M. tuberculosis, or Mycobacterium tuberculosis, is a bacterium that causes tuberculosis (TB), a serious infectious disease primarily affecting the lungs. It spreads through the air when an infected person coughs or sneezes, releasing tiny droplets containing the bacteria. TB can also affect other parts of the body, including the kidneys, spine, and brain. The infection can be latent, meaning the bacteria remain inactive in the body without causing symptoms, or active, where symptoms like cough, fever, and weight loss occur. Treatment typically involves a long course of antibiotics to effectively eliminate the bacteria and prevent transmission.