Karsten U, Lembcke S, Schumann R
Institute of Biological Sciences, Applied Ecology, University of Rostock, Albert-Einstein-Str. 3, 18051 Rostock, Germany.
Planta. 2007 Mar;225(4):991-1000. doi: 10.1007/s00425-006-0406-x.
The effects of artificial ultraviolet radiation [UVR; 8 W m(-2) ultraviolet-A (UVA), 0.4 W m(-2) ultraviolet-B (UVB)] on photosynthetic performance, growth and the capability to synthesise mycosporine-like amino acids (MAAs) was investigated in the aeroterrestrial green algae Stichococcus sp. and Chlorella luteoviridis forming biofilms on building facades, and compared with the responses of two green algae, from soil (Myrmecia incisa) and brackish water (Desmodesmus subspicatus). All species exhibited decreasing quantum efficiency (Fv/Fm) after 1-3 days exposure to UVR. After 8-12 days treatment, however, all aeroterrestrial isolates exhibited full recovery under UVA and UVA/B. In contrast, D. subspicatus showed only 80% recovery after treatment with UVB. While Stichococcus sp. and C. luteoviridis exhibited a broad tolerance in growth under all radiation conditions tested, M. incisa showed a significant decrease in growth rate after exposure to UVA and UVA/B. Similarly D. subspicatus grew with a reduced rate under UVA, but UVA/B led to full inhibition. Using HPLC, an UV-absorbing MAA (324 nm-MAA) was identified in Stichococcus sp. and C. luteoviridis. While M. incisa contained a specific 322 nm-MAA, D. subspicatus lacked any trace of such compounds. UV-exposure experiments indicated that all MAA-containing species are capable of synthesizing and accumulating these compounds, thus supporting their function as an UV-sunscreen. All data well explain the conspicuous ecological success of aeroterrestrial green algae in biofilms on facades. Biosynthesis and accumulation of MAAs under UVR seem to result in a reduced UV-sensitivity of growth and photosynthesis, which consequently may enhance survival in the environmentally harsh habitat.
研究了人工紫外线辐射[UVR；8 W m(-2)紫外线-A（UVA），0.4 W m(-2)紫外线-B（UVB）]对在建筑立面上形成生物膜的气生绿藻Stichococcus sp.和绿球藻Chlorella luteoviridis光合性能、生长以及合成类菌孢素氨基酸（MAAs）能力的影响，并与来自土壤（Myrmecia incisa）和咸水（Desmodesmus subspicatus）的两种绿藻的反应进行了比较。所有物种在暴露于UVR 1-3天后均表现出量子效率（Fv/Fm）下降。然而，在8-12天的处理后，所有气生分离株在UVA和UVA/B条件下均表现出完全恢复。相比之下，Desmodesmus subspicatus在用UVB处理后仅表现出80%的恢复。虽然Stichococcus sp.和Chlorella luteoviridis在所有测试辐射条件下的生长都表现出广泛的耐受性，但Myrmecia incisa在暴露于UVA和UVA/B后生长速率显著下降。同样，Desmodesmus subspicatus在UVA下生长速率降低，但UVA/B导致完全抑制。使用高效液相色谱法，在Stichococcus sp.和Chlorella luteoviridis中鉴定出一种吸收紫外线的MAA（324 nm-MAA）。虽然Myrmecia incisa含有一种特定的322 nm-MAA，但Desmodesmus subspicatus没有任何此类化合物的痕迹。紫外线暴露实验表明，所有含MAA的物种都能够合成和积累这些化合物，从而支持它们作为紫外线防晒剂的功能。所有数据很好地解释了气生绿藻在建筑立面生物膜中显著的生态成功。UVR下MAAs的生物合成和积累似乎导致生长和光合作用的紫外线敏感性降低，从而可能提高在环境恶劣栖息地中的存活率。
