Sensing of phage-triggered ion cascades (SEPTIC) is a prompt bacterium identification method based on

fluctuation-enhanced sensing Fluctuation-enhanced sensing (FES) is a specific type of chemical or biological sensing where the stochastic component, ''noise'', of the sensor signal is analyzed. The stages following the sensor in a FES system typically contain filters and pream ...

in fluid medium. The advantages of SEPTIC are the specificity and speed (needs only a few minutes) offered by the characteristics of phage infection, the sensitivity due to

, and durability originating from the robustness of phages. An idealistic SEPTIC device may be as small as a pen and maybe able to identify a library of different bacteria within a few minutes measurement window.

The mechanism

SEPTIC utilizes

bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacteri ...

s as indicators to trigger an ionic response by the bacteria during phage infection. Microscopic metal electrodes detect the random fluctuations of the electrochemical potential due to the stochastic fluctuations of the ionic concentration gradient caused by the phage infection of bacteria. The electrode pair in the electrolyte with different local ion concentrations at the vicinity of electrodes form an electrochemical cell that produces a voltage depending on the instantaneous ratio of local concentrations. While the concentrations are fluctuating, an alternating random voltage difference will appear between the electrodes. According to the experimental studies, whenever there is an ongoing phage infection, the power density spectrum of the measured ''electronic noise'' will have a noise spectrum while, without phage infection, it is a

1/f noise Pink noise or noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave interval (halving or ...

spectrum. In order to have a high sensitivity, a DC electrical field attracts the infected bacteria (which are charged due to ion imbalance) to the electrode with the relevant polarization.

Advantages

The advantages of SEPTIC are the specificity and speed (needs only a few minutes) offered by the characteristics of phage infection, the sensitivity due to

History

The SEPTIC concept was first conceived by

Laszlo B. Kish Laszlo Bela Kish (born László Béla Kiss) is a physicist and professor of Electrical and Computer Engineering at Texas A&M University. His activities include a wide range of issues surrounding the physics and technical applications of stochast ...

and Maria Dobozi-King in 2004, and developed and demonstrated at the Electrical and Computer Engineering department of

Texas A&M University Texas A&M University (Texas A&M, A&M, or TAMU) is a public, land-grant, research university in College Station, Texas. It was founded in 1876 and became the flagship institution of the Texas A&M University System in 1948. As of late 2021, T ...

in collaboration with Mosong Cheng, Ry Young,

Sergey M. Bezrukov Sergey M. Bezrukov is a Russian born biophysicist notable for his work on ion channels and stochastic resonance. Education He received his MS in Electronics and Theoretical Physics from Saint Petersburg Polytechnical University, 1973; and he ob ...

(NIH), and Bob Biard. A new, related scheme, BIPIF, that has recently been conceived and analyzed by

and Gabor Schmera (SPAWAR,

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

) utilizes the AC impedance fluctuations at related arrangements, and it promises higher sensitivity and less dependence on the electrodes.

References

External links

Homepage of the SEPTIC method at the Department of Electrical and Computer Engineering, Texas A&M University

Ry Young's phage lab at the Department of Biochemistry and Biophysics, Texas A&M University

{{DEFAULTSORT:Sensing Of Phage-Triggered Ion Cascades (Septic) Biological techniques and tools Laboratory equipment