Isolation and Identification of Psychrotrophic Photosynthetic Bacterium from Antarctic Seawater with Antibacterial Activity

The search for new antibiotics is on the rise because of the growing threat of antibiotic resistance. Once the antibiotics fail to work, people are at risk of dying of common infections, and routine operations become difficult to perform, making millions of lives at risk. In our study, the authors found that a photosynthetic bacterium can provide a good potential source of another group of antimicrobial compounds known as photoantimicrobial compounds. This psychrotrophic bacterium was isolated from the Antarctic and grew well at a temperature ranging from 10 °C to 30 °C in the acetate medium, implying minimum energy usage by the bacteria contributing to energy saving for its bioprocessing. The bacteria identified as Stenotrophomonas sp. via 16S rDNA analysis and coded as SZB2 strain was rod shaped. Gram negative and possessed bacteriochlorophyll a and b are usually found in photosynthetic bacteria. SZB2 was found to produce antibacterial substances from the cocultivation assay with both Gram negative and Gram positive bacteria such as Escherichia coli and Staphylococcus aureus. The growth inhibition was higher in S. aureus than that of E. coli. Hence, it may be concluded the bacteria had the ability to produce a wide spectrum antibiotic.