Bacteria surface charge varies across species and is independent of cell wall type.

Variation in the surface charge of the cell envelope across bacterial species is not well understood. The absence of systematic investigations comparing taxonomically diverse bacterial species has led to confusion about the influence of cell wall type (i.e. Gram-negative or Gram-positive bacteria) on surface charge. In this study, dynamic light scattering (DLS) was used to determine surface charge via zeta potential measurements of 12 phylogenetically diverse bacterial species spanning four bacterial phyla. Surface charge of six Gram-positive species (Bacillus subtilis, Streptococcus thermophilus, Paenibacillus polymyxa, Kocuria rosea, Mycobacterium smegmatis, and Streptomyces albus) and six Gram-negative species (Chryseobacterium shigense, Sphingobacterium multivorum, Flavobacterium pectinovorum, Escherichia coli, Stenotrophomonas maltophilia, and Pseudomonas putida) were characterized. Results show that surface charge is not dependent on cell wall type but instead varies across diverse species, as there is significant overlap between the surface charge means of the Gram-positive and Gram-negative bacterial groups. The methodology used in this study provides a consistent, high-throughput technique for assessing surface charge. Data presented herein suggest that routine surface charge measurements are informative for investigations of interactions between bacteria and other systems, such as antimicrobial therapeutics and water purification systems.