Length-based separation of Bacillus subtilis bacterial populations by viscoelastic microfluidics

Ping Liu; Hangrui Liu; Lucie Semenec; Dan Yuan; Sheng Yan; Amy K Cain; Ming Li

doi:10.1038/s41378-021-00333-3

Length-based separation of Bacillus subtilis bacterial populations by viscoelastic microfluidics

Microsyst Nanoeng. 2022 Jan 19:8:7. doi: 10.1038/s41378-021-00333-3. eCollection 2022.

Authors

Ping Liu^#^{1

2}, Hangrui Liu^#³, Lucie Semenec⁴, Dan Yuan⁵, Sheng Yan⁶, Amy K Cain⁴, Ming Li^{2

7}

Affiliations

¹ Suqian University, Suqian, 223800 China.
² School of Engineering, Macquarie University, Sydney, NSW 2109 Australia.
³ Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 Australia.
⁴ ARC Centre of Excellence in Synthetic Biology, Department of Molecular Science, Macquarie University, Sydney, NSW 2109 Australia.
⁵ Centre for Regional and Rural Futures, Deakin University, Geelong, VIC 3216 Australia.
⁶ Institute for Advanced Study, Shenzhen University, Shenzhen, 518060 China.
⁷ Biomolecular Discovery Research Centre, Macquarie University, Sydney, NSW 2109 Australia.

^# Contributed equally.

Abstract

In this study, we demonstrated the label-free continuous separation and enrichment of Bacillus subtilis populations based on length using viscoelastic microfluidics. B. subtilis, a gram-positive, rod-shaped bacterium, has been widely used as a model organism and an industrial workhorse. B. subtilis can be arranged in different morphological forms, such as single rods, chains, and clumps, which reflect differences in cell types, phases of growth, genetic variation, and changing environmental factors. The ability to prepare B. subtilis populations with a uniform length is important for basic biological studies and efficient industrial applications. Here, we systematically investigated how flow rate ratio, poly(ethylene oxide) (PEO) concentration, and channel length affected the length-based separation of B. subtilis cells. The lateral positions of B. subtilis cells with varying morphologies in a straight rectangular microchannel were found to be dependent on cell length under the co-flow of viscoelastic and Newtonian fluids. Finally, we evaluated the ability of the viscoelastic microfluidic device to separate the two groups of B. subtilis cells by length (i.e., 1-5 μm and >5 μm) in terms of extraction purity (EP), extraction yield (EY), and enrichment factor (EF) and confirmed that the device could separate heterogeneous populations of bacteria using elasto-inertial effects.

Keywords: Chemistry; Engineering.