Gillon, A. | Search bioRxiv

bioRxiv2025

Microbes release lower-value metabolites at higher rates

Microbial interactions are shaped by the exchange of metabolites, ranging from intermediates in central carbon metabolism to amino acids, vitamins and fermentation by-products. While specific metabolic processes such as overflow metabolism are well documented, a general principle explaining the chemical diversity of metabolite release and the variation in individual release rates remains elusive. Here, using a combination of computational and experimental approaches on seven different microbes, we show that release rates are negatively correlated with the value of metabolites, and that this relationship explains more variability in release rates than other frequently associated factors. By measuring metabolite release from 67 E. coli mutants lacking individual transport genes, we find that transporters both cause and counteract net metabolite release. These findings suggest that metabolite release constitutes a fitness cost that microbes have evolved to reduce, while revealing the underlying transport mechanism. This unifying explanation reshapes our understanding of how microbial interactions emerge and persist.

microbiology↗

bioRxiv2025

Estrogenic Activity in Tampon Products

Tampons are widely used menstrual products with prolonged mucosal contact, raising questions about their potential role in exposing females to endocrine-disrupting chemicals (EDCs). This study evaluated estrogenic activity in tampon extracts using a cell-based estrogen receptor reporter bioassay. Synthetic and organic tampons sourced from domestic and international markets--both synthetic and organic--were tested for estrogenic bioactivity. Of the 18 brands analyzed, estrogenic activity was detected in nearly half, independent of material type. Comparative chemical analysis of one estrogenic-active brand versus one non-active brand via high-resolution mass spectrometry identified various plasticizers, surfactants, and fragrance agents, that were present in higher concentrations in the estrogenic-active brand. The list of chemicals included known EDCs, such as phthalates and alkylphenols, that may be responsible for the observed estrogenic activity. Notably, estrogenic activity varied by brand, suggesting formulation-dependent risk. Although the detected in vitro activity levels were low, the findings demonstrate that compounds capable of activating estrogen receptors can leach from tampons. These results highlight the importance of including endocrine bioactivity assays in tampon safety assessments and suggest that safer formulations are achievable. Further investigation is warranted to assess long-term health implications of cumulative low-level EDC exposure from menstrual products.

physiology↗