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Abstract Detail



Genetics/Molecular Biology

McCormick, Melissa [1], Hauser, Wesley [2], Whigham, Dennis [1].

Effects of bacteria within fungal hyphae on the function of orchid mycorrhizae.

Mycorrhizal fungi are a fundamental component of nearly all terrestrial ecosystems, creating the critical link between above- and below-ground systems. There is now increasing evidence that bacteria living within fungal hyphae are widespread and may be an important element that drives the development of mycorrhizal associations.  Among mycorrhizal fungi, endobacteria have been reported from arbuscular and ectomycorrhizal fungi but not from orchid mycorrhizal fungi. Most mycorrhizal fungi can be difficult to work with in the laboratory because they are obligately associated with plants. In contrast, many orchid mycorrhizal fungi are only facultatively associated with plants and can be  grown in the laboratory; thus making it possible  to conduct  experiments to better understand the ecology and physiology of endobacteria, with a goal of determining the roles each of three components (i.e., endobacteria, fungi, plants) in the relationship. Given the diversity of orchid mycorrhizal fungi, studies of endobacteria-fungal relationships also have the potential to enrich our understanding of evolutionary relationships.  We used a combination of live/dead staining and fluorescent in-situ hybridization (FISH) to visualize endobacteria in orchid mycorrhizal fungi. Viable bacteria were found within living hyphae of multiple orchid mycorrhizal fungi belonging to the genera Tulasnella and Ceratobasidium. We used DNA sequencing of the ribosomal small subunit to determine that the endobacteria are diverse in fungi that were freshly isolated from orchid mycorrhizae, but were often lacking in fungal cultures that had been maintained in the laboratory for multiple years. This suggested that endobacteria may be lost during long-term storage that relies on periodic sub-culturing of the fungi. This loss occurred preferentially with transfers of the growing edge of mycelia on antibiotic plates. This loss of endobacteria from our orchid-mycorrhizal cultures was also associated with significantly lower fungal growth rates and ability to support the germination of orchid seeds and the growth of protocorms. The loss of endobacteria may explain the loss of mycorrhizal functionality that has been observed in orchid mycorrhizal fungi after significant time in culture. This also supports the possibility of using orchid mycorrhizal fungi with endobacteria as a model system for developing a better understanding of the role of endobacteria in mycorrhizal functioning.


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1 - Smithsonian Institution, Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD, 21037, USA
2 - Wabash College, Department of Biology, 301 W. Wabash Avenue, Crawfordsville, IN, 47933, USA

Keywords:
endobacteria
mycorrhizal fungi
orchid.

Presentation Type: Offered Paper - Paper
Session: 12
Location: Room 104 AB/Kellogg Hotel and Conference Center
Date: Tuesday, June 10th, 2014
Time: 10:30 AM
Number: 12001
Abstract ID:144
Candidate for Awards:None


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