UC Santa Cruz

This study focuses on Citrobacter sp. TSA-1, an arsenate-reducing bacterium found in termites. Initially expecting an ArrA-type respiratory arsenate reductase, genome sequencing revealed the absence of the arr gene cluster. It was then hypothesized that TSA-1 utilizes an ArsC for both arsenate-mediated growth and reduction.Despite the absence of arsC1, TSA-1 was still capable of arsenate reduction, albeit with reduced resistance. This study aimed to understand arsenic toxicity in TSA-1 and identify alternative arsenate reduction pathways, using molecular microbiology, analytical chemistry, and transcriptomics. Chapters reviewed arsenic detoxification mechanisms in bacteria, emphasizing their impact on human health. Arsenate and arsenite resistance patterns in Citrobacter sp. TSA-1 ∆arsC1 hinted at an unidentified arsenate reductase. Bioinformatic tools identified two putative arsC genes, arsC2 and arsC3. I show evidence that ArsC3 has no reductase activity. The chapters explored the impact of arsenate and arsenite exposure on TSA-1 transcriptomics and the consequences of losing the main arsenate reductase. Hypotheses anticipated negative effects on cell health, validated by experimental findings. This study enhances understanding of arsenic detoxification in Citrobacter sp. TSA-1, paving the way for intriguing hypotheses about arsenic exposure effects on bacterial cells under anaerobic conditions.