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101.
R. KÜMMERLI P.
Van Den BERG A. S. GRIFFIN S. A. WEST A. GARDNER 《Journal of evolutionary biology》2010,23(4):699-706
Repression of competition (RC) within social groups has been suggested as a key mechanism driving the evolution of cooperation, because it aligns the individual’s proximate interest with the interest of the group. Despite its enormous potential for explaining cooperation across all levels of biological organization, ranging from fair meiosis, to policing in insect societies, to sanctions in mutualistic interactions between species, there has been no direct experimental test of whether RC favours the spread of cooperators in a well‐mixed population with cheats. To address this, we carried out an experimental evolution study to test the effect of RC upon a cooperative trait – the production of iron‐scavenging siderophore molecules – in the bacterium Pseudomonas aeruginosa. We found that cooperation was favoured when competition between siderophore producers and nonsiderophore‐producing cheats was repressed, but not in a treatment where competition between the two strains was permitted. We further show that RC altered the cost of cooperation, but did not affect the relatedness among interacting individuals. This confirms that RC per se, as opposed to increased relatedness, has driven the observed increase in bacterial cooperation. 相似文献
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A method is presented that will give comparable results for the evaluation of electrophoretic data on hemolyzed mouse serum patterns. Not only may hemoglobin be determined in the serum, but its contribution to the total protein may be calculated with the aid of a reference curve derived from the data obtained from the hemolyzed red cells of mice taken from the corresponding mouse blood pool. 相似文献
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The effect of morphactin (methyl 2-chloro-9-hydroxyfluorene-9-carboxylate)on basipetal transport of auxin (Indol-3-ylacetic acid-2-14C)was studied in bean (Phaseolus vulgaris) hypocotyl with thedonor-receiver block method. Morphactin (5 x 106m) reduced IAA (5 x 106m) transportintensity by an average of 83 per cent and auxin transport capacityby 90 per cent, but transport velocity was not affected. Morphactin did not inhibit uptake of IAA into hypocotyl tissue,but it did prevent transfer of IAA from the tissue into receiverblocks. Chromatographic analysis of the tissue after 4 h IAA-2-14Ctransport showed that 54 per cent of the total activity wasin the form of IAA in the control and 42 per cent in the morphactintreated tissue. No difference was found in the rate of decarboxylationof IAA-1-14C between control and morphactin treated tissue sections.Nor could any difference between control and morphactin be shownin the radioactivity associated with a TCA ppt fraction. Ina study of the transportable auxin pool, morphactin decreasedthe size of the pool and increased the half-life of decay ofauxin transport from 122 h to 385 h. In a kineticanalysis of the reversal of morphactin (5 x 106m) inhibitionby increasing concentration of IAA-2-14C (5 x 106m to2 x 105m), it was shown that IAA transport resemblesMichaelis-Menten enzyme reaction kinetics, and that inhibitionby morphactin fitted a mixed type model. IAA hada dissociation constant of 85 x 106m and morphactinthat of 43 x 107m with a Km for the transport processof 85 x 106m. 相似文献
108.
A study of the development of methanogenic fixed films on pieces of polyvinyl chloride plastic, etched glass and baked clay showed that support material markedly affected the rate of attachment and growth of bacteria converting acetic acid to methane. Film development, as indicated by the rate of acetate conversion to methane and carbon dioxide, was threefold faster on fired clay than on either PVC plastic or etched glass. Scanning electron micrographs showed that the film of bacteria attached to clay was thick and uniform, while the film attached to PVC plastic was thin although still uniform. Attachment to etched glass was spotty. The characteristics of clay which made it a superior support appeared to be its rough, porous surface which offered attachment sites to the micro-organisms and the presence of minerals in the clay, particularly iron which is known to stimulate methanogenesis and growth. 相似文献
109.
HÅKAN ÅBERG 《Physiologia plantarum》1978,44(3):224-230
Branches of Vaucheria dichotoma (L.) Ag. were induced in two ways: by cutting, which led to a branch in the wound area and by exposure to light. Blue and red light were most active in branch formation. The light intensity dependence and the action spectrum of branch formation showed patterns similar to those of photosynthesis. Photosynthetic involvement was also indicated by the DCMU inhibition of branch formation. Elongation-branching studies at different photoperiods showed that branching was increased by the presence of more photosynthetic light than was necessary for elongation. It may be concluded that photosynthesis exerted the main control of the branch formation of V. dichotoma. However, the action spectrum of branch formation showed a higher efficiency in blue light than would be expected from the action spectrum of photosynthesis. It is therefore possible that apart from the main induction via the photosynthetic pigments, other blue light sensitive pigments may have a regulatory effect. Far-red light treatment of filaments pre-exposed to 8-h and 16-h light periods did not affect branch formation. Spectrophotometrical detection of phytochrome was not successful. This may indicate that there is no participation of phytochrome in branch formation. I am indebted to Dr. Lisbeth Fries for her interest. I also wish to thank Prof. Lars Olof Björn and his friendly staff at the Institute of Plant Physiology at the University of Lund, where some of the experiments were carried out. I am grateful to AB Tomaso Minori for revising the English test and to Miss Inga-Britt Jansson for typing it. The investigation was supported financially by a grant to Dr. Lisbeth Fries from the Swedish National Science Research Council. 相似文献
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