Determination of Bacterial Surface Charge Density Via Saturation of Adsorbed Ions

Abstract

Bacterial surface charge is a critical characteristic of the cell's interfacial physiology that influences how the cell interacts with the local environment. A direct, sensitive, and accurate experimental technique capable of quantifying bacterial surface charge is needed to better understand molecular adaptations in interfacial physiology in response to environmental changes. We introduce here the method of second harmonic light scattering (SHS) which is capable of detecting the number of molecular ions adsorbed as counter charges on the exterior bacterial surface, thereby providing a measure of the surface charge. In this first demonstration, we detect the small molecular cation, malachite green, electrostatically adsorbed on the surface of representative strains of Gram-positive and Gram-negative bacteria. Surprisingly, the SHS deduced molecular transport rates through the different cellular ultra-structures are revealed to be nearly identical. However, the adsorption saturation densities on the exterior surfaces of the two bacteria were shown to be characteristically distinct. The negative charge density of the lipopolysaccharide coated outer surface of Gram-negative E. coli (8.7±1.7 nm-2) was deduced to be seven times larger than that of the protein surface layer of Gram-positive L. rhamnosus (1.2±0.2 nm-2). The feasibility of SHS deduced bacterial surface charge density for Gram-type differentiation is presented.

Compare the physicochemical properties of engineered polymer-functionalized silver nanoparticles and evaluate their biological properties against Porphyromonas gingivalis

“…In addition, the positively charged AgNPs, especially polymer-functionalized AgNPs in the current study, generally exhibited stronger antibacterial activity than the negatively charged AgNPs over a short period of time. This is highly correlated with the electrostatic interactions between positively charged materials and the negatively charged surfaces of bacteria [41]. However, in the present study the negatively charged AgNPs undergoing polymer functionalization, such as with PVP, also exhibited similar or even better antibacterial activity.…”

Compare the physicochemical and biological properties of engineered polymer-functionalized silver nanoparticles against Porphyromonas gingivalis

“…In addition, the positively charged AgNPs, especially the polymer-functionalized AgNPs in the present study, generally exhibited stronger antibacterial activity than the negatively charged AgNPs over a short period of time. This is highly correlated with the electrostatic interactions between the positively charged materials and the negatively charged surfaces of bacteria ( Wilhelm et al, 2020 ). However, in the present study the negatively charged AgNPs after polymer functionalization, such as with PVP, also exhibited similar or even better antibacterial activity.…”

Miltefosine Impacts Small Molecule Transport in Gram-Positive Bacteria

“…29,30 Previous studies have demonstrated SHS and SHG can be used to quantify molecule-membrane interactions within model systems, [31][32][33][34][35][36][37][38][39][40] eukaryotic species, 16,[41][42][43][44] and bacterial cells. 24,25,[45][46][47][48][49][50][51][52][53][54][55][56] Specifically, we have implemented this technique to elucidate how structural moieties of small molecules facilitate its transport through the Gram-positive membranes of living S. aureus and Bacillus subtilis. 47 After employing the steady-state fluorescent assays, generalized polarization (GP) of laurdan and anisotropy of diphenylhexatriene (DPH), to determine the impact of MLT on global fluidity of S. aureus membranes, we monitor the trSHS of small molecules (malachite green, 25,48,49,[57][58][59] FM 2-10, 46,47 FM 1-43, 47 and 4-Di-2-ASP 47 ) with previously documented transport behavior to assess the impact of MLT.…”