Anhydrous dextrose

All colloidal silica solutions were prepared using 30% by mass Ludox SM-30 sodium hydroxide-stabilized colloidal silica stock solutions (Grace Chemicals), which contained silica colloids ranging between 7 and 22 nm in diameter and had an initial pH near 10. Solutions included in all experiments contained 6% colloidal silica by mass, prepared by diluting the 30% stock solution with deionized water. Following preparation of a 6% colloidal silica solution, soluble chemical masses were added directly to solutions and solutions were pH-adjusted using either 1 M sodium hydroxide or hydrochloric acid and then filter-sterilized using 0.2-micron filters. Soluble chemicals added to solutions included various concentrations of glucose (anhydrous dextrose, Fisher Scientific), yeast extract (Fisher Bioreagents), and sodium chloride (Fisher Scientific). All solutions apart from those considered in experimental series 1 (described in Section "Experimental series") were pH-adjusted to an initial value of 9.5 intended to prevent abiotic gelation and maintain solution stability in the absence of fermentation activity. All solutions were prepared in equilibrium with atmospheric conditions at 20 °C and were not de-aired prior to use (dissolved oxygen ≈ 9 mg/L).

M63 media (VWR Life Science) solution was made by first diluting 1 liter of presterilized M63 5× (BioWORLD, GeneLinx International Inc.) stock solution using autoclaved Millipore water. Filter-sterilized magnesium sulfate anhydrous (MgSO₄, Fisher Scientific) water solution, of volume 1 mL and molarity of 1 M, was added to the diluted media solution following standard protocol. Sodium arsenate stock solution (RICCA Chemical Company, 100 mM) was first filter-sterilized and then diluted with sterilized DI water to reach concentrations of 0.1 mM and 0.1 µM and stored under 4 °C. Potassium dichromate (Fisher Scientific) solution was made by first dissolving sodium dichromate crystal into sterilized DI water to reach concentrations of 17 mM, and then, the solution was filter-sterilized and diluted with sterilized DI water again to reach concentrations of 0.34 mM and 0.34 µM and stored at 4 °C. Prior to exposure to bacterial cultures, working solutions were placed at room temperature for 30 min to equilibrate to ambient temperature and then titrated to the culture to target exposure concentration. Anhydrous dextrose (glucose, Fisher Scientific), 1 g, was dissolved in 10 mL DI water and filter-sterilized to form 10% (w/v) glucose stock solution, which was added into the media solution later to provide energy source for bacteria.

Erythrocytic stage, strain K1, P. falciparum parasites (gifted by Prof John Hyde, University of Manchester, UK, original source: Thai-K1 clone) were cultured in RPMI 1640 1x (+) L-Glutamine (+) 25 mM Hepes (Gibco, Life Technologies, UK) supplemented with 5% (w/v) lipid rich bovine serum albumin (Albumax II, Gibco, Life Technologies, New Zealand), 5 ng/ml hypoxanthine (Sigma, UK), 0.2% (w/v) glucose (Dextrose Anhydrous, Fisher Scientific, UK) and 50ng/ml gentamycin (Sigma, UK) at 37°C, under a 5% CO₂ 5% O₂ and 90% N₂ gas mixture (BOC Limited, UK) in accordance with Read and Hyde, 1993 [22 (link)]. The parasites were routinely maintained in O+ human blood (NHS Blood Bank, Manchester, UK). All additives were sterile filtered at 0.22μm porosity and the complete medium was stored for no more than 2 weeks at 2–8°C. Continuous cultures were maintained at 5% haematocrit. Sorbitol was used to maintain synchronicity of the culture. Briefly, pelleted parasites (3,400 rpm for 5mins) were re-suspended 1:10 in sterile filtered 5% sorbitol ((w/v) in distilled water) and incubated at room temperature for 5 mins. Prior to continuation of the culture at 5% haematocrit, synchronised parasites were washed 3 x with complete media (3,400 rpm for 5mins). For experimental set up in a 96-well-plate format final well volumes were 200 μl at 2.5% haematocrit unless stated otherwise.