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1.
Résumé Vingt souches deFrankia, isolées à partir de 7 espèces différentes de plantes actinorhiziennes ont été cultivées sur des milieux maintenus à des
pH constants de 5; 4,8; 4,6 et 4,2. Chaque souche a été cultivée 2 à 3 fois consécutives à un même pH. Quatorze souches ne
montrent aucune croissance à pH 5. Seules 3 souches résistent à un séjour de plusieurs semaines à pH 4,6. Aucune souche ne
demeure viable après un séjour dans un milieu à pH 4,2. Les 3 souches acido-résistantes supportent également la présence d'Al+++ libre dans le milieu de culture. Une forte concentration d'H+ dans le milieu stimule beaucoup la sporogénèse.
Inoculée dans un sol acide une souche acido-résistante conserve une chance de survie nettement supérieure à celle d'une souche
neutrophile maintenue dans les mêmes conditions.
相似文献
2.
Two isolates of Metarhizium anisopliae var acridum were tested for their effects on the locust immune system and for comparison with the effects of challenge by injection with laminarin. Isolate IMI 330189 (referred to hereafter as Met 189) is highly pathogenic whether applied topically as conidia or injected as blastospores. However, isolate ARSEF 728 (referred to hereafter as Met 728) is pathogenic only when injected as blastospores, suggesting that the lack of pathogenicity of topically applied conidia from this isolate is due to a failure to penetrate the insect cuticle and gain access to the haemocoel. After topical application of conidia from Met 189, no activation of prophenoloxidase is detected, but injection of blastospores from Met 189 brings about a transient increase in phenoloxidase activity in the haemolymph in both adult locusts and 5th instar nymphs, although this does not prevent fungal-induced mortality. Co-injection of adipokinetic hormone-I (AKH-I) with blastospores prolongs the activation of prophenoloxidase in the haemolymph of adult locusts, and enhances it in nymphs. It is argued that the lack of activation of prophenoloxidase in nymphs shown previously (Mullen, L., Goldsworthy, G., 2003. Changes in lipophorins are related to the activation of phenoloxidase in the haemolymph of Locusta migratoria in response to injection of immunogens. Insect Biochemistry and Molecular Biology 33, 661-670), reflects differences in the sensitivity of the immune system between adults and nymphs rather than distinct qualitative differences, and this is confirmed in this study by the demonstration that doses of laminarin higher than those used previously (>or=100 microg) do activate the prophenoloxidase cascade in 5th instar nymphs. Nodules are formed in locusts of all ages in response to fungal infection or injection of laminarin, although there is wide variation in the number, size and distribution of nodules formed. During the examination of 5th instar nymphs for nodule formation, a previously unknown phenomenon was observed in which the salivary glands melanise in response to injections of blastospores or high doses of laminarin. In c. 85% of such nymphs, this reaction is so strong that the whole salivary gland is intensely black. Such a response is not observed in the salivary glands of mature adult locusts. 相似文献
3.
Lynn Margulis 《Experimental parasitology》1976,39(2):277-349
Permanent stable symbioses, primarily microbial, are analyzed as parasexual phenomena from the evolutionary point of view. Such associations bring together in single individuals heritable traits of high selective advantage in certain environments. By convergent evolution several types of associations have repeatedly arisen: motile photosynthetic forms, nitrogen fixing and wood digesting complexes, and so forth. Many examples are discussed from the point of view of the number of originally independent genomes that comprise the recognizable individuals.The level of partner integration in many associations is analyzed. Examples of many levels: genic, gene product, metabolite, behavioral, and the methods by which they can be distinguished are discussed.The literature concerning a large number of associations is reviewed: Methanobacillus; predatory and consortia bacteria; blue green algal sheath dwelling bacteria; anaerobic worm-bacterial; algal, and foreign chloroplast retention by heterotrophic eukaryotes (ciliates, coelenterates, mollusks); the double nucleated photosynthetic dinoflagellate (Peridinium balticum); hindgut microbes in termites and woodroaches (Pyrsonympha, Barbulanympha and their associated spirochetes and other bacteria); sand dwelling and other ciliates and their associated bacteria; and so forth. The status of observations and artificial systems claiming evidence for transfer of genes between very distantly related organisms is critically discussed.A continuum from nearly completely autonomous partners (e.g., zoochlorellae in invertebrate animals) to nearly unrecognizable merged components (e.g., gamma particles in Blastocladiella) is found to exist among examples of extant organisms. The diversity and prevalence of such associations support the concept that there are many precedents for the steps hypothesized in the serial endosymbiotic theory of the origin of eukaryotic cells. 相似文献
4.
Mycorrhizal fungi increase salt tolerance of Strophostyles helvola in coastal foredunes 总被引:1,自引:0,他引:1
A greenhouse study was conducted to determine the effects of increasing concentrations of salt (NaCl) solutions applied to the soil containing mycorrhizal and non-mycorrhizal plants of the leguminous species Strophostyles helvola (L.) Ell. The dry weight of roots and shoots and leaf chlorophyll content of S. helvola plants decreased with an increase in the concentrations of salt solutions. Although increasing salt concentrations promoted hyphal growth in mycorrhizal plants, the percent uncolonized root surface, arbuscules and vesicles decreased. An increase in the concentration of salt solutions did not decrease the number of root nodules. The data clearly showed evidence of significantly higher chlorophyll content, shoot dry weight and number of root nodules in mycorrhizal than non-mycorrhizal plants. High salt concentrations had a negative effect on the growth of S. helvola plants but the negative effects were partially mitigated by the presence of mycorrhizal fungi. 相似文献
5.
The study on localization of ATP-ase in root nodules of Astragalus sinicus and Sesbania cannabina shows that the particles of lead phosphate precipitates resulting from the reaction of ATP hydrolytic enzyme are distributed in cell wall, plasmolemma, cytoplasm and peribacteroid membranes etc. of the host cells. This ATP-ase plays an important role in the transportation and absorption of substances. Owing to the need of photosynthates provided for the nitrogen fixation of root nodules, the active reaction of ATP-ase in bacteroids varies with their developments. The numbers of bacteroids having ATP hydrolytic enzyme in young root nodules are significantly less than those in senescent nodules. Possibly, this active reaction is related with the physiological function of nitrogen fixation of bacteroids at different development stages. 相似文献
6.
7.
Marcellous Le Roux Ethel Phiri Wesaal Khan Muhammet Şakiroğlu Alex Valentine Sehaam Khan 《Journal of plant physiology》2014
During P deficiency, the increased activity of malate dehydrogenase (MDH, EC 1.1.1.37) can lead to malate accumulation. Cytosolic- and nodule-enhanced MDH (cMDH and neMDH, respectively) are known isoforms, which contribute to MDH activity in root nodules. The aim of this study was to investigate the role of the cMDH isoforms in nodule malate supply under P deficiency. Nodulated lupins (Lupinus angustifolius var. Tanjil) were hydroponically grown at adequate P (+P) or low P (−P). Total P concentration in nodules decreased under P deficiency, which coincided with an increase in total MDH activity. A consequence of higher MDH activity was the enhanced accumulation of malate derived from dark CO2 fixation via PEPC and not from pyruvate. Although no measurable neMDH presence could be detected via PCR, gene-specific primers detected two 1 kb amplicons of cMDH, designated LangMDH1 (corresponding to +P, HQ690186) and LangMDH2 (corresponding to −P, HQ690187), respectively. Sequencing analyses of these cMDH amplicons showed them to be 96% identical on an amino acid level. There was a high degree of diversification between proteins detected in this study and other known MDH proteins, particularly those from other leguminous plants. Enhanced malate synthesis in P-deficient nodules was achieved via increased anaplerotic CO2 fixation and subsequent higher MDH activities. Novel isoforms of cytosolic MDH may be involved, as shown by gene expression of specific genes under P deficiency. 相似文献
8.
Summary Using a series of antibody probes as markers of symbiosome development, we have investigated the impaired development of symbiosomes
in nodules formed by the plant mutant line Sprint2Fix− (sym31). In wild-type pea (Pisum sativum L.) nodules, bacteria differentiate into large pleiomorphic, nitrogen-fixing bacteroids and are singly enclosed within a
peribacteroid membrane. In thesym31 mutant, several small undifferentiated bacteroids were often enclosed within one peribacteroid membrane, or were found
within a vacuole-like compartment. In wild-type nodules, the monoclonal antibody JIM18, which recognizes a plasmalemma glycolipid
antigen, bound to the juvenile peribacteroid membrane, and did not recognize the mature peribacteroid membrane. However, in
the mutant, the antibody bound to all peribacteroid membranes within the nodule, suggesting that differentiation of the peribacteroid
membrane was arrested. Another antibody, MAC266, recognized plant glycoproteins which normally accumulate in symbiosomes at
a late stage of nodule development. Binding of this antibody was much reduced within mutant nodules, labelling only a few
mature cells. Similarly, MAC301, which normally recognizes a lipopolysaccharide epitope expressed on differentiated bacteroids
prior to the induction of nitrogenase, failed to react with rhizobial cell extracts isolated from nodules of thesym31 mutant. On the basis of these developmental markers, the symbiosomes ofsym31 nodules appeared to be blocked at an early stage of development. The distribution of infection structures was also found
to be abnormal in the mutant nodules. Models of symbiosome development are presented and discussed in relation to the morphological
and developmental lesions observed in thesym31 mutant. 相似文献
9.
Summary High perfomance liquid chromatography (HPLC) of the products of [5-3H] tryptophan metabolism byFrankia sp. Avc I1 indicates that small amounts of [3H] indole-3-acetic acid (IAA) are excreted into the growth medium.Frankia has a limited capacity for the catabolism of [2-14C]IAA and the product that accumulates is different from that detected inRhizobium japonicum cultures following inoculation with [2-14C]IAA. The data imply that the rate of turnover of IAA is much more rapid inRhizobium thanFrankia and that the two organisms employ different routes for the catabolism of IAA. 相似文献
10.
摘要 目的:探讨超微血管成像技术(SMI)在乳腺良恶性病变中的鉴别诊断价值以及在乳腺癌新辅助化疗中的疗效评估价值。方法:回顾性分析2014年2月至2019年10月于长沙市第三医院行SMI检查的109例乳腺结节患者的临床资料,根据病理结果将其分为良性组和恶性组,比较两组患者SMI微血管形态分型分布差异,采用受试者工作特征曲线(ROC)分析SMI鉴别诊断乳腺良恶性病变的价值。乳腺癌患者经序贯新辅助化疗后再次接受SMI检查,比较新辅助化疗前后、不同疗效乳腺癌患者SMI血流分级差异。结果:良性组微血管形态分型以无血管型,线型,树枝型为主(97.83%),恶性组以残根型,蟹足型为主(80.99%),两组微血管形态分型分布差异有统计学意义(P<0.05)。以病理检查结果为金标准,SMI鉴别诊断乳腺良恶性病变的曲线下面积(AUC)为0.890,灵敏度为80.99%,特异度为97.83%,准确率为85.63%。68例乳腺癌患者完成新辅助化疗,新辅助化疗有效[完全缓解(CR)+部分缓解(PD)] 47例,无效[稳定(SD)+进展(PD)]21例。化疗前SMI血流分级以Ⅱ、Ⅲ级为主(80.88%),化疗后以0、Ⅰ级为主(69.12%),有效组SMI血流分级以0、Ⅰ级为主(87.23%),无效组SMI血流分级以Ⅰ、Ⅱ级为主(85.71%),化疗前后、不同疗效组SMI血流分级差异均有统计学意义(P<0.05)。结论:SMI能有效检出乳腺结节病灶内微小血管形态和血流改变,对乳腺良恶性病变的鉴别诊断及新辅助化疗的疗效评估均有一定临床应用价值。 相似文献