A marine bacterium Ruegeria atlantica (designated as strain TUF-D) was isolated from a glass plate submerged in the coastal water. Three new chlorine containing compounds (1-3) together with penicillic acid (4) were obtained from a marine-derived fungus Aspergillus ostianus strain TUF 01F313 isolated from a marine sponge at Pohnpei as antibacterial components against R. atlantica. The structures of three new antibiotics were determined based on their spectral data as 8-chloro-9-hydroxy-8, 9-deoxyasperlactone (1), 9-chloro-8-hydroxy-8, 9-deoxyasperlactone (2), and 9-chloro-8-hydroxy-8, 9-deoxyaspyrone (3). Compound 1 inhibited the growth of R. atlantica at 5μg/disc (inhibition zone: 12.7mm), while 2 and 3 were active at 25μg/disc (10.1 and 10.5mm, respectively).