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

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.

Shape-based separation of drug-treated Escherichia coli using viscoelastic microfluidics

“…S2) was designed before each outlet to reduce the effects of reservoir fluid height and capillary pressure on the flow distribution. 39 The ratio of the serpentine channel length relative to the main focusing channel length is about 0.51. Since the seven channel outlets are symmetric about the channel centreline (see Fig.…”

“…In recent years, viscoelastic microfluidics has been widely adopted for shape-based separation of different types of microbial cells, such as Candida Albicans (≥26 μm), 37 Saccharomyces Cerevisiae (singlets: ∼3 to 5 μm, doubles and clusters), 38 Cyanobacterial Anabaena (∼5 μm in diameter and a few microns to hundreds of microns in length) 34 and Bacillus subtilis (i.e., 1-5 um and >20 μm in length). 39 However, it has not been shown whether viscoelastic microfluidics can be used to separate a single species of bacteria with relatively small size (∼0.5 to 4 μm) based on cell shape.…”

“…, 1–5 um and >20 μm in length). 39 However, it has not been shown whether viscoelastic microfluidics can be used to separate a single species of bacteria with relatively small size (∼0.5 to 4 μm) based on cell shape.…”

Investigation of Relaxation Time on Viscoelastic Two‐Dimensional Flow Characteristics Using FreeFem++

“…e set of governing ( 17) and ( 18) along with the associated boundary and initial conditions in (19), (20), and (21) are implemented through FreeFem++ [26]. e numerical results presented and tests are carried out with Reynolds number Re ranging between 200 ≤ Re ≤ 5000. e relaxation time R f is assumed to be in the range of 0…”

“…In connection to the clinical experimentation and microfluidics to study the behaviour of neutrophil genomics and proteomics, the reader is referred to the work of Kotz et al [19]. Liu et al [20] used viscoelastic fluids to study the separation of Bacillus population in microfluidics.…”