Abstract: A bacteria strain FERMBP-7046 belonging to the genus Acinetobacter, a strain FERMBP-7049 belonging to the genus Acinetobacter, a strain FERMBP-7047 belonging to the genus Pseudomonas, and a strain FERMBP-7048 belonging to the genus Alcaligenes are caused to act on an object of treatment, either individually or in a bacteria mixture including at least one of the foregoing strains. Thus it is possible to provide heavy oil degrading bacteria and a heavy oil degrading bacteria mixture which are inexpensively prepared, which simplify degradation and removal operations, and which can be stored and shipped simply, and to provide a nurturing composition for such bacteria, a method of degrading heavy oil using such bacteria, and building and civil engineering materials containing a substance obtained by heavy oil degradation treatment.