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/sci/ - Science & Math

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2316128 No.2316128 [Reply] [Original]

So I was looking at deep sea vent bacteria that use chemosynthesis with H2S, CO2 and O2 to make C6H12O6, but I just don't get how it's working. I know how photosynthesis works, but I can't make the jump to chemosynthesis.

I know with the use of light, an electron from the photosystem II is carried over to an electron transport chain while using photolysis to get its electron back.

But how does that work with chemoautotroph bacteria that use H2S? They don't have a photosystem or anything.

>> No.2316146

Humans don't use light in their metabolism, figure that part out and you've figured out the microorganisms.

>> No.2316153

>>2316146
Also meant to add, look at the oxidation state of those sulfurs in your picture, BOOM electrons

>> No.2316169

>>2316128
They get electrons from oxidation of H2S.

>>2316146
Humans are heterotrophs, chemosynthetic bateria are autotrophs. Big difference.

>> No.2316179

>>2316169
Yeah I realized the metabolic paths are way different, I was just pointing out humans don't need light, for some reason he assumed light needed to be involved. (I'm definitely no biologist)

>> No.2316204

>>2316179
Heterotrophs (humans, animals, fughi, most bacteria) use complex carbon sources, such as glucose, to drive their metabolism. Autotrophs use energy (in the form of electrons) from light or inorganic molecules to produce complex carbon sources which then they use for their metabolic processes. It makes more sense to compare chemosythetic bacteria to photosynthetic then it does to compare them to non-photosynthetic heterotrophs (like humans).

But I'll readily admit that it can be confusing.

>> No.2316247

>>2316169
Sorry to look like a total idiot but just how does the oxidation work inside the bacteria? H2S reacts with O2, right? Thus energy is released and somehow stored inside the Bacteria in order to pump whatever it is inside its membran for later ATP production while being transported to an enzyme that helps forming NADH?

>> No.2316268

bump

>> No.2316346

bump, man I just dont get it.

>> No.2316385

Some kind sould? Anyone?

>> No.2316392

Thermal energy.

>> No.2316404

energy that comes from the oxidation of sulphur

>> No.2316429

>>2316404
>>2316404

google redox reactions...e- are liberated by the oxidation of um...anything.

>> No.2316785

Bump.

Can someone please xplain me, maybe in regards to photosynthesis, how the fuck chemosynthesis works?

>> No.2316805

Bamp

>> No.2316844

Bump

>> No.2316863

bumpp

>> No.2316997

Bump

>> No.2317121

You guessed it

>> No.2317216

Sigh

>> No.2317284

Bump

>> No.2317318

You've already had the answer. Why are you trying to think of this like photosynthesis?

Its not exactly what you're after, but have a look at this;

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2646786/figure/F1/

Here's a graphic of CO2 fixation via the Wood-Ljundali pathway. Keep in mind this is anaerobic fermentation of CO2 with H2 (and its usually powered by CO metabolism) So its CO2 capture using H2 and or CO as an energy source.
But odds are, H2S metabolism have similar pathways.

http://www.2dix.com/view/view.php?urllink=http%3A%2F%2Ffire.biol.wwu.edu%2Fbrodham%2FAutotrophy.ppt&
amp;searchx=Purple%20Sulphur%20Bacteria

Photosynthesis captures energy from light to crack water and CO2. H2S metabolisers capture the energy of of H2S oxidation to crack CO2 and water. Both then build those up into sugars and other biomolicules.

Do you really care about exact enzyme pathways?

Step 1) Oxidize H2S
Step 2) Electron transport
Step 3) ??Enzymes??
Step 4) Profit.

>> No.2317400

>>2317318
Well thanks.

I was thinking in terms of photosynthesis because its pretty easy to get a clear picture of it in your mind. You got all this stuff inside the membrane (photosystem II, I , enzymes), stuff getting transported from one side of the membrane to the other with the use of electrons in order to create a gradient, etc. You know, its pretty easy to understand even if you dont know much about reduction potentials or that stuff. The calvyn cycle isnt the problem aswell.

I just cant get a clear picture of how stuff would look and function inside the bacteria with chemosynthesis. How the bacteria forms atp and nadph in order to use it for the calvyn cycle.

>> No.2317541

Have you got a good reason to think they're doing the Calvin cycle or did you just assume? There are other ways to fix CO2.

FAD/FADH/FADH2 is popular with bacteria when H2 is around, as will be the case when they're metabolizing H2S.

Remember, bacteria have no internal organelles, so they have no membranes or compartments inside like chloroplast or mitochondria. All the gradients they will be setting up will be between their interior and exterior. Fermenting bacteria often set up pH gradients to power their ATP pumps.

Given this one exists in seawater, 8/10 odds its using sodium gradients. It'll actively pump out sodium, maybe with a coport, then let it trickle back into power its ATP pumps. NADH is probably produced in the same enzyme cluster as the H2S oxidation occurs as the electrons and hydrogen are both available in that step.

>> No.2317674

>>2317541

Hmm okay that makes things a little clearer. Ive been looking around the met, especially for those hydrothermal vent bacteria that live in symbiosis with tubeworms, but also those who settle directly ontop of the seamount.

Now what ive read is that its basically two steps (which sounded alot like photosynthesis)

Step 1 oxidation of h2s in order to get the energy For atp and nadph+ h

Step 2 assimilation of co2 (calvyn cycle)

I just never could find more precise descriptions of both of the steps so I assumed it must be similar to photosynthesis.

>> No.2317716

Last bump

>> No.2317784

God OP

You can't be that fucking dumb.

Oh .... Well never mind.

>> No.2318057

Okay last bump I swear

>> No.2319159

Also, are you the same guy who was asking about deep ocean ecologies over the last couple of days?

Bacteria have one hell of a bag of tricks when it comes to electron capture. Most of them are able to utilize more than one. Its part of the reason why they're such successful little bastards.

You probably aren't going to find a lot of extra detail on them as they're difficult to study, given their natural setting. Go read up on purple sulphur bacteria, you might find more info then.

Also, stop assuming the calvin cycle. They may well do something very similar, or they may even use the calvin cycle, but there are other means to fix CO2.

Look; alternatives to the Calvin cycle
http://en.wikipedia.org/wiki/Carbon_fixation

You'd really need to know the species of bacteria in question, and possibly have had someone sequence its genome to know which method its using. Otherwise, just know they're fixing carbon. Somehow.

What else are you not clear on?