SULFUR SCAVENGING BY THE ANOXYGENIC PHOTOTROPH HELIOPHILUM FASCIATUM

Author

Sophia Antonietta Sanguedolce, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2025

Degree Name

Master of Science

Department

Molecular Biology Microbiology and Biochemistry

First Advisor

Bender, Kelly

Abstract

Heliophilum fasciatum is an anoxygenic phototroph belonging to the group known as heliobacteria. One of the common characteristics of heliobacteria is that they all are capable of diazotrophy, but recent findings have failed to locate the nitrogenase genes typical to heliobacteria within the genome of H. fasciatum. Instead, five nitrogenase-like genes, tentatively named NflDK1-5, were discovered that did not clade with other NifDK genes during phylogenic analysis. Here, we suggest that many of these NflDK proteins may, in actuality, be related to the sulfur metabolism and usage. Further phylogenetic analysis and protein sequence comparisons show strong divergence from canonical heliobacterial nitrogenase proteins. Gas chromatography has indicated that in the presence of the sulfur source 2-methylthioethanol, H. fasciatum is able to produce ethylene and methane, which are byproducts of the MarDK system as seen in Rhodospirillum rubrum. The high phylogenetic similarity of NflDK5 to MarDK also lends to the conclusion that it is likely that NflDK5 acts as a MarDK in H. fasciatum. Through RT-PCR we show that the NflDK1-5 genes are being expressed, but efforts at qRT-PCR have thus far failed due to cross reactions occurring between primers. This work has work has allowed for further elucidation of the roles of these NflDK proteins though more work is necessary to definitely ascribe roles to these enzymes.