About

Kasie Raymann is an Assistant Professor in the Department of Plant and Microbial Biology at North Carolina State University. She is an affiliate member of the Global One Health Academy and a faculty member of the Genetics and Genomics Academy. Her educational background includes a BSc in Biology from Indiana University obtained in 2011 and a PhD in Microbiology from the Pasteur Institute completed in 2014. Her research focuses on microbial ecology and evolution, with particular emphasis on the honey bee gut microbiome, opportunistic bacterial pathogens, experimental evolution, genetics, and metagenomics. Raymann's work investigates the impacts of chemicals used in beekeeping on honey bee health and gut microbial communities, as well as broader environmental effects of microplastics and antimicrobials on soil and plant microbiomes. Her contributions include studying the genomic and phenotypic diversification of bacteria under predator-mediated selection, and examining the unintended consequences of antibiotic use in beekeeping, among other topics.

Research topics

• Biology
• Genetics
• Ecology
• Computational biology
• Evolutionary biology
• Artificial Intelligence
• Computer Science
• Immunology
• Programming language
• Toxicology
• Microbiology
• Biotechnology

Selected publications

• SEM images from Parallel and Divergent Evolution in Pseudomonas aeruginosa under Stable and Fluctuating Predator-Mediated Selection

  2026-02-10

  datasetSenior author
  PublisherDOI

• Polyamide Microplastics and Common Antimicrobials in Treated Wastewater: Unveiling their Effects on Rice Plant Growth and Soil Microbiome dynamics

  International Journal of Environmental Research · 2026-05-06

  articleOpen access

  Abstract Agricultural soils are increasingly contaminated with microplastics (MPs) and antimicrobial agents, yet the interplay between these pollutants and their effects on soil health, plant growth and development, and microbial communities remains underexplored. Here we investigated the influence of polyamide (PA) microplastics and three prevalent antimicrobials: sulfamethoxazole (SMX), ciprofloxacin (CIP), and triclosan (TCS) on rice plants. We assessed both the individual and combined effects on physiological and biochemical attributes of rice plants and soil bacterial communities, as well as the bioaccumulation of antimicrobials in soil and plant tissues. Our findings revealed that 1% of PA has a minimal effect on growth parameters and photosynthetic pigments in rice. In contrast, antimicrobials, particularly SMX at 50 mg/Kg, significantly hindered plant growth ( p < 0.0001), when tested alone or in combination with PA. In addition, the accumulation of TCS and CIP was enhanced in shoots and roots in the presence of PA while there was a decrease in SMX concentration in shoots in the presence of PA. PA and antimicrobials caused a slight change in abundance and diversity of soil bacterial communities, though the effects on alpha diversity were not statistically significant at each individual depth. However, when all depths were considered together, the TCS and PA + TCS treated soil displayed increased richness and evenness when compared to the other treatment groups. Similarly, beta diversity was significantly altered as determined by Unweighted_UniFrac analysis ( p < 0.05 ). Moreover, there was a 100 to 200-fold increase in the abundance of various antibiotic resistance genes such as sul1 and sul2 in response to antimicrobials treatment. These findings provide novel evidence on the interaction of antimicrobials loaded on MPs in the agroecosystem and their combined impacts on plants and soil microbiome.

  PublisherOA PDFDOI

• Genomic and phenotypic diversification of <i>Pseudomonas aeruginosa</i> during sustained exposure to a ciliate predator

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-01-13

  articleOpen access

  Abstract Predator-mediated selection is an important ecological force shaping bacterial evolution, but its effects on genomic adaptation and virulence in opportunistic pathogens are not fully understood. Here, we used experimental evolution to study how exposure to the ciliate predator Tetrahymena thermophila affects Pseudomonas aeruginosa . Replicate populations were evolved for 60 days with or without the predator, followed by whole-genome shotgun metagenomic sequencing and phenotypic analyses. Both treatments showed strong selection and evidence of parallel evolution at gene and nucleotide levels, indicating constrained adaptation. However, predator exposure altered evolutionary dynamics. Predator-evolved populations showed a wider distribution of mutation frequencies, with many mutations persisting at intermediate frequencies, consistent with increased clonal interference and ongoing competition among lineages. In contrast, populations evolved without predators showed more high-frequency mutations, consistent with selective sweeps, though some low-frequency variants remained. Despite substantial genomic change, phenotypic outcomes were variable. Virulence in an invertebrate host model did not consistently increase; instead, evolved isolates showed context-dependent changes, including modest decreases or occasional increases. Competition assays also showed no consistent fitness advantage for predator-evolved isolates, suggesting trade-offs between predator resistance and growth in other environments. Overall, predator-mediated selection reshaped evolutionary dynamics by maintaining diversity and altering the balance of lineages rather than producing uniform increases in virulence. These results highlight how ecological complexity influences adaptive evolution and the context-dependent nature of pathogen traits. Importance Opportunistic pathogens like Pseudomonas aeruginosa often evolve in environmental settings before infecting hosts, raising questions about how ecological interactions influence virulence. Predator-mediated selection has been suggested to increase virulence via coincidental evolution, but evidence is inconsistent. Here, we show that exposure to a eukaryotic predator does not consistently elevate virulence but does reshape evolutionary dynamics by altering how mutations spread in populations. Predator-exposed populations retained more intermediate-frequency mutations, consistent with increased clonal interference and ongoing competition among lineages, whereas non-predator populations were dominated by selective sweeps. These differences were also reflected in functional targets of adaptation, with predator exposure favoring mutations in genes involved in environmental sensing and interaction. Together, these findings suggest that ecological complexity shapes the dynamics of adaptation rather than driving a single evolutionary outcome, highlighting that virulence is an emergent property influenced by underlying evolutionary processes.

  PublisherOA PDFDOI

• Impact of Two Common Beekeeper-Applied Chemicals on Honey Bee Queen Fecundity and Gut Microbial Communities

  Microbial Ecology · 2026-04-10

  articleOpen access

  Like many agricultural animal systems, common apiculture (honey bees) practice has led to a reliance on chemical treatments to mitigate parasites and diseases. These agrichemicals typically take the form of acaracides (e.g., amitraz) and antibiotics (e.g., oxytetracycline; OTC), both of which can persist in various hive matrices and have unforeseen effects on colony health, such as the evolution of resistance by disease agents or decreased reproductive fertility of the bees themselves. The honey bee microbiome is a critical component of the food-processing and pathogen response of honey bees and has been shown to be impacted by agrichemicals, although the bulk of the research has been on honey bee workers, rather than the queen, which is commonly the sole reproductive of the colony, possesses her own distinct microbiome, and is strongly buffered from the external environment by alloparental care from the workers. Over the course of three experiments, we exposed queens to amitraz, OTC, or control in an industry-standard apiary. Queens were assessed for morphological, reproductive, and microbiome traits, and male and female brood were assessed for survival to pupation. We found that amitraz negatively impacts the viability of stored sperm in queens (from 87.3 ± 8.9% to 65.4 ± 7.5%) but not egg laying or brood survival. OTC disrupts the microbiome community in queens, altering community composition, but not alpha diversity. In these studies, microbial and reproductive phenotypes appear to be unrelated, suggesting a more nuanced relationship between the honey bee queen microbiome and overall colony social organization.

  PublisherDOI

• Integrated effects of polyamide microplastics and common antimicrobials in reclaimed water on the growth of lettuce (Lactuva sativa L.) and soil bacterial communities

  ENVIRONMENTAL SYSTEMS RESEARCH · 2025-12-24 · 1 citations

  articleOpen access

  Micropollutants coming from wastewater irrigation present a looming threat to agricultural productivity as well as ecological and public health. Reclaimed water from wastewater treatment plants intensifies soil with contaminants of emerging concern, such as microplastics (MPs) and antimicrobials (AMs). However, despite their co-existence in the soil, the impact of MPs on AMs bioavailability and accumulation in crop plants, on the composition and diversity of soil bacterial communities, and the abundance of ARGs in the soil have not been well-studied. In this study, we treated lettuce plants and soil individually with one type of MPs (polyamide) and three types of AMs, i.e., (sulfamethoxazole, ciprofloxacin, and triclosan) alone and in combination, and compared lettuce growth parameters and bacterial communities between the treatment groups and the control. Our findings revealed that lettuce plants exhibited phytotoxicity under AMs alone or in combination with PA-MPs. We observed a significant decrease in shoot and root lengths, their respective biomasses, and photosynthetic pigments. Moreover, bacterial alpha diversity was unaffected, while there were significant differences in beta diversity. Although there was only a slight change in abundance and diversity of bacterial communities, some specific antibiotic resistance genes such as sul1 and sul2 were significantly abundant under the co-treatment of the studied contaminants. The current study provides an insight into the ecological, agricultural, and public health risks of co-occurring contaminants in agroecosystem. Microplastics (MPs) and antimicrobials (AMs) interact in soil-plant continuum. Co-exposures of MPs and AMs significantly affected lettuce growth traits. Individual and combined applications of PA-MPs and AMs induced differential effects on soil bacterial communities. Single AMs or their combination with PA-MPs significantly increased sulfonamide resistance genes in the soil.

  PublisherOA PDFDOI

• Unintended Consequences of Antibiotic Use in Beekeeping: Drone Health as a Hidden Vulnerability

  Research Square · 2025-07-02

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Unintended consequences of antibiotic use in beekeeping: drone health as a potential vulnerability

  Animal Microbiome · 2025-09-30 · 2 citations

  articleOpen accessSenior author

  BACKGROUND: Declines in honey bee queen quality and variability in drone (male) reproductive performance are contributing factors to colony losses reported by beekeepers. While the causes of reduced reproductive fitness remain unclear, recent evidence implicates agrichemical exposure. Oxytetracycline (OTC), an antibiotic used in apiculture for over 70 years to treat brood diseases, is classified as an endocrine-disrupting compound due to its inhibition of mitochondrial function in reproductive cells. In other animals, OTC exposure has been associated with impaired reproductive development, reduced sperm viability, and broader reproductive dysfunction. Although the effects of OTC on worker bee gut microbiota and physiology are well documented, its impact on drone gut microbiota has never been characterized. Additionally, we recently discovered microbial communities in drone reproductive tissues, which could be impacted by OTC exposure. The goal of this study was to determine if OTC has the potential to impact drone development, survival, fecundity, and microbiota composition. RESULTS: Using an in vitro rearing system, we found that larval OTC exposure delays drone development, reduces survival, and results in detectable residues in the gut and reproductive tissues of newly emerged adults. In mature drones, oral exposure to conservative field-relevant OTC concentrations significantly reduced gut bacterial abundance and diversity, although reproductive tissue-associated microbiota appeared largely unaffected. In vitro assays further revealed that OTC is highly toxic to drone sperm at environmentally relevant concentrations. CONCLUSION: Our findings demonstrate that OTC exposure has the potential to negatively affect drone development, survival, gut microbiota, and sperm viability. These results support our hypothesis that the use of OTC in beekeeping may contribute to reduced male reproductive health. Importantly, this work highlights the need for additional studies, particularly field-based investigations, to better understand the impacts of OTC on drone reproductive health and microbiomes. Such research will be critical for evaluating the broader consequences of antibiotic use in apiculture and for developing sustainable strategies to manage brood diseases.

  PublisherOA PDFDOI

• Discovery of reproductive tissue-associated bacteria and the modes of microbiota acquisition in male honey bees (drones)

  mSphere · 2024-12-19 · 6 citations

  articleOpen accessSenior author

  Honey bees are the third most economically important agricultural animal in the world due to their role as pollinators. Honey bee pollination services and all hive duties are performed by female workers, while the male drones have one job to mate and share their genetics with a virgin queen from another colony. Thus, drone fitness is directly tied to queen success and colony survival, yet they have been severely understudied compared to their female counterparts. In other insects, microbes discovered in the gut and reproductive organs have been shown to be important for reproductive success and/or overall host health. To our knowledge, the existence of microbes in drone reproductive tissues has never been investigated. Moreover, our understanding of the gut microbiota of drones is severely limited, especially when compared to honey bee workers. Here, we sampled conventional drones from healthy colonies and used 16S amplicon sequencing to identify and characterize bacteria in the reproductive organs of immature and mature drones. After identifying bacteria in drone reproductive tissues, we performed a controlled experiment in which newly emerged drones were exposed to different rearing conditions in order to determine when and how they acquire their reproductive and gut microbiota. Overall, we discovered a set of core bacteria in the reproductive and gut tissues of conventionally reared drones and revealed that social interactions are important for the proper development of the drone microbiota. Determining if these bacteria play a role in drone fecundity and health should be a goal of future research efforts. IMPORTANCE: Over the last decade, annual honey bee colony loss has increased, resulting in a critical need to determine what factors contribute to honey bee and colony health. Gut microbes have been shown to play important roles in the health of the nonreproductive female honey bee workers, which make up 90% or more of a honey bee colony. However, we currently know very little about the impact of microbes on the health of male honey bees (drones), who only make up a small portion of the colony population but play a very key role in the success of future colonies by mating with virgin queens. Here, we discovered microbes within the reproductive organs of drones and illustrated that social interactions with worker bees are necessary for the proper development of the gut and reproductive tissue microbial communities in drones. Further studies are needed to determine if microbes play an important role in honey bee reproductive health and fitness.

  PublisherDOI

• Making a Pathogen? Evaluating the Impact of Protist Predation on the Evolution of Virulence in <i>Serratia marcescens</i>

  Genome Biology and Evolution · 2024-07-04 · 3 citations

  articleOpen accessSenior authorCorresponding

  Opportunistic pathogens are environmental microbes that are generally harmless and only occasionally cause disease. Unlike obligate pathogens, the growth and survival of opportunistic pathogens do not rely on host infection or transmission. Their versatile lifestyles make it challenging to decipher how and why virulence has evolved in opportunistic pathogens. The coincidental evolution hypothesis postulates that virulence results from exaptation or pleiotropy, i.e. traits evolved for adaptation to living in one environment that have a different function in another. In particular, adaptation to avoid or survive protist predation has been suggested to contribute to the evolution of bacterial virulence (the training ground hypothesis). Here, we used experimental evolution to determine how the selective pressure imposed by a protist predator impacts the virulence and fitness of a ubiquitous environmental opportunistic bacterial pathogen that has acquired multidrug resistance: Serratia marcescens. To this aim, we evolved S. marcescens in the presence or absence of generalist protist predator, Tetrahymena thermophila. After 60 d of evolution, we evaluated genotypic and phenotypic changes by comparing evolved S. marcescens with the ancestral strain. Whole-genome shotgun sequencing of the entire evolved populations and individual isolates revealed numerous cases of parallel evolution, many more than statistically expected by chance, in genes associated with virulence. Our phenotypic assays suggested that evolution in the presence of a predator maintained virulence, whereas evolution in the absence of a predator resulted in attenuated virulence. We also found a significant correlation between virulence, biofilm formation, growth, and grazing resistance. Overall, our results provide evidence that bacterial virulence and virulence-related traits are maintained by selective pressures imposed by protist predation.

  PublisherOA PDFDOI

• Diet affects reproductive development and microbiota composition in honey bees

  Animal Microbiome · 2024-11-05 · 10 citations

  articleOpen accessSenior author

  BACKGROUND: Gut microbes are important to the health and fitness of many animals. Many factors have been shown to affect gut microbial communities including diet, lifestyle, and age. Most animals have very complex physiologies, lifestyles, and microbiomes, making it virtually impossible to disentangle what factors have the largest impact on microbiota composition. Honeybees are an excellent model to study host-microbe interactions due to their relatively simple gut microbiota, experimental tractability, and eusociality. Worker honey bees have distinct gut microbiota from their queen mothers despite being close genetic relatives and living in the same environment. Queens and workers differ in numerous ways including development, physiology, pheromone production, diet, and behavior. In the prolonged absence of a queen or Queen Mandibular Pheromones (QMP), some but not all workers will develop ovaries and become "queen-like". Using this inducible developmental change, we aimed to determine if diet and/or reproductive development impacts the gut microbiota of honey bee workers. RESULTS: Microbiota-depleted newly emerged workers were inoculated with a mixture of queen and worker gut homogenates and reared under four conditions varying in diet and pheromone exposure. Three weeks post-emergence, workers were evaluated for ovary development and their gut microbiota communities were characterized. The proportion of workers with developed ovaries was increased in the absence of QMP but also when fed a queen diet (royal jelly). Overall, we found that diet, rather than reproductive development or pheromone exposure, led to more "queen-like" microbiota in workers. However, we revealed that diet alone cannot explain the microbiota composition of workers. CONCLUSION: The hypothesis that reproductive development explains microbiota differences between queens and workers was rejected. We found evidence that diet is one of the main drivers of differences between the gut microbial community compositions of queens and workers but cannot fully explain the distinct microbiota of queens. Thus, we predict that behavioral and other physiological differences dictate microbiota composition in workers and queens. Our findings not only contribute to our understanding of the factors affecting the honey bee microbiota, which is important for bee health, but also illustrate the versatility and benefits of utilizing honeybees as a model system to study host-microbe interactions.

  PublisherOA PDFDOI

Recent grants

• BEE: Unraveling the ecological and evolutionary factors shaping host-associated microbial communities

  NSF · $763k · 2019–2023

• BEE: Unraveling the ecological and evolutionary factors shaping host-associated microbial communities

  NSF · $145k · 2023–2024

Frequent coauthors

• Patrick Forterre

  Institut Pasteur

  19 shared

• Simonetta Gribaldo

  Institut Pasteur

  18 shared

• Louis‐Marie Bobay

  North Carolina State University

  14 shared

• Claudine Mayer

  Université de Strasbourg

  10 shared

• Céline Brochier‐Armanet

  Laboratoire de Biométrie et Biologie Evolutive

  9 shared

• Zack Shaffer

  8 shared

• Megan E. Damico

  University of North Carolina at Greensboro

  7 shared

• Mart Krupovìč

  Institut Pasteur

  7 shared

Education

• Ph.D., Plant Biology

  University of California, Berkeley

  2008

• B.S., Botany

  University of California, Berkeley

  2003