Hydra is a freshwater cnidarian with many intriguing characteristics that make it a very useful model to study diverse scientific concepts. The control that the simple immune mechanisms of this organism have over its complex microbiota composition has motivated this study to uncover the basics of how its microbial communities are regulated via its immune system. In this study, we aimed to investigate the effect of the outer membrane components of gram-negative bacteria, lipopolysaccharides on the hydra-microbiota regulation. This was achieved by treating the Hydra oligactis polyps of the M83/4 strain in 3 concentration groups of LPS (control with 0µl/ml, 12.5μl/ml and 25μl/ml) and spreading the homogenized treated polyps onto agar plates in order to measure the bacterial colonies formed on the agar plates. Additionally, an inhibition zone assay using the 3 concentration groups was carried out via overlay agar. The diameter of the inhibition zone for each treatment group was measured in order to determine the hydra’s ability to kill another bacterial species, Pseudomonas, after it was treated in different concentrations of LPS. The results revealed that in the LPS treatment of 12.5μl/ml, there is a significant decrease in the number of bacterial colonies formed and in the LPS treatment of 25μl/ml, the bacterial colony growth increases again, indicating that LPS has dose-dependent effects on the growth of bacterial colonies and that the immune activity is the highest at 12.5μl/ml of LPS. This goes to show that a low dosage of LPS shows stronger antimicrobial activity and a high dosage of LPS limits antimicrobial activity.