培养基质对丛枝菌根(AM)真菌生长发育的影响

温室条件下,以盆栽培养方法研究不同培养基质对丛枝菌根(Arbuscular Mycorrhizae,AM)真菌Glomus mosseae生长发育的影响。结果表明：不同理化性质的基质对菌根共生体生长发育的影响不同,综合考虑菌根长度、根外菌丝量及孢子数3项指标,以沙土混合物(体积比3∶1)对G. mosseae菌剂的生长发育最为有利。宿主植物菌根长度及根中的可溶性糖浓度与根外孢子数有正相关关系,而宿主植物中磷浓度与菌根真菌的生长发育也有类似的关系。说明培养基质的养分状况、水分状况、通气状况等诸多因素都会影响菌根共生体的建立和发展。宿主植物的菌根长度、根中可溶性糖浓度以及宿主植物磷浓度对菌根真菌的生长发育有显著影响。因此,工厂化AM菌剂生产中,应以沙土混合物(体积比3∶1)为生产G. mosseae菌剂的培养基质。     

Mycorrhizal inoculation enhances growth and nutrition of cotton plant

Arbuscular Mycorrhizae Fungi (AMF) inoculations may improve growth and nutrient uptake of cotton (Gossypium hirsutum L.) plant. Although the importance of mycorrhizal symbioses for growth and nutrient acquisition of cotton plant is known, less is known about mycorrhizal dependency on P and Zn nutrition under low Zn fertile soil conditions. A greenhouse experiment was conducted to investigate the effect of different of P and Zn fertilizer addition on cotton plant growth as well as Zn and P uptake. Sterilized and non-sterilized low Zn fertile Konya series soil was treated with different levels of P and Zn. Soils were inoculated with two mycorrhizae species like Funneliformis mosseae and Claroideoglomus etunicatum after sterilization. Results showed that mycorrhizal inoculation on plant growth and nutrient uptake has significant effect when soil was sterilized. Cl. etunicatum mycorrhizae species has greater effect than Fu. mosseae mycorrhizae species. Root colonization increased 23–65% due to mycorrhizal amendment. The shoot: root ratio increased by 13 and 22% for non-sterile and sterile condition respectively in mycorrhiza amended soil. Mycorrhizal dependency varies 1–55% and 3–64% for non-sterile and sterile soil respectively on mycorrhizae, P and Zn amended soil. Mycorrhizal dependency analysis showed that cotton plant in both sterile and non-sterile soil conditions depends on mycorrhizae species, P nutrition, however is less depend on Zn nutrition. This study concluded that the inoculation of cotton plant with selected mycorrhizae is necessary under both sterile and non-sterile soil conditions.     

固氮施氏假单胞菌RpoN蛋白对鞭毛合成的影响

选择性σ因子σ~(54)(又称为RpoN)参与到许多细菌特定基因的转录起始过程,如氮同化基因、四碳二羧酸转运基因以及鞭毛基因。为了研究施氏假单胞菌A1501(Pseudomonas stutzeri,A1501)中σ因子RpoN对鞭毛合成的影响,构建了A1501的rpoN缺失突变株与功能回补株,并对野生型、突变株与回补株的鞭毛结构、swimming运动、生物膜形成、根际定殖能力以及鞭毛基因的表达水平进行了比较分析。结果表明:rpo N突变株丧失了鞭毛结构与swimming运动能力,根际定殖与生物膜形成能力相对野生型分别下降了25倍与10倍;此外,rpoN缺失后A1501中大量鞭毛基因发生显著下调;启动子分析发现RpoN除了可能参与调控Ⅱ级、Ⅲ级鞭毛基因外,还可能调控一级基因fli A以及四级基因fliC。以上结果说明RpoN在不同调控等级影响A1501鞭毛的合成,进而影响该菌运动、生物膜形成、根际定殖这些与水稻建立起联合固氮体系息息相关的过程。     

Migration,colonization and seedling growth of rhizobia with matrine treatment in alfalfa (Medicago sativa L.)

Purpose: The purposes of this study were to determine the effect of matrine on the migration and the colonization dynamics of the two fluorescent-tagged rhizobia in Gannong No.5 alfalfa (Medicago sativa L. Gannong No. 5) tissues, and also to determine the effect of the combination treatments on alfalfa seedlings’ growth.

Materials and methods: 0, 100, 200, 300 and 400 mg L^?1 matrine levels were added into two cyan fluorescent protein (CFP)-tagged rhizobia; Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), respectively; and drenched the alfalfa root with the inoculants. Then the migration and colonization of the two rhizobia in alfalfa on D7, D14, D21 and D28, and subsequently seedling growth were investigated.

Results: The results showed that the optimum matrine level enhanced the colonization of both fluorescent-tagged rhizobia in alfalfa roots and the highest colonization densities of log 6.31 cfu g^?1 and log 5.87 cfu g^?1 were achieved by adding 300 mg L^?1 matrine into 12531f and adding 100 mg L^?1 matrine into gn5f, respectively. They could migrate to the aerial tissues and most colonize stems through the application of adding 300 mg L^?1 matrine into 12531f and 100 mg L^?1 matrine into gn5f, respectively. No fluorescent-tagged rhizobia were detected in the control treatment. Alfalfa seedling growth parameters like leaf chlorophyll content, seedling growth rate, root length, seedling biomass and total N percentage also increased the most when 300 mg L^?1 matrine was added into 12531f and 100 mg L^?1 matrine added into gn5f treatments.

Conclusions: Our results suggest that 300 mg L^?1 matrine added into 12531f and 100 mg L^?1 matrine added into gn5f might be exploited to promote the colonization of rhizobia in alfalfa tissue and positively impact growth and yield, indicating possible benefits for plant cultivation.     

Survey of Mycorrhizal Colonization in Native,Open-Pollinated,and Introduced Hybrid Maize in Villages of Chiquimula,Guatemala

Replacing native plant types with introduced cultivars may have unexpected cropping system consequences. Native species and introduced cultivars may vary in their ability to form mycorrhizal symbioses with soil fungi and consequently affect phosphorus (P) nutrition. Low-input cropping systems often depend on mycorrhiza for adequate nutrition and growth, while high-input systems minimize the benefit of and need for colonization. Studies in wheat (Triticum aestivum L.) suggest that improving cultivars reduced the ability to form mycorrhiza. This study was conducted at six sites in the province of Chiquimula, Guatemala, to determine the difference in mycorrhizal infection rates between two maize (Zea mays L.) cultivars—‘Cushpeño,’ a native, open-pollinated variety, and ‘HB-83,’ an introduced, improved hybrid. The ‘HB-83’ was colonized at a significantly lower percentage (67%) than was ‘Cushpeño’ (72%; α = 0.0137). A strong negative correlation (r = ?0.953) existed between Mehlich-3 extractable soil P and differences in mycorrhizal colonization rates between the two genotypes. The full impact of lower colonization rates of the introduced hybrid on sustainability of the village agricultural system needs further investigation.     

Assisted colonization: Integrating conservation strategies in the face of climate change

Global climate change poses an immense challenge for conservation biologists seeking to mitigate impacts to species and ecosystems. Species persistence will depend on geographic range shifts or adaptation in response to warming patterns as novel climates and community assemblages arise. Assisted colonization has been proposed as a method for addressing these challenges. This technique, which consists of transporting species to a new range that is predicted to be favorable for persistence under future climate scenarios, has become the subject of controversy and discussion in the conservation community due to its highly manipulative nature, questions about widespread feasibility, and uncertainty associated with the likelihood of translocated species becoming invasive. We reviewed the discussion and criticism associated with assisted colonization and sought to identify other conservation techniques that also display potential to promote the colonization and adaptation of species in response to climate change. We propose an integrated conservation strategy that includes management for habitat connectivity, conservation genetics, and when necessary, assisted colonization of species that are still unable to shift their ranges even given implementation of the above standard conservation approaches. We argue that this integrated approach will facilitate persistence for a larger proportion of species than is possible by solely using assisted colonization. Furthermore, a multi-faceted approach will likely reduce the uncertainty of conservation outcomes and will become increasingly necessary for conservation of biodiversity in a changing climate.     

Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization

In both managed and natural ecosystems, beneficial plant-associated bacteria play a key role in supporting and/or increasing plant health and growth. Plant growth-promoting bacteria (PGPB) can be applied in agricultural production or for the phytoremediation of pollutants. However, because of their capacity to confer plant beneficial effects, efficient colonization of the plant environment is of utmost importance. The majority of plant-associated bacteria derives from the soil environment. They may migrate to the rhizosphere and subsequently the rhizoplane of their hosts before they are able to show beneficial effects. Some rhizoplane colonizing bacteria can also penetrate plant roots, and some strains may move to aerial plant parts, with a decreasing bacterial density in comparison to rhizosphere or root colonizing populations. A better understanding on colonization processes has been obtained mostly by microscopic visualisation as well as by analysing the characteristics of mutants carrying disfunctional genes potentially involved in colonization. In this review we describe the individual steps of plant colonization and survey the known mechanisms responsible for rhizosphere and endophytic competence. The understanding of colonization processes is important to better predict how bacteria interact with plants and whether they are likely to establish themselves in the plant environment after field application as biofertilisers or biocontrol agents.     

Suppression of the fungal pathogen Magnaporthe grisea by Stenotrophomonas maltophilia,a seed-borne rice (Oryza sativa L.) endophytic bacterium

The present work was carried out to study the potential of bacteria isolated from the seeds of rice plant for the biocontrol of five rice pathogenic fungi. Eleven endophytic bacteria isolated from rice seeds were evaluated for their antagonistic potential. Of five pathogens studied, only the growth of Magnaporthe grisea was inhibited by one bacterial isolate in an in vitro dual culture assay. Based on 16S rDNA sequence analysis, and biochemical and morphological characteristics, this strain was closely related to Stenotrophomonas maltophilia. We named this new isolate to be S. maltophilia SEN₁ (seed endophyte). This isolate was further tested for the production of volatile and diffusible antibiotics against M. grisea, for plant growth-promoting (PGP) traits and colonization of some rice cultivars. In addition, S. maltophilia SEN₁ was tested for its ability to promote plant growth and reduce the incidence of rice blast disease under greenhouse conditions. When applied to the soil, this isolate increased seedling growth and suppressed blast disease in plants of three studied cultivars. This study also showed this isolate could colonize the root interior of other rice cultivars. This study indicates that the S. maltophilia isolate studied has an excellent potential to be used as biocontrol agents of M. grisea or biofertilizer under in vitro and in vivo conditions.     

Colonization of the canine skin with bacteria

Abstract Aspects of colonization of the canine skin with bacteria are reviewed. Owing to variability in sampling techniques, anatomical sites involved and lack of temporal studies, there is still controversy as to which bacteria are residents or transients on the canine skin. The establishment of the cutaneous flora is determined by the ability of bacteria to adhere to canine corneocytes, to use available nutrients from skin secretions and to resist challenge from competing bacteria. Variations in humidity and temperature due to environment, skin folds or differences in the haircoat are also likely to have an effect. Much research has focused around Staphylococcus intermedius, the main pathogen of the canine skin but its cutaneous residency status remains questionable. Pathological conditions such as atopy and seborrhoea favour the colonization of S. intermedius and predispose to infection. Recent studies indicate that bacterial interference as a method of preventing colonization of pathogenic staphylococci may be feasible. Résumé— Les aspects de la colonisation de la peau canine par des bactéries sont étudiées. A cause de la variabilité des techniques de prélèvements, des sites anatomiques, et du caratère ponctuel des études, le doute subsiste toujours quant à savoir quelle sont les bactéries résidentes ou transitoires sur la peau de chien. L'établissement d'une flore cutanée est déterminée par la capacité de la bactérie à adhérer aux cornéocytes canines, à utiliser les nutriments disponibles à partir des sécrétions cutanées et à résister aux autres bactéries qui concourent à l'occupation des memes sites. Les variations d'humidité et de température, dues à l'environnement, aux plis de peau et aux différences de pelage jouent probablement un role. La plupart des études concernent Staphylococcus intermedius, l'agent pathogène principal de la peau du chien, mais son statut de résident cutané est toujours débattu. Des conditions pathologiques telles que l'atopie et la séborrhée favorisent la colonisation par S. intermedius et prédisposent à l'infection. Des études récentes indiquent que l'interférence bactérienne peut être envisagée comme une méthode de prévention de la colonisation cutanée par un staphylocoque pathogène. [Saijonmaa-Koulumies, L. & Lloyd, D. H. Colonization of the canine skin with bacteria (Colonisation de la peau canine par des bactéries). Veterinary Dermatology 1996; 7 : 153–162.] Resumen Se revisan algunos aspectos de la colonización bacteriana en la piel canina. Existe aún controversia sobre qué bacterias son résidentes o transitorias en la piel del perro, debido a la variabilidad en las técnicas de recolección, localización y falta de estudios temporales. El establecimiento de la flora cutánea depende de su capacidad de adhesión a los corneocitos, de utilizar los nutrientes de las secreciones cutáneas y de resistir la competencia de otras bacterias. También es probable que tengan un papel los cambios de humedad y temperatura por los pliegues cutáneos o las diferencias en el pelaje. Se ha centrado mucha investigación en Staphylococcus intermedius, el principal patógeno de la piel canina, aunque se sigue cuestionando su existencia como residente cutáneo. Situaciones patológicas como la atopia o la seborrea favorecen la colonización por S. intermedius y predisponen a infección. Algunos estudios recientes indican que es factible la interferencia bacteriana como método de prevenir la colonización por estafilococos patógenos. [Saijonmaa-Koulumies, L. & Lloyd, D. H. Colonization of the canine skin with bacteria (Colonizacion de la piel cannina con bacterias). Veterinary Dermatology 1996; 7 : 153–162.] Zusammenfassung— Es werden Aspekte der Besiedelung der Hundehaut mit Bakterien dargestellt. Entsprechend der Variabilität in der Probenentnahme, verwendeten anatomischen Regionen und dem Mangel an temporären Studien exisitieren immer noch unterschiedliche Ansichten, ob Bakterien auf der Haut des Hundes als resident oder transient gelten. Die Aufstellung der kutanen Flora wird durch die Fähigkeit der Bakterien bestimmt, sich an die kaninen Korneozyten anzuheften, verfügbare Nährstoffe aus den Hautsekretionen zu verwenden und sich gegenüber konkurrierenden Keimen zu behaupten. Veränderungen in Feuchtigkeit und Temperatur in Abhängigkeit von Umgebung, Hautfalten oder Unterschieden im Haarkleid scheinen ebenfalls einen Effekt zu besitzen. Viele Untersuchungen konzentrierten sich auf Staphylococcus aureus, der hauptpathogene Keim auf der Hundehaut, aber sein Status als residenter Keim bleibt fraglich. Pathologische Zustände wie Atopie und Seborrhoe begünstigen die Besiedelung mit S. intermedius und prädisponieren für eine Infektion. Kürzliche Studien zeigen, daß bakterielle Interferenzen als Methode zur Verhinderung der Ansiedlung von pathogenen Staphylokokken möglich sein könnten. [Saijonmaa-Koulumies, L., Lloyd, D.H. Colonization of the canine skin with bacteria (Besiedelung der Haut des Hundes mit Bakterien). Veterinary Dermatology 1996; 7 : 153–162.]