Real-Time Metabolic Interactions between Two Bacterial Species Using a Carbon-Based pH Microsensor as a Scanning Electrochemical Microscopy Probe

作者：Vrushali S. Joshi, Partha Sarathi Sheet, Nyssa Cullin, Jens Kreth, Dipankar Koley · 发表于：Analytical Chemistry · 年份：2017 · DOI：10.1021/acs.analchem.7b03050 · 被引用次数：61 · 研究领域：Electrochemical Analysis and Applications、Analytical Chemistry and Sensors、Infective Endocarditis Diagnosis and Management

We have developed a carbon-based, fast-response potentiometric pH microsensor for use as a scanning electrochemical microscopy (SECM) chemical probe to quantitatively map the microbial metabolic exchange between two bacterial species, commensal Streptococcus gordonii and pathogenic Streptococcus mutans . The 25 μm diameter H + ion-selective microelectrode or pH microprobe showed a Nernstian slope of 59 mV/pH and high selectivity against major ions such Na +, K +, Ca 2+, and Mg 2+ . In addition, the unique conductive membrane composition aided us in performing an amperometric approach curve to position the probe and obtain a high-resolution pH map of the microenvironment produced by the lactate-producing S. mutans biofilm. The x -directional pH scan over S. mutans also showed the influence of the pH profile on the metabolic activity of another species, H 2 O 2 -producing S. gordonii . When these bacterial species were placed in close spatial proximity, we observed an initial increase in the local H 2 O 2 concentration of approximately 12 ± 5 μM above S. gordonii, followed by a gradual decrease in H 2 O 2 concentration (>30 min) to almost zero as lactate was produced, and a subsequent decrease in pH with a more pronounced metabolic output of S. mutans . These results were supported by gene expression and confocal fluorescence microscopic studies. Our findings illustrate that H 2 O 2 -producing S. gordonii is dominant while the buffering capacity of saliva is valid (∼pH 6.0) but...