Active matter
Do the tiny hairs on algal flagella help the cell swim?
Open access · cc by · source: Europe PMC
Removing the fine hairs from Chlamydomonas flagella does not change how fast the cells swim, how their flagella beat, or how much fluid they push.
Study at a glance
- Design
- Other — Lab comparison of a hairless mutant (mstg) with two hair-bearing strains using free-swimming tracking, flagellar waveform analysis, optical-tweezers flow measurements and boundary-element Stokes simulations of smooth flagella.
- N
- No single N: 51, 53 and 52 swimming tracks (cc125, cw15, mstg); 6 cells per strain for waveform analysis; 9 to 14 cells per strain for flow measurements.
- Population
- Three strains of the green alga Chlamydomonas reinhardtii: wild type cc125, cell-wall-deficient cw15, and mastigoneme-deficient mutant mstg
- Outcome
- Swimming speed, beat frequency and turning rate; flagellar waveform parameters; local flow velocities around beating flagella and agreement with smooth-flagellum simulations
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Mean and maximum swimming speeds did not differ significantly between cells with and without hairs, and waveform curvature, amplitude and wavelength were also statistically indistinguishable. The measured flows decayed with distance as expected for a point force and showed no differences between strains beyond normal cell-to-cell variation. The smooth-flagellum simulation matched all three strains equally well, with errors around 0.15 of the flow amplitude, whereas rigid hairs would have raised flagellar drag by an estimated 30% to 50%. The hairless mutant did turn more often, but this was traced to asymmetric or desynchronised beating rather than to hydrodynamics.
Methodology
The researchers compared a mutant alga lacking flagellar hairs (mastigonemes) with its hair-bearing parent strain and with wild-type cells, after confirming the hairs' presence or absence by electron microscopy. They filmed freely swimming cells at high speed, measured the flagellar waveform of cells held on a micropipette, and used an optically trapped bead as a flow probe to measure the flow generated near beating flagella. They then simulated the flow around each cell with a Stokes-flow model that treats the flagella as smooth cylinders and compared it with the measurements.
Limitations
The study does not reveal what the hairs are for; the authors suggest sensing, adhesion or feeding but test none of these. The mutant also lacks a cell wall, so comparisons depend on the cell-wall-deficient cw15 strain as the proper control, and wall loss itself changed beat frequency. The proposed explanation, that the hairs are too flexible to add drag, was not measured, since hair bending stiffness was not determined. Waveform analysis used only six cells per strain, so small differences could have been missed.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
The alga's flagellar hairs do not help it swim.
A hairless Chlamydomonas mutant swam at speeds not significantly different from hair-bearing strains, and smooth-flagellum Stokes simulations matched all strains' measured flows; rigid hairs would have been expected to raise drag by 30-50%.
Evidence for the claim as stated.
The alga's flagellar hairs do not help it swim.
A hairless Chlamydomonas mutant swam at speeds not significantly different from hair-bearing strains, and smooth-flagellum Stokes simulations matched all strains' measured flows; rigid hairs would have been expected to raise drag by 30-50%.
Scope note — Waveform analysis used only six cells per strain; hair stiffness was not measured.
Limits the claim's scope: a different population, assay, or outcome.
Discoveries this paper informs or conflicts with
- The fine hairs on algal flagella do not change swimming or flow
This paper informs this development.
Related papers in this topic
Same topic cluster — not a recommendation engine.