Nitrogen is a common limiting nutrient for growth and biomass production in algae and plants. Understanding uptake, assimilation, and regulation of nitrogen metabolism to maximize biomass production with minimal nitrogen input is of great interest environmentally, for large-scale algal culturing, and for crop plants. We have characterized a new strain of Chlamydomonas reinhardtii that has a tolerance to low nitrogen (TLN) with higher growth under nitrogen stress compared to an isogenic wild-type (WT) strain. When grown in reduced ammonium the TLN1 strain has a significantly higher cell density, viable cell count, and biomass than WT. In 0.75 mM ammonium (one tenth the normal concentration in TAP medium) TLN1 has 30–40% more growth and ~55% higher biomass than WT. In 1.8 mM ammonium (one fourth the normal concentration in TAP) TLN1 has ~17% more growth and ~28% higher biomass than WT grown in normal high ammonium (7.5 mM), suggesting an altered regulation of nitrogen metabolism when under nitrogen stress. TLN1 also showed higher growth under nitrogen stress with urea and arginine as alternative sources of nitrogen. Genetic analysis indicates that the tln1 trait is inherited and due to a loss-of-function recessive mutation. In addition to the TLN1 phenotype, this strain is nonflagellated and non-motile. When compared to five known C. reinhardtii flagellar and basal body mutants, TLN1 was unique in having higher growth under nitrogen stress. The tln1 trait has potential benefits to large-scale algal and plant culturing under reduced nitrogen.

氮是藻类和植物生长和生物量生产的常见限制营养素。对于大型藻类培养和农作物而言，了解氮吸收，吸收和调节氮代谢以最大程度地利用最少的氮输入来最大化生物量生产是非常重要的。我们鉴定了一种新的莱茵衣藻菌株与同基因野生型（WT）菌株相比，它对低氮（TLN）具有耐受性，并且在氮胁迫下具有更高的生长。当在还原铵中生长时，TLN1菌株的细胞密度，活细胞数和生物量均显着高于WT。在0.75 mM的铵中（在TAP培养基中为正常浓度的十分之一），TLN1比WT增长30–40％，生物量提高约55％。在1.8 mM铵（TAP中正常浓度的四分之一）中，TLN1的生长比普通高铵盐（7.5 mM）中的WT高出17％，生物量高出〜28％，这表明在氮胁迫下氮代谢的调控发生了变化。TLN1在氮胁迫下还表现出更高的生长，尿素和精氨酸是氮的替代来源。遗传分析表明tln1性状是遗传的，并且是由于功能丧失的隐性突变引起的。除TLN1表型外，该菌株是无鞭毛的和不运动的。与五个已知的莱茵衣藻鞭毛和基体突变体相比，TLN1在氮胁迫下具有更高的生长率。该TLN1特质有大型藻类和植物的潜在效益降低氮下培养。