Degradation of Cyanobacterium Nostoc muscorum via Air, Oxygen, and Nitrogen low temperature plasmas

Abdelhamid Elshaer; Eithar El-Mohsnawy; Mohamed Mokhtar Hefny; Mohammed Shihab; Nabil M. El-Siragy; Samaa Salah

REVIEW 4 major objections 5 minor 6 references

Degradation of Cyanobacterium Nostoc muscorum via Air, Oxygen, and Nitrogen low temperature plasmas

T0 review · 4 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash

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Pith's one-line read This paper claims that a 15-minute exposure to air-source low-temperature plasma completely destroys the cyanobacterium Nostoc muscorum, whereas oxygen or nitrogen plasma needs at least an hour.

desk verdict Useful comparative data point on plasma inactivation of Nostoc muscorum, but the missing sham vacuum control means the key 15-minute air-plasma claim is not yet supported. read the letter →

arxiv 2412.13723 v1 pith:WTIHWQM3 submitted 2024-12-18 physics.plasm-ph

Samaa Salah , Mohamed Mokhtar Hefny , Nabil M. El-Siragy , Abdelhamid Elshaer , Eithar El-Mohsnawy , Mohammed Shihab This is my paper · ORCID

classification physics.plasm-ph

keywords cyanobacteriaNostocmuscorumlow-temperatureplasmareactiveoxygenandnitrogenspeciesopticalemissionspectroscopyRamanUV-Visabsorptioncolonyformingunits

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper sets out to show that a low-temperature air plasma can completely destroy the cyanobacterium Nostoc muscorum in 15 minutes, while oxygen plasma and nitrogen plasma need at least an hour for the same outcome. The explanation offered is that air plasma produces higher concentrations of reactive oxygen and nitrogen species, including ionized nitrogen molecules, nitrogen ions, and hydroxyl radicals, which attack the cells. The evidence is a set of parallel disappearance signals: after treatment, the cyanobacteria no longer grow when transferred to BG-11 medium, pigment absorption bands for chlorophyll a, carotenoids, and phycobilins fade, and the characteristic Raman peaks of carotenoids vanish. If the claim holds, air plasma would be a fast, reagent-free way to inactivate cyanobacteria, which matters for controlling harmful blooms and treating contaminated water.

What carries the argument

The central mechanism is the generation of reactive oxygen and nitrogen species (RONS) by a direct-current glow discharge operated at 600 V and 0.2 mbar between two copper electrodes with a 2.5 cm gap, with the cyanobacteria placed between them. Electrons heated to a few electronvolts collide with the background gas and create radicals and excited species, including hydroxyl ($\mathrm{OH^-}$) and excited nitrogen ($\mathrm{N_2^+}$), that break chemical bonds in the cells; a second, concurrent channel is bombardment by accelerated ions in the plasma sheath. The optical emission spectrum measured during treatment is the key instrument: it shows which reactive species are present and that their intensities are highest for air plasma. Colony counting, absorption spectroscopy, and Raman spectroscopy are then used as destruction readouts rather than as parts of the killing mechanism.

What would settle it

Run the same 15, 30, 45, and 60 minute exposures with the electrodes unpowered, keeping the chamber at 0.2 mbar, then culture the samples on BG-11 for one week and count colonies with the same NICE method. If the vacuum-only survival curve falls as fast as the plasma-treated curve, the 15-minute air-plasma kill cannot be attributed to the plasma.

Watch

Extended reading notes

Core claim

On the paper's own terms, the discovery is that air plasma degrades Nostoc muscorum completely in 15 minutes, whereas oxygen plasma and nitrogen plasma require at least 60 minutes. The authors attribute the difference to the chemical species produced in the discharge: the optical emission spectra show higher concentrations of reactive nitrogen and oxygen species for air than for the single gases, and those species are the agents that break the cells down. The degradation is read out in three independent ways: no colony regrowth on BG-11 medium after treatment, decreasing absorption of chlorophyll a, carotenoid, and phycobilin bands with exposure time, and loss of the carotenoid Raman peaks at roughly 1516, 1156, and 1006 cm$^{-1}$, with new Raman bands appearing in their place. The air discharge is characterized as a cold plasma with an electron temperature of about 2.4 eV and an electron density near $2.48\times10^{16}$ cm$^{-3}$.

Load-bearing premise

The load-bearing premise is that the cell death is caused by plasma-generated reactive species rather than by the 0.2 mbar vacuum exposure and desiccation that every sample experienced before the discharge was switched on, since no vacuum-only control is reported.

Editorial extensions

If this is right

A 15-minute air-plasma exposure is sufficient to prevent regrowth of Nostoc muscorum in culture, so treatment time can be as short as a quarter of the time needed with oxygen or nitrogen plasma.
The choice of feed gas sets the required exposure time: air works fastest, while oxygen and nitrogen each need at least four times longer for the same complete degradation.
The gradual loss of pigment absorption and carotenoid Raman peaks as exposure time increases gives a quantitative way to track the progress of cyanobacteria destruction without waiting for regrowth.
Because the discharge runs at room temperature, the method is positioned for use on biological samples where thermal damage would be a problem, such as water-treatment or surface-decontamination settings.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The paper's 15-minute figure was measured on a 1 g wet pellet mounted on a substrate in a vacuum chamber, not on cyanobacteria suspended in water; a reader should not yet assume the same speed for planktonic cells in wastewater, where transport of reactive species is different.
A sham control that pumps the chamber to 0.2 mbar for the same durations without switching on the discharge would be needed to separate plasma chemistry from vacuum desiccation; the paper reports no such control.
If the reactive-species explanation is right, the same approach should degrade other filamentous cyanobacteria, and tuning the air feed's oxygen-to-nitrogen ratio or pressure could push the 15-minute time lower; neither extension is tested here.
The paper itself acknowledges that the electron-density estimate uses Stark broadening only, without instrumental, van der Waals, or Doppler corrections, so the absolute plasma parameters are approximate; the comparative RONS spectra carry the main argument.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

First, the genuinely new thing: a direct comparison of air, oxygen, and nitrogen low-pressure DC plasmas against the same cyanobacterium, with air coming out far faster. That comparative result is not in the cited literature, and the colony-count, absorption, and Raman data all point in the same direction. The authors also do some real work on the diagnostics: OES identification of RONS, a Stark-broadening estimate of electron density, and a Boltzmann plot for temperature, with a caveat that the broadening method is approximate. That is honest and useful.

The soft spots are real, though. The most serious is the missing sham control. The methods describe mounting 1 g of cyanobacteria on FTO, sealing the chamber, pumping to 0.2 mbar, and then igniting the discharge. The only “control” never entered the chamber. At 0.2 mbar, desiccation and vacuum stress can damage cyanobacteria on their own, so the 15-minute air-plasma kill cannot be cleanly attributed to plasma chemistry or plasma bombardment. This does not sink the comparative claim entirely—if vacuum alone were lethal, you would not obviously expect air to beat oxygen and nitrogen by a factor of four—but it does mean the absolute claim of complete destruction in 15 minutes is unproven. Adding a no-discharge vacuum exposure group at matched times would settle it.

A few smaller issues: the Raman data show new peaks after treatment, so “complete degradation” is overstatement; the text says “plasma plasma” and “comlplete”; the colony-count method is described as having error less than 2% but no error bars or statistical details are actually shown. The absorption and Raman trends are still consistent with progressive pigment loss and chemical transformation.

Overall, this is a straightforward, incremental plasma-disinfection study that does what it says, with honest limitations acknowledged in the diagnostics. The missing control is fixable and should be fixed before publication. I would send the revised version to a referee; as it stands, the central causal claim is not fully supported.

Referee Report

4 major / 5 minor

Summary. The paper reports an experimental study in which Nostoc muscorum samples are exposed to low-pressure DC plasmas generated in air, oxygen, and nitrogen at 0.2 mbar, with treatment times of 15, 30, 45, and 60 min. The central claim is that air plasma completely destroys the cyanobacterium within 15 min, whereas oxygen and nitrogen plasmas require at least 1 h (Abstract; Results, 'Cyanobacteria growth behavior'). Supporting measurements include optical emission spectroscopy (OES) that identifies nitrogen and oxygen species, Stark-broadening and Boltzmann-plot estimates of electron density and temperature, UV-Vis absorption spectra of pigments, Raman spectra before and after treatment, and colony counting using the NIST Integrated Colony Enumerator (NICE). The paper concludes that air plasma is the most effective condition and attributes this to higher concentrations of RONS.

Significance. If the 15-min air-plasma inactivation claim were rigorously established, the work would be practically relevant for controlling harmful cyanobacterial blooms and for wastewater treatment. The paper has useful strengths: it uses a straightforward DC plasma setup, combines OES with UV-Vis and Raman characterization, and employs an automated colony-counting tool with three repetitions. However, the causal role of the plasma is not isolated because no sham vacuum control is reported, and several quantitative claims rest on unverified diagnostics and incomplete statistics. The significance of the reported results is therefore conditional on resolving these load-bearing issues.

major comments (4)

[Materials and Methods, 'Plasma generation' and 'Cyanobacteria growth behavior'] The experiment lacks a sham control that is subjected to the same 0.2 mbar vacuum, the same chamber, and the same handling but with no discharge. The only control mentioned is the 'control sample (without any plasma treatment)' in the absorption section, which was never placed in the vacuum chamber. Vacuum exposure and desiccation at 0.2 mbar are stressors that can kill cyanobacterial cells independently of plasma. Without a no-discharge control at matched pressure and duration, the claim that 'air plasma is able to kill all cyanobacteria after 15 min treatment' does not isolate the plasma effect from the vacuum effect. The comparison among air, oxygen, and nitrogen does not resolve this confounder. This is load-bearing for the central claim.
[Results, 'Cyanobacteria growth behavior' and Fig. (4)] The colony-counting results are reported as having 'an error less than 2%', but no replicate data, standard deviations, error bars, or statistical tests are shown in Fig. (4) or the text. The description of the NICE procedure is qualitative, and the relationship between pixel counts and colony-forming units is not validated. Without quantitative uncertainty and statistical comparison, the dose–response curves and the claimed ranking of air versus oxygen versus nitrogen plasma are not supported to the stated precision. This affects the central comparative claim.
[Results, 'Ramman spectrum' and Abstract/Conclusion] The text states that after plasma treatment the Raman peaks 'disappeared and replaced with new peaks, indicating the degradation of the cyanobacteria and the formation of new compounds.' The appearance of new peaks indicates chemical transformation rather than 'complete degradation' as claimed in the Abstract and Conclusion. The evidence supports modification of the sample, but 'complete destruction' or 'complete degradation' is a stronger conclusion than the Raman data alone can justify. Either the language should be tempered or additional evidence of complete cell death and removal should be provided.
[Results, 'Optical emission measurement' and Table (1)] The electron density is estimated from the Stark broadening of the 'N2 391 nm' line, while Table (1) lists the same 391 nm line as an 'N II' transition with atomic N II parameters. In air plasmas, the 391 nm feature is typically the head of the N2+ first negative system (B2Σu+–X2Σg+), not an atomic N II line. Using atomic data for a molecular band, and carrying this identification into the Boltzmann plot for the electron temperature estimate, makes the quantitative values (ne ≈ 2.48 × 10^16 cm−3 and Te ≈ 2.4 eV) unreliable. The authors acknowledge broadening limitations but do not address the line-identification problem. This is secondary to the biological claim but affects the plasma diagnostics, which are part of the paper's stated contribution.

minor comments (5)

[Abstract] The phrase 'air-source plasma plasma' contains a duplicated word; it should be 'air-source plasma'.
[Results, 'Cyanobacteria growth behavior'] There is a typo: 'comlplete disappearance' should be 'complete disappearance'.
[Results, 'Ramman spectrum'] The section heading should be 'Raman spectrum', not 'Ramman spectrum'.
[Results, 'Optical emission measurement'] The text refers to 'OH- excited species at 314 nm'; the OH radical is neutral, so the superscript minus sign is likely a typographical error, and the notation should be clarified.
[Throughout] The references contain formatting inconsistencies (e.g., 'Pathak el al.' instead of 'et al.'), and some citations lack complete page ranges or DOIs. A careful copyedit is needed.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the paper reports direct measurements and an empirical inactivation comparison, with no fitted parameter or self-citation chain bearing the central claim.

full rationale

The paper does not attempt a derivation of its central claim; it presents direct experimental observations. The claim that air plasma destroys Nostoc muscorum in 15 min while O2 and N2 plasmas require about 1 h is supported by colony-count estimates, UV-vis absorption spectra, and Raman spectra of treated samples. The electron density and temperature are estimated from the air plasma OES using Stark broadening and a Boltzmann plot (Eqs. 1 and 2), with no parameter fitted to the biological outcome, so these diagnostics are independent of the degradation result. The cited prior work by the authors (e.g., Shihab et al. on capacitively coupled plasmas) is contextual background on plasma sources and does not carry the inactivation claim. The most serious experimental concern, the absence of a sham vacuum control at 0.2 mbar, is a validity threat rather than a circularity: it does not show that any prediction is equivalent to an input by construction. Therefore no circular step is identifiable and the circularity score is 0.

Assumptions & free parameters 0 free parameters · 3 assumptions · 0 invented entities

The paper introduces no free parameters or invented entities. It relies on standard plasma diagnostic formulas and the domain assumption that OES intensities correspond to reactive species concentrations. The main uncontrolled assumption is the absence of a sham vacuum control, which is captured as a red flag.

assumptions (3)

standard math Stark broadening of the N2 391 nm line yields electron density via Eq. (1).
The paper uses a Lorentzian fit and a published formula; the authors admit other broadening mechanisms are ignored, making this an approximate diagnostic.
standard math Boltzmann plot of five N II lines gives electron excitation temperature.
The method assumes a Boltzmann distribution among the chosen upper levels; the paper applies it to N II lines and obtains 2.4 eV.
domain assumption OES line intensities are proportional to RONS concentrations and reflect plasma-induced chemistry.
The paper states that higher OES intensities for air plasma 'appears clearly' and attributes faster killing to higher RONS, but no calibration or quantitative correlation is provided.

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Cite this review

Pith. "Pith review of Degradation of Cyanobacterium Nostoc muscorum via Air, Oxygen, and Nitrogen low temperature plasmas." pith.science (2026). https://pith.science/paper/WTIHWQM3

@misc{pith2026241213723,
  author       = {Pith},
  title        = {Pith review of: Degradation of Cyanobacterium Nostoc muscorum via Air, Oxygen, and Nitrogen low temperature plasmas},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/WTIHWQM3}},
  note         = {Machine review of arXiv:2412.13723}
}

read the original abstract

Cyanobacteria are prokaryotic microorganisms that possess the capability to convert light energy into chemical energy through the process of photosynthesis. These organisms exhibit numerous potential applications, including the production of bioethanol, the synthesis of food colorants, the development of dietary supplements, and the provision of raw materials. Cyanobacteria demonstrate a wide ecological distribution, inhabiting diverse environments such as freshwater and terrestrial ecosystems, as well as extreme habitats including hot springs, hypersaline aquatic systems, polar regions, and low-oxygen environments. Plasma proves to be a highly effective method for cellular degradation. When Nostoc muscorum, a type of cyanobacterium, was exposed to air-source plasma plasma, it was completely destroyed within fifteen minutes. In contrast, the use of oxygen and nitrogen plasma required at least an hour to achieve the same result. The atmospheric plasma generated chemical species such as N2^+ , N^+ and OH^- at higher concentrations than the oxygen and nitrogen plasma. The plasma spectrum was measured during the treatment of the cyanobacteria, and the electron temperature and density of the air plasma were also estimated. The light absorption of the cyanobacteria's pigments and the characteristic Raman peaks disappeared after the plasma treatment, which served as clear evidence of the complete degradation of the cyanobacterium.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

6 extracted references · 6 canonical work pages

[1]

Ahmed, K.M

Abd El -Latif, S.T. ; Ahmed, K.M. ; Elkalashy, S.I. and Zaki, M.F., (2024). Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films. Inorganic Chemistry Communications, 161: 112048. Abdel-Wahed, M.S. ; Hefny, M.M. ; Abd- Elmaksoud, S. ; El-Liethy, M.A. ; Kamel, M.A. ; El-Kalliny, A.S. and Hamza, I....

work page 2024
[7]

and Glamuzina, B., (2016)

Pinzaru, S.C.; Muller, C.; Brezestean, I., Barchewits, D. and Glamuzina, B., (2016). Cyanobacteria detection and Raman spectroscopy characterization with a highly sensitive, high resolution fiber optic portable Raman system. Studia Universitatis Babes -Bolyai, Physica, 61(1). Polívka, T.; Hiller, R.G. and Frank, H.A., (2007). Spectroscopy of the peridinin...

work page 2016
[386]

and Walsh, C.T., (2011)

Balskus, E.P.; Case, R.J. and Walsh, C.T., (2011). The biosynthesis of cyanobacterial sunscreen scytonemin in intertidal microbial mat communities. FEMS Microbiology Ecology , 77(2): 322-332. Bekeschus, S.; Wende, K.; Hefny, M.M.; Rödder, K.; Jablonowski, H.; Schmidt, A.; Woedtke, T.V.; Weltmann, K.D. and Benedikt, J., (2017). Oxygen atoms are critical in...

work page 2011
[2022]

Springer

The marine microbiome. Springer. Storme, J.Y., Golubic, S., Wilmotte, A., Kleinteich, J., Velázquez, D. and Javaux, E.J., (2015). Raman characterization of the UV -protective pigment gloeocapsin and its role in the survival of cyanobacteria. Astrobiology, 15(10): 843-857. Takeuchi, N. and Yasuoka, K., (2020). Review of plasma -based water treatment techno...

work page 2015
[4445]

and Castenholz, R.W., (1991)

Garcia-Pichel, F. and Castenholz, R.W., (1991). Characterization and biological implications of scytonemin, a cyanobacterial sheath pigment. Journal of Phycology, 27(3): 395-409. Hamza, I.A.; El-Kalliny, A.S. ; Abd-Elmaksoud, S. ; Marouf, M.A. ; Abdel-Wahed, M.S. ; El-Liethy, M.A. and Hefny, M.M., (2023). Cold atmospheric plasma: a sustainable approach to...

work page 1991
[9850]

and Han, I., (2020)

Akter, M.; Jangra, A.; Choi, S.A.; Choi, E.H. and Han, I., (2020). Non -thermal atmospheric pressure bio -compatible plasma stimulates apoptosis via p38/MAPK mechanism in U87 malignant glioblastoma. Cancers, 12(1):245. Allakhverdiev, E.S.; Khabatova, V.V.; Kossalbayev, B.D.; Zadneprovskaya, E.V.; Rodnenkov, O.V.; Martynyuk, T.V.; Maksimov, G.V.; Alwasel, ...

work page 2020

Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.

[1] [1]

Ahmed, K.M

Abd El -Latif, S.T. ; Ahmed, K.M. ; Elkalashy, S.I. and Zaki, M.F., (2024). Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films. Inorganic Chemistry Communications, 161: 112048. Abdel-Wahed, M.S. ; Hefny, M.M. ; Abd- Elmaksoud, S. ; El-Liethy, M.A. ; Kamel, M.A. ; El-Kalliny, A.S. and Hamza, I....

work page 2024

[2] [7]

and Glamuzina, B., (2016)

Pinzaru, S.C.; Muller, C.; Brezestean, I., Barchewits, D. and Glamuzina, B., (2016). Cyanobacteria detection and Raman spectroscopy characterization with a highly sensitive, high resolution fiber optic portable Raman system. Studia Universitatis Babes -Bolyai, Physica, 61(1). Polívka, T.; Hiller, R.G. and Frank, H.A., (2007). Spectroscopy of the peridinin...

work page 2016

[3] [386]

and Walsh, C.T., (2011)

Balskus, E.P.; Case, R.J. and Walsh, C.T., (2011). The biosynthesis of cyanobacterial sunscreen scytonemin in intertidal microbial mat communities. FEMS Microbiology Ecology , 77(2): 322-332. Bekeschus, S.; Wende, K.; Hefny, M.M.; Rödder, K.; Jablonowski, H.; Schmidt, A.; Woedtke, T.V.; Weltmann, K.D. and Benedikt, J., (2017). Oxygen atoms are critical in...

work page 2011

[4] [2022]

Springer

The marine microbiome. Springer. Storme, J.Y., Golubic, S., Wilmotte, A., Kleinteich, J., Velázquez, D. and Javaux, E.J., (2015). Raman characterization of the UV -protective pigment gloeocapsin and its role in the survival of cyanobacteria. Astrobiology, 15(10): 843-857. Takeuchi, N. and Yasuoka, K., (2020). Review of plasma -based water treatment techno...

work page 2015

[5] [4445]

and Castenholz, R.W., (1991)

Garcia-Pichel, F. and Castenholz, R.W., (1991). Characterization and biological implications of scytonemin, a cyanobacterial sheath pigment. Journal of Phycology, 27(3): 395-409. Hamza, I.A.; El-Kalliny, A.S. ; Abd-Elmaksoud, S. ; Marouf, M.A. ; Abdel-Wahed, M.S. ; El-Liethy, M.A. and Hefny, M.M., (2023). Cold atmospheric plasma: a sustainable approach to...

work page 1991

[6] [9850]

and Han, I., (2020)

Akter, M.; Jangra, A.; Choi, S.A.; Choi, E.H. and Han, I., (2020). Non -thermal atmospheric pressure bio -compatible plasma stimulates apoptosis via p38/MAPK mechanism in U87 malignant glioblastoma. Cancers, 12(1):245. Allakhverdiev, E.S.; Khabatova, V.V.; Kossalbayev, B.D.; Zadneprovskaya, E.V.; Rodnenkov, O.V.; Martynyuk, T.V.; Maksimov, G.V.; Alwasel, ...

work page 2020