A methodology of microarray using the fluorescent DNA intercalating agent propidium monoazide (PMA) to selectively block DNA of dead cells from amplification and its application in detecting and enumerating viable microbes in complex microbial communities is described. A phylogenetic array is used in the preferred embodiment to enhance the sensitivity of the method. The PMA-Microarray assay is particularly applicable for monitoring samples from environments with extremely low microbial burden such as spacecraft surfaces.
STATEMENT OF GOVERNMENTAL SUPPORT
 The invention claimed herein was made in the performance of work under DOE and NASA contracts, and is subject to the provisions of Public Law 96-517 (35 USC 202) in which the Contractor has elected to retain title. This invention was made in part under Contract DE-AC02-05CH11231 awarded by the Department of Energy and under Contract Nos. NNH09ZDA001N and NAS7-1407 awarded by NASA. The government has certain rights in this invention.