The aim of this study was to isolate and identify marine bacterium with anti-methicillinresistant Staphylococcus aureus (MRSA) activity, and to purify the anti-MRSA compound, as well as to determine its activity and synergistic effects. Among the marine bacteria isolated in this study, the YJ-1 isolate had the strongest anti-MRSA activity. The YJ-1 isolate was identified on the basis of its biochemical characteristics and an analysis of 16S rRNA gene sequences. The YJ-1 isolate showed over 99.2% homology with Pseudomonas stutzeri, and was designated as a Pseudomonas sp. YJ-1. The optimal culture conditions were 25℃ and initial pH 7.0. For the purification of the anti-MRSA compounds, the YJ-1 was cultured in Pa PES-II medium, and the culture filtrates were extracted by ethyl acetate, hexane, and 80% MeOH. The 80% MeOH fraction was separated by a C18 ODS column, silica gel chromatography and a reverse phase HPLC, to yield three anti-MRSA agents, the MR1, MR2, and MR3 compounds. When the MR1 compound of 250 μg mL-1 concentration was applied to the MRSA cells, over 95% of bacterial cells was killed within 48 hr. Compared with vancomycin and ampicillin, the MR1 compound showed significant anti-MRSA activity. In addition, the anti-MRSA activity was increased by dose and time dependent manners. Furthermore, the combination of an MR1 compound with vancomycin produced a more rapid decrease in the MRSA cells than did the MR1 compound alone. Taken together, our results suggest that the Pseudomonas sp. YJ-1 and its anti-MRSA compounds could be employed as a natural antibacterial agent in MRSA infections.

Microorganisms producing bioemulsifier were isolated from the sea water in Pusan coastal area. The isolated strain which had the highest emulsification activity and stability was identified as the genus Acinetobacter from the results of morphological, cultural and biochemical tests and named Acinetobacter sp. EL-C6 for convenience. The compositions of optimum medium for emulsification of crude oil by Actnetobacter sp. EL-C6 were crude oil 2.0%, NH_4NO_3 0.2%, K_2HPO_4 0.01%, MgSO_4·7H_2O 1.0%, CaCl_2·2H_2O 0.1% and NaCl 3.0% at initial pH 7.5 and 30℃, respectively. The cultivation for emulsification of crude oil was carried out in 500㎖ shaking flask containing 100㎖ of the optimum medium at 30℃. The highest emulsification was observed after 5 days. The utilization on the various hydrocarbon of the Acinetobacter sp. EL-C6 showed that utilization of n-alkane compounds were better than that of aromatic compounds. Among the petroleum compounds, crude oil was best utilized by the Actnetobacter sp. EL-C6.