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206 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGYcell toxicity, were also toxic to normal cells. And in our study, it seems that the bacterial strains do not have a positive correlation between antagonistic activity and cytotoxic activity, because there are strains with strong antagonistic activity, but weak cancer cell cytotoxicity and vice versa. For example, the two strains N2 GII14 and N6 GII4 have strong antagonistic activity against the two tested pathogenic strains. Still, they are almost non-toxic or very lowly toxic to the two tested cancer cell lines. The strain N1 AIA6 has only moderate antagonistic activity against the E. coli ATCC 11105 strain but is very toxic to the two breast cancer cell lines MCF-7 and liver cancer cell lines Hep G2, but is not toxic to the normal HEK 293T cell line.This is the first study on isolation, screening, and testing of antibacterial, antifungal, and anticancer activities of bacteria isolated from the coastal lagoon environment of Central Vietnam. The research results have shown that coastal lagoons in Vietnam have great potential to exploit valuable sources of biologically active microorganisms. In the world, some scientists have also begun to pay attention to this ecosystem. In particular, the study of Al-Amoudi (2016) showed that from sediment samples collected at the Al-Kharrar Lagoon along the Red Sea, ten bacterial strains were screened with the ability to resist four types of pathogenic bacteria including Staphylococcus aureus, Salmonella typhimurium, Escherichia coli and Pseudomonas syringae [14]. Next, the study of Davies-Bolorunduro et al. (2019), isolated 32 strains of actinomycetes from Lagos Lagoon sediment samples, and the secondary metabolites extracted from these strains were tested on cancer cells such as K562 (Human acute myelocytic leukemia), Hela (cervical carcinoma), AGS (Human gastric), MCF-7 (breast adenocarcinoma), and HL-60 (Human acute promyelocytic leukemia). These extracts exhibited cytotoxicity with IC50 values ranging from 0.030 mg/mL to 4.4 mg/mL. In particular, the