creator Kunkel, Stephanie advisor Stark, Benjamin C. The dominance of hemoglobin (Hb)-expressing bacteria in biological wastewater treatment systems could improve oxygen utilization under low dissolved oxygen (DO) conditions. Hb-proteins are versatile molecules that have several biological functions. Here, Nitrosomonas europaea has been transformed with various plasmids; of particular interest is a recombinant plasmid bearing the constitutive Amo1 promoter and the gene (vgb) encoding the hemoglobin from the bacterium Vitreoscilla. Expression of VHb was assayed using various visible spectral methods, and VHb production seen in this recombinant strain. There were several positive effects on N. europaea metabolism related to VHb expression that were seen, specifically the ability of cultures to convert ammonia to nitrite at a slightly higher rate as well as higher specific oxygen uptake rates (SOUR) at both high (near saturation, 7 mg O2/ L) and low (< 2 mg O2/L) dissolved oxygen (DO) conditions. In parallel to this, two activated sludge cultures from the same source were cultivated using synthetic wastewater seeded with activated sludge from the same source and were operated at high DO (near saturation) and low DO (0.25 mg O2/L) concentrations for 370 days. There were significant changes in the bacterial species and phyla present in each of the cultures at various time points during the 370 day operational period. In the low DO culture, over time, there was a much greater expression of single domain and truncated Hbs which may enhance utilization and delivery of oxygen to various enzymes as well as to the respiratory chain. A larger increase in heme b was also observed which coincides with this observation. By the end of the acclimation period, the SOUR values were about 30% greater in the low DO culture compared to the high DO culture. This indicated the successful adaption of the low DO culture to respire more efficiently and eventually outperform the high DO culture. Submitted by Erma Thomas (thomase@iit.edu) on 2015-05-04T21:24:27Z No. of bitstreams: 2 PhDthesisSK_master_0718_FINAL.pdf: 1416400 bytes, checksum: 42dd15826a2a74061aa6b4bfef1d8cfc (MD5) Signed title page.pdf: 61621 bytes, checksum: 954a1d1bc1866da2a3c66e7351035baf (MD5) Made available in DSpace on 2015-05-04T21:24:28Z (GMT). No. of bitstreams: 2 PhDthesisSK_master_0718_FINAL.pdf: 1416400 bytes, checksum: 42dd15826a2a74061aa6b4bfef1d8cfc (MD5) Signed title page.pdf: 61621 bytes, checksum: 954a1d1bc1866da2a3c66e7351035baf (MD5) Previous issue date: 2014-07 Ph.D. in Biology, July 2014 2014 2014-07 http://hdl.handle.net/10560/3401 en Dissertation born digital application/pdf In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access BIOL / Biology Illinois Institute of Technology Affiliated department