Identification of Characteristic Macromolecules of Escherichia coli Genotypes by Atomic Force Microscope Nanoscale Mechanical Mapping

Abstract

The categorization of microbial strains is conventionally based on the molecular method, and seldom are the morphological characteristics in the bacterial strains studied. In this research, we revealed the macromolecular structures of the bacterial surface via AFM mechanical mapping, whose resolution was not only determined by the nanoscale tip size but also the mechanical properties of the specimen. This technique enabled the nanoscale study of membranous structures of microbial strains with simple specimen preparation and flexible working environments, which overcame the multiple restrictions in electron microscopy and label-enable biochemical analytical methods. The characteristic macromolecules located among cellular surface were considered as surface layer proteins and were found to be specific to the Escherichia coli genotypes, from which the averaged molecular sizes were characterized with diameters ranging from 38 to 66 nm, and the molecular shapes were kidney-like or round. In conclusion, the surface macromolecular structures have unique characteristics that link to the E. coli genotype, which suggests that the genomic effects on cellular morphologies can be rapidly identified using AFM mechanical mapping. Graphical AbstractQuantification of surface macromolecules of E. coli cells using AFM mechanical mapping. Surface macromolecules of cellular surface of three E. coli genotypes, MG1655, CFT073, and RS218, were characterized with the sizes ranging from 38 to 66 nm and with round or kidney-like shapes. The topography images were colored with adhesion mapping with the scale bars = 200 nm. Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2452-2) contains supplementary material, which is available to authorized users.

In-Situ Investigation on Nanoscopic Biomechanics of Streptococcus mutans at Low pH Citric Acid Environments Using an AFM Fluid Cell

“…The S. mutans cells were harvested from a Bacto TM brain–heart infusion (BHI) agar plate after two days and then continuously sub-cultured in a 6 mL BHI solution for approximately 16 h in an incubator at 37 °C. To process an AFM measurement, the microcolony cells were deposited onto a silanized glass substrate for 30 min as specified in our previous works [ 23 , 54 ]. Afterwards, we marked the substrate at the center of the fluid cell and injected acid solution for an AFM measurement.…”

Quantitative study of early-stage transient bacterial adhesion to bioactive glass and glass ceramics: Atomic Force Microscopic observations

“…These features correspond to accumulation of macromolecules on the bacterial surface which are characteristic of a bacterial strain. High resolution images of such macromolecules (proteins, lipids) have been reported in literature [59]. These macromolecules include surface proteins which are responsible for initial adhesion of bacteria.…”

Multilocus Variable Number of Tandem Repeat Analysis for molecular typing of uropathogenic Escherichia coli

“…There are several methods for typing of E. coli from environmental samples including traditional and modern molecular methods [7][8][9][10][11][12][13]. With the advent of the molecular age, scientists changed their approach from phenotyping to genotyping methods [14,15].…”