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Two new piperazine-triones lansai E and F (<b>1</b>, <b>2</b>), together with four known secondary metabolites lansai D (<b>3</b>), 1-<i>N</i>-methyl-(<i>E,Z</i>)-albonoursin (<b>4</b>), imidazo[4,5-<i>e</i>]-1,2,4-triazine (<b>5</b>), and streptonigrin (<b>6</b>) were isolated from a deep-sea-derived <i>Streptomycetes</i> sp. strain SMS636. The structures of the isolated compounds were confirmed by comprehensive spectroscopic analysis, including HRESIMS, 1D and 2D NMR. Compound <b>4</b> exhibited moderate antibacterial activities against <i>Staphylococcus aureus</i> and methicillin resistant <i>S. aureus</i> (MRSA) with Minimum Inhibitory Concentration (MIC) values of 12.5 and 25 &#956;g/mL, respectively. Compound <b>6</b> displayed significant antibacterial activities against <i>S. aureus</i>, MRSA and Bacillus Calmette-Gu&#233;rin (BCG) with MIC values of 0.78, 0.78 and 1.25 &#956;g/mL, respectively.