Caffeine is a prevalent chemical in the environment, often being found in aquatic ecosystems. Past studies have shown that some bacterial species can metabolize caffeine, but little research has been done to study the effect of different caffeine concentrations on the growth of the bacteria. The goal of the current study is to gain a better understanding of how aquatic bacteria, which have been selected for growth on caffeine, utilize caffeine as a source of carbon. To study the effect of caffeine concentrations on bacterial growth, we isolated a bacterium from an aquarium that had been exposed to caffeine. The organism was able to grow on both solid and liquid media containing only caffeine and potassium phosphate buffer. Colonies formed on caffeine concentrations as low as 300 mg/L and up to 20,000 mg/L. However, caffeine concentrations at 20,000 mg/L began to inhibit the growth of the organism. The DNA sequence analysis of the 16S rRNA gene indicated the organism belongs to the Pseudomonas putida bacterial group. Our results indicate that aquatic microbiota can effectively utilize a wide range of environmental concentrations of caffeine as a nitrogen and carbon source.