Date of Award

2019

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Biological Sciences (MS)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Stephen M. Techtmann

Committee Member 1

Rupali Datta

Committee Member 2

Ebenezer Tumban

Abstract

Biocides are antimicrobial compounds that are designed to kill diverse groups of microbes in an untargeted fashion. Glutaraldehyde and DBNPA are commonly used to manage microbial growth in different industries. It is possible that biocide use may result in the development of bacterial resistance. However, resistance to DBNPA is believed to be limited under normal use conditions. We isolated a number of bacteria from produced water from a hydraulically fractured site in West Texas. We then tested the ability of these isolates to resist Glutaraldehyde and DBNPA. In this study, we found that these isolates have varying resistance to these biocides. Importantly we show that some of these isolates are resistant to DBNPA. Isolates had higher minimum inhibitory concentrations (MICs) for glutaraldehyde after twenty-four hour incubation than after one hour. The opposite was seen with DBNPA, where cells that survived one hour of treatment were killed after the twenty-four hour incubation. Previous work has shown that many bacteria that are resistant to biocides can also be resistant to antibiotics. We determined the minimum inhibitory concentration (MIC) of Tetracycline, Ampicillin and Streptomycin. We found that the resistance profiles for these isolates varied. There was little relationship between the bacteria resistant to biocide and antibiotics. To determine the genetic mechanism for biocide and antibiotic resistance we sequenced the genomes of several of these isolates. Genomes were sequenced using Illumina sequencing. Raw reads were Quality filtered, assembled using SPAdes, and annotated using RAST. Antibiotic Resistance genes (ARGs) were identified for each of these isolates using the RGI from the CARD database. The number of ARGs varied from eight in some organisms to zero in others. There was no relationship between the number of genes and high antibiotic resistance. Our results suggest a complex relationship between the presence of antibiotic resistance genes and the antimicrobial resistance profiles. More work is needed to understand the prevalence and genetic basis for biocide resistance

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