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    • #13124
      sixpence
      Participant

      after i leave my plates out for 4-5 days, fungus starts growing on them. is this caused by contamination while pouring them? or is it unavoidable because they were left out a long time. is it caused by some moisture buildup?

    • #99074
      JackBean
      Participant

      what do you mean by "left out a long time"? Did you sterilize the media properly?

    • #99084
      mith
      Participant

      depends on whether you poured them in the steril hood or not

    • #99127
      sixpence
      Participant

      no we never pour them in the sterile hood, just next to a flame. i have extras that i end up not using and like one or two out of a stack of ten will start growing mold… i’m not sure why this happens to me. I’m very careful when i pour the plates and immediately cap them. is it something on my hands? i usually don’t wear gloves when i pour plates.

    • #99300
      DanielSan
      Participant
      quote sixpence:

      no we never pour them in the sterile hood, just next to a flame. i have extras that i end up not using and like one or two out of a stack of ten will start growing mold… i’m not sure why this happens to me. I’m very careful when i pour the plates and immediately cap them. is it something on my hands? i usually don’t wear gloves when i pour plates.

      Hmmm… I think it would make sense to wear gloves. Sometimes i also pour my plates outside the laminar flow. But i always sterilize the whole place and also the gloves i’m wearing- and I never had any contamination.

    • #99315
      JackBean
      Participant

      You don’t have you wear gloves (they are even not sterile;), but you should sterilize your hands 😉

    • #99328
      Trex
      Participant

      study the fungal,maybe you will discover new something 😆

    • #99359
      hokosan
      Participant

      The gloves or hands without gloves should be disinfected using 75% ethanol solution before experimental operation. Before experiment, the tools and the place must sterilized thoroughly.

    • #100182
      victor
      Participant

      I think it’s better to follow the steps in Laboratory Experiments in Microbiology book written by Ted R. Johnson and Christine L. Case. You’ll find some steps to prepare workbench and also steps in pouring media (also with pictures) :mrgreen:

    • #100379
      khalaphallah
      Participant

      i think that if the growth appered after " or ‘ days that fungi and if u show that after( or – days tha’s actinomycetes ,
      in the two cases , there are two reasons for that
      1 the plate petri not sterilization or the time of sterilization in autocalved didn’t enught
      2 when u pour the media it’s contimnated

    • #100485
      skeptic
      Participant

      It is worth remembering that air is full of fungal spores. More in some places than in others.

      You should pour plates in a clean environment with still air, to minimise the movement of such spores. Also, open each plate only briefly. It is when you open them that spores drift in.

      Spores also fall off anything unclean. Washing hands first and drying them well is good practise. Also, if you have clothing with sleeves, make sure the clothes are clean, since fungal spores can shake off those sleeves if they are not clean.

      An interesting experiment to try is to check fungal spore numbers in the area you pour your plates. Open the plates to the air for different periods of time, and incubate, to see how much exposure is needed to guarantee infection. A clean environment should permit at least 50% of all plates to remain uncontaminated after 2 minutes exposure.

    • #100509
      JackBean
      Participant

      after 2 minutes? LOL we did similar experiment, but let the dishes opened for half an hour 🙂

    • #109192
      michimichi
      Participant

      the source of the contamination would be from air since you said you didnt pour it under the hood.
      It might also be from the plate or the media which was not properly sterilized.
      Its okay not to wear gloves but be sure to disinfect you hands and do proper aseptic technique.
      ..and also, dont talk when pouring agar…if you cant help it, use mask instead.

    • #109202
      JorgeLobo
      Participant

      Don’t worry about your hands being the source (you can’t "sterilize" them and fungi are not flora you’d expect) and it’s doubtful you’re seeing actinomycetes. Think skeptic has the right idea. Unless your sterilization is inadequate (is your autoclave validated?) it may be more a function of air contaminants in room or frig finding theirinto your plates. What do you do with plates after pouring and solidification? Try replacing poured plates in the plastic sleeves or even in stainless steel canisters

    • #109203
      michimichi
      Participant

      another thing is ,how did you store the unused plates with agar?
      put it in a zip lock and store it (upside down) on the fridge (do not freeze) for future use.

    • #111749
      tom1193
      Participant

      I always pour from a beaker covered with sterilized foil, with only the mouth uncovered to pour. Do this right after it is done autoclaving. Doing it next to a flame is not enough to keep contamination out of the agar. I also flame the mouth before every pour. The contamination usually comes when your pouring; your plates shouldn’t become contaminated after a few days if you properly poured.

    • #111849
      citroenboom
      Participant

      In my lab the cold room is a nice source of some black fungi (we need to clean). Only carefully closed bags are good enough to keep it out. So I think it is air and water droplets in in the air.
      Just be carefull when pouring and storing. Pouring next to the flame and storing upside down in a bag in a clean room or fridge (works for me). The bag is mainly to prevent it to dry out.

    • #112011
      Atropa
      Participant

      If you don’t want contamination, then you need to control for it. You should be using a sterile technique for everything. And your plates should never be open and exposed to air longer than it takes to pour the agar or inoculate your medium with a sample…

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