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1.
Burkholderia pseudomallei, the bacterial agent of melioidosis, causes disease through inhalation of infectious particles, and is classified as a Tier 1 Select Agent. Optical diagnostic imaging has demonstrated that murine respiratory disease models are subject to significant upper respiratory tract (URT) colonization. Because human melioidosis is not associated with URT colonization as a prominent presentation, we hypothesized that lung-specific delivery of B. pseudomallei may enhance our ability to study respiratory melioidosis in mice. We compared intranasal and intubation-mediated intratracheal (IMIT) instillation of bacteria and found that the absence of URT colonization correlates with an increased bacterial pneumonia and systemic disease progression. Comparison of the LD50 of luminescent B. pseudomallei strain, JW280, in intranasal and IMIT challenges of albino C57BL/6J mice identified a significant decrease in the LD50 using IMIT. We subsequently examined the LD50 of both capsular polysaccharide and Type 3 Secretion System cluster 3 (T3SS3) mutants by IMIT challenge of mice and found that the capsule mutant was attenuated 6.8 fold, while the T3SS3 mutant was attenuated 290 fold, demonstrating that T3SS3 is critical to respiratory melioidosis. Our previously reported intranasal challenge studies, which involve significant URT colonization, did not identify a dissemination defect for capsule mutants; however, we now report that capsule mutants exhibit significantly reduced dissemination from the lung following lung-specific instillation, suggesting that capsule mutants are competent to spread from the URT, but not the lung. We also report that a T3SS3 mutant is defective for dissemination following lung-specific delivery, and also exhibits in vivo growth defects in the lung. These findings highlight the T3SS3 as a critical virulence system for respiratory melioidosis, not only in the lung, but also for subsequent spread beyond the lung using a model system uniquely capable to characterize the fate of lung-delivered pathogen. 相似文献
2.
Background
Extensive use of antibiotics as growth promoters in the livestock industry constitutes strong selection pressure for evolution and selection of antibiotic resistant bacterial strains. Unfortunately, the microbial ecology and spread of these bacteria in the agricultural, urban, and suburban environments are poorly understood. Insects such as house flies (Musca domestica) and German cockroaches (Blattella germanica) can move freely between animal waste and food and may play a significant role in the dissemination of antibiotic resistant bacteria within and between animal production farms and from farms to residential settings. 相似文献3.
Fernando Dini Andreote Ulisses Nunes da Rocha Welington Luiz Araújo João Lúcio Azevedo Leonard Simon van Overbeek 《Antonie van Leeuwenhoek》2010,97(4):389-399
Beneficial bacteria interact with plants by colonizing the rhizosphere and roots followed by further spread through the inner
tissues, resulting in endophytic colonization. The major factors contributing to these interactions are not always well understood
for most bacterial and plant species. It is believed that specific bacterial functions are required for plant colonization,
but also from the plant side specific features are needed, such as plant genotype (cultivar) and developmental stage. Via
multivariate analysis we present a quantification of the roles of these components on the composition of root-associated and
endophytic bacterial communities in potato plants, by weighing the effects of bacterial inoculation, plant genotype and developmental
stage. Spontaneous rifampicin resistant mutants of two bacterial endophytes, Paenibacillus sp. strain E119 and Methylobacterium mesophilicum strain SR1.6/6, were introduced into potato plants of three different cultivars (Eersteling, Robijn and Karnico). Densities
of both strains in, or attached to potato plants were measured by selective plating, while the effects of bacterial inoculation,
plant genotype and developmental stage on the composition of bacterial, Alphaproteobacterial and Paenibacillus species were determined by PCR-denaturing gradient gel-electrophoresis (DGGE). Multivariate analyses revealed that the composition
of bacterial communities was mainly driven by cultivar type and plant developmental stage, while Alphaproteobacterial and
Paenibacillus communities were mainly influenced by bacterial inoculation. These results are important for better understanding the effects
of bacterial inoculations to plants and their possible effects on the indigenous bacterial communities in relation with other
plant factors such as genotype and growth stage. 相似文献
4.
Misas-Villamil JC Kolodziejek I van der Hoorn RA 《The Plant journal : for cell and molecular biology》2011,67(5):774-782
The ability to move from the primary infection site and colonize distant tissue in the leaf is an important property of bacterial plant pathogens, yet this aspect has hardly been investigated for model pathogens. Here we show that GFP‐expressing Pseudomonas syringae pv. syringae DC3000 that lacks the HopQ1‐1 effector (PtoDC3000ΔhQ) has a strong capacity to colonize distant leaf tissue from wound‐inoculated sites in N. benthamiana. Distant colonization occurs within 1 week after toothpick inoculation and is characterized by distant colonies in the apoplast along the vasculature. Distant colonization is blocked by the non‐host resistance response triggered by HopQ1‐1 in an SGT1‐dependent manner and is associated with an explosive growth of the bacterial population, and displays robust growth differences between compatible and incompatible interactions. Scanning electron microscopy revealed that PtoDC3000ΔhQ bacteria are present in xylem vessels, indicating that they use the xylem to move through the leaf blade. Distant colonization does not require flagellin‐mediated motility, and is common for P. syringae pathovars that represent different phylogroups. 相似文献
5.
Silvia Caballero Rebecca Carter Xu Ke Bo?e Su?ac Ingrid M. Leiner Grace J. Kim Liza Miller Lilan Ling Katia Manova Eric G. Pamer 《PLoS pathogens》2015,11(9)
Antibiotic resistance among enterococci and γ-proteobacteria is an increasing problem in healthcare settings. Dense colonization of the gut by antibiotic-resistant bacteria facilitates their spread between patients and also leads to bloodstream and other systemic infections. Antibiotic-mediated destruction of the intestinal microbiota and consequent loss of colonization resistance are critical factors leading to persistence and spread of antibiotic-resistant bacteria. The mechanisms underlying microbiota-mediated colonization resistance remain incompletely defined and are likely distinct for different antibiotic-resistant bacterial species. It is unclear whether enterococci or γ-proteobacteria, upon expanding to high density in the gut, confer colonization resistance against competing bacterial species. Herein, we demonstrate that dense intestinal colonization with vancomycin-resistant Enterococcus faecium (VRE) does not reduce in vivo growth of carbapenem-resistant Klebsiella pneumoniae. Reciprocally, K. pneumoniae does not impair intestinal colonization by VRE. In contrast, transplantation of a diverse fecal microbiota eliminates both VRE and K. pneumoniae from the gut. Fluorescence in situ hybridization demonstrates that VRE and K. pneumoniae localize to the same regions in the colon but differ with respect to stimulation and invasion of the colonic mucus layer. While VRE and K. pneumoniae occupy the same three-dimensional space within the gut lumen, their independent growth and persistence in the gut suggests that they reside in distinct niches that satisfy their specific in vivo metabolic needs. 相似文献
6.
The spread of arbuscular mycorrhizal (AM) fungi from tree to crop roots was examined by molecular and microscopic methods
in a glasshouse study. Growth of Calliandra calothyrsus Meissner trees inoculated with isolates of the AM fungi Glomus etunicatum Becker and Gerdemann and Gigaspora albida Schenck and Smith was monitored over an 18-month period. Three successive ‘intercrops’ of beans or maize were sown at 25,
50 and 75 cm distances from the tree and harvested during this period. At each crop harvest, the distribution of tree and
crop roots and the spread of the inoculant fungi were determined using traditional microscopic methods and fungal specific
primers. Both inoculants greatly improved the growth of the trees and colonization spread to the crops once the trees were
6 months old. However, benefits of inoculation to crop growth were not observed due to increased competition from the larger
inoculated trees growing in a restricted soil volume. Of the two inoculant fungi, Glomus etunicatum appeared to be more mobile as it spread more rapidly, formed higher levels of colonization at increasing distances from the
tree and was responsible for most of the mycorrhizal cross-contamination. In contrast, colonization of tree and crop roots
by Gigaspora albida was higher nearest the tree. This work demonstrated the benefits of mycorrhizal fungus inoculation for tree growth and confirmed
that trees and crops share the same AM fungi. Trees may therefore act as reservoirs of mycorrhizal fungi, either inoculant
or indigenous, for surrounding crops or other annual vegetation. It was also shown that tree pruning, the normal practice
in agroforestry systems, did not reduce mycorrhizal colonization or prevent spread to crops. However, the slow rates of inoculant
spread found here suggest that it may take years before inoculants benefit the growth of crops sown several metres from the
tree. The work also demonstrated that microscopic quantification of mycorrhizal colonization and the use of molecular probes
to identify specific fungi within roots can complement each other effectively. Molecular probes were more sensitive at detecting
mycorrhizal fungi than microscopic methods, but did not discriminate between full mycorrhizal structures and traces of hyphae. 相似文献
7.
Timothy C. Barnett Jason N. Cole Tania Rivera‐Hernandez Anna Henningham James C. Paton Victor Nizet Mark J. Walker 《Cellular microbiology》2015,17(12):1721-1741
Group A Streptococcus (Streptococcus pyogenes), group B Streptococcus (Streptococcus agalactiae) and Streptococcus pneumoniae (pneumococcus) are host‐adapted bacterial pathogens among the leading infectious causes of human morbidity and mortality. These microbes and related members of the genus Streptococcus produce an array of toxins that act against human cells or tissues, resulting in impaired immune responses and subversion of host physiological processes to benefit the invading microorganism. This toxin repertoire includes haemolysins, proteases, superantigens and other agents that ultimately enhance colonization and survival within the host and promote dissemination of the pathogen. 相似文献
8.
Prathiba Kurupati Claire E. Turner Ioanna Tziona Richard A. Lawrenson Faraz M. Alam Mahrokh Nohadani Gordon W. Stamp Annelies S. Zinkernagel Victor Nizet Robert J. Edwards Shiranee Sriskandan 《Molecular microbiology》2010,76(6):1387-1397
SpyCEP is a Streptococcus pyogenes protease that cleaves CXCL8/IL‐8 and its activity is associated with human invasive disease severity. We investigated the role of SpyCEP in S. pyogenes necrotizing fasciitis and respiratory tract infection in mice using isogenic strains differing only in SpyCEP expression. SpyCEP cleaved human CXCL1, 2, 6 and 8 plus murine CXCL1 and 2 at a structurally conserved site. Mice were infected in thigh muscle with a strain of S. pyogenes that expresses a high level of SpyCEP, or with an isogenic non‐SpyCEP expressing strain. SpyCEP expression by S. pyogenes hindered bacterial clearance from muscle, and enhanced bacterial spread, associated with cleavage of murine chemoattractant CXCL1. Mice were then infected with Lactococcus lactis strains that differed only in SpyCEP expression. In contrast to the parent L. lactis strain (lacks SpyCEP), which was avirulent when administered intramuscularly, infection with a strain that expressed SpyCEP heterologously led to dramatic systemic illness within 24 h, failure to clear bacteria from muscle and marked dissemination to other organs. In the upper airways, SpyCEP expression was required for survival of L. lactis but not S. pyogenes. However, dissemination of S. pyogenes to the lung was SpyCEP‐dependent and was associated with evidence of chemokine cleavage. Taken together, the studies provide clear evidence that SpyCEP is necessary and sufficient for systemic bacterial dissemination from a soft tissue focus in this model and also underlies dissemination in the respiratory tract. 相似文献
9.
Fabio Pisano Wiebke Heine Maik Rosenheinrich Janina Schweer Aaron M. Nuss Petra Dersch 《PloS one》2014,9(7)
The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections. However, the influence of PhoP on virulence varied greatly between different murine models of infection and its role in natural oral infections with frequently used representative isolates of Y. pseudotuberculosis was unknown. To address this issue, we constructed an isogenic set of phoP
+ and phoP
− variants of strain IP32953 and YPIII and analyzed the impact of PhoP using in vitro functionality experiments and a murine oral infection model, whereby we tested for bacterial dissemination and influence on the host immune response. Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome. Our work further revealed certain strain-specific differences in virulence properties, which do not strongly rely on the function of PhoP, but affect tissue colonization, dissemination and/or persistence of the bacteria. Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host. 相似文献
10.
The effect of cellulase and pectinase on bacterial colonization of wheat was studied by three different experiments. In the
first experiment, the root colonization of 3 wheat cultivars (Ghods, Roshan and Omid) by two A. brasilense strains (Sp7 and Dol) was compared using pre-treated roots with cellulase and pectinase, and non-treated with these enzymes
(control). Although the root colonization varied greatly among strain-plant combinations in controls, the pre-treatment of
roots with polysaccharide degrading enzymes significantly increased the bacterial count in roots, regardless of the strain-plant
combination. This might be an indication that cell wall may act as an important factor in plant-Azospirillum interaction. In the second experiment, the root cellulase activity of the same wheat cultivars treated with and without the
two Azospirillum brasilense, strains (Sp7 and Dol) was compared. The pre-treatment of wheat roots with Azospirillum enhanced the cellulase activity of wheat root extracts. Thus, the cellulase activity might participate in the initial colonization
of wheat roots by Azospirillum. The comparison of the cellulase activity of root extracts within inoculated and non-inoculated seedlings showed that the
inoculation had enhanced the cellulase activity in root extracts, but this effect was directly dependent on the strain-plant
combination. Strain Sp7 stimulated the highest cellulase activity in cv. Roshan, but strain Dol induced the highest enzyme
activity in cv. Ghods. In the third experiment, several growth parameters of those 3 wheat cultivars treated with and without
those two bacterial strains (Sp7 and Dol) were compared. The highest magnitude of growth responses caused by Sp7 strain was
in the cv Roshan, but Dol strain stimulated the highest growth in cv Ghods. Therefore, effective colonization may contribute
to more growth responses. 相似文献
11.
This article correlates colonization with parameters, such as chemotaxis, biofilm formation, and bacterial growth, that are
believed to be connected. We show here, by using two varieties of soybean plants that seeds axenically produced exudates,
induced a chemotactic response in Bacillus amyloliquefaciens, whereas root exudates did not, even when the exudates, also collected under axenic conditions, were concentrated up to 200-fold.
Root exudates did not support bacterial cell division, whereas seed exudates contain compounds that support active cell division
and high cell biomass at stationary phase. Seed exudates of the two soybean varieties also induced biofilm formation. B. amyloliquefaciens colonized both seeds and roots, and plant variety significantly affected bacterial root colonization, whereas it did not
affect seed colonization. Colonization of roots in B. amyloliquefaciens occurred despite the lack of chemotaxis and growth stimulation by root exudates. The data presented in this article suggest
that soybean seed colonization, but not root colonization, by B. amyloliquefaciens is influenced by chemotaxis, growth, and biofilm formation and that this may be caused by qualitative changes of the composition
of root exudates. 相似文献
12.
Riccardo Soldan Nattapong Sanguankiattichai Marcel Bach-Pages Indra Bervoets Wei E. Huang Gail M. Preston 《Environmental microbiology》2021,23(4):2070-2085
Bacterial bioluminescence is widely used to study the spatiotemporal dynamics of bacterial populations and gene expression in vivo at a population level but cannot easily be used to study bacterial activity at the level of individual cells. In this study, we describe the development of a new library of mini-Tn7-lux and lux::eyfp reporter constructs that provide a wide range of lux expression levels, and which combine the advantages of both bacterial bioluminescence and fluorescent proteins to bridge the gap between macro- and micro-scale imaging techniques. We demonstrate that a dual bioluminescence-fluorescence approach using the lux operon and eYFP can be used to monitor bacterial movement in plants both macro- and microscopically and demonstrate that Pseudomonas syringae pv phaseolicola can colonize the leaf vascular system and systemically infect leaves of common bean (Phaseolus vulgaris). We also show that bacterial bioluminescence can be used to study the impact of plant immune responses on bacterial multiplication, viability and spread within plant tissues. The constructs and approach described in this study can be used to study the spatiotemporal dynamics of bacterial colonization and to link population dynamics and cellular interactions in a wide range of biological contexts. 相似文献
13.
A Monogenic Dominant Resistance of Tomato to Bacterial Wilt in Hawaii 7996 is Associated with Plant Colonization by Pseudomonas solanacearum 总被引:1,自引:0,他引:1
Hawaii 7996, a tomato cultivar resistant to bacterial wilt caused by P. solanacearum was crossed with Floradel, a susceptible cultivar and the F1 and F2 seeds were obtained. Inoculated plants were tested in the field for bacterial wilt resistance and colonization by P. solanacearum. The F1 did not wilt and a significant 3:1 segregation for non wilting: wilting was observed in the F2, indicating a monogenic dominant resistance in Hawaii 7996. In the F2 and in Hawaii 7996, resistance was, associated to the limitation of bacterial spread in the stem. The degree of resistance of Floradel, the F2 and Hawaï 7996 was correlated to colonization at midstem. The usefulness of plant colonization criteria for breeding programs is discussed. 相似文献
14.
The mycotrophic character of Annona cherimola (Magnoliales), a tropical/subtropical plantation crop of interest, is described for the first time. This crop seems to depend on mycorrhizae (arbuscular) for optimal growth, with Glomus deserticola being the most effective endophyte tested. Study of the morphology of the arbuscular mycorrhizae in Annona roots showed exclusively intracellular hyphal development, with cell-to-cell fungal passage and an abundance of arbuscules and coiled hyphae within cells. Intercellular distributive hyphae were not observed. The morphology and the pattern of spread of the mycorrhizal colonization were similar for the different endophytes involved and appeared to be dependent on the host root. Such features of mycorrhizal colonization are characteristic of host species lacking intercellular air channels and have been described for some species of ecological interest, but they are not commonly noted in the mycorrhizal literature, especially that dealing with crop species. Some ecophysiological consequences of this pattern of colonization are discussed. 相似文献
15.
Epilithic bacterial and algal biomass were compared among a run, riffle, and pool along an open-canopy section of a third-order, temperate stream. Epilithic biofilms were sampled after 3, 7, 14, 21, 28, and 35 days colonization on unglazed ceramic tiles that were attached to plastic trays (n = 3) placed across each of the three habitats (i.e., run, riffle, pool). The diverse habitats and sampling regime were selected to provide a range in algal biomass so that potential covariation between epilithic bacterial and algal biomass could be assessed. There were significant differences among habitats and among trays within each habitat for both chlorophyll a and AFDM. Chlorophyll a and AFDM increased in the run and pool throughout the colonization period. In the riffle, chlorophyll a and AFDM increased rapidly early in colonization, then decreased. Epilithic bacterial biomass increased rapidly with no significant differences among the three habitats throughout colonization. Further, bacterial biomass did not correlate with either chlorophyll a or AFDM in any of the three habitats or on any of the sampling days. These results suggest that epilithic algal and bacterial biomass may be regulated by independent controls in some stream environments. 相似文献
16.
Shiveta Sharma Shailendra Sharma Ramesh K. Singh Akhauri Vaishampayan 《World journal of microbiology & biotechnology》2008,24(7):1169-1175
Colonization behavior of endophytic bacteria Burkholderia cepacia strains RRE-3 and RRE-5 was studied in the seedlings of rice variety NDR97 using confocal laser scanning microscopy under
controlled laboratory and greenhouse conditions. For studying colonization pattern, bacterial strains were tagged with pHRGFPGUS
plasmid. The role of bacterial strains (both gfp/gus-tagged and untagged) in growth promotion was also studied. After coming into contact with the host root system the bacteria
showed an irregular spreading. Dense colonization was observed on the primary and secondary roots and also on the junction
of emergence of the lateral roots. Results showed that the colonization pattern of Burkholderia cepacia strains was similar to that of other endophytic bacteria isolated from non-legumes. Burkholderia cepacia got entry inside the root at the sites of emergence of lateral roots, without formation of infection threads as in the case
of symbiotic rhizobacteria. Observations suggested that the endophytic bacterial strains RRE-3 and RRE-5 entered inside the
rice roots in a progressive manner. Bacteria were found to line up along the intercellular spaces of adjoining epidermal cells
adjacent to the lateral root junction, indicating endophytic colonization pattern of Burkholderia cepacia strains. Experiments with the rice seedlings inoculated with RRE-3 and RRE-5 strains revealed that both strains enhanced
plant growth considerably when observed under laboratory and greenhouse conditions and produced significantly higher plant
biomass. No considerable difference was observed between the gfp/gus-tagged and non-gfp/gus-tagged strains in the plant growth experiments both in the laboratory and greenhouse conditions. 相似文献
17.
Longhuan Ma Kalyan K. Dewan Dawn L. Taylor-Mulneix Shannon M. Wagner Bodo Linz Israel Rivera Yang Su Amanda D. Caulfield Uriel Blas-Machado Eric T. Harvill 《PLoS pathogens》2021,17(8)
Whooping cough is resurging in the United States despite high vaccine coverage. The rapid rise of Bordetella pertussis isolates lacking pertactin (PRN), a key vaccine antigen, has led to concerns about vaccine-driven evolution. Previous studies showed that pertactin can mediate binding to mammalian cells in vitro and act as an immunomodulatory factor in resisting neutrophil-mediated clearance. To further investigate the role of PRN in vivo, we examined the functions of pertactin in the context of a more naturally low dose inoculation experimental system using C3H/HeJ mice that is more sensitive to effects on colonization, growth and spread within the respiratory tract, as well as an experimental approach to measure shedding and transmission between hosts. A B. bronchiseptica pertactin deletion mutant was found to behave similarly to its wild-type (WT) parental strain in colonization of the nasal cavity, trachea, and lungs of mice. However, the pertactin-deficient strain was shed from the nares of mice in much lower numbers, resulting in a significantly lower rate of transmission between hosts. Histological examination of respiratory epithelia revealed that pertactin-deficient bacteria induced substantially less inflammation and mucus accumulation than the WT strain and in vitro assays verified the effect of PRN on the induction of TNF-α by murine macrophages. Interestingly, only WT B. bronchiseptica could be recovered from the spleen of infected mice and were further observed to be intracellular among isolated splenocytes, indicating that pertactin contributes to systemic dissemination involving intracellular survival. These results suggest that pertactin can mediate interactions with immune cells and augments inflammation that contributes to bacterial shedding and transmission between hosts. Understanding the relative contributions of various factors to inflammation, mucus production, shedding and transmission will guide novel strategies to interfere with the reemergence of pertussis. 相似文献
18.
Yosuke Tashiro Rita E. Monson Joshua P. Ramsay George P. C. Salmond 《Environmental microbiology》2016,18(4):1264-1276
Different modes of bacterial taxis play important roles in environmental adaptation, survival, colonization and dissemination of disease. One mode of taxis is flotation due to the production of gas vesicles. Gas vesicles are proteinaceous intracellular organelles, permeable only to gas, that enable flotation in aquatic niches. Gene clusters for gas vesicle biosynthesis are partially conserved in various archaea, cyanobacteria, and some proteobacteria, such as the enterobacterium, Serratia sp. ATCC 39006 ( S39006 ). Here we present the first systematic analysis of the genes required to produce gas vesicles in S39006 , identifying how this differs from the archaeon Halobacterium salinarum. We define 11 proteins essential for gas vesicle production. Mutation of gvpN or gvpV produced small bicone gas vesicles, suggesting that the cognate proteins are involved in the morphogenetic assembly pathway from bicones to mature cylindrical forms. Using volumetric compression, gas vesicles were shown to comprise 17% of S39006 cells, whereas in Escherichia coli heterologously expressing the gas vesicle cluster in a deregulated environment, gas vesicles can occupy around half of cellular volume. Gas vesicle production in S39006 and E. coli was exploited to calculate the instantaneous turgor pressure within cultured bacterial cells; the first time this has been performed in either strain. 相似文献
19.
Abstract
Genetically engineered microorganisms (GEMs) released into the environment may persist and spread, depending on their features
and conditions encountered. In streams, the extent of dispersion depends largely on cycles of attachment to, and detachment
from, biofilms, because distribution of microorganisms is limited only by stream flow and settling rates, and because biofilms
are the primary generator of bacterial cells. To simulate dissemination of introduced bacteria, multiple antibiotic-resistant
bacteria (Chryseobacterium (Flavobacterium) indologenes) were introduced into microcosms containing water, sediments, and leaves. Marked bacteria reached greatest abundances in
sediments, and contributions of bacteria from sediments to other habitats was relatively low. Bacterial attachment and detachment
occurred rapidly, but the ability of marked bacteria to successfully exploit receiving habitats was comparatively low. Current
speed influenced bacterial dissemination. A mechanistic model, using mortality and attachment/detachment rates, determined
experimentally, was developed to predict bacterial exchanges in nature. The model was predictive of experimental results when
only 5% of bacteria in sediments were available for detachment. Based on model results, an introduced bacterial strain, with
mortality rates comparable to those of the model strain, is predicted to maintain highest abundances in sediments. However,
within a month, abundance was predicted to be reduced by 98%; long-term persistence is possible if these low population sizes
can be sustained.
Received: 11 August 1997; Accepted: 9 December 1997 相似文献
20.
[背景] 生防菌在作物根系的有效定殖是其功能发挥的前提,而直观的跟踪技术和有效的定量方法是研究生防菌根系分布规律的重要工具。[目的] 研究马铃薯黑痣病病原菌立枯丝核菌(Rhizo ctonia solani) JT18的拮抗菌QHZ11在马铃薯植株上的定殖特征及对马铃薯的促生效果。[方法] 采用绿色荧光蛋白(Green Fluorescent Protein,GFP)对QHZ11进行标记,将标记菌株菌悬液、生物有机肥和无菌水分别接种至灭菌土壤,通过激光共聚焦显微技术和实时荧光定量PCR等方法观察和测定标记菌株在马铃薯植株不同部位的定殖特征、数量变化及对马铃薯的促生效果。[结果] pHAPII质粒成功导入QHZ11并可稳定遗传40代,记为QHZ11-gfp;菌株标记前后的菌落形态、生长曲线和对R.solani JT18的拮抗能力等基本一致。从第7天开始,相继在马铃薯芽上和根上发现了绿色荧光,说明QHZ11-gfp成功定殖到了马铃薯的芽、根等部位。QHZ11-gfp在根系和匍匐茎的定殖数量均呈现先升高至块茎形成期达到峰值后下降的趋势,并且在整个生育期根系的定殖数量始终大于匍匐茎。菌悬液和生物有机肥处理均显著促进了马铃薯根系的生长,并通过增加株高等农艺性状提高了块茎产量。其中,生物有机肥处理在各部位的荧光强度、定殖数量和对马铃薯的促生效果均显著优于菌悬液。[结论] QHZ11-gfp可在马铃薯植株上成功定殖并对马铃薯有良好的促生效果,将其制成生物有机肥促进了其定殖,使促生效果也更好。 相似文献