Desulfovibrio (DSV) species have been linked to Parkinson’s disease (PD) and demonstrated to enhance alpha-synuclein (alpha-syn) aggregation, a pathological hallmark of PD, in a Caenorhabditis elegans model. However, the bacterial factors underlying this virulence remain unclear. We investigated whether DSV-induced alpha-syn aggregation and toxicity are more strongly driven by bacterial viability-dependent processes or by bacterial structures retained after paraformaldehyde (PFA) treatment.

Live or paraformaldehyde (PFA)-treated (non-viable) DSV cells, and curli-producing or curli-deficient E. coli as controls were fed to C. elegans . Worm survival, alpha-syn aggregation, hydrogen sulfide production, and expression of genes associated with inflammation, oxidative stress, proteostasis and dopaminergic function were evaluated.

Curli-producing E. coli retained its ability to induce alpha-syn aggregation, whereas PFA-treated DSV strains lost this effect, showing reduced aggregate number and volume ( P   <  0.05). Worm survival improved when fed PFA-treated cells, although the difference was not statistically significant. Expression of pmk-1 , skn-1 and hsf-1 did not differ between worms fed live and PFA-treated DSV bacteria, while cat-2 expression increased in worms fed PFA-treated bacteria compared to those fed live cells. Patient-derived DSV strains produced substantially higher levels of H ₂ S than healthy control strains (1058.11 vs. 710.30 ppm/OD ₆₀₀ ; P  = 0.003), and H ₂ S levels were positively correlated with aggregate volume (Spearman’s r _s = 0.886, P  = 0.019).

DSV-derived viability-dependent processes, including metabolic activity, more strongly promote alpha-syn aggregation and toxicity than structural components. These findings highlight the important contribution of bacterial viability-dependent processes to DSV-mediated pathogenic effects relevant to Parkinson’s disease.