Distinguishing between metabolically active and dormant bacteria on paper

Abstract

Switching between metabolically active and dormant states provides bacteria with protection from environmental stresses and allows rapid growth under favorable conditions. This rapid growth can be detrimental to the environment, e.g., pathogens in recreational lakes, or to industrial processes, e.g., fermentation, making it useful to quickly determine when the ratio of dormant to metabolically active bacteria changes. While a rapid increase in metabolically active bacteria can cause complications, a high number of dormant bacteria can also be problematic, since they can be more virulent and antibiotic-resistant. To determine the metabolic state of Escherichia coli and Salmonella Typhimurium, we developed two paper-based colorimetric assays. The color changes were based on oxidoreductases reducing tetrazolium salts to formazans, and alkaline phosphatases cleaving phosphates from nitrophenyl phosphate salt. Specifically, we added iodophenyl-nitrophenyl-phenyl tetrazolium salt (INT) and methylphenazinium methyl sulfate to metabolically active bacteria on paper and INT and para-nitrophenyl phosphate salt to dormant bacteria on paper. The color changed in less than 60 min and was generally visible at 10 CFU and quantifiable at 10 CFU. The color changes occurred in both bacteria, since oxidoreductases and alkaline phosphatases are common bacterial enzymes. On one hand, this feature makes the assays suitable to a wide range of applications, on the other, it requires specific capture, if only one type of bacterium is of interest. We captured Salmonella or E. coli with immobilized P22 or T4 bacteriophages on the paper, before detecting them at levels of 10 or 10 CFU, respectively. Determining the ratio of the metabolic state of bacteria or a specific bacterium at low cost and in a short time, makes this methodology useful in environmental, industrial and health care settings.

Dust deposition drives microbial metabolism in a remote, high-elevation catchment

“…The metabolic activity of bacteria has been monitored to evaluate bacterial respiration (e.g. using tetrazolium salts that change color when organic matter (OM) is oxidized (Hice et al, 2018; Roslev and King, 1993)). This rapid colorimetric technique may also serve as an approach to demonstrate that biodegradable organic substrate is available to viable bacteria.…”

Microfluidic thread‐based electrode system to detect glucose and acetylthiocholine

“…Since its introduction by the Whitesides group in 2007, microfluidic paper-based analytical devices (PADs) have become an expanding research field with applications encompassing a breadth of scientific disciplines [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. A wide array of fabrication processes has been detailed in the literature as have detection techniques focused mainly on colorimetric types.…”

Polymer Electrochromism Driven by Metabolic Activity Facilitates Rapid and Facile Bacterial Detection and Susceptibility Evaluation

“…Therefore, ox‐PPE is capable to differentiate live bacteria from dead bacteria and can be potentially used to detect slow‐growing bacteria. [ 19 ]…”

“…Therefore, ox-PPE is capable to differentiate live bacteria from dead bacteria and can be potentially used to detect slow-growing bacteria. [19] We then moved forward to study what metabolic products cause the reduction of ox-PPE. Previously, we have demonstrated that the broad-absorbing conjugated polymer could be imaged with a transient-absorption (TA) microscope.…”