Which of the following is a gram-negative microbe?

Pseudomonas is a gram-negative microbe, which means it has a thinner peptidoglycan layer in its cell wall compared to gram-positive bacteria, and it is surrounded by an outer membrane containing lipopolysaccharides. This structural characteristic is crucial because it affects the bacterium's staining properties, antibiotic susceptibility, and pathogenicity.

In contrast, Staphylococcus and Streptococcus are both gram-positive microbes. They possess a thicker peptidoglycan layer that retains the crystal violet stain used in the Gram staining procedure, which gives them a purple appearance under the microscope. Clostridium is also a gram-positive bacterium, known for its ability to form spores and its anaerobic metabolic characteristics. Understanding the differences between gram-negative and gram-positive microbes helps in diagnosing infections and determining the appropriate treatment options, particularly when it comes to antibiotic therapy.