Fig. 1.

Overview on potential sources of microorganisms in liquid nitrogen tanks storing organs, tissues, and cells of human, animals, plants, and microorganisms. The shading of the arrow (cell counts) shows the increase in the number of microbial cells with increasing storage time and number of openings which indicates the likelihood of consequences for human health and welfare if the material is contaminated (light: low, dark: high). ¹Bajerski et al. 2020, ²Fountain et al. 1997, ³Ramin et al. 2014, ⁴Morris 2005, ⁵Molina et al. 2016, ⁶Knierim et al. 2017, ⁷Pessoa et al. 2014, ⁸Tedder et al. 1995, ⁹Bielanski et al. 2003, ¹⁰Vitrenko et al. 2017, ¹¹Drexler and Uphoff 2002, ¹²Schafer et al. 1976. *Microoragnisms detected in LN tanks most probably originating from the stored material itself displayed in boxes with solid lines