Polystyrene Nanoplastics Impact the Growth and Architecture of a “Synthetic” Small Intestinal Microbiota

Authors: Shirmin Islam, Gretchen J. Mahler, Cláudia N. H. Marques

Field of Study: Biological Sciences

Faculty Mentors: Cláudia N.H. Marques

Easel: 103

Timeslot: Midday

Abstract: Small intestinal biofilms support nutrient absorption and host–microbe interactions but are difficult to study due to the dynamic intestinal environment. Commensal biofilms contribute to barrier integrity, immune signaling, and mucosal balance. This study examined how polystyrene nanoplastics (NPLs) with different surface charges influence growth and biofilm behavior of key small intestinal bacteria. Single- and four-species in vitro models of Bifidobacterium bifidum, Enterococcus faecalis, Lacticaseibacillus rhamnosus, and Streptococcus salivarius were exposed to positively, neutral, and negatively charged polystyrene NPLs (100 mg/L). Planktonic growth was measured by optical density, biofilm biomass by crystal violet assay, and viability by CFU counts and 16S rDNA. Biofilm structure was analyzed by confocal microscopy, and NPL stability by zeta potential and dynamic light scattering. NPLs aggregated in c-BHI medium, reducing surface charge. Positively charged NPLs inhibited growth and biofilm formation, while all NPLs disrupted mature biofilm structure without major viability loss.