Recovery of a rhizosphere-colonizing GEM from inside wheat roots

1999 ◽  
Vol 45 (7) ◽  
pp. 612-615 ◽  
Author(s):  
James D Nairn ◽  
Christopher P Chanway
Keyword(s):  
Rhizosphere Soil ◽  
Genetically Engineered ◽  
Root Tissue ◽  
Marker Genes ◽  
Wheat Roots ◽  
Genetically Engineered Microorganisms ◽  
Population Sizes ◽  
Genetically Engineered Microorganism ◽  
Root Tissues ◽  
Fresh Root

Pseudomonas chloroaphis 3732 RN-L11 is a genetically modified bacterial strain that contains the lacZY marker genes in its chromosome. This strain is known to be a vigorous colonizer of plant roots and rhizosphere soil, and has been used as a model to evaluate survival and persistence of field-released genetically engineered microorganisms (GEMs). However, the possibility that strain 3732 RN-L11 may also colonize internal plant tissues has not previously been investigated. Using spring wheat as a model system, we studied the ability of strain 3732 RN-L11 to colonize external and internal root tissues after seed inoculation. Strain 3732 RN-L11 was recovered from rhizosphere soil of 28-, 42-, and 56-day-old seedlings with mean population sizes of 3.3 × 105, 7.5 × 104, and 2.2 × 105CFU·g-1fresh root tissue, respectively. In addition, this strain was consistently recovered from surface-sterilized root tissues of 28- to 56-day-old seedlings with mean population sizes of 1.0 × 102to 6.2 × 103CFU·g-1fresh root tissue. Our results indicate that evaluation of plant-associated GEM populations after field release should include all possible colonization niches, including internal plant tissues.Key words: genetically engineered microorganism, rhizosphere, endophyte.

External and internal root colonization of lodgepole pine seedlings by two growth-promoting Bacillus strains originated from different root microsites

1995 ◽  
Vol 41 (8) ◽  
pp. 707-713 ◽  
Author(s):  
M. Shishido ◽  
B. M. Loeb ◽  
C. P. Chanway
Keyword(s):  
Root Colonization ◽  
Lodgepole Pine ◽  
Substrate Utilization ◽  
Root Tissue ◽  
Pine Seedlings ◽  
Growth Promoting ◽  
Root Tissues ◽  
Bacillus Strains ◽  
Fresh Root

Root colonization and in vitro carbon substrate utilization by two seedling growth-promoting Bacillus strains that originated from different root microsites were studied in greenhouse and growth chamber experiments. Strain L6, identified as Bacillus polymyxa, was previously isolated from rhizosphere soil containing roots of pasture plants, and Pw-2, tentatively identified also as B. polymyxa, was isolated from within surface-sterilized lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) roots. Rifamycin-resistant strains derived spontaneously from wild-type strains L6 and Pw-2, designated strain L6-16R and Pw-2R, respectively, were used to monitor lodgepole pine root colonization in a closed tube assay system. Three-week-old pine seedlings were inoculated with 105 colony-forming units (cfu) of strain Pw-2R or 106 cfu of strain L6-16R, and external and internal root colonization was assessed 2 and 4 weeks later. Strains L6-16R and Pw-2R were both recovered from pine rhizosphere samples with > 5 × 107 cfu/g fresh root tissue 2 weeks after inoculation, but neither strain was detected in the root interior. When root colonization was assessed 4 weeks after inoculation, the rhizosphere populations of both strains had declined slightly to between 5 × 106 and 5 × 107 cfu/g fresh root tissue, but strain Pw-2R was also detected within root tissues with 105 cfu/g fresh root tissue. Lateral root formation was abundant 4 weeks after inoculation and may have facilitated colonization of internal root tissues by strain Pw-2R. Both strains possessed pectolytic activity, although differences between the strains were detected in in vitro substrate utilization capabilities using BIOLOG assays. These differences may be related to their abilities to colonize internal root tissues. On the basis of our results, we hypothesize that internal root colonization by Bacillus strains is not a random event and that root-endophytic Bacillus strains possess specific physiological and (or) biochemical characteristics that facilitate colonization of internal root tissues.Key words: Bacillus, PGPR, rhizosphere, endophytes, colonization.

Ecologically significant effects of Pseudomonas putida PPO301(pRO103), genetically engineered to degrade 2,4-dichlorophenoxyacetate, on microbial populations and processes in soil

1991 ◽  
Vol 37 (9) ◽  
pp. 682-691 ◽  
Author(s):  
Jack D. Doyle ◽  
Kevin A. Short ◽  
Guenther Stotzky ◽  
Rick J. King ◽  
Ramon J. Seidler ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Pseudomonas Putida ◽  
Dehydrogenase Activity ◽  
Parental Strain ◽  
Genetically Engineered ◽  
Microbial Populations ◽  
Rate Of Evolution ◽  
Genetically Engineered Microorganisms ◽  
Fungal Propagules ◽  
Genetically Engineered Microorganism

Pseudomonas putida PPO301(pRO103), genetically engineered to degrade 2,4-dichlorophenoxyacetate, affected microbial populations and processes in a nonsterile xeric soil. In soil amended with 2,4-dichlorophenoxyacetate (500 μg/g soil) and inoculated with PPO301(pRO103), the rate of evolution of carbon dioxide was retarded for approximately 35 days; there was a transient increase in dehydrogenase activity; and the number of fungal propagules decreased below detection after 18 days. In unamended soil inoculated with PPO301(pRO103), the rate of evolution of carbon dioxide and the dehydrogenase activity were unaffected, and the numbers of fungal propagules were reduced by about two orders of magnitude. The numbers of total, spore-forming, and chitin-utilizing bacteria were reduced transiently in soil either amended or unamended with 2,4-dichlorophenoxyacetate and inoculated with PPO301(pRO103). The activities of arylsulfatases and phosphatases in soil were not affected by the presence of PPO301(pRO103), either in the presence or absence of 2,4-dichlorophenoxyacetate. In soil amended with 2,4-dichlorophenoxyacetate and inoculated with the parental strain (PPO301) or not inoculated, the evolution of carbon dioxide, the numbers of fungal propagules and of total, spore-forming, and chitin-utilizing bacteria, and the dehydrogenase activity were not affected as in soil inoculated with PPO301(pRO103). These results demonstrated that a genetically engineered microorganism, in the presence of the substrate on which its novel genes can function, is capable of inducing measurable ecological effects in soil. Key words: genetically engineered microorganisms, soil, ecology, 2,4-dichlorophenoxyacetate, Pseudomonas putida.

Physical and chemical control of released microorganisms at field sites

1991 ◽  
Vol 37 (9) ◽  
pp. 708-712 ◽  
Author(s):  
Katherine Donegan ◽  
Ramon Seidler ◽  
Carl Matyac
Keyword(s):  
Genetically Engineered ◽  
Control Treatment ◽  
Control Field ◽  
Genetically Engineered Microorganisms ◽  
Cupric Hydroxide ◽  
Genetically Engineered Microorganism ◽  
Rate Of Decline ◽  
The Individual ◽  
Physical And Chemical ◽  
Field Plots

An important consideration in the environmental release of a genetically engineered microorganism is the capability for reduction or elimination of microorganism populations once their function is completed or if adverse environmental effects are observed. In this study the decontamination treatments of burning and biocide application, alone and in combination with tilling, were evaluated for their ability to reduce populations of bacteria released on the phylloplane. Field plots of bush beans (Phaseolus vulgaris), sprayed with the bacterium Erwinia herbicola, received the following treatments: control; control + till; burn; burn + till; Kocide (cupric hydroxide); Kocide + till; Agri-Strep (streptomycin sulfate); and Agri-Strep + till. Leaves and soil from the plots were sampled −1, 1, 5, 8, 12, 15, 19, and 27 days after application of the decontamination treatments. Burning produced a significant reduction in the number of E. herbicola, whereas tilling, alone or in combination with the biocide treatments, stimulated a significant increase in E. herbicola populations, which persisted for several weeks. The individual treatments of the biocides, Kocide and Agri-Strep, produced a rate of decline in E. herbicola populations that did not significantly differ from that of the control treatment. Key words: decontamination, risk control, field release, genetically engineered microorganisms.

Sign in / Sign up

Export Citation Format

Share Document