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Biotechnology of single cells in controlled microenvironments
Andreas Schmid*, Frederik Fritzsch, Katrin Rosenthal, Christian Dusny
Department of Solar Materials, Helmholtz Center for Environmental Research–UFZ,
Permoser Str 15, 04318 Leipzig, Germany
*
E-mail: [email protected]
Single cell analysis (SCA) enables an unbiased disclosure of cellular functionality in biotechnology [1].
In contrast to conventional bulk analysis strategies, SCA grants access to mechanistic data of individual
cells – the minimal functional unit of cell based bioprocesses [2]. These data are usually masked behind
an average value of a clonal, but heterogeneous population. It was shown that the extent of heterogeneity
is strongly linked to frequency and amplitude of physicochemical changes in the extracellular
environment. Hence not only the identification of individual physiological phenotypes, but also the
ability to analyze single cells in a controlled and steady environment is a fundamental requirement for
the accurate description of cellular features. We tackle the challenge of creating controlled
physicochemical microenvironments for a precise analysis of individual cellular physiology with the
Envirostat single cell analysis system [3, 4]. In contrast to most other microfluidic systems for SCA,
which mostly rely on the mechanical trapping of cells, the Envirostat uses contactless retention via
negative dielectrophoresis, which excludes cell-surface interaction and resultant changes in the cellular
phenotype. Furthermore, the immediate removal of potentially inhibiting metabolites and unlimited
availability of nutrients and dissolved oxygen is guaranteed by a continuous medium flow. CFD
simulations indicate that the microenvironment of the target cell has indeed a virtually static composition
[3]. We experimentally validated the Envirostat principle with single cell growth studies [5]. We
observed significant differences between specific growth rates of single cells and populations in bulk
cultivations. Two yeast species and one bacterial strain consistently exhibited increased specific growth
rates of up to 120% when cultivated with the Envirostat system [5]. Our results imply that the
extracellular environment can dictate the specific growth rate of unicellular microbial eukaryotes and
prokaryotes and a constant extracellular environment diminishes the influence of physiological cell-tocell differences [6]. Moreover, our experiments demonstrate the Envirostat as a platform for systems
biology that may be used for disclosing the impact of controlled perturbations on cellular physiology
unbiased by population activity or analytical/technical constraints [7].
References
[1] F.S.O. Fritzsch, C. Dusny, O. Frick, A. Schmid, Single cell analysis in biotechnology, systems
biology, and biocatalysis. Ann. Rev. Chem. Biomol. Eng. 3 (2012) 129-155.
[2] C. Dusny, A. Schmid, Challenging biological limits with microfluidic single cell analysis. Microb.
Biotechnol. 8(1) (2015) 23-25.
[3] H. Kortmann, P. Chasanis, L.M. Blank, J. Franzke, E.Y. Kenig, A. Schmid, The envirostat - a new
bioreactor concept. Lab. Chip. 9 (2009) 576–585.
[4] F. S. O. Fritzsch, K. Rosenthal, A. Kampert, S. Howitz, C. Dusny, L.M. Blank, A. Schmid, Picoliter
nDEP traps enable time-resolved contactless single bacterial cell analysis in controlled
microenvironments. Lab. Chip. 13(3) (2013) 397-408.
[5] C. Dusny, F.S.O. Fritzsch, O. Frick, A. Schmid, Isolated microbial single cells and resulting
micropopulations grow faster in controlled environments. Appl. Environ. Microbiol. 78(19) (2012)
7132-7136.
[6] C. Dusny, A. Schmid, Microfluidic single cell analysis links boundary environments and individual
microbial phenotypes. Environ. Microbiol., (2015) DOI: 10.1111/1462-2920.12667.
[7] C. Dusny, A. Grünberger, C. Probst, W. Wiechert, D. Kohlheyer, A. Schmid, Technical bias of
microcultivation environments on single cell physiology. Lab. Chip. 15 (2015) 1822-1834.