Vulvovaginal candidiasis (VVC) is a common and recurrent infection despite the availability of antifungal therapies. One major reason is the ability of Candida albicans to form biofilms, which enhances its resistance to treatment and immune elimination (Intra et al., 2022). Fluconazole is widely used, but reduced efficacy against biofilms is a major concern (Intra et al., 2022). While newer antifungals like ibrexafungerp and oteseconazole are alternatives, their long-term activity against biofilm-driven infections is still under evaluation (Intra et al., 2022). Misdiagnosis and frequent use of non-prescription antifungals lead to a delay in proper treatment, leading to recurrent episodes (Duar et al., 2017). These disadvantages raise an important question: can we develop simpler strategies to improve current therapies?

Lactobacilli belong to a genus of Gram-positive, rod-shaped lactic acid bacteria that actively compete with C. albicans in the vaginal microbiome (Intra et al., 2022). These bacteria are broadly classified into free-living, host-adapted, and nomadic variants (Duar et al., 2017). Among these, certain species, particularly the nomadic variants (Lactiplantibacillus plantarum, Lacticaseibacillus rhamnosus, and Lacticaseibacillus casei), seem promising for antibiofilm therapy (Rajasekharan and Shemesh, 2022). The nomadic lifestyle of Lactobacillii refers to their ability to survive and adapt across different environments, rather than being localized to a singular habitat. These bacteria can shift between various environmental habitats such as soil, plant surfaces, aquatic environments, fermented foods, the oral cavity and the gastrointestinal tract (Duar et al., 2017). They maintain their genomic and metabolic flexibility that allows them to reshape their phenotype according to the habitat. The current thinking in the field is that the geometrical structuring facilitates the nomadic lifestyle, leading to successful adaptation of Lactobacilli to different environmental niches, though the mechanistic understanding of structural changes enabling their nomadic lifestyle remains an active area of research. L. plantarum is one such nomadic variant that was recently shown to demonstrate multifaceted cell structures such as cone-shaped colonies, sacrifice-for-survival bundles, and V-shaped cell chaining in response to acidic pH conditions ( Figure 1a ) (Rajasekharan and Shemesh, 2022; Venugopal et al., 2025). Findings reveal that in acidic environment, mimicking the vaginal niche, L. plantarum transitions are linked to LuxS quorum-sensing pathways (Venugopal et al., 2025). This structural state coincides with modified metabolite secretion and raises questions about whether morphology-driven metabolic shifts enhance its antifungal capacity. This is particularly relevant in the context of VVC, a common mucosal infection affecting up to 75% of women during their reproductive years (Sobel, 2007; Intra et al., 2022). C. albicans, the primary causative agent, often forms drug-resistant biofilms and evades host immunity (Zeise et al., 2021; Poon and Hui, 2023). While conventional antifungals face increasing resistance, probiotics, particularly those containing Lactobacilli, offer an emerging alternative by restoring microbial balance, inhibiting Candida adhesion, biofilm formation and modulating immune responses ( Table 1 ). Clinical studies have shown that species like L. plantarum underscoring their therapeutic value (Bertarello et al., 2024). We propose that structural shifts in L. plantarum, especially the formation of V-shaped structures alleviate symptoms and reduce recurrence in VVC-infected cells, which may be a functional adaptation for enhanced antifungal activity. This explores how the morphology-metabolite interplay could influence the next generation of probiotic design to target Candida biofilms and overcome antifungal resistance.

Biofilm formation is a key survival strategy for microbes in mucosal environments. In the vaginal niche, L. plantarum typically dominates through acidification and spatial exclusion, but not all species are equally effective against C. albicans. The environment provides signals such as acid stress, bile salts, osmotic stress, temperature fluctuations and nutrient availability that can have a direct impact on the morphology of Lactobacilli. The V-shaped structuring can be formed predominantly in the vaginal environment, where relatively high acidity may facilitate such cellular transformation. The structured cells possess enhanced biochemical defense mechanisms that effectively inhibit hyphal extension and biofilms, as was shown in a C. elegans model (Rajasekharan and Shemesh, 2022). This V-shaped structuring correlates with increased surface adherence and more cohesive biofilm formation compared to other known shapes, allowing it to physically outcompete C. albicans establishment (Rajasekharan and Shemesh, 2022). ( Figure 1b ). In our experimental models, V-shaped L. plantarum cells effectively inhibited yeast virulence in in vitro and in vivo nematode models (Rajasekharan and Shemesh, 2022). This suggests that the V-shaped morphology is not a passive stress response, but rather an adaptive strategy for enhanced mucosal colonization and spatial exclusion of fungal pathogens. The role of Candida in shaping Lactobacilli morphology remains unclear, but it is conceivable that the dysbiosis caused by the colonization of Candida may indeed be related to its possible impact on Lactobacilli morphology. Further studies are warranted to elucidate possible role during microbial competition and antagonistic interactions. Figure 1b illustrates how the geometrical structuring may lead to physical suppression of Candida colonization through dense probiotic biofilms.

Although numerous antimicrobial compounds of Lactobacilli are well established, how they relate to structural morphology remains unexplored. Based on the results discussed in Section 3, we found that L. plantarum under acidic stress exhibits a distinct metabolic shift associated with the previously described chaining morphology. Notably, this morphotype displayed increased secretion of metabolites of cyclic dipeptides, which are stable and interfere with the maturation of biofilms (Narasimulu et al., 2024). These compounds were more abundant in the V-shaped state compared to rod-shaped cells, indicating that the structural adaptation also enhances metabolite secretion. This observation proposes a novel concept in probiotic design; morphological states may directly influence the potency and spectrum of antimicrobial metabolites. Notably, formulated V-shaped cells hold significant potential to be made into probiotic products, thus merging the structural advantages with practical formulating benefits. Such structure-informed probiotic strategies could yield targeted solutions for recurrent Candida infections. In the following section, we detail the intracellular targets of these metabolites and how they plausibly disrupt C. albicans biofilm formation ( Figure 2 ).

We examine the proposed role of morphology-driven metabolite adaptation on how Lactobacilli-secreted metabolites (LSMs) interfere with intracellular pathways that regulate the formation and survival of C. albicans biofilms. Several LSMs have been shown to inhibit adenylate cyclase, which can disrupt the RAS-cAMP-MAPK signaling cascade and downstream regulators such as tpk1, efg1, flo8, and tec1, which are crucial transcription factors that drive hyphal transition and biofilm maturation (Alonso-Roman et al., 2022). LSMs, such as pyruvate and oxaloacetate, may interfere with metabolism for competitive inhibition of isocitrate lyase, which inhibits the glyoxylate cycle and C. albicans ability to grow in nutrient-poor mucosal environments. Other targets include lanosterol 14α-demethylase, which disrupts ergosterol synthesis and destabilizes fungal membranes. Compounds like 1-acetyl-β-carboline (1-ABC) directly inhibit Yak1, a kinase critical for morphogenesis and biofilm development (MacAlpine et al., 2021). Additionally, sodium butyrate, a short-chain fatty acid and histone deacetylase inhibitor (HDACi), impairs fungal gene expression by altering chromatin organization and structure (Poon and Hui, 2023). These proposed mechanisms are illustrated in Figure 2 , which integrates our hypothesis with known fungal regulatory pathways. Increased biofilm inhibitory activity of V-shaped L. plantarum may not only come from competitive exclusion but also from a specialized LSM profile that precisely targets fungal virulence factors. Understanding these molecular interactions will open a path toward next-generation probiotic therapies for persistent biofilm-associated infections such as recurrent VVC.

Our investigation indicates that structural adaptation of L. plantarum, more especially, its transition to V-shaped cells in vaginal-like acidic environments, may have a major impact on the synthesis of antifungal metabolites. This presents an intriguing hypothesis that cell morphology is a functional state that improves probiotic competitiveness against C. albicans. A promising bioactive profile for preventing biofilm-associated infections might be attributed to cyclic dipeptides and other specialized LSMs, including Prolyl-arginine, Valyl-threonine, and Valyl-glutamine (Narasimulu et al., 2024). Future research should focus on characterizing these metabolic pathways and understanding how they interface with fungal signaling and host immunity. Unlocking the regulatory controls behind such transitions could lead to novel bioengineered probiotic therapies designed not just by strain selection, but by regulating growth conditions and structure to maximize antifungal efficacy. This structure-guided approach may open a new path to address drug resistance and design more robust microbiome-based interventions for Biofilm-associated infection. While our research highlights the structural and metabolic role of L. plantarum, other nomadic Lactobacilli such as L. rhamnosus and L. casei remain largely unexplored and warrants further studies.