Bacterial pattern in petri dish. Macrophotograph of a coloured pattern of Paenibacillus bacteria growing in a culture in a petri dish. This is a tip-splitting morphotype (T-type). Certain bacterial species and strains produce various patterns when grown on special nutrient media. Some of these media are made deficient in certain nutrients, which provokes changes in the patterns produced. Paenibacillus bacteria are anaerobic. They are found in a range of environments, including soil, water, plants and medical samples. They are being studied for their pattern-forming properties and their resistance to drugs.