Cultures of uncontaminated bacteria

*Using sterilised equipment (e.g. petri dish). *The equipment is normally sterilised by heating them to high temperatures. *This is done to kill any bacteria on the equipment. *The inoculating loop, which is used to transfer bacteria from the culture to the agar, is passed through a Bunsen flame to kill any bacteria on the loop. *The loop should be allowed to cool before it is put in to the culture so it doesn’t kill bacteria in the culture you are trying to collect bacteria from. *The loop should not be placed on the bench to cool as it could be contaminated with bacteria from the bench. *The lid of the petri dish is removed as little as possible and replaced quickly to prevent bacteria entering from the air and prevent bacteria from the petri dish escaping in to the air. *The petri dish is sealed with two small pieces of tape so that oxygen can enter the dish, which the bacteria need to grow. If the dish is sealed all the way around and no oxygen can enter then harmful pathogens can grow. *The petri dish is incubated in warm conditions to allow the bacteria to grow.