Our group focuses on unraveling the complex interactions within the gut microbiota and their critical impact on host health. We are currently investigating three main research lines:

Deciphering the Microbiota’s Chemical Lexicon

Following our discovery that chemical signaling by quorum sensing influences gut microbiota composition, namely during antibiotic disruptions, we want to identify the molecular players involved in these processes. This includes investigating the potential effect of a novel bacterial signal on the gut-brain axis and its implications for animal behavior.

Enhancing Microbiota Protection Against Infections and Inflammation

Our identification of a protective Klebsiella species opened new avenues for microbiota management. We aim to understand how this bacterium aids in microbiota recovery post-perturbation and how it protects against inflammation to strengthen our current results that already support its use as a potential treatment to ameliorate disease pathologies in a pre-clinical inflammatory bowel disease mouse model. We will expand these findings through the isolation and characterization of human isolates, which we will test for colonization resistance against Multidrug-Resistant Enterobacteriaceae.

Determine how the Microbiota Affects Host Response to Dietary

Using a new model to study microbiota-mediated responses to dietary perturbation, we aim to identify bacterial functions that modulate host responses to diet. This involves comparing the response to dietary perturbation of mice with different microbiota compositions, from complex communities to simplified and germ-free setups, to determine microbiota function involved in diet-related weight gain, inflammation, and infection susceptibility.

Overall, our research will contribute significantly to the fields of microbiology and host-microbe interaction, offering innovative perspectives on the role of the microbiota in modulating host behavior, protecting against infections and inflammatory-related diseases, and enhancing problems associated with response to dietary imbalances.

Human Frontier Science Program. Hormone-like Bacterial Signaling Molecules of Gut-Brain Dialogues. RGP024/2024. Total consortia Award: $1,200,000.00; $400,000.00 for KX. Oct 2024 – Nov 2027.

Gordon and Betty Moore Foundation. Promoting PhD training on Host-Microbe Symbioses. Grant GBMF11550. Award: $298,125. From Nov. 2022 – Nov. 2025.

Fundação para a Ciência e Tecnologia, Ministério da Ciência e Ensino superior. Projectos de I&D. Manipulating Quorum Sensing to promote Muribaculum resilience in gut microbiota dysbiosis. ID: PTDC/BIA-MIC/6990/2020. Award: € 249,953.19. From Mar. 2021 –Aug. 2024.

Oliveira RA, Cabral V, Torcato I, Xavier KB. (2023) Deciphering the quorum-sensing lexicon of the gut microbiota. Cell Host Microbe. 31:500–512.

Cabral V, Oliveira RA, Correia MB, Pedro MF, Ubeda C, Xavier KB. (2023) Gut protective Klebsiella species promotes microbiota recovery and pathobiont clearance while preventing inflammation. bioRxiv.https://doi.org/10.1101/2023.11.14.566997

Dapa T, Ramiro RS, Pedro MF, Gordo I, Xavier KB. (2022) Diet leaves a genetic signature in a keystone member of the gut microbiota. Cell Host Microbe. 30(2):183–199.e10.

Oliveira RA, Ng KM, Correia MB, Cabral V, Shi H, Sonnenburg JL, Huang KC, Xavier KB. (2020) Klebsiella michiganensis transmission enhances resistance to Enterobacteriaceae gut invasion by nutrition competition. Nat Microbiol. 5:630–641.

Barroso-Batista J, Pedro MF, Sales-Dias J, Pinto CJG, Thompson JA, Pereira H, Demengeot J, Gordo I, Xavier KB. (2020) Specific eco-evolutionary contexts in the mouse gut reveal Escherichia coli metabolic versatility. Curr Biol.30:1049–1062.

Torcato IM, Kasal MR, Brito PH, Miller ST, Xavier KB. (2019) Identification of novel autoinducer-2 receptors in Clostridia reveals plasticity in the binding site of the LsrB receptor family. J Biol Chem. 294(12):4450–4463.

Valente RS, Nadal-Jimenez P, Carvalho AFP, Vieira FDJ, Xavier KB. (2017) Signal integration in quorum sensing enables cross-species induction of virulence in Pectobacterium wasabiae. MBio. 8(3):e00398-17.

Thompson JA, Oliveira RA, Djukovic A, Ubeda C, Xavier KB. (2015) Manipulation of the quorum-sensing signal AI-2 affects the antibiotic-treated gut microbiota. Cell Rep. 10:1861–1871.

Marques JC, Oh IK, Ly DC, Lamosa P, Ventura MR, Miller ST, Xavier KB. (2014) LsrF, a coenzyme A-dependent thiolase, catalyzes the terminal step in processing the quorum-sensing signal autoinducer-2. Proc Natl Acad Sci USA.111(39):14235–14240.

Xavier KB, Bassler BL. (2005) Interference with AI-2-mediated bacterial cell-cell communication. Nature. 437:750–753.

A complete list of publications can be found here.

Fellow of American Academy of Microbiology (AAM) – Elected in 2022

Member of European Molecular Biology Organization (EMBO) – Elected in 2021

Member of European Academy of Microbiology (EAM) – Elected in 2019

FCT Investigator Programme – Coordinator Award, 2017.

PLOS Genetics Research Prize 2015 (as co-author).

Howard Hughes Medical Institute International Early Career Award. February 2012.

https://karinaxavierlab.weebly.com/

Karina Bivar Xavier (0000-0001-5210-1434) – ORCID

‪Karina B. Xavier – ‪Google Scholar

Organizer of the:

SymbNET PhD Summer School on  Host-Microbe Symbioses

6-19 July 2025

https://gimm.idloom.events/phd-summer-school-2025