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Abstract：
Nano-sized archaeota, with their small genomes and limited metabolic capabilities, are known to associate with other microbes, thereby compensating for their own auxotrophies. These diminutive and yet ubiquitous organisms thrive in hypersaline habitats that they share with haloarchaea. Here, we reveal the genetic and physiological nature of a nanohaloarchaeon-haloarchaeon association, with both microbes obtained from a solar saltern and reproducibly cultivated together in vitro. The nanohaloarchaeon Candidatus Nanohalobium constans LC1Nh is an aerotolerant, sugar-fermenting anaerobe, lacking key anabolic machinery and respiratory complexes. The nanohaloarchaeon cells are found physically connected to the chitinolytic haloarchaeon Halomicrobium sp. LC1Hm. Our experiments revealed that this haloarchaeon can hydrolyze chitin outside the cell (to produce the monosaccharide N-acetylglucosamine), using this beta-glucan to obtain carbon and energy for growth. However, LC1Hm could not metabolize either glycogen or starch (both alpha-glucans) or other polysaccharides tested. Remarkably, the nanohaloarchaeon\'s ability to hydrolyze glycogen and starch to glucose enabled growth of Halomicrobium sp. LC1Hm in the absence of a chitin. These findings indicated that the nanohaloarchaeon-haloarchaeon association is both mutualistic and symbiotic; in this case, each microbe relies on its partner\'s ability to degrade different polysaccharides. This suggests, in turn, that other nano-sized archaeota may also be beneficial for their hosts. Given that availability of carbon substrates can vary both spatially and temporarily, the susceptibility of Halomicrobium to colonization by Ca Nanohalobium can be interpreted as a strategy to maximize the long-term fitness of the host.
摘要：
纳米的古细菌,他们的小基因组和有限的代谢能力，已知与其他微生物有关，从而补偿自己的营养缺陷。这些小型但无处不在的生物在与haloarchea共享的高盐栖息地中茁壮成长。这里,我们揭示了纳米卤代古菌-卤代古菌协会的遗传和生理性质，两种微生物都是从太阳盐池中获得的，并在体外可重复地培养在一起。纳米卤代古菌念珠菌LC1Nh是一种耐氧物质，糖发酵厌氧菌，缺乏关键的合成代谢机制和呼吸复合物。发现纳米卤代古菌细胞与几丁质分解的卤代古菌Halomicrobiumsp。LC1Hm.我们的实验表明，这种卤代古菌可以在细胞外水解几丁质（产生单糖N-乙酰葡糖胺），利用这种β-葡聚糖来获得生长所需的碳和能量。然而,LC1Hm不能代谢糖原或淀粉(α-葡聚糖)或其他测试的多糖。值得注意的是,纳米卤古菌将糖原和淀粉水解为葡萄糖的能力使Halomicrobiumsp。LC1Hm在没有几丁质的情况下。这些发现表明，纳米卤代古菌-卤代古菌协会既是共生的又是共生的；在这种情况下，每一种微生物依赖于其伙伴降解不同多糖的能力。这表明,反过来,其他纳米级古细菌也可能对它们的宿主有益。鉴于碳底物的可用性可以在空间和暂时变化，Halomicroum对CaNanohalobium定植的敏感性可以解释为最大化宿主长期适应性的策略。
