Abstract
Micropatterning of bacteria using aqueous two phase system (ATPS) enables the localized culture and formation of physically separated bacterial communities on human epithelial cell sheets. This method was used to compare the effects of Escherichia coli strain MG1655 and an isogenic invasive counterpart that expresses the invasin (inv) gene from Yersinia pseudotuberculosis on the underlying epithelial cell layer. Large portions of the cell layer beneath the invasive strain were killed or detached while the non-invasive E. coli had no apparent effect on the epithelial cell layer over a 24 h observation period. In addition, simultaneous testing of the localized effects of three different bacterial species; E. coli MG1655, Shigella boydii KACC 10792 and Pseudomonas sp DSM 50906 on an epithelial cell layer is also demonstrated. The paper further shows the ability to use a bacterial predator, Bdellovibrio bacteriovorus HD 100, to selectively remove the E. coli, S. boydii and P. sp communities from this bacteria-patterned epithelial cell layer. Importantly, predation and removal of the P. Sp was critical for maintaining viability of the underlying epithelial cells. Although this paper focuses on a few specific cell types, the technique should be broadly applicable to understand a variety of bacteria-epithelial cell interactions.
Highlights
In the human body, the interactions occurring between the epithelial cells and bacteria are diverse and complicated, ranging from commensalism to invasion and parasitism [1]
To test the possibility of using aqueous two phase system (ATPS) technology to pattern bacteria on epithelial cell monolayers, we first compared three different ATPS formulations (Table 1) with regards to their effects on a confluent layer of human mammary epithelial cells (MCF 10a). Two of these formulations were used before for printing mammalian cells [14] while the third was a more viscous formulation used in a recent study for patterning bacterial cells and biofilms on polystyrene or PDMS surfaces [13]
The diameter of the resulting bacterial community can be as small as 2 mm with possibility of producing even smaller ones using optimized protocols
Summary
The interactions occurring between the epithelial cells and bacteria are diverse and complicated, ranging from commensalism to invasion and parasitism [1]. Attempts to study these interactions and their mechanisms in depth have been made with the goal being improved infection prevention and treatment options. The bacterial cells tend to overgrow in the nutrient rich and favorable temperatures of epithelial cell culture conditions This causes rapid nutrient depletion and dramatic changes in pH, rendering the medium unsuitable for growth of the epithelial cells [5]. Research groups have generated dynamic co-cultures using a flow-through continuous culturing system [8,9] or microfluidic devices, such as the one used by Jayaraman’s group to study the role of commensal bacteria in preventing
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