Two novel Microbacterium species are described on the basis of phenotypic, chemotaxonomic and genotypic studies. The two strains, designated YM10-847(T) and YM11-607(T), were isolated from river sediment and unidentified hydroid, respectively, of a marine lake. The strains were Gram-positive, catalase-positive bacteria with l-ornithine as the diagnostic diamino acid of the peptidoglycan. The acyl type of the peptidoglycan was N-glycolyl. The major menaquinones were MK-10 and MK-11 for YM10-847(T), and MK-11 and MK-12 for YM11-607(T). Mycolic acids were not detected. The DNA G+C content of strains YM10-847(T) and YM11-607(T) was 67.8 and 71.6 mol%, respectively. Comparative 16S rRNA gene sequence analysis revealed that the two strains belong to the genus Microbacterium. DNA-DNA relatedness data showed that YM10-847(T) and YM11-607(T) are two novel species of this genus. On the basis of these results, strains YM10-847(T) and YM11-607(T) represent two novel species of the genus Microbacterium, for which the names Microbacterium sediminicola sp. nov. and Microbacterium marinilacus sp. nov. are proposed. The type strains are YM10-847(T) (=MBIC08264(T)=DSM 18905(T)) and YM11-607(T) (=MBIC07778(T)=DSM 18904(T)), respectively.