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@ARTICLE{Bajerski:148222,
      author       = {F. Bajerski and A. Bürger and B. Glasmacher and E. R. J.
                      Keller and K. Müller and K. Mühldorfer and M. Nagel and H.
                      Rüdel and T. Müller and J. Schenkel$^*$ and J. Overmann},
      title        = {{F}actors determining microbial colonization of liquid
                      nitrogen storage tanks used for archiving biological
                      samples.},
      journal      = {Applied microbiology and biotechnology},
      volume       = {104},
      number       = {1},
      issn         = {1432-0614},
      address      = {New York},
      publisher    = {Springer},
      reportid     = {DKFZ-2019-02790},
      pages        = {131-144},
      year         = {2020},
      abstract     = {The availability of bioresources is a precondition for life
                      science research, medical applications, and diagnostics, but
                      requires a dedicated quality management to guarantee
                      reliable and safe storage. Anecdotal reports of bacterial
                      isolates and sample contamination indicate that organisms
                      may persist in liquid nitrogen (LN) storage tanks. To
                      evaluate the safety status of cryocollections, we
                      systematically screened organisms in the LN phase and in ice
                      layers covering inner surfaces of storage tanks maintained
                      in different biobanking facilities. We applied a
                      culture-independent approach combining cell detection by
                      epifluorescence microscopy with the amplification of
                      group-specific marker genes and high-throughput sequencing
                      of bacterial ribosomal genes. In the LN phase, neither cells
                      nor bacterial 16S rRNA gene copy numbers were detectable
                      (detection limit, 102 cells per ml, 103 gene copies per ml).
                      In several cases, small numbers of bacteria of up to 104
                      cells per ml and up to 106 gene copies per ml, as well as
                      Mycoplasma, or fungi were detected in the ice phase formed
                      underneath the lids or accumulated at the bottom. The
                      bacteria most likely originated from the stored materials
                      themselves (Elizabethingia, Janthibacterium), the technical
                      environment (Pseudomonas, Acinetobacter, Methylobacterium),
                      or the human microbiome (Bacteroides, Streptococcus,
                      Staphylococcus). In single cases, bacteria, Mycoplasma,
                      fungi, and human cells were detected in the debris at the
                      bottom of the storage tanks. In conclusion, the limited
                      microbial load of the ice phase and in the debris of storage
                      tanks can be effectively avoided by minimizing ice formation
                      and by employing hermetically sealed sample containers.},
      cin          = {W430},
      ddc          = {570},
      cid          = {I:(DE-He78)W430-20160331},
      pnm          = {319H - Addenda (POF3-319H)},
      pid          = {G:(DE-HGF)POF3-319H},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31781817},
      doi          = {10.1007/s00253-019-10242-1},
      url          = {https://inrepo02.dkfz.de/record/148222},
}