Bacteria Colony

[jowrose]

Ok, I'm not very knowedgeable in the field of Biology (I've taken high school biology, and planning on taking a college level course next year), but I find it very interesting. I made some agar from gelatin and a few other ingredients and have been growing bacteria colonies. I started this one on December 22, and this picture shows its growth by December 29. Does anyone have any ideas to possible bacteria species? The colony is roughly 4.4 cm tall, and about 2.5 cm wide (i'm talking about the colony on the side, not in the middle).

 

[ecoli]

I'm almost 100% sure that's mold you got there... a fungus, not bacteria.

[Helix]

Yeah it looks like your petri dish was contaminated by some type of mold. If you prepare another dish, try to make sure you wear gloves, don't put the dish plates on a table etc.

 

That is a nice mold colony though, why don't you examine that while you have it?

[jowrose]

Are bacteria colonies more homogenous in structure (lacking the "rings" that I have gotten)? How can you so easily determine the difference?

[Yggdrasil]

In general, mold looks kind of fuzzy. Bacteria should give you nice, round yellowish dots. After overnight growth on complete media, bacterial colonies generally don't get more than a few mm in diameter.

[ecoli]

Also, it would be peferable to autoclave your medium, to make sure that there is no fungus or bacteria living there before you even start growing your desired organism.

[jowrose]

Immediately after making the batch of agar and pouring it into the petri dishes, I placed the dishes in a freezer after sealing them in a ziploc back. I'm pretty sure that they are reasonably pure. The inner layer of the "colony" is very thin, not fuzzy at all, but the middle and outer rings are filamentous.

 

Ok, I'm going to try purifying my system and see if I can avoid growing more fungi. Thanks for the help.

[Yggdrasil]

Immediately after making the batch of agar and pouring it into the petri dishes' date=' I placed the dishes in a freezer after sealing them in a ziploc back. I'm pretty sure that they are reasonably pure. The inner layer of the "colony" is very thin, not fuzzy at all, but the middle and outer rings are filamentous.

 

Ok, I'm going to try purifying my system and see if I can avoid growing more fungi. Thanks for the help.[/quote']

 

Still even if you immediately freeze the plates (freezing plates probably isn't the best for them anyway), the materials you used to make the plates are contaminated. One way to help remove this contamination if autoclaving is not an option is to pass over the surface of the plates with a bunsen burner flame after pouring the plates. This should kill some of the contaminants on the surface of the agar.

[jowrose]

Is there a special device needed to autoclave? Or could I just make my own with a hot plate, flask, water, and some tubing?

[Yggdrasil]

Probably not. An autoclave heats liquid media to about 120 C in a pressurized chamber, which prevents the liquid from boiling. You may be able to make fairly sterile media by bringing your meda to a boil for a few minutes, covering your flask with some foil, and cooling it to ~ 40 C in a hot water bath before pouring your plates. Also it would help to disinfect down any benchtops you're going to use with 70% ethanol or isopropanol (rubbing alcohol) beforehand.

[badchad]

You need an autoclave to be able to "autoclave" something. From looking at the size of the machines around my lab, I'd think the pressure is pretty darn high inside them (not something you could achieve at home). Although, I'm sure someone knows more about this than I.

[jowrose]

Ok, thanks for the advice. I don't have much extra money lying around (If I did, an autoclave would be one of the last things I'd buy...), so I'll just boil the growth medium and kill off all the unwanted organisms.

[ecoli]

I suppose you could use a pressure cooker. That might do a better job then simply boiling it.

[jeskill]

Yeah, amateur mycologists use pressure cookers to autoclave agar before plating. The green colony looks like a penicillium species to me (a fungus). They can be very pretty, they grow very quickly and after a while, they start to produce droplets of liquid in the centre of the colony. If you have a microscope, make a slide and look at it. You'll be able to tell what kind of fungus it is for sure by looking at the architecture of the sporulating hyphae.

 

If you wait long enough, bacteria will probably grow on the dish too. Then you can isolate the bacteria if you want. But IMO, fungus is WAY more interesting .

[romunov]

I agree, that might be Penicillium. Pretty common on old fruit. Rhizopus/Mucor are also quite common.

[Hegemony]

That agar look a little funky. I'd be interested to see the recipe. There are a lot of types of agar that won't grow fungi very well.

[Steph]

I agree, that might be Penicillium. Pretty common on old fruit. Rhizopus/Mucor[/i'] are also quite common.

 

Rhizopus and Mucor are usually darker. Penicillium makes sense, although I'm not a mycologist... its actually hard to not have fungi in bacterial cultures left at room temperature. you have be careful and sterile. I don't know how you inoculated or anything. if you left it to the air, this happens, if you just swabbed something, again this would happen. The best way to get bacteria (as well as fungi but less) is to incubate at closer to human temp 35-37oC. how? uhm... only way i can think of right now... an idle (recent AMD) computer runs at about this temperature. Pentiums are a little higher. so if you can make a box around one, and leave it there, it could work. oh and the computer chips can withstand around 80oC so you wouldn't have to worry about that (as long as your box doesn't catch fire)

 

EDIT: btw, the white colony is also fungi

[Mindtaker]

You definately have fungus on your plate. Althought it's hard to tell what exact type of fungus it is I'm not an expert. I'm assuming those are blood agar plates? Follow the steps below in order to get better results for bacterial growth. It sounds as if your plate preparation needs work.

 

Once you make the agar you will want to autoclave it (or sterilize it somehow, pressure cooking is a good option if you don't have an autoclave). Once the agar is autoclaved you will want to wait until it is cool enough to touch, it is better to let it cool in a water bath (usually mine are around 55 degrees C). Then if you can light a continuous flame (like a bunsen burner) by the agar and the sterile petri dishes. Then just pour the plates by the flame. Then let them cool until they are hard (or at least not fluid-like) but don't put them in the freezer (I'm not sure why, but my professors have always told me not too). Just remember that nothing is sterile around you except the sterile petri dishes and the autoclaved agar (not even the air which is probably where your fungus came from).

 

Sorry this is so long.