Paper mills processing recycled paper suffer from biofouling causing roblems both in the mill and final product. The total bacterial ommunity composition and identification of specific taxa in the process ater and biofilms at the stock preparation and paper machine areas in a ill with recycled paper pulp was described by using a DNA-based pproach. Process water in a similar mill was also analyzed to nvestigate if general trends can be found between mills and over time. acterial community profiles, analyzed by terminal-restriction fragment ength polymorphism (T-RFLP), in process water showed that the dominant eaks in the profiles were similar between the two mills, although the verall composition was unique for each mill. When comparing process ater and biofilm at different locations within one of the mills, we bserved a separation according to location and sample type, with the iofilm from the paper machine being most different. 16S rRNA gene clone ibraries were generated and 404 clones were screened by RFLP analysis. rouping of RFLP patterns confirmed that the biofilm from the paper achine was most different. A total of 99 clones representing all RFLP atterns were analyzed, resulting in sequences recovered from nine acterial phyla, including two candidate phyla. Bacteroidetes epresented 45% and Actinobacteria 23% of all the clones. Sequences with imilarity to organisms implicated in biofouling, like Chryseobacterium pp. and Brevundimonas spp., were recovered from all samples even though he mill had no process problems during sampling, suggesting that they re part of the natural paper mill community. Moreover, many sequences howed little homology to as yet uncultivated bacteria implying that aper mills are interesting for isolation of new organisms, as well as or bioprospecting.