Blue-green algae appeared on the earth about 3.5 ~ 3.3 billion years ago. There are about 2000 known cyanobacteria and 900 recorded cyanobacteria in China. As an autotrophic organism, it has very strong adaptability, and can tolerate high temperature, freezing, hypoxia, dryness, high salinity and strong radiation, so it can survive in tropical to polar regions, from ocean to mountain top, hot springs at 85℃, snow springs at MINUS 62℃, lakes and swamps with 27% high salinity, dry rocks and other environments.
Basic introduction of Chinese name: Latin scientific name of blue-green algae: blue-green algae alias: cyanobacteria, cyanobacteria, myxoalgae kingdom: cyanobacteria kingdom: cyanophyta diasptribution area: most (about 75%) freshwater production, a few marine organisms: prokaryote reproduction mode: vegetative reproduction or spore production is classified into asexual reproduction, morphological characteristics, distribution range, main value, reproduction method, harm and treatment, teratogenic cases, and so on. Cyanophyta is divided into two categories: Chromophyta and Algae. Algal cells are single cells or groups; The phycomycetes are filamentous and have phycomycetes. Morphological characteristics Blue-green algae is a unicellular organism, which has no nucleus, but the center of the cell contains nuclear substances, usually granular or reticulate, and chromosomes and pigments are evenly distributed in the cytoplasm. This nuclear substance has no nuclear membrane and nucleoli, but it has nuclear function, so it is called pronucleus. Cyanobacteria, like bacteria, belong to "prokaryotes". Together with prokaryotic bacteria, it is a unique kingdom of monera. Blue-green algae have no organelles such as chloroplasts, mitochondria, Golgi apparatus, endoplasmic reticulum and vacuoles, but contain chlorophyll a, chlorophyll b, lutein and carotene, as well as phycobiliproteins (phycoerythrin, phycocyanin and allophycocyanin). Generally speaking, cells containing chlorophyll a and phycocyanin are mostly blue-green. Similarly, there are a few species that contain more phycoerythrin, and the algae are mostly red. For example, a blue-green algae born in the Red Sea is called Chaetomium rubrum. Because it contains a lot of phycoerythrin, the algae are red and reproduce quickly, so the sea water is also red, hence the name of the Red Sea. Although cyanobacteria have no chloroplasts, there are many photosynthetic membranes in the cytoplasm, called thylakoids, to which various photosynthetic pigments are attached, and the photosynthesis process is carried out here. The cell wall of cyanobacteria is similar to bacteria in chemical composition, mainly mucin; The stored photosynthetic products are mainly cyanobacteria starch and cyanobacteria particles. The cell wall is divided into two layers, the inner layer is cellulose, and a few people think it is pectin and hemicellulose. The outer layer is a colloid sheath, mainly pectin or a small amount of cellulose. The inner wall can continue to secrete colloid and increase into the rubber sheath. Some kinds of rubber sheaths are very firm and dense, and can be layered. Some kinds of rubber sheaths are easy to hydrate, and rubber sheaths of adjacent cells can dissolve each other. There may be non-photosynthetic pigments such as brown, red and gray in the rubber sheath. Cyanobacteria have single cells, colonies and filaments. The simplest is a single cell. Some unicellular organisms become groups because the daughter cells are embedded in the gelatinized mother cell wall after cell division. If they divide repeatedly, there will be many cells in the group, and the larger group can be divided into several smaller groups. Some single-celled organisms are polarized at the bottom and top because of their attachment to life. Filaments are formed by repeated division of cells along the same division plane and connection of daughter cells. Some filaments have the same cells, and some filaments have heteromorphism; Some filaments have false branches or true branches, and some cells at the top of filaments gradually become trichomes, which is also called polar differentiation. Filaments can also be connected into a group and wrapped in the colloid sheath of the male, which is a group of multicellular individuals. Distribution Scope Blue-green algae are widely distributed all over the world, but most of them (about 75%) are produced in fresh water, and a few are seafood. Some cyanobacteria can survive in hot springs at 60 ~ 85℃; Some species are related to fungi, mosses, ferns and gymnosperms; Some can also penetrate into calcareous rocks or shells (such as calcareous algae) or deep soil (such as soil cyanobacteria). The main value of blue-green algae Blue-green algae is the earliest photosynthetic oxygen-releasing organism, which has played a great role in transforming the anaerobic atmospheric environment on the earth's surface into aerobic environment. There are many blue-green algae (such as ANABAENA) that can directly fix nitrogen in the atmosphere to improve soil fertility and increase crop yield. There are also cyanobacteria for people to eat, such as the famous Nostoc flagelliforme and Nostoc commune (Nostoc commune), Spirulina and so on. Breeding methods There are two breeding methods for cyanobacteria. One is vegetative propagation, which includes direct cell division (i.e. fission), population disruption and filamentous algae production segments. The other is that some cyanobacteria can produce endospore or ectospores for asexual reproduction. Spores have no flagella. No real cyanobacteria have been found to reproduce sexually. Harm and treatment In some nutrient-rich water bodies, some cyanobacteria often multiply in summer, forming a layer of foul-smelling blue-green floating foam on the water surface, which is called "bloom", and a large-scale cyanobacteria outbreak is called "green tide" (corresponding to the red tide in the ocean). Green tide causes the deterioration of water quality, and when it is serious, it will exhaust the oxygen in the water, leading to the death of fish. The outbreak of cyanobacteria will lead to serious water pollution incidents, and the most serious crisis is the cyanobacteria pollution incident in Taihu Lake in 2007. In June of that year, cyanobacteria broke out in Taihu Lake, and dozens of centimeters thick cyanobacteria covered all the water surface. Statistics released by Wuxi * * * show that except Wuxi Waterworks, the water quality of other waterworks, which account for 70% of the city's water supply, is polluted, the water discharged from faucets is yellow and smelly, the drinking water of 2 million Wuxi citizens is polluted, and the city's pure water is looted. Although * * * has taken timely measures, it has had a great impact on people's lives. Since then, although the country has made great efforts to control the pollution of Taihu Lake, cyanobacteria still erupt every year. More seriously, some kinds of cyanobacteria (such as Microcystis) also produce toxins (MC for short), and about 50% of green tides contain a lot of MC. MC is not only directly toxic to fish, humans and animals, but also an important cause of liver cancer. MC is heat-resistant, not easily decomposed by boiling water, but can be adsorbed by activated carbon, so the polluted water source can be purified by activated carbon water purifier. Algae, such as cyanobacteria, are food for silver carp. Adding such fry can control algae and prevent algae from breaking out. Teratogenic cases Those waters containing a large number of blue-green algae have a high content of retinoic acid, which may be the reason for the deformity of more and more amphibians. Perhaps these microorganisms named cyanobacteria were not intentional, but their existence did enrich the waters with some chemicals, and caused deformities of frogs and other wild vertebrates. Hu Jianying, an environmental toxicologist in Peking University, said that cyanobacteria, also known as blue-green algae, can cause retinoic acid in water, which was previously neglected but widely spread. In a paper published in the Proceedings of the National Academy of Sciences on May 29th, 20th1February, Dr. Hu and her colleagues said that 13 of the 24 cyanobacteria cultured in their laboratory can produce some types of retinoic acid or retinoids. Retinoic acid is a derivative of vitamin A, which can play a role in the limb development of vertebrates. Researchers have studied deformed frogs that have appeared since the 1990s and found that retinoids may be one of the reasons. Hu and his colleagues also analyzed the samples of Taihu Lake, the third largest freshwater lake in China, which is rich in cyanobacteria. It is found that Taihu Lake contains high concentration of retinoic acid. "This new research opens up a new potential research field," said Carl Havens, a plankton ecologist and course director at Florida Ocean Foundation College in Gainesville, USA. "I really want to know whether these compounds also exist in other lakes with cyanobacteria, and I am looking forward to further research." The concentration of retinoic acid in Taihu Lake is as high as 20 ng/L, which is 1 10,000 times higher than that found in Japanese lakes by KunimitsuKaya of Tsukuba University and his colleagues. 20 1 1, Kaya reported that cyanobacteria can produce a retinoid (called 7- hydroxyretinoic acid); This large amount of compounds may lead to an extreme environment like Taihu Lake. The planktonic algae and foam it caused probably blocked the sunlight, making the high-concentration retinoic acid that could have been degraded unable to be degraded. Andrew Brausch Stein, an ecologist at Oregon State University in Corvallis, said there was not enough information to link cyanobacteria with the high incidence of amphibian malformations. He and other researchers have suggested some other reasons, including ultraviolet radiation and trematode parasites. Peter Zhan Sen, a disease ecologist at the University of Colorado at Boulder, said that parasites can cause some limb deformities, but they can't explain all cases. Toxicological cyanobacteria produce a variety of biotoxins, including neurotoxins, hepatotoxins, cytotoxins and endotoxin. It poses a serious danger to the health or safety of people and animals: 1. Neurotoxin BMAA, whether native cyanobacteria or aquatic cyanobacteria, contains neurotoxin BMAA(β-N- methylamino -L- alanine), which may produce biomagnification through food chain accumulation, and the harm to human beings will gradually increase. BMAA has been proved to be highly toxic to animals, accelerating the degeneration of animals' brains and atrophy of limbs muscles. A small amount of BMAA accumulation has been able to selectively kill neurons in mice. 2. Some kinds of cyanobacteria (such as Microcystis) also produce microcystins (MCs). MCs is a kind of hepatotoxin, which is one of the causes of liver cancer and has very strong toxicity. About 50% of the green tide contains a lot of MC. MCs has water solubility and heat resistance. Soluble in water, methanol or acetone, non-volatile, resistant to pH change. The molecular formula of MC-LR is C49H74N 10O 12, and its molecular weight is 995.2 (often calculated as 1000). MCs is not easily decomposed by boiling water, but can be adsorbed by activated carbon, so it can be used to purify the polluted water source. After drinking water containing cyanobacteria toxin, domestic animals and wild animals will have symptoms such as diarrhea, fatigue, anorexia, vomiting, drowsiness, increased mouth and eye secretions, and even death. Pathological changes include liver enlargement, congestion or necrosis, enteritis bleeding, pulmonary edema and so on. Long-term drinking may lead to liver cancer. Medical departments found that microcystins in drinking water have a great correlation with the incidence of primary liver cancer in the population. 1996 caused acute liver failure in Brazil 100, and at least 50 people died within 7 months due to the acute effect of microcystins, which attracted worldwide attention. Cyanotoxin in fresh water has become a global environmental problem, and cyanotoxin poisoning incidents often occur all over the world. 3. Toxins in another kind of cyanobacteria have * * effects on the skin. When cyanotoxin cells rupture or die, the above-mentioned toxins will be released into water. When people bathe, swim and do other water recreation and sports, skin contact with water containing microcystins will cause sensitive parts (such as eyes) and skin allergies.