Genomic and Molecular Characterization of Microbial Ice Nucleation

The temperature at which water freezes can be significantly increased by particles known as ice nucleating particles (INPs). The presence of these particles in the atmosphere plays an important role in determining weather patterns and climate by helping ice crystals to form. INPs can come from different sources, but biological organisms, especially microbes, are some of the most efficient producers. For decades, scientists have known about the ice-nucleating abilities of certain bacteria, but much of the research has focused on a specific gene found in a single group of bacteria. However, little is known about how other microbes can induce freezing. This study aims to fill this gap by characterizing INPs and exploring the genetics and regulation of microbial ice nucleation in one bacterium and several fungi. The goals of this research were threefold: (1) to create a detailed family tree of a group of bacteria called Pantoea, (2) to study how changes in a specific gene cluster in a bacterium called Lysinibacillus parviboronicapiens affect its ability to nucleate ice, and (3) to identify genes in fungi that may also be responsible for ice nucleation. To do this, I used advanced genetic analysis methods to compare the DNA sequences of different Pantoea species, studied gene expression in L. parviboronicapiens, and used computational tools to predict which genes in fungi (specifically in Fusarium and Mortierellaceae) might play a role in ice nucleation. vii One of the main findings was the creation of a new, more reliable family tree for Pantoea, based on 2,509 genes. This tree helps scientists better understand the relationships between different Pantoea species, allowing scientists to be able to identify and study them more easily and safely by determining which of them are pathogenic and which are harmless or even beneficial. In L. parviboronicapiens, changes in the gene cluster responsible for ice nucleation caused the bacteria to grow differently, and the study also uncovered a connection between ice nucleation and molecular transport across the bacterial cell wall. For the fungi, I identified several potential genes that may be involved in ice nucleation, and modeled their structures to better understand how they might work. This research provides new insights into the diversity of microbes that contribute to ice formation and advances our understanding of how they nucleate ice. These findings could improve how scientists model weather and climate and could have practical applications in biotechnology and environmental science.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Plant Pathology, Physiology and Weed Science

Department dc:contributor.department

Plant Pathology, Physiology and Weed Science

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2025

Author dc:creator

• Rojas, Mariah I.

Chair dc:contributor.committeechair

• Vinatzer, Boris A.

Committee members dc:contributor.committeemember

• Lindow, Steven
• Stevens, Ann M.
• Zhao, Bingyu

• ice nucleation
• genomics
• transcriptomics
• proteomics

Statement dc:rights

• Creative Commons Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:42508

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/124607