Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biotechnology Science and Engineering

Committee Chair

Tatyana Sysoeva

Committee Member

Kyung Ho Roh

Committee Member

Luis Cruz Vera

Committee Member

Judith Schneider

Committee Member

Anuradha Subramanian

Research Advisor

Tatyana Sysoeva


Plasmids--Genetics, Biofilms--Prevention, Biofilms, Space vehicles--Water-supply


Space exploration imposes unique challenges on the human body and engineered systems alike. One such challenge is the control of microbial life, specifically biofilms, within the water processor assembly of the International Space Station (ISS). This investigation aimed to determine the feasibility of using an innovative bioremediation approach to mitigate biofilm growth in the water processor assembly. This approach entails the dissemination of a desired anti-biofilm gene across the microbial population of the water processor assembly through horizontal gene transfer via conjugation. To ascertain the viability of this method, the research was divided into two primary focuses. The first part sought to identify the microbial inhabitants of the Water Processor Assembly (WPA), characterizing their genomes and their capacity for gene exchange. The second part was devoted to evaluating the potential for transferring a previously studied anti-biofilm gene -alterocin- to various organisms through a plasmid, thereby modeling future tests for the conjugative spread of bioremediation strategies. Sequencing of the genomes of five biofilm-forming gram-negative bacterial strains isolated from the ISS was performed to understand the genetic mechanisms that confer resistance and biofilm formation. The work further extends to analyzing the genetic features and functions of these bacteria by comparing their chromosomes and plasmids against a broader dataset, consisting of 48 plasmids from other flight bacteria. An in-depth analysis of the bacterial chromosomes revealed genetic differences compared to their ground-based counterparts, thereby showing potential adaptive strategies in the given ISS conditions. Our analysis also identified resistances to hexavalent chromium, a key component in the urine pretreat system of the ISS, along with resistances to zinc and nickel. Several plasmids showed high levels of similarity and were identified in different organisms, suggesting horizontal gene transfer as a potential mechanism for spreading resistance traits. Evaluation of flight bacterial prevalence in the ISS water systems was conducted to comprehend the overall microbial landscape. Furthermore, this research aimed to engineer a mobilizable plasmid capable of expressing the alterocin protein to mitigate biofilm formation. These findings contribute to the growing body of knowledge on microbial life in space built environments, such as water systems in ISS, and offer potential avenues for the design of measures to control microbial growth, including the development of engineered plasmids that could aid in effective biofilm management.

Available for download on Wednesday, May 06, 2026