Micro-Eukaryote Diversity in Freshwater Ponds That Harbor the Amphibian Pathogen Batrachochytrium Dendrobatidis (Bd)

Article excerpt

To spark an interest in biology for students in K-12 institutions and beyond, it is important to bring current research topics into the classroom. Freshwater environments such as ponds are ideal for making students aware of the diversity and complex interactions of its inhabitants. In the project described here, we focused on the detection of the fungal pathogen Batrachochytrium dendrobatidis (Bd), which is responsible for the decline of many amphibian populations worldwide. At the same time, we also investigated the diversity of its natural predators, filter-feeding micro-crustaceans that prey on motile zoospores of the fungus. It is exciting to include modern technologies in lab experiments similar to those used in environmental and clinical biology research facilities throughout the world. The cost of supplies for these technologies is becoming more affordable, and students are excited to realize that these "complicated techniques" are, in fact, not that complicated at all. Students who are confident about what they can achieve in a science class, and who have been trained in modern molecular biological methods in addition to traditional techniques, will be better prepared for graduate school and possible careers in microbiology. Being included in a meaningful research project also enforces critical-thinking skills that are important for literature research, development and understanding of a project, evaluation of research data, and the presentation of results. Along with acquiring these skills, students also become educated citizens who gain an understanding of microbial interactions based on a topic of global concern: the ongoing amphibian decline due to chytridiomycosis.

* Concept Explanation

Batrachochytrium dendrobatidis is a fungal pathogen that has been identified as the causative agent in the decline of many amphibian populations in California and worldwide (for an extensive discussion of amphibian decline due to chytridiomycosis and amphibian conservation strategies, see Woodhams et al., 2011).

A decline of diverse microcrustacean species, which can be natural predators of Bd (Buck et al., 2011; Woodhams et al., 2011), has been observed in some areas (e.g., Lake Tahoe and the Sierra Nevada Mountains) (Goldman et al., 1979; Nielsen et al., 2000). The identification of diapausing eggs from microcrustaceans can serve as an indicator for the diversity of microcrustaceans in the past (Limburg & Weider, 2002).

After obtaining water and sediment samples from different ponds, we determined the micro-crustacean diversity in the water samples using microscopy, and then used molecular tools to detect Bd and to analyze the diversity of microeukaryotes in water and sediment samples. We also identified the amphibian species present at each pond.

Modern clinical and environmental research labs are nowadays using molecular techniques to investigate microbial diversity and community structure in various environments and to identify microbial pathogens. Molecular techniques have revolutionized biological sciences by allowing organism identification without cultivation. Unfortunately, as currently structured, many microbiology teaching labs do not expose undergraduate students to these current, and now somewhat standard, techniques. To address this, we developed and successfully conducted a lab that links traditional microbiological techniques such as microscopy, with electrophoresis techniques based on the polymerase chain reaction (PCR). Along with making students excited about microbiology and teaching important techniques that are standard in many laboratories, the aim of this lab exercise was to make students and their teachers aware of the connection between amphibians, an amphibian pathogen, and microcrustaceans as predators of single-celled prokaryotes and eukaryotes (including motile zoospores of the chytrid pathogen). This was accomplished by investigating water and sediment from ponds of different altitudes and environments near Bakersfield, California. …