Cyanobacteria

Cyanobacteria are examples of the prokaryotic cell type. They are photosynthetic and were thought to be examples of bluegreen algae until it was discovered that they had no membrane-bound nucleus and had no chloroplasts. With a size range of 0.5 to 60 micrometers, they are perhaps the largest prokaryotic organisms. (Britannica) Their metabolism utilizes energy from the sun and they release oxygen into the atmosphere. In fact, it is thought that they are some of the oldest forms of life and may have played a major role in giving the Earth an oxygen-containing atmosphere. Along with that, it is proposed that cyanobacteria were actually involved in originating the chloroplasts that enable photosynthesis in plants.

This is a sketch of a cyanobacteria from an electron micrograph displayed by Karp, Chapter 1.3, showing the multiple internal membranes that participate in photosynthesis. It also shows the lack of a nucleus and the other organelles characteristic of eukaryotic cells.

这是一张由Karp在第1.3章中展示的蓝藻细胞电子显微照片，显示了参与光合作用的多个内部膜。该图还展示了真核细胞中缺乏细胞核和其他细胞器的特征。

蓝藻是原核细胞的一种例子。它们是光合的，并且曾被认为属于蓝绿色藻类，直到发现它们没有膜结合的细胞核，也没有叶绿体。它们的大小范围在0.5到60微米之间，可能是最大的原核生物。（Britannica）它们的代谢利用太阳的能量，并向大气释放氧气。事实上，人们认为它们可能是最早的生命形式之一，并可能在给地球带来含氧大气方面发挥了重要作用。此外，有人提出蓝藻实际上参与了产生使植物能够光合作用的叶绿体。

Unlike most prokaryotes, cyanobacteria have internal membranes in the form of flattened sacs called thylakoids where photosynthesis takes place. The similarity of these thylakoids to the structures in the chloroplasts of plants has led to the proposal that cyanobacteria were the origin of those chloroplasts by a process called endosymbiosis into the developing plant forms.

与大多数原核生物不同，蓝细菌具有内部膜结构，这些膜以扁平囊状结构存在，称为类囊体，光合作作用在此进行。这些类囊体的结构与植物细胞质体的结构相似，因此有人提出蓝细菌可能是通过一种称为内共生的过程成为植物发育过程中质体的起源。

The great age of cyanobacteria is affirmed by their presence in ancient stromatolites. Strong evidence for the presence of cyanobacteria dates back to 2.1 Ga (1 Ga= 10⁹ years). Their contributions to the stromatolites are viewed as some of the oldest known fossils on the Earth, stretching into the precambrian period. Stromatolites date back to perhaps 3.5 Ga, with evidence for cyanobacteria to 2.7 Ga. Cyanobacteria release oxygen into the atmosphere, and they may have made a major contribution to the rapid rise of atmospheric oxygen about 2.4 Ga which is called the "Great Oxygenation Event". It is also sometimes called "the rusting of the Earth" because the increased oxygen in the sea oxidized the large amount of dissolved iron, producing the extensive "banded iron" mineral deposits of iron oxide. (Wiki ) The rapid rise in atmospheric oxygen followed the oxidizing of most of the dissolved iron in the oceans.

蓝藻的繁盛时期得到了古叠层石中存在它们的证据的证实。蓝藻存在的有力证据可追溯至21亿年前（1 Ga=10⁹年）。它们对叠层石的贡献被视为地球上已知最古老的化石之一，可追溯到前寒武纪时期。叠层石可能追溯到35亿年前，而蓝藻的证据则可追溯到27亿年前。蓝藻将氧气释放到大气中，并可能对约24亿年前大气氧迅速上升作出了重大贡献，这一事件被称为“大氧化事件”。它有时也被称为“地球的锈蚀”，因为大气中氧气的增加使海洋中大量溶解的铁氧化，产生了广泛的“带铁”矿物沉积物，即铁氧化物。（Wiki）大气中氧气的迅速上升发生在海洋中大部分溶解铁氧化之后。

Cyanobacteria are found in almost every terrestrial and aquatic habitat. They contribute significantly to the global ecology. "The tiny marine cyanobacterium Prochlorococcus was discovered in 1986 and accounts for more than half of the photosynthesis in the ocean."(Wiki) Some of the cyanobacteria are nitrogen-fixing, and are abundant in moist soils and waterways.

蓝藻几乎存在于所有的陆地和水生环境中。它们对全球生态有重要贡献。“这种微小的海洋蓝藻Prochlorococcus于1986年被发现，占海洋光合作用的一半以上。”(Wiki) 一些蓝藻能够固氮，并广泛分布于湿润的土壤和水体中。

The photosynthesis in cyanobacteria provides light energy to drive the synthesis of organic compounds from carbon dioxide. They have several carbon concentrating mechanisms for collecting CO₂ and optimize the effectiveness of the CO₂-fixing enzyme, RuBisCo. They are able to use CO₂ as their sole source of carbon. They make use of the PPP cycle in fixing CO₂.

蓝藻的光合作用提供光能，以驱动从二氧化碳合成有机化合物的过程。它们具有几种碳浓缩机制，用于收集CO₂，并优化CO₂固定酶RuBisCo的效率。它们能够将CO₂作为唯一的碳源。它们利用PPP循环固定CO₂。

Cyanobacteria accomplish both respiration for the cells energy needs alongside the photosynthesis which synthesizes carbohydrates. "They appear to separate these two processes with their plasma membrane containing only components of the respiratory chain, while the thylakoid membrane hosts an interlinked respiratory and photosynthetic electron transport chain. Cyanobacteria only respire during the night (or in the dark) because the facilities used for electron transport are used in reverse for photosynthesis while in the light." (Wiki).

蓝藻菌同时完成细胞的能量需求所需的呼吸作用，以及光合作用，后者合成碳水化合物。'它们似乎将这两个过程分开，其细胞膜仅包含呼吸链的成分，而类囊体膜则包含相互关联的呼吸和光合作用的电子传递链。蓝藻菌只在夜间（或在黑暗中）进行呼吸，因为用于电子传递的设施在光照时会被逆向用于光合作用。'（维基）

Cyanobacteria can have harmful environmental and health effects (CDC article) when they have large growth events referred to as "blooms". They can use up the oxygen and block sunlight from other organisms, and they can produce toxins called CyanoHABs or cyanotoxins. The rapid growth of cyanobacteria poses human and animal hazards in lakes like Bantam Lake in Connecticut and in lakes and waterways in California.

They give a bluegreen color to water, and can survive at high temperatures, producing the beauty of hot springs like the Morning Glory Pool in Yellowstone. (Cyanobacteria, Britannica)

它们使水呈现蓝绿色，能在高温下生存，产生如黄石公园晨光池般的温泉美景。（蓝藻菌， Britannica）

当蓝藻出现大规模生长现象，称为“水华”时，它们可能对环境和健康产生有害影响（CDC文章）。它们会消耗氧气并阻挡其他生物的阳光，还能产生称为CyanoHABs或蓝藻毒素的毒素。蓝藻的快速生长会对人类和动物造成危害，例如康涅狄格州的巴纳姆湖以及加利福尼亚州的湖泊和水道。