(IMAGE) European Molecular Biology Laboratory Caption The illustration shows sections of Mycobacterium tuberculosis bacteria. The Pac-Man symbolizes the toxin, which in the absence of its antitoxin counterpart, ‘eats up’ the NAD+, causing the cell to die. In the bacterium in the back, the Pac-Man’s mouth is blocked by the antitoxin, preventing the degradation of NAD+ and allowing the cell to grow normally. Credit Beata Edyta Mierzwa Usage Restrictions Only use with provided caption and credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.