Document Type

Master's Research

Degree Name

Master of Science




Tanya T. Soule

Date of Award



As phototrophic bacteria, cyanobacteria are continually exposed to ultraviolet radiation as they harvest solar energy. In particular, long-wavelength ultraviolet radiation (UVA) damages living cells by releasing reactive oxygen species. To mitigate damage to the cell, some cyanobacteria produce a UVA-absorbing pigment in the extracellular sheath, known as scytonemin. Scytonemin is a heterocyclic, dimeric molecule that is only produced upon induction by UVA. In Nostoc punctiforme ATCC 29133, it is hypothesized that scytonemin is regulated by the two component regulatory system (TCRS) of NpF1277 (sensor kinase) and NpF1278 (response regulator). Gene expression of the TCRS was studied after exposure to UVA, UVB, high light, and oxidative stress after 20, 40, 60 min. The TCRS genes were significantly up-regulated after 20 min for the light-associated stresses (UVA, UVB, and high light) and after 60 min for high light, however they were down-regulated by 60 min under UVB. Furthermore, these genes did not significantly respond to oxidative stress for any of the tested time points. It was also concluded that the TCRS genes are co-transcribed in N. punctiforme. Finally, progress was made in the construction of an NpF1277 mutant strain. To do this, a deletion fragment of NpF1277 was created by fusion PCR and inserted into a conjugal vector. While mutants were not obtained, the construct has been constructed for future studies.