Gram-negative bacteria are a group of microorganisms characterized by their cell wall structure. They have a thin peptidoglycan layer surrounded by an outer membrane, which contains lipopolysaccharides. This unique structure makes them more resistant to certain antibiotics compared to Gram-positive bacteria, which have a thicker peptidoglycan layer. These bacteria are often found in various environments, including soil, water, and the human body. Some Gram-negative bacteria can cause infections and diseases, such as Escherichia coli and Salmonella. Understanding their structure and behavior is crucial for developing effective treatments and preventing infections.