Microbial Metal Resistance within Structured Environments Is Inversely Related to Environmental Pore Size.

The physical environments in which microorganisms naturally reside rarely have homogeneous structure, and changes in their porous architecture may have effects on microbial activities that are not typically captured in conventional laboratory studies. In this study, to investigate the influence of environmental structure on microbial responses to stress, we constructed structured environments with different pore properties (determined by X-ray computed tomography). First, using glass beads in different arrangements and inoculated with the soil yeast Saitozyma podzolica, increases in the average equivalent spherical diameters (ESD) of a structure's porous architecture led to decreased survival of the yeast under a toxic metal challenge with lead nitrate. This relationship was reproduced when yeasts were introduced into additively manufactured lattice structures, comprising regular arrays with ESDs comparable to those of the bead structures. The pore ESD dependency of metal resistance was not attributable to differences in cell density in microenvironments delimited by different pore sizes, supporting the inference that pore size specifically was the important parameter in determining survival of stress. These findings highlight the importance of the physical architecture of an organism's immediate environment for its response to environmental perturbation, while offering new tools for investigating these interactions in the laboratory.