Agar-phenopthalein jelly

[dime]

Gosh, I'm just making up 189 nutrient plates for 6 bio kids in year 12 for their own pracs. Talk about go thru agar.

And Lada, re the mind reading thing, I've got the best answer for anyone who tries that, by saying the name's Angel not J.... C.....

[RosalieM]

WOW!!! I can't imagine making that many all at once. I don't know that I'd have enough space to put them once made, either!

[dime]

Well, the staff are about to find out what the staffroom fridge was bought for. Not for their lunches and drinks.

[bindibadgi]

Anyway was thinking can we substitute gelatine or something for plates for junior classes?????
For cost saving.
Or if anyone knows how to buy agar powder cheap.Let us know your secret
Trish.
ps. just searched google and some mention guar gum or xanthan gum any one tried these substitutes??????

Hi Trish,

if you want a cheap way to grow basic bacteria etc for junior classes, you can use the humble old potato :

Potato as an alternative culture medium for fungus and bacteria.

Peel a large potato and cut into 6mm thick slices.
Place potato slices in boiling water and boil for 1 minute.
Use sterilised tweezers to transfer each slice to a sterile petri dish and allow to cool.
Inoculate the same way as for agar plates.

Potato is particularly good for culturing microbes from soil.

I know what you mean re the cost of agar & how time consuming it is too......I make up several hundred at a time because we have 5 year 11 biology classes + 2 year 11 IB classes - at least it keeps me off the streets
Currently I've also got 5 year 12 IB kids doing micro pracs but for them we bought Petrifilm plates - brilliant things ($$$ but worth it for the results & quality of data they get)

Cheers,

[judygee]

Dear All - Just wondering how you cut the blocks of agar into the 1,2,3cm cubes. I always have trouble using a knife and ruler, I find the knife seems to skid off to one side in the jelly-like substance and I can never get a reasonably accurate square. I was trying to talk one of the maintenance fellows into making me something akin to a cheese/butter cutter so I could cut them accurately in one fell swoop, but no success so far. What do others do? I would be interested to know. Cheers. Judy

[matchstick]

I prepare the three agar trays then the students cut the cubes.
here its part of thier prac to cut the cubes themselves
M

[macca]

I give the kid a ruler and scapel and they do it. heaps easier

part of our prac too!

[bindi]

I find a 30cm metal ruler cuts long neat sections

[Ocker]

If you have trouble cutting agar blocks straight, buy one of thoes cheese cutters like a gillotine with a fine wire as the cutter or ask your TAS section for a bench hook to have on permanent loan the bench hook is a flat board with a a piece on top and bottom at oppsite ends for cutting wood with a tennon saw the bit that sticks up you use as a guide
Hope that's clear

[judygee]

Thanks Graeme - will definately look into the cheese cutter and TAS bench hook thingee. Cheers. Judy