1. Nutrients: Bacteria, like all living things, require nutrients to build new cells and provide energy for growth. These nutrients can include sugars, amino acids, vitamins, and minerals.

2. Favorable conditions: Bacteria thrive within a certain range of temperature, pH, and moisture. They also need the right amount of oxygen, depending on the type of bacteria. Some bacteria are aerobic (need oxygen), while others are anaerobic (can't tolerate oxygen).