo erythroblasts fused with other avian fibroblasts were studied with regard to globin production. After the incorporation of radioactive amino acids, soluble proteins were separated on SDS-urea polyacrylamide gels. There was a striking increase in radioactivity above background in the globin region from lysates of fusion cultures when compared with fibroblast cultures. This was maximal at 24 hours after fusion, and then declined. Electrophoresis on acid-or alkaline-urea gels further identified the material as globin chains. Tryptic digestion and fingerprinting revealed methionine-labeled peptides characteristic of chick embryo erythroblast globin. An apparent stimulation of globin chain synthesis by heterokaryons compared to erythroblasts was found to be due to a difference in the specific activity of the precursor amino acid pools in the different cell types.     

When should we expect early bursts of trait evolution in comparative data? Predictions from an evolutionary food web model

Conceptual models of adaptive radiation predict that competitive interactions among species will result in an early burst of speciation and trait evolution followed by a slowdown in diversification rates. Empirical studies often show early accumulation of lineages in phylogenetic trees, but usually fail to detect early bursts of phenotypic evolution. We use an evolutionary simulation model to assemble food webs through adaptive radiation, and examine patterns in the resulting phylogenetic trees and species' traits (body size and trophic position). We find that when foraging trade-offs result in food webs where all species occupy integer trophic levels, lineage diversity and trait disparity are concentrated early in the tree, consistent with the early burst model. In contrast, in food webs in which many omnivorous species feed at multiple trophic levels, high levels of turnover of species' identities and traits tend to eliminate the early burst signal. These results suggest testable predictions about how the niche structure of ecological communities may be reflected by macroevolutionary patterns.