In indoor air, bacteria are derived from building occupants and
the environment. The characterization of airborne bacteria is
important for understanding disease transmission from person-toperson.
Unfortunately, building monitoring is generally limited to
total colony forming units (CFUs). It is extremely time-consuming
for all of the diverse colony types in indoor air to be characterized
by conventional means and is rarely undertaken. Common
genera found in the human skin microbiome include Staphylococcus
and Micrococcus [1,2]; these organisms are believed to be
released into indoor air [3]. Staphylococcus and Micrococcus are
difficult to distinguish morphologically (both being observed as
tetrads). Clinical samples have been reported to rarely contain
micrococci (w4% of isolates are micrococci and 96% staphylococci)
[4]. However, wtwo thirds of the environmental isolates in studies
by us and others were micrococci [5,6]. Thus, for environmental
samples there is a greater need for the characterization of micrococci.
Of the five known Micrococcus species, Micrococcus luteus is
the only one whose primary habitat is human skin [7e9]; Micrococcus
lylae is only occasionally isolated from this organ [7].