[asihall]

Greetings chemists and other equally awesome people!

I am a student of microbiology so I apologize if this is too "easy" of a question in this forum or poorly worded (English isn't my first language) or even inappropriate for the forum.

I'm growing a whole bunch of different strains of bacteria and searching for ones that reduce the iron content in soil (mainly clay, this is done aerobically and most likely by using secreted organic acids to remove the iron). Does anyone have a good protocol on measuring the amount of iron (Sort of like total Fe content, even though I'd be happy just to know the Fe2+ content) that's present in solution.

I'd like to be able to do this by myself with a spectrophotometer, I have looked online and found a whole bunch of protocols that seem to look for iron content within cells, but I'm not concerned with the iron that the bacteria take up in their cells. Later on, when I've checked the samples that I do have I'll have access to electron microscopy and ICP for final results. This would just be to see if the bacteria are removing the iron or not.

I don't want to order some chemicals that may be expensive if they don't work for what I need them for.

Thanks in advance!

[wildfyr]

Do you mind killing the cells to get the iron content?

[Arkcon]

So what you're looking for is a colorimetric iron assay.  There are many, based on the particular reactions of iron salts.  If you do a before and after, or better still, multiple points ongoing while the bacteria work on your media, you should get in the ballpark.  See what a literature search along those lines will get you, you should get to see what others have done.

[wildfyr]

Potassium ferrocyanide perhaps?

[pcm81]

I'll byte...
Honest question from a non-chemist:
Why can't OP use KMnO4 titration? Or perhaps acidic dissolution of iron in the sample followed by KMnO titration?
Perhaps OP can use a centrifuge to separate bacteria from solution and determine iron in each separately?

[asihall]

Hey all, thanks for your replies.

Do you mind killing the cells to get the iron content?

I don't mind killing the bacteria in order to do the assay and I'll look into potassium ferrocyanide, thanks.

So what you're looking for is a colorimetric iron assay.  There are many, based on the particular reactions of iron salts.  If you do a before and after, or better still, multiple points ongoing while the bacteria work on your media, you should get in the ballpark.  See what a literature search along those lines will get you, you should get to see what others have done.

I've found so many and not being a chemist I'm not 100% sure which one is appropriate. But I'll keep googling, thanks.
In the first steps I'd love to just be able to see a ballpark amount that the bacteria are releasing, later on I'll do a series of ongoing points as you suggest, when I have filtered out which ones of my 75 strains actually remove iron from the clay. I have 5 different clays and 75 strains to check so I'm working with 375 test tubes.

Why can't OP use KMnO4 titration? Or perhaps acidic dissolution of iron in the sample followed by KMnO titration?

I was hoping I wouldn't have to do more titrations after my undergrad gen.chem practicals but I'll keep it in mind thanks


This one looks simple enough, but would it be appropriate? Maybe I'm overthinking this and the Fe³⁺ content will be enough for me to accurately select the strains that are doing the work I want them to.
http://www.canterbury.ac.nz/media/documents/science-outreach/iron_colorimeter.pdf

Thanks again!

[Corribus]

You might find this somewhat relevant.

http://www.spectroscopyonline.com/single-cell-icp-ms-analysis-quantifying-metal-concentration-unicellular-organisms-cellular-level