Can Borrelia burgdorferi Form Biofilms? What New Research Shows

Laboratory studies show Borrelia burgdorferi can form biofilms and other pleomorphic forms
New research found biofilms have distinct gene-expression patterns
Clinical significance and treatment implications remain under investigation

Can Borrelia burgdorferi form biofilms? Laboratory studies suggest that it can. Researchers have identified biofilms, round bodies, and bleb forms under experimental conditions and have shown that these morphologic forms differ biologically from the familiar spiral-shaped spirochete. More recent studies have reported biofilm-associated structures in infected mouse heart tissue and demonstrated increased antibiotic tolerance in laboratory-grown biofilms.

Although these findings provide important insights into the biology of Lyme disease, they do not prove that biofilms explain persistent symptoms or establish that biofilm-directed therapies improve outcomes in patients.

For years, investigators have recognized that Borrelia burgdorferi is not limited to its classic corkscrew-shaped spirochete form. Under different environmental conditions, the organism can adopt several alternative morphologic states, including round bodies, membrane blebs, and biofilm-like aggregates. Researchers continue to investigate whether these forms contribute to bacterial survival, immune evasion, or persistence.

What Are Borrelia Biofilms?

Biofilms are organized communities of bacteria embedded within a self-produced extracellular matrix. In many bacterial species, biofilms may help organisms survive hostile environments by limiting antibiotic penetration, altering bacterial metabolism, and protecting bacteria from immune defenses.

Laboratory studies have shown that Borrelia burgdorferi can form biofilms containing spirochetes, round bodies, blebs, extracellular DNA, calcium, and alginate. These biofilms also demonstrate structural features commonly seen in biofilms formed by other bacterial species, including channel-like architecture and extracellular matrix formation.

Although biofilms are well recognized in many chronic bacterial infections, their role in Lyme disease remains an active area of investigation.

Borrelia Morphology: Biofilms and Other Pleomorphic Forms

Borrelia burgdorferi is described as pleomorphic because it can appear in several morphologic forms. These include the familiar spiral-shaped spirochete, round bodies, membrane blebs, and organized biofilm-like aggregates.

These forms should not automatically be assumed to have the same biological behavior. Recent research suggests that some retain gene-expression patterns similar to spirochetes, while others undergo much broader changes in gene activity.

Researchers Studied Four Different Borrelia Forms

A 2023 study by Čorak and colleagues compared the complete gene-expression profiles of four laboratory-grown Borrelia burgdorferi morphotypes:

• Spirochetes
• Round bodies
• Blebs
• Biofilm-dominated cultures

Using RNA sequencing, the investigators found that round bodies shared gene-expression patterns remarkably similar to spirochetes despite their different appearance. In contrast, blebs and biofilms exhibited markedly different transcriptomes, suggesting that these morphotypes represent biologically distinct states rather than simply different shapes.

Biofilms Activate Different Genes

The investigators found that biofilm formation involved substantial changes in gene expression. Compared with spirochetes, biofilm-dominated cultures upregulated many genes located on plasmids rather than the main chromosome. Many of these genes originated relatively late in the evolution of the Borreliaceae family and remain poorly understood.

Interestingly, several known Lyme disease virulence genes involved in immune evasion and tissue adhesion also arose during this evolutionary period. The authors proposed that these findings may indicate a role for biofilm and bleb morphotypes in dissemination or persistence, although they emphasized that additional research is needed to establish their biological significance.

Round Bodies Behaved Differently Than Biofilms

One of the more surprising findings was that round bodies were much more similar to spirochetes than expected. Only a relatively small number of genes changed expression during the transition from spirochetes to round bodies, whereas hundreds of genes differed in blebs and biofilms.

This observation suggests that round bodies may represent a relatively modest physiologic adaptation, while biofilms and blebs involve much broader biological reprogramming.

Why These Findings Matter

The study provides important evidence that Borrelia burgdorferi can alter its biology substantially under different environmental conditions. Rather than existing as a single static organism, the bacterium appears capable of transitioning among several morphologic states with distinct patterns of gene activity.

These observations may help researchers better understand how Borrelia burgdorferi survives changing environments within ticks and mammalian hosts. However, the authors appropriately caution that laboratory findings alone cannot determine how often these morphotypes occur during human infection or what role they play in clinical disease.

Researchers Identified Biofilm-Associated Structures in Mouse Heart Tissue

Laboratory observations of Borrelia burgdorferi biofilms have recently been extended into an animal model. In 2024, Thippani and colleagues reported evidence of biofilm-associated aggregates in the hearts of experimentally infected mice.

Using immunohistochemistry, fluorescence in situ hybridization, confocal microscopy, three-dimensional imaging, and atomic force microscopy, the investigators identified structures that stained positively for both Borrelia burgdorferi and alginate, a marker commonly associated with bacterial biofilms.

The researchers also observed increased C-reactive protein staining surrounding some of these aggregates, suggesting an associated inflammatory response. The authors concluded that these findings support the presence of biofilm-associated structures during experimental infection in mice.

Importantly, this study was performed in an animal model. Although it extends previous laboratory observations beyond cell culture, it does not establish that biofilms explain persistent symptoms in humans or demonstrate that biofilm-targeted therapies improve clinical outcomes.

Biofilms Showed Greater Antibiotic Tolerance in Laboratory Studies

Another important advance came from a 2025 study by Fabrizio and colleagues. The investigators examined clinical isolates of Borrelia afzelii and Borrelia garinii obtained from patients with erythema migrans. After confirming that these organisms formed biofilms in the laboratory, they compared antibiotic activity against free-floating bacteria and biofilm-associated bacteria.

The researchers found that substantially higher antibiotic concentrations were required to inhibit bacteria growing within biofilms than bacteria growing in their free-living, or planktonic, form. This finding is consistent with observations in many other bacterial species, where biofilms can reduce antibiotic susceptibility through altered bacterial physiology rather than permanent genetic resistance.

Equally important, whole-genome sequencing did not identify antimicrobial resistance genes in these clinical isolates. The authors concluded that their findings reflected biofilm-associated antibiotic tolerance rather than acquired genetic antibiotic resistance.

This distinction is clinically important. Laboratory evidence of antibiotic tolerance should not be interpreted as proof that Borrelia has developed true antibiotic resistance. It also does not establish that higher antibiotic doses or prolonged treatment will improve patient outcomes.

What Do These Studies Mean for Patients?

These three recent investigations substantially expand our understanding of Borrelia burgdorferi biology.

• Laboratory studies demonstrate that Borrelia can adopt several morphologic forms, including biofilms, blebs, and round bodies.
• Transcriptomic studies show that biofilms and blebs express gene programs that differ markedly from classic spirochetes.
• Animal studies have identified biofilm-associated structures in infected mouse heart tissue.
• Laboratory susceptibility studies demonstrate increased antibiotic tolerance during biofilm growth while finding no evidence of acquired genetic antibiotic resistance.

Together, these findings support continued investigation into the biology of Lyme disease. At the same time, they do not prove that biofilms are responsible for persistent symptoms in patients, nor do they establish that biofilm-directed therapies improve clinical outcomes. Additional studies in humans remain necessary.

Clinical Perspective

In my practice, many patients ask whether persistent symptoms mean that Borrelia burgdorferi is hiding inside biofilms. Some have read about biofilms online or have pursued treatments specifically intended to disrupt them. It is understandable why this topic generates so much interest.

Current clinical evidence has not established that biofilms are the primary explanation for persistent symptoms or that targeting biofilms alone improves patient outcomes. This does not make the research unimportant. Rather, it means that laboratory and animal findings should be interpreted carefully while clinical research continues.

Persistent symptoms following Lyme disease require a thoughtful evaluation that considers many possibilities. Depending on the patient, these may include ongoing inflammation, autonomic dysfunction, neurologic complications, coinfections such as Babesia, immune-mediated illness, treatment response, and alternative diagnoses when appropriate.

Research into biofilms continues to evolve. Until stronger clinical evidence becomes available, treatment decisions should remain individualized and guided by each patient’s history, examination, prior treatment, response to therapy, and overall clinical presentation rather than by laboratory observations alone.

Frequently Asked Questions

Can Borrelia burgdorferi form biofilms?

Yes. Laboratory studies have shown that Borrelia burgdorferi can form biofilms under experimental conditions. These biofilms may contain spirochetes, round bodies, blebs, extracellular DNA, alginate, and other components commonly found in bacterial biofilms. More recent research has also identified biofilm-associated structures in infected mouse heart tissue.

What are pleomorphic forms of Borrelia?

Pleomorphic forms are alternative morphologic states that Borrelia burgdorferi can adopt under different environmental conditions. Researchers have described spirochetes, round bodies, membrane blebs, and biofilms. Laboratory studies indicate that some of these forms have distinct patterns of gene expression, suggesting that they may be biologically different rather than simply different shapes.

Do Borrelia biofilms cause persistent Lyme disease symptoms?

Current evidence has not established that Borrelia biofilms are responsible for persistent Lyme disease symptoms. Laboratory and animal studies demonstrate that biofilms can form and possess unique biological characteristics, but carefully designed human studies are still needed to determine their clinical significance.

Do Borrelia biofilms mean the bacteria are antibiotic resistant?

Not necessarily. Recent laboratory studies found that bacteria growing within biofilms required higher antibiotic concentrations for inhibition than free-living bacteria. However, investigators did not identify genes associated with acquired antimicrobial resistance. Biofilm-associated antibiotic tolerance is different from true genetic antibiotic resistance.

Should every patient with Lyme disease follow a biofilm protocol?

There is currently no clinical consensus that every patient with Lyme disease requires a biofilm-directed protocol. Laboratory studies show that Borrelia can form biofilms under certain experimental conditions, but human clinical studies have not established that routine biofilm-targeted treatment improves outcomes for all patients. Treatment decisions should remain individualized.

What kills Lyme disease biofilms?

Laboratory studies have evaluated antibiotics and other compounds against biofilm-associated Borrelia, but laboratory activity does not necessarily predict safety or effectiveness in patients. No biofilm-disrupting medication or supplement has been established as a universally effective clinical treatment for Lyme disease biofilms.

Why is this research important?

Understanding how Borrelia burgdorferi adapts to changing environments may help researchers better understand Lyme disease biology and identify new targets for future investigation. However, laboratory discoveries must ultimately be confirmed in carefully designed human clinical studies before they can change patient care.

Clinical Takeaway

Laboratory, transcriptomic, and animal studies provide evidence that Borrelia burgdorferi can form biofilms and other pleomorphic forms. These studies also demonstrate distinct gene-expression patterns and increased laboratory antibiotic tolerance without evidence of acquired genetic resistance.

These findings advance our understanding of Lyme disease biology, but they do not prove that biofilms explain persistent symptoms or establish that biofilm-directed therapies improve outcomes in patients.

Biofilm research is important, but clinical decisions should remain individualized and grounded in the patient’s complete clinical picture.

Related Articles

Is Lyme Disease Becoming Antibiotic Resistant? What the Research Shows
Persistent Lyme Disease: An Overview
Post-Treatment Lyme Disease Syndrome (PTLDS)
Autonomic Dysfunction and Lyme Disease
Tick-Borne Coinfections: Babesia, Bartonella, Ehrlichia and More
Lyme Disease Treatment: What Patients Should Know

References

1. Čorak N, Anniko S, Daschkin-Steinborn C, et al. Pleomorphic variants of Borreliella (syn. Borrelia) burgdorferi express evolutionary distinct transcriptomes. Int J Mol Sci. 2023;24(6):5594.
2. Thippani S, Patel NJ, Jathan J, et al. Evidence for the presence of Borrelia burgdorferi biofilm in infected mouse heart tissues. Microorganisms. 2024;12(9):1766.
3. Fabrizio G, Cavallo I, Sivori F, et al. Genomic characterization and antibiotic susceptibility of biofilm-forming Borrelia afzelii and Borrelia garinii from patients with erythema migrans. Front Cell Infect Microbiol. 2025;15:1619660.
4. Meriläinen L, Brander H, Herranen A, Schwarzbach A, Gilbert L. Pleomorphic forms of Borrelia burgdorferi induce distinct immune responses. Microbes Infect. 2016;18(7-8):484-495.
5. Rudenko N, Golovchenko M, Kybicova K, Vancová M. Metamorphoses of Lyme disease spirochetes: Phenomenon of Borrelia persisters. Parasit Vectors. 2019;12:237.
6. Bamm VV, Ko JT, Mainprize IL, Sanderson VP, Wills MKB. Lyme disease frontiers: Reconciling Borrelia biology and clinical conundrums. Pathogens. 2019;8(4):299.
7. Wong KH, Shapiro ED, Soffer GK. A review of post-treatment Lyme disease syndrome and chronic Lyme disease for the practicing immunologist. Clin Rev Allergy Immunol. 2022;62(2):264-271.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention