This study aims to assess the impact of chemotherapy on the gut microbiota of pediatric patients diagnosed with acute lymphoid leukemia (ALL). We will analyze 90 stool samples collected from these patients during the initial and induction phases of chemotherapy treatment. The microbiota composition will be evaluated by extracting metaproteins from the stool samples, followed by peptide fingerprinting techniques to identify microbial proteins. This approach will allow for a detailed assessment of how chemotherapy influences the microbial communities in the gut, which could potentially affect patient health and treatment outcomes. Understanding these changes could provide insights into the management of microbiota-related complications and aid in developing microbiota-friendly therapeutic strategies for ALL patients undergoing chemotherapy.