Which of the following statements about bacteria is false?
- a relatively small proportion of the species are pathogenic
- oxygen is necessary for the growth of all bacteria
- their "chromosome" is a single molecule of circular dna
- some possess membrane infoldings or invaginations that increase surface area available for respiration or photosynthesis
- they reproduce by binary fission

Oxygen is necessary for the growth of all bacteria.

Explanation:

This statement is false, because not all bacteria require oxygen to produce energy and grow. The bacteria that need oxygen to grow are called aerobic bacteria. But there are also bacteria that can produce energy without oxygen, these are called anaerobic. Some bacteria can adapt to both environments, these are called facultative anaerobes bacteria.