Bacterial communities associated with flowering plants of the Ni hyperaccumulator Thlaspi goesingense

• Published in: Applied and Environmental Microbiology 2004-05, Vol.70 (5), p.2667-2677
• Main Authors: Idris, R, Trifonova, R, Puschenreiter, M, Wenzel, W.W, Sessitsch, A
• Format: Article
• Language: English
• Subjects: 1-aminocyclopropane-1-carboxylic acid; ACC deaminase; Acidobacterium; amidine hydrolases; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - isolation & purification; Bacteroides; Biological and medical sciences; Carbon-Carbon Lyases - metabolism; community ecology; Culture Media; Cytophaga; DNA, Ribosomal - analysis; Ecology; Ecosystem; endophytes; Flexibacter; Flowers & plants; Flowers - microbiology; Fundamental and applied biological sciences. Psychology; genes; hyperaccumulators; metal tolerance; Methylobacterium mesophilicum; Microbial Ecology; microbial physiology; Microbiology; Molecular Sequence Data; nickel; Nickel - metabolism; Nickel - pharmacology; Nitrogen; nucleotide sequences; nutrients; Plant Roots - microbiology; Plant Shoots - microbiology; Proteobacteria; restriction fragment length polymorphism; rhizosphere; Rhodococcus; ribosomal RNA; RNA, Ribosomal, 16S - genetics; Sequence Analysis, DNA; serpentine soils; siderophores; Siderophores - metabolism; soil bacteria; species diversity; Sphingomonas; terminal restriction fragment length polymorphism; Thlaspi; Thlaspi - drug effects; Thlaspi - growth & development; Thlaspi - metabolism; Thlaspi - microbiology; Thlaspi goesingense; Verrucomicrobia
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.70.5.2667-2677.2004

Thlaspi goesingense is able to hyperaccumulate extremely high concentrations of Ni when grown in ultramafic soils. Recently it has been shown that rhizosphere bacteria may increase the heavy metal concentrations in hyperaccumulator plants significantly, whereas the role of endophytes has not been investigated yet. In this study the rhizosphere and shoot-associated (endophytic) bacteria colonizing T. goesingense were characterized in detail by using both cultivation and cultivation-independent techniques. Bacteria were identified by 16S rRNA sequence analysis, and isolates were further characterized regarding characteristics that may be relevant for a beneficial plant-microbe interaction--Ni tolerance, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and siderophore production. In the rhizosphere a high percentage of bacteria belonging to the Holophaga/Acidobacterium division and alpha-Proteobacteria were found. In addition, high-G+C gram-positive bacteria, Verrucomicrobia, and microbes of the Cytophaga/Flexibacter/Bacteroides division colonized the rhizosphere. The community structure of shoot-associated bacteria was highly different. The majority of clones affiliated with the Proteobacteria, but also bacteria belonging to the Cytophaga/Flexibacter/Bacteroides division, the Holophaga/Acidobacterium division, and the low-G+C gram-positive bacteria, were frequently found. A high number of highly related Sphingomonas 16S rRNA gene sequences were detected, which were also obtained by the cultivation of endophytes. Rhizosphere isolates belonged mainly to the genera Methylobacterium, Rhodococcus, and Okibacterium, whereas the majority of endophytes showed high levels of similarity to Methylobacterium mesophilicum. Additionally, Sphingomonas spp. were abundant. Isolates were resistant to Ni concentrations between 5 and 12 mM; however, endophytes generally tolerated higher Ni levels than rhizosphere bacteria. Almost all bacteria were able to produce siderophores. Various strains, particularly endophytes, were able to grow on ACC as the sole nitrogen source.