McLachlan Deirdre H, Brownlee Colin, Taylor Alison R, Geider Richard J, Underwood Graham J C
Department of Biological Sciences, University of Essex, Colchester, CO7 3SQ, UKMarine Biological Association, Citadel Hill, Plymouth, PL1 2PB, UKDepartment of Biological Sciences, University of Essex, Colchester, CO7 3SQ, UK.
J Phycol. 2009 Jun;45(3):592-9. doi: 10.1111/j.1529-8817.2009.00681.x. Epub 2009 May 21.
Motility of estuarine epipelic (mud-inhabiting) diatoms is an important adaptation to living in biofilms present within fine sediments. Motility allows cells to migrate within the photic zone in response to a wide range of environmental stimuli. The motile responses of two species of benthic diatoms to photon fluence rates and spectral quality were investigated. Cultures of Navicula perminuta (Grunow) in van Heurck and Cylindrotheca closterium (Ehrenb.) J. C. Lewin et Reimann both exhibited photoaccumulation at ∼200 μmol · m(-2) · s(-1) and photodispersal from photon flux densities (PFDs) of ∼15 μmol · m(-2) · s(-1) . Photokinesis (changing cell speed) contributed toward photodispersal for both species, and red light (λ = 681-691 nm) was most effective at inducing this process. N. perminuta showed a phototactic (directional) response, with active movement in response to a light gradient. Although this response was exhibited in white light, these directional responses were only elicited by wavelengths from 430 to 510 nm. In contrast, C. closterium did not exhibit phototaxis under any light conditions used in this study. Motile benthic diatoms thus exhibit complex and sophisticated responses to light quantity and quality, involving combinations of photokinesis and phototaxis, which can contribute toward explaining the patterns of large-scale cell movements observed in natural estuarine biofilms.
河口浅滩（栖息于泥中的）硅藻的运动性是其适应生活在细颗粒沉积物中生物膜的一项重要特性。运动性使细胞能够在光合带内迁移，以应对多种环境刺激。研究了两种底栖硅藻对光子通量率和光谱质量的运动反应。微小舟形藻（Grunow）van Heurck培养物和新月柱鞘藻（Ehrenb.）J. C. Lewin et Reimann培养物在约200 μmol·m⁻²·s⁻¹时均表现出光积累，在约15 μmol·m⁻²·s⁻¹的光子通量密度（PFD）下表现出光扩散。光动力学（改变细胞速度）对两种硅藻的光扩散都有作用，红光（λ = 681 - 691 nm）在诱导这一过程方面最为有效。微小舟形藻表现出趋光性（定向）反应，即对光梯度做出主动运动反应。尽管这种反应在白光下表现出来，但这些定向反应仅由430至510 nm的波长引发。相比之下，新月柱鞘藻在本研究使用的任何光照条件下都未表现出趋光性。因此，运动性底栖硅藻对光的数量和质量表现出复杂而精妙的反应，涉及光动力学和趋光性的组合，这有助于解释在天然河口生物膜中观察到的大规模细胞运动模式。
