Functional Role of Bacteria from Invasive Phragmites australis in Promotion of Host Growth.
We hypothesize that bacterial endophytes may enhance the competitiveness and invasiveness of Phragmites australis. To evaluate this hypothesis, endophytic bacteria were isolated from P. australis. The majority of the shoot meristem isolates represent species from phyla Firmicutes, Proteobacteria, and Actinobacteria. We chose one species from each phylum to characterize further and to conduct growth promotion experiments in Phragmites. Bacteria tested include Bacillus amyloliquefaciens A9a, Achromobacter spanius B1, and Microbacterium oxydans B2. Isolates were characterized for known growth promotional traits, including indole acetic acid (IAA) production, secretion of hydrolytic enzymes, phosphate solubilization, and antibiosis activity. Potentially defensive antimicrobial lipopeptides were assayed for through application of co-culturing experiments and mass spectrometer analysis. B. amyloliquefaciens A9a and M. oxydans B2 produced IAA. B. amyloliquefaciens A9a secreted antifungal lipopeptides. Capability to promote growth of P. australis under low nitrogen conditions was evaluated in greenhouse experiments. All three isolates were found to increase the growth of P. australis under low soil nitrogen conditions and showed increased absorption of isotopic nitrogen into plants. This suggests that the Phragmites microbes we evaluated most likely promote growth of Phragmites by enhanced scavenging of nitrogenous compounds from the rhizosphere and transfer to host roots. Collectively, our results support the hypothesis that endophytic bacteria play a role in enhancing growth of P. australis in natural populations. Gaining a better understanding of the precise contributions and mechanisms of endophytes in enabling P. australis to develop high densities rapidly could lead to new symbiosis-based strategies for management and control of the host.
Department of Botany and Ecology, Federal University of Mato Grosso, Cuiabá, Mato Grosso, 78060-900, Brazil. drmasoares@gmail.com.
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MA
Soares
Faculty of Life Sciences and Technology, Kunming University of Science and Technology, Kunming, 650500, Yunnan Province, China.
H-Y
HY
Li
US Geological Survey, Great Lakes Science Center, Ann Arbor, MI, USA.
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KP
Kowalski
Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Road, New Brunswick, NJ, 08901-8520, USA.
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M
Bergen
Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Road, New Brunswick, NJ, 08901-8520, USA.
M S
MS
Torres
Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Road, New Brunswick, NJ, 08901-8520, USA.
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JF
White
D000898:Antibiosis; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D018533:Biomass; D005658:Fungi / Q000254:growth & development; D007210:Indoleacetic Acids / Q000378:metabolism; D055666:Lipopeptides / Q000096:biosynthesis; D009586:Nitrogen Fixation; D010710:Phosphates / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology*; D006109:Poaceae / Q000254:growth & development / Q000382:microbiology*; D012988:Soil Microbiology; D013559:Symbiosis
D007210:Indoleacetic Acids; D055666:Lipopeptides; D010710:Phosphates; C030737:indoleacetic acid
Achromobacter spanius; Bacillus amyloliquefaciens; Lipopeptide; Microbacterium oxydans; Plant growth promotion