Final answer:
The bacteria that needs oxygen at lower levels than the atmosphere and forms a narrow band in liquid media in a test tube are known as microaerophiles.
Step-by-step explanation:
The type of bacteria you are describing, which requires oxygen but at lesser amounts than ambient air and forms a narrow band in thioglycolate tube culture, is characterized as a microaerophile. Microaerophiles need a minimum level of oxygen for growth, typically around 1%-10%, which is well below the 21% found in the atmosphere. They perform aerobic respiration and may also ferment sugars when oxygen levels are not ideal. By forming a narrow band where the oxygen concentration is optimal for their growth, microaerophiles demonstrate their precise oxygen requirements.
In a thioglycolate tube culture, the position of bacterial growth can indicate the oxygen requirements of the bacteria. The narrow band of growth you describe is a hallmark of a microaerophile environment. These bacteria are uniquely adapted to survive in conditions where oxygen is present but at lower levels than what is found in normal atmospheric conditions.