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131.
132.
The ability of virulent and avirulent strains ofVibrio vulnificus to overcome iron limitations by using iron bound to iron-binding proteins was examined. While no strains were able to obtain iron from lactoferrin or ferritin when these proteins were not fully saturated with iron, growth was enhanced by the iron-saturated form of these proteins. None of the strains was able to scavange iron from 30% saturated transferrin, but there were strain differences in the ability to obtain iron from the saturated form. The virulent strains were able to compete more efficiently with transferrin when it was fully saturated with iron than were the avirulent strains. 相似文献
133.
The partition of native Escherichia coli -galactosidase and of two different fusion proteins comprised mainly of -galactosidase from E. coli was studied in aqueous two-phase systems composed of polyethylene glycol (PEG) and dextran. These fusions contain an amino-terminal segment from the E. coli outer membrane protein F (OmpF) and a linker peptide. Differences in the partition pattern could be observed for the three enzymes despite their similarity. Decreased polymer concentrations in the phase system increased the partition coefficient for all three -galactosidases. 相似文献
134.
135.
James M. Mason Nita N. Scobie Akihiko H. Yamamoto 《Molecular & general genetics : MGG》1989,215(2):190-199
Summary The mutagen-sensitive mutant mus(1)104
D1
of Drosophila melanogaster maps to a position on the X chromosome very close to the meiotic mutant mei-41
D5
. Both mutants have been characterized as mutagen-sensitive and defective in post-replication repair. In the present report we show by complementation studies that mus(1)104 and mus(1)103 are allelic with mei-41. In addition, two reported alleles of mus(1)104 lie between the mei-41 alleles A10 and D5. The size of the mei-41 locus is estimated to be about 0.1 centimorgans (cM). Because several alleles of mei-41 have been shown to reduce recombination and increase meiotic chromosome loss and nondisjunction, mus(1)104
D1
females were examined for defects in meiosis. Although there was no evidence for reduced recombination on the second chromosome in homozygous mus(1)104
D1
females, heterozygous mus(1)104
D1
/mei-41
>D5
and mus(1)104
D1
/deficiency females showed reduced levels of recombination. However, there was no evidence of an increase in nondijunction in these females.We dedicate this article to the memory of Larry Sandler, who passed away suddenly on February 7, 1987 相似文献
136.
Dennis L. Welker Arturo De Lozanne James A. Spudich 《Molecular & general genetics : MGG》1989,216(2-3):498-502
Summary A mutation (mhcA1 in strain HMM) created by insertional gene inactivation was used to map the Dictyostelium discoideum myosin heavy chain gene (mhcA) to linkage group IV. Three phenotypic traits associated with this mutation (slow colony growth, inability of the mutant to develop past aggregation, and the presence of five to ten integrated vector copies) cosegregated as expected for the consequences of a single insertional event. This linkage was confirmed using a restriction fragment length polymorphism. The mhcA1 mutation was recessive to wild type and was nonallelic with mutations at the following loci on linkage group IV: aggJ, aggL, couH, minA, phgB and tsgB. This work demonstrates the ability to apply standard techniques developed for D. discoideum parasexual genetic analyses to mutants generated by transformation, which is of particular relevance to analysis of genes for which no classical mutations or restriction fragment length polymorphisms are available. 相似文献
137.
138.
Summary Fifty four microcosmic communities were assembled over 4 months from a 28-species source pool of phytoplankton using nine different invasion patterns each replicated six times. Three communities from each set of replicates then were invaded with a cladoceran that feeds on phytoplankton. All communities were then treated identically for an additional 4 months. In all nine invasion categories species richness was greater in predated communities. Predation opened communities to invasion by increasing the representation of infrequently sampled species at the expense of more common species. Invasion rate was four times more influential than predation and over eleven times more important than either invasion order or the timing pattern of interspecific arrivals in determining species richness in this system of communitites. 相似文献
139.
Perspectives on measurement of denitrification in the field including recommended protocols for acetylene based methods 总被引:7,自引:1,他引:6
Of the biogeochemical processes, denitrification has perhaps been the most difficult to study in the field because of the inability to measure the product of the process. The last decade of research, however, has provided both acetylene and15N based methods as well as undisturbed soil core andin situ soil cover sampling approaches to implementing these methods. All of these methods, if used appropriately, give comparable results. Thus, we now have several methods, each with advantages for particular sites or objectives, that accurately measure denitrification in nature. Because of the general usefulness of the acetylene methods, updated protocols for the following three methods are given: gas-phase recirculation soil cores; static soil cores; and the denitrifying enzyme assay also known as the phase 1 assay. Despite the availability of these and other methods, denitrification budgets remain difficult to accurately establish in most environments because of the high spatial and temporal variability inherent in denitrification. Appropriate analysis of those data includes a distribution analysis of the data, and if highly skewed as is typically the case, the most accurate method to estimate the mean and the population variance is the UMVUE method (uniformly minimum variance unbiased estimator). Geostatistical methods have also been employed to improve spatial and temporal estimates of denitrification. These have occasionally been successful for spatial analysis but in the attempt described here for temporal analysis the approach was not useful.Discussions of the importance of denitrification have always focused on quantifying the process and whether particular measured quantities are judged to be a significant amount of nitrogen. A second line of evidence discussed here is the extant genetic record that results from natural selection. These analysis lead to the conclusion that strong selection for denitrification must currently be occurring, which implies that the process is of general significance in soils. 相似文献
140.
Jane J. Turner James G. Herndon Maria-Carmen Ruiz de Elvira Delwood C. Collins 《Primates; journal of primatology》1989,30(4):523-529
Endogenous testosterone levels were measured in association with sexual, aggressive, and social/affiliative behaviors in 11
outdoor-housed female rhesus monkeys over a ten-month period. Several behaviors (sex directed toward the male, sex received
from the male, aggression directed toward the male, submission directed toward the male, submission directed toward the female,
and groom another female) were significantly (p<0.05) positively correlated with testosterone in from one to five females. No trends were strong enough across all females
to suggest that any of these correlations have species-wide significance. Factor analysis revealed clearcut clusters of behaviors,
but elevations in testosterone were not strongly associated with any of these clusters. It is concluded that endogenous testosterone
levels have little measurable effect on overt behavior in female rhesus monkeys. 相似文献