Final answer:
The causative organism for syphilis is Treponema pallidum, a gram-negative spirochete bacterium. It triggers an immune response in the host, causing tissue damage and evading the immune system.
Step-by-step explanation:
The causative organism for syphilis is Treponema pallidum. Syphilis is a sexually transmitted infection caused by this gram-negative spirochete bacterium. It has a relatively simple genome and lacks lipopolysaccharide endotoxin characteristic of gram-negative bacteria. T. pallidum contains lipoproteins that trigger an immune response in the host, causing tissue damage and enabling the pathogen to evade the host immune system.