About

Professor David Baltrus leads a research lab that emphasizes an open and inclusive environment where ideas can be freely discussed and vigorous scientific discourse is encouraged. He prioritizes respect among lab members and the broader community, fostering a culture that values diversity, equality, and acceptance. His management style is characterized by a non-micromanaging approach, allowing lab members autonomy in their work while remaining engaged and enthusiastic about new data, ideas, and experimental directions. Professor Baltrus is committed to supporting a healthy work-life balance for his researchers, recognizing the importance of mental and physical health alongside scientific progress. His goal is to provide a variety of experimental suggestions to push the boundaries of knowledge, particularly during critical discussions related to manuscripts, papers, and grants.

Research topics

• Biology
• Genetics
• Botany
• Computer Science
• Microbiology
• Computational biology
• World Wide Web
• Database
• Evolutionary biology
• Chemistry
• Biochemistry

Selected publications

• Genome sequences of four endophytic Bacillaceae from wild lettuce

  Microbiology Resource Announcements · 2025-09-12

  articleOpen access

  ABSTRACT Endophytic bacteria were isolated from roots and stems of prickly lettuce ( Lactuca serriola L.), a wild relative of cultivated lettuce ( Lactuca sativa L.) in Tucson, Arizona, USA. Here, we report draft genome sequences of four strains: Priestia megaterium SY0032, Bacillus velezensis SY1154, Bacillus inaquosorum SY1167, and Bacillus subtilis SY1483, assembled using reads arising from Oxford Nanopore 10.4 flow cells.

  PublisherDOI

• Nearly a century of discoveries in bacterial genetics and their continuing impact on the field

  G3 Genes Genomes Genetics · 2025-11-01

  articleOpen access1st authorCorresponding

  With this special issue on the Genetics of Bacteria, the authors shine new light on selections and screens from the past (and on the people that carried these out) while also pointing towards many future directions for bacterial genetics. Their goal is to highlight the GSA journals as a welcome home for reporting discoveries across bacterial systems building on their rich history.

  PublisherOA PDFDOI

• Exploring the open (host) range

  Cell Host & Microbe · 2025-01-01

  article1st authorCorresponding
  PublisherDOI

• Unified Classification of the Type III Secreted Effectors of Bacterial Plant Pathogens to Advance Phytopathology Research

  Phytopathology · 2025-06-17 · 4 citations

  article

  Many diverse bacterial phytopathogens deploy type III secreted effectors (T3SEs) to promote virulence by interrupting host immunity and other critical plant processes. However, the virulence of T3SEs has been countered on the host side through the evolution of a multitude of resistance genes ( R genes) capable of recognizing the presence of T3SEs and eliciting a response termed effector-triggered immunity. This dynamic sets up an evolutionary arms race that has led to enormous diversification of both bacterial T3SEs and plant R genes. Over the past decade, efforts to document and characterize the pangenome T3SE profiles of individual pathogens have generated indispensable resources that have facilitated collaborative research progress on these focal pathogens. However, despite the deeply integrated evolutionary history of T3SEs, the lack of a concerted effort to synthesize T3SE conventions across diverse pathosystems has resulted in a lack of connectivity across the literature. Here, we catalog the distribution of T3SEs across six of the most globally significant genera of bacterial phytopathogens. We show that the number of T3SEs per genome varies dramatically within and between genera and that many T3SE families are present in multiple genera despite their sparse distributions across closely related strains. We also document all inter-genera evolutionary relationships for each T3SE family and propose integrated nomenclature conventions for all phytopathogen T3SEs. Ultimately, our expanded T3SE collection includes thousands of newly classified alleles, catalogs several previously unestablished homologies between distinct genera, and will enable more comprehensive studies on the implications of T3SE diversification for virulence and immunity.

  PublisherDOI

• Genomic correlates of tailocin sensitivity in <i>Pseudomonas syringae</i>

  G3 Genes Genomes Genetics · 2025-08-29 · 4 citations

  articleOpen access1st authorCorresponding

  Phage-derived bacteriocins, also referred to as tailocins, are structures encoded by bacterial genomes and deployed into the extracellular environment to kill sensitive cells. Tailocins display great potential as agricultural antimicrobials due to their durability, efficiency, and specificity of killing with prophylactic application demonstrated to prevent infection by multiple phytopathogens. Previous reports suggest that tailocins of Pseudomonas syringae interact with sugar moieties in the lipopolysaccharide (LPS) to target sensitive cells. However, it remains unclear how genetic and genomic variation at loci encoding LPS biosynthesis influences tailocin resistance and/or sensitivity across the species. We therefore carried out a genome-wide association study investigating tailocin sensitivity across a diverse set of P. syringae genomes. Our results demonstrate that genes strongly correlated with tailocin sensitivity are localized to one contiguous region on the chromosome encoding LPS structures similar to the common polysaccharide antigen of P. aeruginosa. We further find that enzymes involved in the biosynthesis and transport of D-rhamnose and L-rhamnose are associated with tailocin sensitivity classes A and B, respectively, with large-scale recombination of the O-antigen biosynthesis region likely underlying rapid and fundamental changes in LPS structure between strains. Building on these results, we identify rfbD as a genomic indicator for predicting tailocin sensitivity and use this information to test tailocin interactions with previously unscreened strains, including some in which LPS chains have been characterized. Overall, our results strongly support that tailocin sensitivity for P. syringae is broadly determined by recombination events across strains that leads to differential production of either d or L-rhamnose moieties in the main O-antigen chain.

  PublisherOA PDFDOI

• Tailocin tail fiber diversity correlates with rfbD variation in the <i>Pseudomonas syringae</i> species complex

  ISME Communications · 2025-01-01 · 7 citations

  articleOpen access

  Abstract Community assembly dynamics are in part driven by competition between community members. Diverse bacteria can antagonize competitors through the production of toxic compounds, such as bacteriophage-derived tailocins. These toxins are highly specific in their targeting, which is determined by interactions between the tailocin’s tail fiber and competitors’ lipopolysaccharide O-antigen moieties. Tailocins play a pivotal role in mediating microbial interactions among the economically significant plant pathogens within the Pseudomonas syringae species complex, with the potential to alter community structure and disease progression in host plants. Previous work looking at 45 P.syringae strains has demonstrated that at least two phylogenetic clades of tail fibers are encoded in the conserved tailocin region across the species complex, which roughly corresponds to two clusters of targeting activity. To better understand the full diversity of tail fibers associated with tailocins in the species complex, we screened 2161 publicly available genomes for their tailocin tail fiber content, predicted protein structures that represent the diversity of fibers, and investigated forces possibly driving the distribution of fibers throughout the species complex. Here we present evidence that, while the two previously described tail fiber clades are indeed widespread among virulent P. syringae strains, their distribution displays low congruency with phylogeny. Instead, we found that the presence of one tail fiber or the other is strongly correlated with the allelic diversity of another gene, associated with lipopolysaccharide O-antigen structure, dTDP-4-dehydrorhamnose reductase. Our findings suggest the presence of two reciprocally targeting groups of strains distributed throughout the P. syringae species complex that transcend phylogenetic relationships.

  PublisherOA PDFDOI

• Genomic Correlates of Tailocin Sensitivity

  Figshare · 2025-01-01

  datasetOpen access1st authorCorresponding

  Compressed folders containing input/output files for Roary and Scoary analyses as well as phylogenetic analyses from the associated manuscript are included. We also include a raw unedited image used to create overlay assay images in the associated manuscript. File S1 includes documentation of methods for genome sequencing of various strains mentioned in the manuscript, while Table S1 include sequencing statistics for these genomes.

  PublisherDOI

• Nearly a century of discoveries in bacterial genetics and their continuing impact on the field

  Genetics · 2025-11-01

  articleOpen access1st authorCorresponding
  PublisherOA PDFDOI

• Erratum for Stice et al., “Pantailocins: phage-derived bacteriocins from <i>Pantoea ananatis</i> and <i>Pantoea stewartii</i> subsp. <i>indologenes</i> ”

  Applied and Environmental Microbiology · 2024-05-09

  erratumOpen accessSenior author
  PublisherOA PDFDOI

• A complete genome sequence of <i>Pseudomonas amygdali</i> pathovar <i>lachrymans</i> YM7902

  Microbiology Resource Announcements · 2024-10-22

  articleOpen accessSenior author

  YM7902 was originally isolated as a pathogen of cucumber in Japan. Here, we report a nearly complete genome sequence for this strain, assembled using a hybrid approach combining Illumina paired-end reads and longer reads sequenced using technology from Oxford Nanopore.

  PublisherDOI

Recent grants

• How a phage-derived weapon system shapes interbacterial interactions within and across species

  NSF · $550k · 2019–2023

• Bacterial Controls of Endophyte Phenotypes: an Unexplored Dimension of Diverse Plant-fungal Symbioses

  NSF · $653k · 2014–2019

• NIH Grant F32GM082279

  NIH · $142k · 2010

Frequent coauthors

• Meara Clark

  University of Arizona

  32 shared

• Kevin Dougherty

  Foundation Medicine (United States)

  28 shared

• Brian A. Smith

  University of Minnesota

  28 shared

• Kevin L. Hockett

  Pennsylvania State University

  26 shared

• Brian H. Kvitko

  Plant (United States)

  19 shared

• A. Elizabeth Arnold

  University of Arizona

  17 shared

• Jeffery L. Dangl

  University of North Carolina at Chapel Hill

  14 shared

• Joseph E. Spraker

  Paragon Genomics (United States)

  13 shared

Education

• PhD, Ecology and Evolution

  University of Oregon

  2006

• B.A., Biology

  University of Delaware

  2001