Gram-negative bacteria are a group of bacteria characterized by their thin peptidoglycan cell wall and an outer membrane containing lipopolysaccharides. This structure makes them more resistant to certain antibiotics compared to Gram-positive bacteria, which have a thicker cell wall. They are often found in various environments, including soil, water, and the human body. These bacteria can be pathogenic, causing infections such as E. coli and Salmonella. Their outer membrane can act as a barrier to many substances, making treatment of infections more challenging. Understanding their structure is crucial for developing effective antibiotics and treatments.