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Isolation and characterization of endophytic colonizing bacteria from agronomic crops and prairie plants.

ABSTRACT: Endophytic bacteria reside within plant hosts without causing disease symptoms. In this study, 853 endophytic strains were isolated from aerial tissues of four agronomic crop species and 27 prairie plant species. We determined several phenotypic properties and found approximately equal numbers of gram-negative and gram-positive isolates. In a greenhouse study, 28 of 86 prairie plant endophytes were found to colonize their original hosts at 42 days postinoculation at levels of 3.5 to 7.7 log(10) CFU/g (fresh weight). More comprehensive colonization studies were conducted with 373 corn and sorghum endophytes. In growth room studies, none of the isolates displayed pathogenicity, and 69 of the strains were recovered from corn or sorghum seedlings at levels of 8.3 log(10) CFU/plant or higher. Host range greenhouse studies demonstrated that 26 of 29 endophytes were recoverable from at least one host other than corn and sorghum at levels of up to 5.8 log(10) CFU/g (fresh weight). Long-range dent corn greenhouse studies and field trials with 17 wild-type strains and 14 antibiotic-resistant mutants demonstrated bacterial persistence at significant average colonization levels ranging between 3.4 and 6.1 log(10) CFU/g (fresh weight) up to 78 days postinoculation. Three prairie and three agronomic endophytes exhibiting the most promising levels of colonization and an ability to persist were identified as Cellulomonas, Clavibacter, Curtobacterium, and Microbacterium isolates by 16S rRNA gene sequence, fatty acid, and carbon source utilization analyses. This study defines for the first time the endophytic nature of Microbacterium testaceum. These microorganisms may be useful for biocontrol and other applications.

SUBMITTER: Zinniel DK

PROVIDER: S-EPMC127535 | biostudies-literature | 2002 May

REPOSITORIES: biostudies-literature

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Isolation and characterization of endophytic colonizing bacteria from agronomic crops and prairie plants.

Zinniel Denise K DK Lambrecht Pat P Harris N Beth NB Feng Zhengyu Z Kuczmarski Daniel D Higley Phyllis P Ishimaru Carol A CA Arunakumari Alahari A Barletta Raúl G RG Vidaver Anne K AK

Applied and environmental microbiology 20020501 5

Endophytic bacteria reside within plant hosts without causing disease symptoms. In this study, 853 endophytic strains were isolated from aerial tissues of four agronomic crop species and 27 prairie plant species. We determined several phenotypic properties and found approximately equal numbers of gram-negative and gram-positive isolates. In a greenhouse study, 28 of 86 prairie plant endophytes were found to colonize their original hosts at 42 days postinoculation at levels of 3.5 to 7.7 log(10) ...[more]

PMID: 11976089

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Project description:The present investigation was carried out to isolate arsenic (As)-resistant endophytic bacteria from the roots of alfalfa and chickpea plants grown in arsenic-contamination soil, characterize their As tolerance ability, plant growth-promoting characteristics, and their role to induce As resistance by the plant. A total of four root endophytic bacteria were isolated from plants grown in As-contaminated soil (160-260-mg As kg-1 of soil). These isolates were studied for plant growth-promoting (PGP) characteristics through siderophore, phosphate solubilization, nitrogen fixation, protease, and lipase production, and the presence of the arsenate reductase (arsC) gene. Based on 16S rDNA sequence analysis, these isolates belong to the genera Acinetobacter, Pseudomonas, and Rahnella. All isolates were found As tolerant, of which one isolate, Pseudomonas sp. QNC1, showed the highest tolerance up to 350-mM concentration in the LB medium. All isolates exhibited phosphate solubilization activity. Siderophore production activity was shown by only Pseudomonas sp. QNC1, while nitrogen fixation activity was shown by only Rahnella sp. QNC2 isolate. Acinetobacter sp. QNA1, QNA2, and Rahnella sp. QNC2 exhibited lipase production, while only Pseudomonas sp. QNC1 was able to produce protease. The presence of the arsC gene was detected in all isolates. The effect of endophytic bacteria on biomass production of alfalfa and chickpea in five levels of arsenic concentrations (0-, 10-, 50-, 75-, and 100-mg kg-1 soil) was evaluated. The fresh and dry weights of roots of alfalfa and chickpea plants were decreased as the arsenic concentration of the soil was increased. Results indicate that the fresh and dry root weights of alfalfa and chickpea plants were significantly higher in endophytic bacteria-treated plants compared with non-treated plants. Inoculation of chickpea plants with Pseudomonas sp. QNC1 and Rahnella sp. QNC2 induced lower NPR3 gene expression in chickpea roots grown in soil with the final concentration of 100-mg kg-1 sodium arsenate compared with the non-endophyte-treated control. The same results were obtained in Acinetobacter sp. QNA2-treated alfalfa plants grown in the soil plus 50-mg kg-1 sodium arsenate. These results demonstrated that arsenic-resistant endophytic bacteria are potential candidates to enhance plant-growth promotion in As contamination soils. Characterization of bacterial endophytes with plant growth potential can help us apply them to improve plant yield under stress conditions.

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Dataset Information

Isolation and characterization of endophytic colonizing bacteria from agronomic crops and prairie plants.

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Isolation and characterization of endophytic colonizing bacteria from agronomic crops and prairie plants.

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