Two strains, 8-4-E12(T) and 8-4-E13(T), were isolated from a biowaste composting reactor. Based on 16S rRNA gene sequences, both strains belong to the genus Bacillus. Strain 8-4-E12(T) was most closely related to the type strains of Bacillus shackletonii, B. acidicola, B. sporothermodurans and B. oleronius (96.4, 96.3, 96.0 and 95.6 % 16S rRNA gene similarity, respectively), whereas strain 8-4-E13(T) was most closely related to the type strain of Bacillus humi (96.5 % sequence similarity). Strains 8-4-E12(T) and 8-4-E13(T) shared 94 % 16S rRNA gene sequence similarity. The fatty acid profile of strain 8-4-E12(T) was dominated by saturated iso- and anteiso-branched fatty acids (iso-C15 : 0, anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0), and also contained considerable amounts of C16 : 0. The fatty acid profile of strain 8-4-E13(T) showed a predominance of iso-C15 : 0 (65 %), with smaller amounts of other saturated branched-chain fatty acids along with an unsaturated alcohol. Both strains contained diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine as major polar lipids. Additionally, strain 8-4-E12(T) contained an unknown lipid and strain 8-4-E13(T) two unknown (amino-)phospholipids. The diagnostic diamino acid found in the cell-wall peptidoglycan of 8-4-E12(T) and 8-4-E13(T) was meso-diaminopimelic acid. The predominant menaquinone was MK-7. The results of physiological and biochemical tests also allowed phenotypic differentiation of the two strains from each other and from related Bacillus species. On the basis of their phylogenetic, phenotypic and chemotaxonomic properties, strains 8-4-E12(T) and 8-4-E13(T) represent novel species of the genus Bacillus, for which the names Bacillus pervagus sp. nov. (type strain 8-4-E12(T) = DSM 23947(T) = LMG 27601(T)) and Bacillus andreesenii sp. nov. (type strain 8-4-E13(T) = DSM 23948(T) = LMG 27602(T)) are proposed.