Rifamycin S and its geometric isomer produced by a newly found actinomycete, Micromonospora rifamycinica.

Strain AM105 was separated from mangrove sediment in the South China Sea in this research. The morphological and genomic data showed that the strain merits description as a novel species, proposed as Micromonospora rifamycinica. From the acetate ethyl extract of its fermentation broth, two antibiotics against Gram-positive bacteria (including MRSA), rifamycin S and its geometric isomer were isolated. Their structures were elucidated on the basis of spectroscopic analyzes. (1)H and (13)C NMR data of the isomer of rifamycin S were first described in this paper.