When I was still doing lab work, many people would just wear gloves and work next to a bunsen burner because the clean benches were all in use.

This was mostly for plating bacteria like Bacillus subtilis. The equipment had been autoclaved, of course, but is just having the bunsen burner next to you without working in a clean bench really enough to avoid contaminating your plates?

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    $\begingroup$ Nice question. Although the upward flow of air does likely reduce the chance of falling something on your plate, I always wondered if it doesn't equally increase the chance of sucking something into it from below :/ $\endgroup$
    – AliceD
    Nov 18 '15 at 10:42

For doing bacterial work on an open bench, this is standard "Sterile Technique." The updraft from the heat generated by the Bunsen Burner should create a relatively sterile field with which to work, so long as you aren't breathing directly on your plates.

Also part of sterile technique is to "flame" all of your pipets, agar plates, and the openings of bottles to remove any contaminants from those areas, and also to protect them from getting into sterile mediums. Every time you uncap or cap a media bottle or test tube you are suppose to quickly pass it over the flame. Obviously these days, plastic equipment makes that a little less practical, but it still can be done if you pass quickly and aren't too close to the flame.

Disposable serological pipettes should remain covered until just before use and then the "banana peel" method of removing the wrapper should be used. If the tip touches anything it should be discarded.

The true test of your sterile technique is whether or not you are getting contamination. Some labs that work with recombinant bacteria don't even bother with sterile technique for bacteria work as they are using antibiotic selection, and contamination becomes much less of a concern. That being said, an ounce of prevention is worth a pound of cure, so if you keep your work space clean, and there isn't a risk of fire, i.e. you don't have organic solvents in the area or the stack of lab reports you are supposed to grade spilling over onto your bench, then it doesn't hurt to light up a burner even if you are using selection.

You are also supposed to have cleaned your work space prior to lighting the burner with 70% ethanol, which will rather quickly kill most bacteria on the surface. Wearing gloves and proper glove technique also helps keep contamination to a minimum. Keeping hair tied back and wearing a clean lab coat can also help, though lab coats are usually more for your protection and for the protection of others (not transmitting hazardous materials on your personal clothing) than to prevent contamination.

Most people get the false impression about BSL-2 Laminar flow cabinets or glove boxes are suppose to be sterile and prevent contamination. Their real purpose is to keep things in, not really to keep things out. Laminar flow hoods will keep aerosolized particles within them from getting to you, so long as you keep the hood area fairly clear and do not block vents, but as you pass your hands through the flow, you are bring whatever is on you and has tagged along for the ride into to work field. Glove boxes can maintain a sterile field, so long as it, and everything going into it, other than your samples have been sterilized, and your sample hasn't already been contaminated.


you must work near a lit Bunsen burner when culturing microorganisms because it helps stop your results from getting contaminated because heat sterilises (kills bacteria). Also, the upward flow of air reduces the chance of anything falling onto your plate and contaminating it. this is the best way to get true results if you don't have lots of fancy equipment.


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