Linkage of the Nitrilase-Encoding Nit1C Gene Cluster to Cyanotrophy in Acinetobacter haemolyticus

The Nit1C cluster is a conserved gene cluster of seven genes that confers bacterial growth on cyanide as the sole nitrogen source. Bacteria with this ability are referred to as cyanotrophs. To date, the linkage between Nit1C and cyanotrophy has only been demonstrated for environmental isolates but the cluster also exists in certain medically related bacteria. In this study, a nosocomial isolate, Acinetobacter haemolyticus ATCC 19194, carrying Nit1C also displayed the ability to grow on cyanide. Growth on cyanide was accompanied by the induction of the cluster as was the mere exposure of cells to cyanide. Expression of the cluster was determined by measuring the activity of the nitrilase (NitC) coded for by the cluster and by transcriptional analysis (qRT-PCR). However, a disconnect between nitC message and NitC protein was observed depending on the phase of the growth cycle, the disconnect being related to proteolytic digestion of the NitC protein. Ironically, the cluster was also discovered to be upregulated in the absence of cyanide under nitrogen starvation conditions paralleling biofilm formation. The basis of the genetic linkage to cyanotrophy is not understood but taken together with results showing that nitrogen starvation and biofilm formation are also physiologically associated with Nit1C …
Date: July 2023
Creator: Dale, Layla Momo
System: The UNT Digital Library
Comparative Resistomics of Ancient and Modern Human Microbiomes (open access)

Comparative Resistomics of Ancient and Modern Human Microbiomes

Increased exposure to antibiotics has led to the dissemination of genes conferring resistance to antimicrobial metabolites throughout human microbiomes globally via horizontal gene transfer (HGT). This has resulted in the emergence of new resistant strains leading to a rising epidemic of deaths from previously treatable infections. Evidence suggests that before the age of anthropogenic antibiotic use, microbes living within a community produced antibiotic metabolites and, subsequently, maintained such genes for several useful functions and a balance of diversity in nature. The question of the origin of these resistant genes is difficult to answer, but with continued advancements in ancient genomic analysis, researchers have developed methods of acquiring a more accurate representation of the microbiome associated with our human ancestors by extracting fossilized microbial specimens from dental calculus and directly sequencing the metagenomes. This thesis outlines the production of taxonomic and functional profiles of 20 different human and non-human oral microbiome samples using metagenomics tools originally developed for living individuals, altered for use with ancient microbial specimens. Putative antimicrobial resistant (AMR) genes derived from these profiles were reconstructed and conserved functional regions were identified. From the data that is available regarding the human microbiome from a range of time points throughout …
Date: August 2020
Creator: Johnson, Sarah
System: The UNT Digital Library