Antibacterial and antifungal activities of two Pseudomonas aeruginosa associated with Eucheuma cottonii

Eucheuma cottonii is a seaweed species that has been cultivated largely in many aquaculture farms across Indonesia mainly for pharmaceutical and food industry purposes. Like any other marine organisms, E. cottonii build a close relationship with various endophytic bacteria and these associated bacteria have been assigned to play a prominent role to produce secondary metabolite to protect their hosts from environmental threats such as infection and predation. The obtained crude extract was tested against four bacterial tests namely Staphylococcus aureus, Streptococcus mutans, Escherichia coli and Klebsiella pneumoniae using disc diffusion assays. Subsequently, these extracts were also tested against two fungal test Candida albicans and Aspergillus flavus. Molecular identification indicated that both isolates were phylogenetically related to Pseudomonas aeruginosa. Antibacterial screening showed that both P. aeruginosa ISP1RL5 and P. aeruginosa ISP1RL6 inhibited the four bacterial tests at diameter of 9-12 mm. Similarly, antifungal tests showed diameter inhibition of 9-12 mm. Overall, these findings served as preliminary important data of seaweeds endophytic bacteria for potential antibacterial and antifungal production.