The Effect of Rotational Gravitational Field on Bioconvection Pattern.

Itoh, Akitoshi; Amagai, Kenji; Arai, Masataka; Mifune, Hiroshi

doi:10.1299/kikaib.65.698

Cited by 7 publications

(7 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dependence of the pattern spacing upon gravity we report is the opposite to that reported by Noever (1991), where the polygonal pattern size in bioconvection of Polytomella parva and Tetrahymena pyriformis increased in the hypergravity (1.8-2·g) phases during parabolic flights of an airplane. It might be possible that the discrepancy between the results of the two experiments is due to differences in the methods of increasing gravity, since a tendency of decreasing pattern spacing similar to ours was reported in a separate centrifuge experiment (Itoh et al, 1999). As noted by Noever (1991), hypergravity during flight experiments occurred and continued for 20·s before and after the short-term (25·s) microgravity, so that the changes in the pattern size were transitional during the limited period of hypergravity and also occurred with the oscillatory changes in gravity (normalhyper--micro--hyper--normal) within a few minutes.…”

Section: Discussionsupporting

confidence: 69%

Bioconvective pattern formation ofTetrahymenaunder altered gravity

Mogami

Yamane

Gino

et al. 2004

Journal of Experimental Biology

View full text Add to dashboard Cite

SUMMARY Bioconvection is a result of the negative gravitactic behavior of microorganisms. When the top-heavy density gradient generated by gravitaxis grows sufficiently large, an overturning convection occurs leading to a formation of characteristic patterns, which involve highly concentrated aggregation of cells into extended two-dimensional structures. Although gravity is a crucial factor, few experiments have been done with reference to gravity as an experimental variable. In order to gain an insight into the hydrodynamic as well as biological dependence of the convective motion on gravity, we investigated changes in bioconvective patterns of Tetrahymena under altered gravity acceleration generated by a long-arm centrifuge. Bioconvective patterns recorded of three different cell strains (T. pyriformis, T. thermophila and its behavioral mutant,TNR) were analyzed quantitatively using space-time plot and Fourier analysis. For example, under subcritical conditions, when T. pyriformis(1.0×106 cells ml-1) was placed in a 2 mm-deep chamber, no spatial pattern was observed at 1 g. When the suspension was centrifuged, however, patterns began to appear as acceleration increased over a critical value (1.5 g), and then remained steady. The formation was reversible, i.e. the patterns disappeared again as acceleration decreased. Under supracritical conditions, i.e. when a suspension of the same density was placed in a 4 mm-deep chamber, a steady state pattern was formed at 1 g. The pattern spacing in the steady state was observed to decrease stepwise in response to step increases in acceleration. Fourier analysis demonstrated that for TNR the mean wave number changed almost simultaneously with step changes in acceleration, whereas the responses were less sharp in the wild-type strains. This may suggest that the locomotor phenotype of the cell, such as its avoiding response ability, has a crucial role in bioconvective pattern formation. These findings are discussed in relation to former theoretical studies.

show abstract

Section: Discussionsupporting

confidence: 69%

Bioconvective pattern formation ofTetrahymenaunder altered gravity

Mogami

Yamane

Gino

et al. 2004

Journal of Experimental Biology

View full text Add to dashboard Cite

show abstract

“…Our findings from the horizontal pattern observations are consistent with those from the previous two centrifugal experiments (Itoh et al, 1999;Mogami et al, 2004), but not with those obtained in the parabolic flight-induced hypergravity (Noever, 1991). Findings obtained from the vertical pattern observation support those from the horizontal ones, and reveal some important facts about responses of bioconvection to altered gravity.…”

Section: Introductionsupporting

confidence: 75%

“…Conflicting experimental results have been reported on the pattern wave number in hypergravity. Hypergravity induced by centrifugation caused an increase in wave number of the horizontal patterns (Itoh et al, 1999;Mogami et al, 2004). In constrast, the patterns were observed to decrease in wave number during the hypergravity phases of parabolic flight (Noever, 1991).…”

Section: Discussionmentioning

confidence: 91%

“…Noever (1991) reported on an experiment of altered gravity using parabolic flight of an aircraft, where the size of polygonal patterns in bioconvection of Polytomella parva and Tetrahymena pyriformis increased in hypergravity (1.8-2 g) phases. In contrast, the results of two independent hypergravity experiments (Itoh et al, 1999;Mogami et al, 2004), both of which used a centrifuge as a means of obtaining hypergravity and Tetrahymena as a material, conflicted with the hypergravity results of Noever (1991). In these recent studies, wavelengths of the steady-state bioconvection patterns became smaller in hypergravity.…”

Section: Introductionmentioning

confidence: 95%

“…Two types of observations were made. The first is the topview, or horizontal pattern observation, which is the same as that used in all of the previous three altered gravity experiments (Noever, 1991;Itoh et al, 1999;Mogami et al, 2004). The other is the side-view, or vertical pattern observation, in which we can directly observe the settling blobs of microorganisms.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations