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A killer strain was discovered in cellular slime molds. The wild isolate CK-8 of Polysphondylium pallidum kills all other strains in Polysphondylium and Dictyostelium, as far as could be determined, except strain CK-8 itself and its complementary mating type strain CK-9. Growth-phase cells of CK-8 excrete a killer factor which is sensitive to heat, above 60°C for 5 min, and trypsin. The apparent molecular mass of the factor was determined at 10 000–12 000.Abbreviations BSS
Bonner's salt solution
- CM
conditioned medium 相似文献
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Daniel Dignard Malcolm Whiteway Doris Germain Daniel Tessier David Y. Thomas 《Molecular & general genetics : MGG》1991,227(1):127-136
Summary A cDNA copy of the M2 dsRNA encoding the K2 killer toxin ofSaccharomyces cerevisiae was expressed in yeast using the yeastADH1 promoter. This construct produced K2-specific killing and immunity functions. Efficient K2-specific killing was dependent
on the action of the KEX2 endopeptidase and the KEX1 carboxypeptidase, while K2-specific immunity was independent of these
proteases. Comparison of the K2 toxin sequence with that of the K1 toxin sequence shows that although they share a common
processing pathway and are both encoded by cytoplasmic dsRNAs of similar basic structure, the two toxins are very different
at the primary sequence level. Site-specific mutagenesis of the cDNA gene establishes that one of the two potential KEX2 cleavage
sites is critical for toxin action but not for immunity. Immunity was reduced by an insertion of two amino acids in the hydrophobic
amino-terminal region which left toxin activity intact, indicating an independence of toxin action and immunity. 相似文献
5.
José Cansado Elisa Longo Dolores Agrelo Tomás G. Villa 《FEMS microbiology letters》1989,65(1-2):233-237
Acridine orange, an intercalating dye usually employed in the curing of bacterial plasmids, was tested for its ability to cure K1 and K2 killer strains (laboratory and wine strains). The results showed a high curing percentage of the killer character. This was demonstrated by the loss of M1 or M2 dsRNAs (responsible for toxin production and resistance to it) and because the meiotic products exhibited non-Mendelian segregation. The curing percentages varied, depending on the strain but not on the killer type, and showed similar efficiency as compared with other known curing agents. 相似文献
6.
The present experiments attempt to find the meridian phenomenon and how the needle feeling propagates along the given meridian channels. The neurobiological mechanisms of the meridian were studied with neuroelectrical recording from the motor neurons and CB-HRP retrograde histochemistry technique in both rats and cats. The results demonstrated that most, but not all, of alpha motor neurons supplying a muscle group of a given meridian were selectively activated by afferent inputs originating not only from homonymous or heterogeneous, but synergistic muscle, but also from the skin nerve overlying the muscle group of the homonymous meridian. However, the afferent inputs from the heterogeneous meridian have very weak or no effect. On the other hand, the labeled motor neurons supplying a given meridian muscles form a discrete longitudinal column with a definite bound in the lateral ventral horn. There are oriented dendro-dendristes projections between the labeled motor neurons.The characteristics of both sel 相似文献
7.
Changes in DNA supertwist as a response of Bacillus subtilis towards different kinds of stress 总被引:1,自引:0,他引:1
Abstract The silent parD ( kis/kid ) stability operon of plasmid R1 is normally repressed by the co-ordinated action of the Kis and Kid proteins. In this report it is shown that a mutation in repA , the gene of the plasmid replication protein, that reduces two-fold the copy number of the plasmid, leads to the derepression of the parD system. This derepression can be prevented by a suppressor mutation in copB, a copy number control gene of plasmid R1, that increases the efficiency of replication of the repA mutant. Derepression of the wild-type parD system leads to high plasmid stability. These data show the activation of a plasmid stability operon by a mutation that reduces the efficiency of wild-type plasmid replication. 相似文献
8.
Comparison of the killer toxin of several yeasts and the purification of a toxin of type K2 总被引:5,自引:0,他引:5
A total of 13 killer toxin producing strains belonging to the genera Saccharomyces, Candida and Pichia were tested against each other and against a sensitive yeast strain. Based on the activity of the toxins 4 different toxins of Saccharomyces cerevisiae, 2 different toxins of Pichia and one toxin of Candida were recognized. The culture filtrate of Pichia and Candida showed a much smaller activity than the strains of Saccharomyces. Extracellular killer toxins of 3 types of Saccharomyces were concentrated and partially purified. The pH optimum and the isoelectric point were determined. The killer toxins of S. cerevisiae strain NCYC 738, strain 399 and strain 28 were glycoproteins and had a molecular weight of Mr=16,000. The amino acid composition of the toxin type K2 of S. cerevisiae strain 399 was determined and compared with the composition of two other toxins. 相似文献
9.
Summary Mechanically dividing an insect egg into anterior and posterior fragments results in a segment gap (Sander 1976), a loss of non-terminal segments in the constricted region. By altering the stage and duration of constriction, we produced different types of egg fragments in the pea beetleCallosobruchus. The patterns formed by these fragments suggest the existence of interactions between anterior and posterior egg regions that influence segment patterning and placement. Segments in excess of the numbers expected on the basis of permanent constrictions were produced in fragments when: (1) the constriction was released before cellularization occurred and (2) in addition the complementary fragment degenerated. Apparently the degenerating fragment induced the formation of excess segments in the developing fragment. Differences in the time and extent of excess segment formation in anterior versus posterior fragments suggest an asymmetric distribution of prerequisites for segment formation. This conclusion is consistent with our finding that a partial reversal of segment sequence (double abdomen formation) can be induced only in posterior fragments by a degenerating fragment, but not in anterior fragments (see companion paper).The formation of excess segments shows that the segment gap observed after permanent separation cannot be due to non-specific damage, caused by the process of constriction as such, to the egg or to localized putative segment precursors. 相似文献
10.
The monokaryotic yeast phase of the heterobasidiomycete Itersonilia perplexans, unlike the hyphal phase, was found to be sensitive to mycocins produced by killer strains of Cryptococcus humicola, Cr. laurentii, Cystofilobasidium bisporidii and Rhodotorula fujisanense. Both the yeast and hyphal phases wer resistant to mycocins of Cr. podzolicus, Filobasidium capsuligenum, Rhodotorula glutinis, Rh. mucilaginosa, Rh. pallida, Sporidiobolus johnsonii, Sb. pararoseus and Sporobolomyces alborubescens. The different sensitivity patterns of yeast and hyphal phases are probably caused by biochemical differences in the cell walls. 相似文献