Biofilm formation on spacecraft and medical materials

Who it is for

• Life-support (ECLSS) hardware suppliers qualifying water-system materials, tubing and filters
• Medical device makers testing catheter-grade silicone and other indwelling-device surfaces
• Antimicrobial and anti-fouling coating companies, including lubricant-impregnated and laser-textured surfaces
• Antibiotic and anti-biofilm drug developers who want a growth condition that changes biofilm robustness
• Space agencies and habitat operators writing material-selection and cleaning rules
• Hospital infection-control and surface-science research groups

What earlier flights found

How LELP-1 runs it

Sample. Pseudomonas aeruginosa PA14 (BSL-2 model biofilm organism) plus a customer coupon panel: up to 24 coupons of about 1 cm2, for example stainless steel 316, catheter-grade silicone, a candidate coating and a cellulose membrane reference. Container. 24-well sealed cassette in one large bay. Each well has a glass window on the bottom and holds one coupon above it; three fluid lines serve each well: growth medium, 4% paraformaldehyde, and RNA preservative, plus a shared PBS line for post-fixation washing and staining. Launch. Live inoculum held in stasis in PBS at 4 C (not frozen), diluted to about OD595 0.001; medium, fixative and preservative loaded cold in separate sealed reservoirs; coupons cleaned, sterilised by a method each material tolerates, and mounted in the cassette. Light and gas. No light needed; wells kept dark except during microscope imaging. No CO2 and no gas supply: the cassette is sealed and the medium carries nitrate as a terminal electron acceptor, so growth becomes anaerobic, as in both heritage flights. An aerobic variant with gas-permeable well lids is flown as a separate bay; on the shuttle, more oxygen removed the flight-ground difference.

1. day 0

   After orbit insertion and attitude settling, the bay ramps from 4 C to 37 C over about 2 h. Pumps fill all 24 wells with medium over the coupons, then inject the stasis inoculum. Static growth starts; first brightfield images and a transmission turbidity reading are taken.

2. day 1

   Daily automated run: brightfield image stack of each well through the glass window, turbidity reading, and a log of bay temperature, pressure, seal state, dosimeter dose and accelerometer data.

3. day 2

   Repeat the daily imaging and sensor run. No pumping or arm motion is scheduled, to keep the quasi-steady level near 1e-6 g.

4. day 3

   Repeat the daily run. Optional single transfer of the bay by the robotic arm to the central 40x microscope for a closer look at two wells; the arm motion is logged because it raises acceleration to about 1e-4 to 1e-3 g.

5. day 4

   Repeat the daily run.

6. day 5

   Termination. Twelve wells receive 4% paraformaldehyde and twelve receive RNA preservative, added directly as in the ISS heritage, with no rinse first. After about 1 h the fixed wells are washed with PBS, stained with a nucleic-acid dye and a lipid dye, and imaged on both bay fluorescence channels. The bay then cools to 4 C and holds there.

7. day 6

   Hold at 4 C. Housekeeping data only; seal and pressure checks confirm containment before deorbit.

8. day 7

   Deorbit, entry, splashdown and recovery. The sealed cassette stays at 4 C until handover to the customer courier on the recovery ship.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• The XY stage travels 96.5 x 57.9 mm, so every one of the 24 wells reaches the objective; with the stage the imaging stack is 232 x 151 mm, which sets the module's depth budget.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass.
• Fluid pack: 4 reagent bags in 1 layer (199 x 83 x 23 mm), every port on a front edge.
• The catalog gives 0.60 kg for structure and containment; as an aluminium box that is a 0.30 mm skin on 0.18 kg of posts and shelves. Thin: the bay rails have to carry the launch loads, or the module needs more structure mass.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

An identical flight-spare module runs at the Swiss ground segment with the same cassette, coupons, medium lot and inoculum, started about 2 h after the flight module and terminated on the same offset. The recorded flight temperature profile is played back on the ground unit. A third, non-inoculated cassette is put through the launch vibration and entry load profile to show coupons and seals survive. The bay has no on-orbit centrifuge, so the ground 1 g run is the only gravity reference; the two heritage flights disagreeing shows why that matters.

Coming home

Fixed and preserved wells come back in the sealed cassette at 4 C, the lowest the bay can hold. Fixation is on day 5 and splashdown on day 7; the cassette reaches the courier about 20 min after splashdown and the lab 1-2 days later, so about 4-5 days pass from preservation to the lab. Fixed samples tolerate this; on ISS the fixed samples were held at 4 C for weeks before return. The ISS RNA samples were kept at -80 C on orbit and returned at -20 C; LELP-1 bays cannot freeze, so RNA stays in preservative at 4 C and quality may be lower unless a passive -80 C return cassette is flown.

Limits of this flight

• Two to fourteen days is short for this field. Spacecraft water-system biofilms build up over months, so the flight shows early attachment and growth, not mature fouling or long-term material damage.
• No crew. Everything runs on a timer, so there is no re-dosing if a well looks wrong and no fixing a stuck valve.
• One fixation point per well set. A time course needs several bays or relies on the daily in-flight images, which are lower resolution than post-flight confocal.
• The bay cannot freeze. RNA stays in preservative at 4 C rather than frozen as on ISS, so transcriptomics may be weaker unless a passive cold cassette is flown.
• No in-flight 1 g control. Without a centrifuge, the only reference is the ground run, and the heritage flights show flight-versus-ground results on this organism can go either way.
• Static culture only. The bay has no flow loop, so it does not reproduce flowing water or condensate lines where spacecraft biofilms form.
• In-flight imaging cannot see films on opaque coupons; those are measured only after return.
• Entry and splashdown loads act on fixed films. Shear or sloshing can detach or smear them; the non-inoculated cassette on the ground load test is the only check.
• 24 wells per bay gives a few replicates per material: enough for clear effects, not for small ones or dose-response work.
• Results may be material-specific. On ISS, biofilm form depended on the material, not on gravity.
• The column-and-canopy structure is not a safe expectation. It was reported on the shuttle flights and not seen on ISS with the same strain and an anaerobic setup but a different medium, so we do not promise it.