Aseptic procedures insure that cultures are free of microbes that can overwhelm and kill a tissue culture explant.
Microbial contaminants, consisting of yeasts and various species of fungi and bacteria, usually appear on the agar surface within a few days to a week.
These may be white or opaque slime or variously colored colonies, sometimes with black spores and mycelium.
Microorganisms occur primarily as spores on the explant, resting on surfaces of tables, hands, arms, clothing, and various objects and settling out of the air or blown in the dust on air currents.
Aseptic procedures start with disinfesting the explant usually with a bleach solution and using sterile tools.
Aseptic transfer procedures are done in some kind of transfer hood to minimize the movement of dust and contaminants.
The technician is subculturing shoots using a sterile scalpel and forceps under a laminar flow hood.