Bacillus species predominated in an incineration ash layer at a landfill

This study was designed to analyze the diversity of aerobically growing bacteria in a landfill area, compared to those from a forest and a cultivated area at four different depths. The viable cell number of aerobes in the incineration ash layer (3.5(+/-0.4)x10(2)/g) was 10(3)- to 10(4)-fold lower than those in the other areas. On 16S ribosomal DNA similarity analysis of a total of 727 colonies, only the class Bacilli was detected in the incineration ash layer whose pH was extremely high (12.8), while five to seven classes were detected in the forest and the cultivated area. Of the genus Bacillus, B. licheniformis and the recently discovered Bacillus were predominant in the incineration ash layer. These analyses indicate that the incineration ash layer of a landfill might be a source that includes valuable or hitherto unreported Bacillus species.