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jjoyner@unc.edu |
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jjoyner@unc.edu |
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I am a graduate student at the Institute of Marine Sciences from the Marine Sciences Department at UNC-CH. My thesis project involves the molecular characterization of Lyngbya species and strains. Lyngbya is a cosmopolitan, non-heterocystous benthic cyanobacterial genus found in both freshwater and marine environments. Lyngbya is often found in nutrient-deprived waters, but can undergo explosive growth in response to eutrophication. Lyngbya blooms occur in the summer months and have been problematic in lakes around High Point, NC, and Australia’s Moreton Bay. It is also found in the St. Petersberg/Tampa Bay and Panhandle regions of Florida and slow-moving rivers and lakes in the US Southeast and mid-Atlantic regions.
Species of the Lyngbya genus also contain toxins that are harmful to humans. L. majuscula blooms in Australia’s Moreton Bay and has been responsible for respiratory irritation, eye inflammation, and severe contact dermatitis in fishermen and swimmers. L. wollei is a freshwater analog and has bloomed in High Point’s City Lake during the summer months for the past 3 years. Fishermen at City Lake have complained of irritated sinuses, teary eyes, and sore throats after fishing beside the blooms. There is much interest in eliminating Lyngbya blooms where they occur.
Many cyanobacteria have the ability to make or fix biologically available NH4 from atmospheric N2. This gives them a competitive advantage in a nitrogen-limited environment. I have grown L. wollei quickly and successfully on plates containing nitrogen, and I am in the process of growing L. wollei on nitrogen-free agar media plates. Thus far, the N-free plates are showing promise with quick growth. I have also detected nitrogen fixation occurring in a L. wollei bloom through an acetylene reduction experiment.
Cyanobacteria are able to fix nitrogen if they
are able to make the N2 fixing enzyme, nitrogenase. The nifH gene
encodes for the Fe protein subunit of nitrogenase. Like many other
cyanobacteria, Lyngbya also contains this gene. The nifH gene is
highly conserved and therefore useful for comparing evolutionary relationships,
much like the more typical 16S and 18S ribosomal DNA comparisons.
The 16S small subunit ribosomal DNA is too conservative to be useful for
my purposes because it does not provide enough differentiation at the genus
and species level. Phylogenetic data will hopefully prove interesting
for comparisons between geographical locations and ecological constraints.
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The Lyngbya flourishes in the calcium-rich waters coming up through the limestone beneath. |
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has grown so thick that oxygen produced by photosynthesis became trapped within the bloom and forced the bloom to the surface. |
Questions and goals:
1) Do Lyngbya species take advantage of nutrient
enrichment in our estuarine and coastal waters undergoing eutrophication?
2) Which nutrients or combination of nutrients
are bloom promoters for the species L. wollei?
3) Is Lyngbya an indicator of eutrophication?
4) Could toxic strains of L. majuscula or other
Lyngbya species find their way to estuaries currently being impacted by
anthropogenic nutrient enrichment?
5) Develop oligonucleotide probes for quick identification
of various Lyngbya species and strains.
