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81.
Protoplast fusion was investigated as a technique for genetically manipulating two lignin-degrading Streptomyces strains, Streptomyces viridosporus T7A and Streptomyces setonii 75Vi2. Four of 19 recombinants tested showed enhanced production of acid-precipitable polymeric lignin (APPL), producing 155 to 264% more APPL from corn stover lignocellulose than was produced by the wild-type S. viridosporus T7A. APPLs are lignin degradation intermediates known to be potentially valuable chemical products produced by bioconversion of lignin with Streptomyces spp. The prospects of utilizing protoplast fusion to construct APPL-overproducing Streptomyces strains was considered especially promising. 相似文献
82.
Familial phenotypic resemblance for six quantitative neuromuscular performance traits is analyzed by path analysis using data from the Mennonite community of Goessel, Kansas. Of the six traits only one, dominant hand strength, shows no evidence of parent-offspring transmission (t2 = 0.001) and only one, trunk flexibility, shows evidence of a high degree of transmissibility (t2 = 0.662). The four remaining traits display low to moderate levels of transmissibility (t2 = 0.073 to t2 = 0.245). A substantial residual sibling resemblance due to shared environmental effects is seen for all six traits. It is suggested that the high heritabilities found for many of these traits by other methods result from the inability of these methods to account for the shared nongenetic effects. 相似文献
83.
Crawford NA Sutton CW Yee BC Johnson TC Carlson DC Buchanan BB 《Archives of microbiology》1984,139(2-3):124-129
Enzymes that are regulated by the ferredoxin/thioredoxin system in chloroplasts — fructose-1,6-bisphosphatase (FBPase), sedoheptulose-1,7-bisphosphatase purified from two different types of photosynthetic prokaryotes (cyanobacteria, purple sulfur bacteria) and tested for a response to thioredoxins. Each of the enzymes from the cyanobacterium Nostoc muscorum, an oxygenic organism known to contain the ferredoxin/thioredoxin system, was activated by thioredoxins that had been reduced either chemically by dithiothreitol or photochemically by reduced ferredoxin and ferredoxin-thioredoxin reductase. Like their chloroplast counterparts, N. muscorum FBPase and SBPase were activated preferentially by reduced thioredoxin f. SBPase was also partially activated by thioredoxin m. PRK, which was present in two regulatory forms in N. muscorum, was activated similarly by thioredoxins f and m. Despite sharing the capacity for regulation by thioredoxins, the cyanobacterial FBPase and SBPase target enzymes differed antigenically from their chloroplast counterparts. The corresponding enzymes from Chromatium vinosum, an anoxygenic photosynthetic purple bacterium found recently to contain the NADP/thioredoxin sytem, differed from both those of cyanobacteria and chloroplasts in showing no response to reduced thioredoxin. Instead, C. vinosum FBPase, SBPase, and PRK activities were regulated by a metabolite effector, 5-AMP. The evidence is in accord with the conclusion that thioredoxins function in regulating the reductive pentose phosphate cycle in oxygenic prokaryotes (cyanobacteria) that contain the ferredoxin/thioredoxin system, but not in anoxygenic prokaryotes (photosynthetic purple bacteria) that contain the NADP/thioredoxin system. In organisms of the latter type, enzyme effectors seem to play a dominant role in regulating photosynthetic carbon dioxide assimilation. 相似文献
84.
85.
Summary A group of chlorophyll deficient mutants (br
s mutants) of Chlamydomonas accumulates protoporphyrin and has poorly developed chloroplast membrane systems (Wang et al. 1974). In order to determine whether a poorly developed chloroplast membrane system is the reason for, or the result of, the inability of the br
s mutants to metabolize protoporphyrin to chlorophyll, a second mutation was selected which restored chlorophyll synthesis in br
s mutants. One such double mutant (br
s-2 g-4) was analyzed. The double mutant br
s-2 g-4 has partially restored chlorophyll synthesis, but has defective photosystem II and photosystem I electron transport as well as abnormal chloroplast ultrastructure. Since these defects are not present in cells carrying only the g-4 mutation, they are presumed to be caused by the br
s-2 mutation. It is concluded that a defect in chloroplast membrane development resulting from the br
s-2 mutation causes an apparent defect in magnesium chelation by protoprophyrin. This is consistant with evidence that chlorophyll biosynthesis from magnesium protoporphyrin to chlorophyll takes place on the chloroplast membranes. 相似文献
86.
Heat inactivation of Mycobacterium avium-Mycobacterium intracellulare complex organisms in aqueous suspension. 总被引:3,自引:3,他引:0
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Isolants from swine and from humans representing serotypes 1, 2, 4, 8, and 10 of the Mycobacterium avium-Mycobacterium intracellulare complex were compared for heat tolerance in aqueous suspension. The most heat-resistant isolant found was a serovar 10 isolated from a human. This isolant was examined further to determine the rate of kill at various temperatures and pH's, the effect of meat protein and fat, and the effect of nitrite. Kill rates were not significant at 60 degrees C or below. Decimal reduction values were 4 min or less at 65 degrees C and 1.5 min or less at 70 degrees C. Kill rates were slightly higher at pH values of 6.5 and 7.0 than at 5.5 or 6.0. the water-soluble fraction of wiener emulsion did not alter kill rates, but the saline-soluble fraction protected the organism somewhat. Fat did not affect the survival of the organisms except to eliminate the protective effect of saline extract when the suspension contained 50% fat. The addition of sodium nitrite to the suspension did not alter the heat sensitivity of the organisms. 相似文献
87.
14C-most-probable-number method for enumeration of active heterotrophic microorganisms in natural waters. 总被引:10,自引:9,他引:1
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A most-probable-number method using 14C-labeled substrates is described for the enumeration of aquatic populations of heterotrophic microorganisms. Natural populations of microorganisms are inoculated into dilution replicates prepared from the natural water from which the organisms originated. The natural water is supplemented with a 14C-labeled compound added so as to approximate a true environmental concentration. 14CO2 evolved by individual replicates is trapped in NaOH and counted by liquid scintillation techniques for use in scoring replicates as positive or negative. Positives (14CO2 evolution) are easily distinguished from negatives (no 14CO2 evolution). The results from a variety of environments using the 14CO2 procedure agreed well with previously described methods, in most instances. The 14C-most-probable-number method described here reduces handling procedures over previously described most-probable-number procedures using 14C-labeled substrates. It also appears to have advantages over other enumeration methods in its attempt to approximate natural conditions more closely. 相似文献
88.
The lignin-degrading actinomycete Streptomyces viridosporus T7A readily degrades the lignin model compound dehydrodivanillin. Four mutants of this organism (produced by irradiation of spores with ultraviolet light) were shown to have lost the ability to catabolize dehydrodivanillin. These mutant strains retained an undiminished ability to degrade Douglas-fir lignin (14C-lignin 14CO2) as compared to the wild-type strain. None of the strains accumulated detectable quantities of dehydrodivanillin when grown on lignocellulose. Thus it appears that the enzymes involved in dehydrodivanillin catabolism are not a part of the streptomycete's system for degrading polymeric lignin. It is concluded that dehydrodivanillin is probably not a relevant model compound for study of lignin polymer degradation by Streptomyces viridosporus. Since many stable mutants completely lacking DHDV-degrading ability were readily obtained, it is suggested that the relevant catabolic enzymes may be encoded on a plasmid.Abbreviations DHDV
dehydrodivanillin 相似文献
89.
D J Back A M Breckenridge F E Crawford K J Cross M L Orme P H Rowe E Smith K Todd 《Life sciences》1978,23(10):1053-1056
87.9% of a given dose of [3H]Norethisterone ([3H]N) and 76.7% of [3H]Ethinyloestradiol ([3H]EE2) were excreted in the bile of male heterozygous Gunn rats in 2 hours Similarly, 86.9% of a given dose [3H]N and 84.0% of [3H]EE2 were excreted in the bile of male homozygous Gunn rats in 2 hours. In both heterozygous and homozygous rats glucuronide conjugates were present. Despite the lesion in UDP-glucuronyltransferase, the homozygous rats is able to conjugate the synthetic steroids apparently normally. 相似文献
90.
Contractions of isolated iris sphincter muscles were measured in response to several free fatty acids, hydroperoxy and hydroxy derivatives of 20:3(n-3), 20:3(n-6) and 20:4, PGH2, and the epoxymethano methano analogs of PGH2. The free acids of prostaglandin precursors elicited comparatively strong contractions, hydroperoxy and hydroxy acids gave intermediate and nonspecific response whereas nonprostaglandin precursor acids elicited little response. PGH2 was 100 to 1000 times more effective than arachidonic acid or the epoxymethano analogs. The latter compounds inhibited the production of contractions by PGH2. These results allow an interpretation that the iris sphincter muscle contains an active thromboxane synthase and receptors for endoperoxide and thromboxane that initiate contraction. 相似文献