# What is the electric field strength of microalgae?

Question: What is the electric field strength of microalgae?

Background: So I have been having some problems with fungi contaminating my chromera velia algae cell cultures. I haven't determined what fungi are contaminating it yet, but I will figure that out with microscopy. I tried using some antifungal agents, such as cycloheximide, on petri dishes to separate the algae from the fungus. However, fungi with their obvious hyphae are growing happily on the petri dishes despite the antifungal agent.

So I thought maybe use some physics for algae separation science, instead, so I came upon a patent which proposes using a pulsed electric field to kill bacteria and rotifers without harming the algae ( Green, Michael P., et al.) . However, I'm not sure what the electric field strength of the microalgae is so this is not clear to me. But the patent states that algae can have a lipid content of up to 50% of their cell mass so that would seem to me to make the cell wall of algae strong and have a high electric field strength.

In order to irreversibly restructure/lyse a cell membrane, a trans-membrane potential of at least 1 volt must be induced locally in the cell membrane generally governed by the equation:

Δφg = F * a * E * cos(x),

where "a" is the radius of the cell, "F" is determined by the shape of the cell, and "x" is orientation of the electric field (Grahl, T., and H. Märkl). "E" (kV/cm) is the important parameter which is the critical electric field strength of the cell membrane that induces a trans-membrane potential of 1 volt.

This equation would mean that the greater the radius of the cell the lower the electric field strength would be required to lyse the cell. Experimentally, the critical electric field strength of Escherichia coli is 13.7 kV/cm, for S. cerevisiae (Baker's yeast) it's 4.7 kV/cm ( Grahl, T., and H. Märkl). For algae, I don't know what that is.

Yeast is about 5 - 10 uM in diameter and for chromera velia the diameter is like ~ 5 uM so based on size if this equation is valid for algae then a pulsed electric field should not be effective for isolating algae from fungal contamination. If the algae cell wall and membrane is stronger than the equation presented, a pulsed electric field might work for reducing competing organisms such as fungus in growth medium. I came upon this conference abstract which states that a pulsed electric field with a field strength of 40 kV/cm for 30 minutes at a pulse duration of 25 nanoseconds is nonlethal and promotes algae growth ( Gusbeth, Christian A., et al). I don't know how much stock to put into this because it's a not a full scientific paper.

If bacteria can be killed at 99.99% efficiency at an electric field strength of 20 kV/cm and several milliseconds of pulses (Hülsheger, H., J. Potel, and E-G. Niemann) and if that abstract is accurate and algae can survive 40 kV/cm just fine then I think I could significantly remove fungal and bacterial contamination with a pulsed electric field strength greater than 20 kV/cm for 30 minutes with 25 nanoseconds pulse duration + antibiotics + cycloheximide.

Is an algae cell membrane + cell wall really that strong? Does it have a large electric field strength despite its size? What is the composition of an algae cell membrane + wall like? If you think this method of applying a pulsed electric field would work for my problem, give me some advice please.

Thank you!

Sources: Green, Michael P., et al. "Enhancing algae growth by reducing competing microorganisms in a growth medium." U.S. Patent Application No. 13/419,062.

Grahl, T., and H. Märkl. "Killing of microorganisms by pulsed electric fields." Applied microbiology and biotechnology 45.1-2 (1996): 148-157.

Hülsheger, H., J. Potel, and E-G. Niemann. "Electric field effects on bacteria and yeast cells." Radiation and environmental biophysics 22.2 (1983): 149-162

Gusbeth, Christian A., et al. "Boost of algae growth by ultra short pulsed electric field treatment." 2013 Abstracts IEEE International Conference on Plasma Science (ICOPS). IEEE, 2013.

Hülsheger, H., J. Potel, and E-G. Niemann. "Electric field effects on bacteria and yeast cells." Radiation and environmental biophysics 22.2 (1983): 149-162.