Team:KULeuven/Discussion

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Sound/vibration sensor system for E.coli

--Erwinswinnen 10:06, 8 June 2011 (CDT)

   presence of mechanosensors MscL/MscS in E.coli: could they function as sensors?? 

Jonas: general info on mechanosensitive channels (like MscL etc): http://en.wikipedia.org/wiki/Mechanosensitive_channels, Question for any engineer or physics student: can we generate, by sound, enough force on the membrane of e coli (possibly spheroblasts, so without cell wall, to make them more sensitive) to force channel opening? We would need about 5.5 dyne/cm for MscS or so. Is this possible with sound?

Jochem: as for the channels in e.coli, 5.5 dyne/cm^2 is apparently 5.5 N/m^2, thus 5.5 Pa which translated to about 110 dB (20 log(P/Pref)) But this is in air, I don't know the attenuation coefficient for sound in water, but it might be quite high... However, from what I understand from the article it works on pressure difference over the membrane, to compensate for too high osmotic pressure and release some osmolytes. Which means that it requires a higher pressure inside the cell compared to outside, not possible with sound. Also it appears to already be in e.coli and many other organisms to compensate for osmotic pressure (which can be quite high).

Jonas: In the end, the channel is activated by lateral tension in the membrane. Would this not be induced (on-off) in the bacterial membrane when it is hit by soundwaves (perhaps amplified and transferred into the medium of a liquid culture)? Is this provable with a sonicator on very low intensity (so no bacterial cell lysis)? The channels (MscL/M/L) are indeed present in e.coli etc. But might be interesting to biobrick/overexpress/make hypersensitive (mutants described)/ ... as they can apparently also be removed without compromising viability of the culture under normal conditions)

Jochem:I am not sure how a membrane would respond to a higher or lower pressure... I guess it would have some effect in the same way as temperature can induce phase changes in the membrane. But I am unsure if it would result in any lateral tension keep in mind that sound waves are orders of magnitude larger then bacteria, but ultrasonic sound wave can be in the order of a bacteria and might result in some memrbane tension? Maybe it is an idea to tether the bacteria at two sides to two paralel flexible surfaces (see improvised picture below, 0=bacteria), which are then allowed to vibrate due to sound (away and towards each other); sort of stretching and squeezing the bacteria? (that should result in lateral tension ^^)

0

or maybe this 'piezophilic' bacteria can be of use? http://www.ncbi.nlm.nih.gov/pubmed/10941789

I forgot what was in the slides of the guys who presented this idea, what did they find again/are the slides somewhere? :-) Also, is the wiki up yet?

    use of human hair cells?

Koen: Is it recommended to work with E.coli? We can also use human hair cells, then we could make a direct sound sensor in stead of a pressure sensor. Good websites with the basics of hearing: http://www.ks.uiuc.edu/Research/hearing/ and http://www.beyonddiscovery.org/content/view.page.asp?I=259 In the ear the crucial point is converting the mechanical stimulation of the hair cells into a membrane electric potential which leads to neural signalling. Maybe it is possible to visualize this electic potential and make a correlation between the frequency of the sound and the colour we use. For example a blue colour is generated when the frequency of the sound is X MHz. Another advantage of working with human hair cells is having much more previous research literature. Now we only need the time to explore it ... ;-) It is impossible to detect sound with only one hair cell (like proposed in my previous mail), of course you need the whole ear organ. However we can still use hair cells for detecting pressure pulses but E. coli is also possible.

Jonas: The advantage of e. coli is that it's easy to work with + the registry is mainly aimed at this bacterium.

Jochem: Like Jonas said, the advantage of E.coli is the ease of work and the immensive amount of literature there is for e.coli. But it is not forbidden to work with anything else... However the main problem in working with human hair cells is the difficulty in growing this (btw afaik the rest of the ear is only there for amplification, so might be ignored). I do think the mechanism of the hair cells is mechanosensitive channelsl as well.

Koen: While learning about nanomotors, my course mentioned a protein, prestin, which is a motor protein in the inner ear. Its shape apparently responds to changes in the electrical potential across a membrane. Because of this, it can amplify sounds up to a 1000 fold. Maybe it could be useful since it amplifies sound (maybe we can implement it so that the bacteria detects small of changes in environmental sound)? This link gives a small introduction of the protein: http://en.wikipedia.org/wiki/Prestin

Coupling an output to the sound/vibration input signal

--Erwinswinnen 10:07, 8 June 2011 (CDT)

    coupling mechanism will depend on the signal generated by the sensor --Erwinswinnen 10:17, 8 June 2011 (CDT)

if, for instance, the bacterial MscL/MscS proteins would be sound sensitive, how are we going to detect this? In order words, how are we going to couple activation (channel opening) to a measurable output? --Erwinswinnen 10:05, 8 June 2011 (CDT)

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