For the first time, the ability to photosynthesize appeared. Photosynthesis, section “Biologist”

Find three errors in the given text. Indicate the numbers of the sentences in which errors were made and correct them.

1. Algae are a group of lower plants that live in the aquatic environment.

2. They lack organs, but have tissues: integumentary, photosynthetic and educational.

3. In unicellular algae, both photosynthesis and chemosynthesis occur.

4. In the development cycle of algae, there is an alternation of sexual and asexual generations.

5. During sexual reproduction, gametes fuse, fertilization occurs, as a result of which the gametophyte develops.

6. In aquatic ecosystems, algae serve as producers.

Explanation.

1) 2 - green algae consist of identical cells and do not have tissues;

2) 3 - chemosynthesis does not occur in algae cells;

3) 5 - when gametes merge, a zygote is formed, from which a sporophyte develops, and a gametophyte develops from a spore.

Source: Demo version of the Unified State Exam 2016 in biology.

Natalia Evgenievna Bashtannik

Can be supplemented, subject to other corrections :)

Anna Bondarenko 20.12.2016 20:26

2. They lack organs, but have tissues: integumentary, photosynthetic and educational.

Algae have neither tissues nor organs.

Natalia Evgenievna Bashtannik

yes, and this proposal is wrong, it needs to be corrected

Ekaterina Gromova 02.11.2017 18:58

The division into sporophyte and gametophyte appears only in higher plants

Natalia Evgenievna Bashtannik

Gametophyte and sporophyte - alternation of generations, this is a characteristic of plants. Sporophyte is a diploid (2n) multicellular phase that develops from a fertilized egg (zygote) and produces haploid (1n) spores. Gametophyte is a haploid (1n) multicellular phase that develops from spores and produces sex cells, or gametes. Accordingly, there are male and female gametophytes.

If the sporophyte and gametophyte are morphologically the same, then an isomorphic alternation of generations occurs; if they are different, it is heteromorphic. Algae have both forms, while higher plants have only heteromorphic forms.

Vasily Rogozhin 09.03.2019 13:54

Some algae may have true tissues. These are algae with the so-called tissue (parenchymatous) type of differentiation of the thallus. These include, for example, the well-known Porphyra (from Red algae, wrapper for rolls), Laminaria (brown seaweed), Ulva (green seaweed).

Algae cannot have ORGANS! Fabrics may be In such “tissue” algae, even the type of differentiation of the thallus was called tissue (parenchymatous). Link to source: "Botany, Algae and Fungi", Volume 1 and 2, Belyakova G.A., Dyakov Yu.T., Tarasov K.L., Moscow State University, 2006.

Therefore, an amendment should be made to the first element of the answer: “some algae may have real tissues, but they are not divided into integumentary, photosynthetic and educational (this is the name of the tissues of higher plants).

Support

However, in this task from the demo version of the Unified State Examination 2016, it is the specified answer that is considered correct by the exam compilers. Unfortunately, such inaccuracies are not uncommon in the Unified State Examination in biology.

Diana Yesherova 24.04.2019 19:43

1.they live not only in the aquatic environment, but even in the mountains under a layer of snow.

5. when gametes fuse, a zygote is formed, isn’t it?

Natalia Evgenievna Bashtannik

Point 5 - corrected in the criteria.

And if you add a correction of 1 point to those specified in the criteria, then this will not be an error.

Oxidative phosphorylation is a step

1) photosynthesis

2) glycolysis

3) plastic exchange

4) energy metabolism

Explanation.

Oxidative phosphorylation is a metabolic pathway in which the energy generated during the oxidation of nutrients is stored in the mitochondria of cells in the form of ATP.

Answer: 4.

Answer: 4

1. Plastids are found in the cells of plant organisms and some bacteria and animals, capable of both heterotrophic and autotrophic nutrition. 2. Chloroplasts, like lysosomes, are double-membrane, semi-autonomous cell organelles. 3. Stroma - the inner membrane of the chloroplast, has numerous projections. 4. Membranous structures - thylakoids - are immersed in the stroma. 5. They are stacked in the form of cristae. 6. Reactions of the light phase of photosynthesis occur on thylakoid membranes, and dark phase reactions occur in the stroma of the chloroplast.

Explanation.

Errors were made in the sentences:

1) 2 - Lysosomes are single-membrane structures of the cytoplasm.

2) 3 - Stroma - semi-liquid contents of the inner part of the chloroplast.

3) 5 - Thylakoids are stacked in the form of grana, and cristae are folds and outgrowths of the inner membrane of mitochondria.

Note.

1 sentence in the criteria has not been corrected, but we believe that it also needs to be corrected.

1 - Plastids are found in the cells of plant organisms and some animals, capable of both heterotrophic and autotrophic nutrition.

From this proposal bacteria need to be removed, because Bacteria do not have membrane organelles. Among prokaryotic organisms, many groups have photosynthetic apparatuses and therefore have a special structure. It is characteristic of photosynthetic microorganisms (blue-green algae and many bacteria) that their photosensitive pigments are localized in the plasma membrane or in its outgrowths directed deep into the cell.

Guest 05.02.2016 08:50

1. Plastids are found in the cells of plant organisms and some bacteria and animals, capable of both heterotrophic and autotrophic nutrition

This sentence was not marked as incorrect. But it contains an error: plastids are found only in eukaryotes and are semi-autonomous descendants of prokaryotes. Photosynthetic bacteria carry out photosynthesis using thylakoids and phycobilisomes. Please correct the inaccuracy.

Natalia Evgenievna Bashtannik

If you correct the inaccuracy you indicated when writing your answer, the score will not be counted, but will not be reduced.

Note.

Structure plastid in lower photosynthetic plants (green, brown and red algae) and the chloroplasts of cells of higher plants are generally similar. Their membrane systems also contain photosensitive pigments. Chloroplasts of green and brown algae (sometimes called chromatophores) also have outer and inner membranes; the latter forms flat bags arranged in parallel layers; granae are not found in these forms.

Plastids are membrane organelles found in photosynthetic eukaryotic organisms (higher plants, lower algae, some unicellular organisms).

Regina Singer 09.06.2016 13:33

Plastids (from ancient Greek πλαστός - fashioned) are semi-autonomous organelles of higher plants, algae and some photosynthetic protozoa. Plastids have from two to four membranes, their own genome and a protein synthesizing apparatus. Source: Wikipedia. No mention of bacteria. It is EXTREMELY WRONG to use plastids in relation to prokaryotes.

Natalia Evgenievna Bashtannik

Using Wikipedia as a SOURCE without double-checking is extremely incorrect.

Sentence 1 can be corrected, if it is not indicated in the criteria, this does not mean that it does not need to be corrected. Read the explanatory note.

Which process provides eukaryotic cells with energy most efficiently?

1) photosynthesis

2) glycolysis

3) alcoholic fermentation

4) oxidative phosphorylation

Explanation.

Oxidative phosphorylation most effectively provides eukaryotic cells with energy.

Oxidative phosphorylation is a step in energy metabolism.

Oxidative phosphorylation is a metabolic pathway in which the energy generated during the oxidation of nutrients is stored in the mitochondria of cells in the form of ATP.

The oxidation of two molecules of three-carbon acid, formed during the enzymatic breakdown of glucose to CO 2 and H 2 O, leads to the release of a large amount of energy, sufficient to form 36 ATP molecules.

During glycolysis, one molecule of glucose produces two molecules of ATP.

Answer: 4.

Answer: 4

1) photosynthesis

2) oxidative phosphorylation

3) glycolysis

4) reduction of carbon dioxide

Explanation.

Pyruvic acid is formed during glycolysis. This is one of the stages of energy metabolism.

Answer: 3

1) oxidize minerals

2) create organic substances during photosynthesis

3) accumulate solar energy

4) decompose organic substances to minerals

Explanation.

Saprotrophic bacteria in the lake ecosystem decompose organic substances into minerals.

Saprotrophs (saprophytes) feed on dead organisms and process corpses into inorganic substances.

Saprotrophic bacteria are decomposers; they decompose organic substances (proteins, fats, carbohydrates) to inorganic substances (carbon dioxide, water, ammonia). Inorganic substances are needed by producers (plants) for the synthesis of organic substances. Thus, decomposers, including saprotrophic bacteria, close the cycle of substances in nature.

Answer: 4.

Answer: 4

Source: Unified State Exam in Biology 04/09/2016. Early wave

All of the characteristics listed below, except two, are used to describe the cell shown in the figure. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated in the table.

1) the presence of chloroplasts

2) presence of glycocalyx

3) ability to photosynthesize

4) ability to phagocytose

5) ability for protein biosynthesis

Explanation.

The figure shows a plant cell (as the dense cell wall, large central vacuole and chloroplasts are clearly visible). Moreover, all types of cells are capable of protein biosynthesis. Characteristics that “drop out” from the general list: the presence of a glycocalyx and the ability to phagocytose.

Answer: 24.

Answer: 24

Source: Demo version of the Unified State Exam 2017 in biology.

Explanation.

1) chromatography method

2) the method is based on the separation of pigments due to differences in the speed of movement of pigments in the solvent (mobile phase over stationary phase)

Note.

For the first time, an accurate idea of the pigments of green leaves of higher plants was obtained thanks to the work of the largest Russian botanist M.S. Colors (1872-1919). He developed a chromatographic method for separating substances and isolated the leaf pigments in their pure form. The chromatographic method for separating substances is based on their different adsorption abilities. This method has been widely used. M.S. The color passed the extract from the leaf through a glass tube filled with powder - chalk or sucrose (chromatographic column). The individual components of the pigment mixture differed in the degree of adsorbability and moved at different speeds, as a result of which they concentrated in different zones of the column. By dividing the column into separate parts (zones) and using the appropriate solvent system, each pigment could be isolated. It turned out that the leaves of higher plants contain chlorophyll a and chlorophyll b, as well as carotenoids (carotene, xanthophyll, etc.). Chlorophylls, like carotenoids, are insoluble in water, but highly soluble in organic solvents. Chlorophylls a and b differ in color: chlorophyll a is blue-green and chlorophyll b is yellow-green. The content of chlorophyll a in the leaf is approximately three times greater than chlorophyll b.

Photosynthesis is the process of organisms absorbing light from the sun and converting it into chemical energy. In addition to green plants and algae, other organisms are capable of photosynthesis - some protozoa, bacteria (cyanobacteria, purple, green, halobacteria). The process of photosynthesis in these groups of organisms has its own characteristics.

During photosynthesis under the influence of light with the obligatory participation of pigments (chlorophyll in higher plants and bacteriochlorophyll in photosynthetic bacteria), organic matter is formed from carbon dioxide and water. Green plants release oxygen during this process.

All photosynthetic organisms are called phototrophs because they use sunlight to obtain energy. Due to the energy of this unique process, all other heterotrophic organisms on our planet exist (see Autotrophs, Heterotrophs).

The process of photosynthesis occurs in the cell plastids - chloroplasts. The components of photosynthesis - pigments (green - chlorophylls and yellow - carotenoids), enzymes and other compounds - are orderedly located in the thylakoid membrane or stroma of the chloroplast.

The chlorophyll molecule has a system of conjugated double bonds, due to which, when absorbing a light quantum, it is able to go into an excited state, that is, one of its electrons changes its position, rising to a higher energy level. This excitation is transferred to the so-called main chlorophyll molecule, which is capable of charge separation: it gives an electron to an acceptor, which sends it through a system of carriers into the electron transport chain, where the electron gives up energy in redox reactions. Due to this energy, hydrogen protons are “pumped” from the outside of the thylakoid membrane to the inside. A potential difference of hydrogen ions is formed, the energy of which is used for the synthesis of ATP (see Adenosine triphosphate acid (ATP). The formation of ATP during photosynthesis is called photophosphorylation in contrast to oxidative phosphorylation, i.e. the formation of ATP due to the respiration process.

The chlorophyll molecule gives up an electron and becomes oxidized. A so-called electron deficiency occurs. In order for the photosynthesis process not to be interrupted, it must be replaced by another electron. Where does it come from? It turns out that the source of electrons, as well as protons (remember, they create a potential difference on both sides of the membrane) is water. Under the influence of sunlight, as well as with the participation of a special enzyme, a green plant is capable of photo-oxidizing water:

2H 2 O →light, enzyme → 2H + + 2ẽ + 1/2O 2 + H 2 O

The electrons obtained in this way fill the electron deficiency in the chlorophyll molecule, while the protons go to the reduction of NADP (the active group of enzymes that transport hydrogen), forming another energy equivalent of NADP H in addition to ATP. In addition to electrons and protons, the photo-oxidation of water produces oxygen, which makes the Earth's atmosphere suitable for breathing.

The energy equivalents of ATP and NADP H spend their energy from macroergic bonds for the needs of the cell - for the movement of the cytoplasm, transport of ions through membranes, synthesis of substances, etc., and also provide energy for the dark biochemical reactions of photosynthesis, as a result of which simple carbohydrates are synthesized and starch. These organic substances serve as a substrate for respiration or are spent on the growth and accumulation of plant biomass.

The productivity of agricultural plants is closely related to the intensity of photosynthesis.

Imagine what it would be like if people, like plants, could be powered directly by solar energy. This would definitely make our lives easier: the countless hours spent buying, preparing and eating food could be spent on something else. Overexploited agricultural lands would return to natural ecosystems. Rates of hunger, malnutrition and diseases spread through the digestive tract would plummet.

However, humans and plants have not had a common ancestor for hundreds of millions of years. Our biology is fundamentally different in almost every aspect, so it may seem that there is no way to engineer humans to perform photosynthesis. Or is this still possible?

This problem is being carefully studied by some synthetic biologists who have even tried to create their own plant-animal hybrids. Although we are still a long way from creating photosynthetic humans, new research has uncovered an intriguing biological mechanism that could advance the development of this nascent field of science.

Elysia chlorotica is an animal that can carry out photosynthesis like plants

Recently, representatives of the Marine Biological Laboratory, located in the American village of Woods Hall, reported that scientists had unraveled the secret of Elysia chlorotica - a brilliant green sea slug that looks like a plant leaf, eats the sun like a leaf, but is actually an animal. It turns out that Elysia chlorotica maintains such a bright color by eating algae and taking over their genes that ensure photosynthesis. It is the only known example of a multicellular organism to adopt the DNA of another organism.

In a statement, study co-author and professor emeritus at the University of South Florida Sidney C. Pierce said: “It is impossible on Earth for algae genes to operate inside an animal cell. And yet it happens. They allow the animal to receive nutrition from the sun.” According to scientists, if people wanted to hack their own cells to make them capable of photosynthesis, a similar mechanism could be used to do this.

When it comes to solar energy, we can say that humans have been moving in the wrong evolutionary direction for a billion years. As plants became thin and transparent, animals became thick and opaque to light. Plants get their small but constant share of the sun's sap while remaining in one place, but people like to move and need energy-rich food to do so.

If you look at the cells and genetic code of humans and plants, it turns out that we are not so different. This amazing similarity of life at its fundamental levels allows such extraordinary things to happen as animals stealing photosynthesis. Today, thanks to the emerging field of synthetic biology, we may be able to reproduce such phenomena in a single evolutionary blink, making biopunk ideas about creating photosynthetic patches of skin seem less fantastical.

According to Pierce, “usually, when genes from one organism are transferred into the cells of another, it does not work. But if it works, it can change a lot overnight. It's like accelerated evolution."

Sea slugs are not the only animals capable of photosynthesis through a symbiotic relationship. Other classic examples of such creatures are corals, whose cells store photosynthetic dinoflagellates, and the spotted salamander, which uses algae to supply its embryos with solar energy.

However, sea slugs differ from similar animals in that they have found a way to cut out the middlemen and perform photosynthesis only for themselves, absorbing chloroplasts from algae and covering the walls of their digestive tract with them. After this, the animal-plant hybrid can live for months, feeding only on sunlight. But how exactly the slugs support their stolen solar factories remained a mystery until now.

Now Pirsa and the study's other co-authors have found the answer to that question. It seems that slugs not only steal chloroplasts from algae, but also steal important DNA codes. An article published in The Biological Bulletin suggests that a gene that encodes an enzyme used to repair chloroplasts may help keep slugs running their solar machines long after they eat algae.

In nature, genetic expropriation may be a rare phenomenon, but scientists have been experimenting with it in laboratories for many years. By transferring genes from one organism to another, humans have created many new forms of life, from corn that produces its own pesticides to plants that glow in the dark. Given all this, is it so crazy to think that we should follow nature's example and give animals - or even humans - the ability to photosynthesize?

Biologist, designer and author Christina Agapakis, who received her PhD in synthetic biology from Harvard, has spent a lot of time thinking about how to create a new symbiosis in which animal cells would be able to photosynthesize. Billions of years ago, plant ancestors absorbed chloroplasts, which were free-living bacteria, Agapakis said.

The problem with creating a sun-eating organism, Agapakis said, is that it requires a very large surface area to absorb enough sunlight. With the help of leaves, plants manage to absorb a huge amount of energy relative to their size. Fleshy people, with their surface to volume ratio, most likely do not have the necessary carrying capacity.

“If you're wondering whether you can gain the ability to photosynthesize, the answer is that firstly, you would have to stop moving completely, and secondly, become completely transparent,” says Agapakis, who estimates that every human cell would need thousands of algae to carry out photosynthesis. .

In fact, the sunlight-feeding Elysia chlorotica may be the exception that proves the rule. The slug began to look and behave so much like a leaf that in many ways it became more of a plant than an animal.

But even if a person can't survive on the sun alone, who says he can't supplement his diet with a little sunny snack from time to time? In fact, most photosynthetic animals, including several relatives of Elysia chlorotica, rely on more than just energy from the sun. They use their photosynthetic machinery as a backup generator in case of food shortage. Thus, the ability to photosynthesize is insurance against starvation.

Perhaps humans could find a completely new use for photosynthesis. For example, says Agapakis, “there might be green spots on human skin, a wound-healing system activated by sunlight. Something that doesn’t require the amount of energy that a person needs.”

In the near future, a person will not be able to completely switch to providing sunlight alone - at least until he decides to radically modify the body - so for now we can only continue to be inspired by the example of nature.

Scientists have discovered animals capable of independently absorbing solar energy. At least that's what it says in a journal published by the reputable Nature Publishing Group. This amazing animal turned out to be the common aphid. The outwardly unsightly insect has been regularly providing biologists with scientific sensations lately. What are its unique abilities and whether there really are animals that do not need to find food, Lenta.ru tried to find out.

Generally speaking, a self-photosynthesizing multicellular animal is a sensation. Moreover, it is a sensation of the kind that causes biologists to react “this cannot be, because this can never happen.” However, the article about the amazing aphid was published in a peer-reviewed journal, which means it contains no obvious errors. On the other hand, she did not appear in the very Nature, and in her “little brother”, a young magazine Scientific Reports. Before understanding what the essence of the work is and how fair it is to call it a sensation, it is necessary to understand what the study of the inconspicuous aphid has provided for modern biology.

It's hard to believe, but biologists quite seriously call the bean aphid a superorganism. This term is largely artificial and in the case of many animals it looks far-fetched. They are called “organisms consisting of many organisms” and usually mean colonial insects. Aphids, however, are by no means colonial insects, but they are certainly a superorganism.

This modest insect feeds on plant sap, sucking it directly from the vessels that transport sugar from the leaves to the roots. It’s good that aphids work closely with ants. The latter provide her with protection from enemies in exchange for drops of sugar syrup. Aphids do not mind the sweet tribute for ants - they still cannot absorb the amount of sugar contained in plant sap.

This is one of the paradoxes of aphid nutrition - despite the fact that the animals consume much more sugar than they can absorb, in a sense they are constantly starving. The fact is that plant juice contains almost nothing except sugar, and insects live in conditions of constant lack of amino acids, fats, vitamins and microelements. Even when there are no ants nearby, the aphid still secretes a sweet solution, having previously filtered substances useful to it from it.

Soon after the discovery of symbiotic buchneria in aphids, entomologists found their neighbors. They turned out to be bacteria Serratia symbiotica, which settled in aphids significantly later than Bukhneria and have not yet lost the ability to live outside the host. In some aphids, however, the cooperation of aphids, buchneria and serratia has already greatly advanced - it turned out that some amino acids of serratia help synthesize some amino acids in pampered buchneria, which have lost this ability.

The third tenant of the aphid superorganism turned out to be protective bacteria. Scientists have found that Hamiltonella defensa helps aphids in the fight against parasites. These wasps are, along with ladybugs, one of the main enemies of aphids. Riders lay eggs in their bodies. The ichneumon ichneumon larva, when hatching from the egg, eats the aphids from the inside and uses their mummified body as a cocoon. At one time, this cruelty of the riders made such a strong impression on Charles Darwin that he put forward their existence as one of the arguments against the existence of an all-good God.

The last of the currently known tenants of aphids were bacteria that help synthesize bright pigments. It turned out that the bright green color of aphids is determined by intracellular bacteria Ricketsiella, which help aphids synthesize their specific polycyclic dyes - athens. It is difficult to say why insects need it, but it is known that color plays an important role in the interaction of insects with predators. Of the individuals of the same species, parasites, for example, prefer green aphids, and ladybugs prefer red aphids.

Speaking about animals with an unusual way of feeding, one cannot fail to mention the unique mollusk Elysia chlorotica who have mastered “green technologies”. In the early stages of its development, it looks and behaves like an ordinary sea slug - it feeds on algae and has a brownish color. However, unlike all other herbivorous animals, he, as economists would say, prefers a fishing rod to a fish. Simply put, the mollusk consumes photosynthetic chloroplasts from algae Vaucheria litorea, and keeps them alive inside its cells. Plants did the same at the dawn of their evolution, once absorbing blue-green algae. The difference is that chloroplasts enter the mollusk cells helpless - over millions of years of coevolution, they have delegated the synthesis of ninety percent of the necessary proteins to their owners. Therefore, the mollusk has to resort to tricks to preserve the fragile endosymbionts. He copied some genes responsible for photosynthesis directly from the genome Vaucheria, as a result of which it was able to maintain the life of chloroplasts for about nine months. This is how long its life cycle lasts.

The coloring of aphids is also not so simple. It is partly determined by athens, and partly by carotenoids. Rickettsiella are responsible for the synthesis of the former, as already mentioned, but the situation with carotenoids is even more interesting. The fact is that carotenoids are very common pigments, but not a single animal can synthesize them. Retinol, or vitamin A, is half a carotene molecule. As a pigment that directly perceives light, it is used in the eyes of absolutely all organisms - from single-celled organisms to humans. In addition, carotenoids play an important and still not fully understood role in interaction with reactive oxygen species. However, all animals must obtain carotenoids from their diet.

However, even the authors of the article themselves remain unclear - why do aphids independently synthesize carotenoids and why their bodies contain such amounts of these substances.
Two years later, French scientists know why - in their opinion, aphids use carotenoids to feed on solar energy.

It must be said right away that biologists call photosynthesis the fixation of carbon dioxide from the air and its conversion into organic substances using the energy of the sun. The use of light energy itself is called phototrophy, and the organisms in which it occurs are called photoheterotrophs. However, this phenomenon is so rare compared to photosynthesis that even the scientific editors of Nature News made an error in the headline.

It was phototrophy that was discussed in the latest article by French scientists. They found that insects that are raised at different ambient temperatures acquire different colors. This, according to the authors, occurs through epigenetic mechanisms - making changes not to the DNA itself, but to the way it is read. Be that as it may, those animals that were raised at 8 degrees Celsius turned green, and those that grew at 22 degrees turned orange. There was also a group of simply pale insects that lived in conditions of increased crowding and lack of resources. Green aphids contained the highest amount of carotenoids among all their fellows.

Elysia pusilla. Click to enlarge. Photo from blogs.ngm.com

So, it turned out that if an aphid, after being imprisoned in the dark, is brought into the light, the concentration of ATP in its body, the energy currency of every cell, increases significantly. Moreover, in green aphids, energy recharging occurs much faster than in orange ones. In pale insects, devoid of any pigments, it is clear that there was no difference in ATP reserves in the dark and in the light. In addition, the pigment was distributed directly under the surface of the insect's cuticle, where the penetration of sunlight is greatest.

It turns out that aphids have finally learned to extract the energy of the sun? Moreover, they have surpassed the specialists in this - plants, since they do without chloroplasts and chlorophyll at all, and use ordinary carotenoids for this, synthesized by seven genes stolen from fungi?

To be honest, this is very hard to believe. To the credit of the authors, they only propose the possibility of phototrophy as a hypothesis, and do not consider it proven. Every reader of the article in Scientific Reports Many questions immediately arise. Firstly, it is not clear how exactly the electronic excitation accumulated by carotene is transmitted. The authors believe that excited electrons are transferred to ATP synthase, but there is no evidence for this yet. Secondly, it is not clear which genes are involved in the process. Thirdly, it is not shown in which cells the ATP content increases - in those that contain carotenoids or not. Fourthly, it is not shown - do the observed changes occur in the cells of the aphid or inside its numerous, as we have seen, endosymbionts?

However, all these questions seem like ordinary quibbles after you remember the most important fact about the life of aphids - what they eat. One of the authors of that very article in Science, which showed horizontal transfer of genes for carotenoid synthesis, commented on the new work as follows: “Obtaining energy is the most minor problem in the life of an aphid. Its diet consists less than entirely of sugar, most of which it is unable to use.”
In light of this fact, the discovery of plant abilities in an insect looks very suspicious.

Photosynthetic bacteria (another name is phototrophic) are a type of autotrophic microorganisms capable of independently producing organic substances from inorganic substances. The pigments present in their cells absorb the energy of the Sun and use it for photosynthesis. This ability brings together photosynthetic bacteria, algae and higher plants. An alternative in the absence of light is chemosynthesis (from the Latin chemo - chemical) - obtaining energy from the oxidation of chemical compounds.

Currently, more than 50 species of photosynthetic microorganisms have been described. Their ability to photosynthesize was proven by the Dutch-American scientist Cornelis Bernardus van Niel in 1931. He also discovered one feature of photosynthesis in sulfur bacteria - that the donor of hydrogen atoms in them are sulfur compounds, in particular hydrogen sulfide. They proposed an equation for photosynthesis that combined higher plants and photosynthetic bacteria.

Autotrophic bacteria are often residents of water bodies. In the natural environment, single cells are rarely found - more often they form associations in the form of chains, stars, cells or plates, surrounded by protective mucus. Cell length ranges from 1-2 to 50 µm. They have different geometries - cocci, rods, convoluted ones are known; can be mobile or immobile, have outgrowths, villi or flagella. This structure allows them to demonstrate various types of oriented movement - photo-, chemo- and aerotaxis (movement in the direction of a light source, an increase or decrease in the concentration of chemicals or air in water). The largest are purple sulfur bacteria. They reproduce by simple (binary) fission or budding and do not stain with Gram (Gram-negative).

The structure of autotrophic bacteria has a number of features, most of which are associated with their ability to chemo- and photosynthesis. In particular, the membranes of photosynthetic forms form structures in cells called thylakoids, on the surface of which the photosynthetic apparatus is assembled. The structure of autotrophic bacteria has given biologists reason to believe that higher plants owe the presence of chloroplasts to symbiont bacteria.

An interesting feature of bacterial photosynthesis is that it does not always produce oxygen. Moreover, many photosynthetic bacteria are anaerobes and cannot live in the presence of oxygen, preferring to oxidize hydrogen sulfide, thiosulfates, molecular hydrogen, sulfur, which can then be converted into sulfates.

Bacterial photosynthesis does not always occur with the consumption of carbon dioxide. Instead, photosynthetic microorganisms can use other substances - sulfur compounds, for example.

There are photoautotrophic and photoheterotrophic bacteria. The former are able to live without organic substances, synthesizing everything they need on their own, while the latter do not have this ability and need organic matter for full growth.

Photosynthetic bacteria include oxygenic and anoxygenic microorganisms.

Oxygenic

As a result of photosynthesis, oxygen is released. These include cyanobacteria (including nitrogen-fixing bacteria), which contain chlorophyll A in their cells, just like photosynthetic plants. The assimilation of carbon dioxide in photosynthetic cyanobacteria, also called blue-green algae, occurs using hydrogen from water molecules.

Anoxygenic

These photosynthetic microorganisms carry out photosynthesis without releasing oxygen. They contain bacteriochlorophylls that differ from those used by plants for photosynthesis. This group includes two types of microorganisms:

Purple non-sulfur bacteria for which organic compounds act as hydrogen donors. Among them there are species that can live in environments in which there is no organic matter. However, the majority of them are considered obligate heterotrophs, that is, they require organic substances for their existence.
Purple and green sulfur bacteria that use hydrogen sulfide rather than water as a hydrogen supplier. The latter form colored layers of water and deposits on the stones of fresh and salt water bodies and accumulate sulfur in their cells.
Green sulfur bacteria and cyanobacteria are obligate phototrophs and cannot exist without light. Purple non-sulfur bacteria are facultative phototrophs and can exist for long periods of time without light or in low light conditions. Purple sulfur bacteria occupy an intermediate position.
Recently, filamentous green non-sulfur bacteria were discovered that are unable to deposit sulfur inside cells. They represent a homogeneous group of species that differ in their mode of nutrition (heteroautotrophic) and are able to live on organic substrates that contain hydrogen sulfide and molecular hydrogen. Among them there are many gram-positive and gram-variable species, the color of which depends on the conditions of their existence.

Photosynthesis and nitrogen fixation

Nitrogen fixation is a process that only prokaryotes, organisms that do not have formed and membrane-surrounded nuclei, could master. It occurs with the help of a special enzyme called nitrogenase. Nitrogen fixation is a type of chemosynthesis. It is interesting that nitrogen-fixing chemosynthetic bacteria, obligate anaerobes, can simultaneously have the ability to photosynthesize and vice versa, that is, they are chemo- and photosynthetic.

Many nitrogen-fixing bacteria are capable of photosynthesis. First of all, these are cyanobacteria. The structure of the cells of these microorganisms allows them to separate two phases in time - during the day they photosynthesize with the formation of oxygen, and at night they engage in nitrogen fixation. A study of the life cycle of the cyanobacterium anabena (anabena) demonstrated another mechanism that allows chemo- and photosynthesis to be combined in a bacterial colony. When the amount of carbon dioxide in the environment decreases, some cells stop photosynthesis and turn into heterocysts, within which nitrogen fixation begins. Interestingly, neighboring cells that have different metabolisms are able to exchange its products with each other, ensuring the existence of the entire colony.

Pigments

The color of photosynthetic bacterial colonies depends on what pigments are contained in their cells. There are three types of photosynthetic pigments - green chlorophylls, orange carotenoids and brown phycobilins, which are part of the so-called pigment antennas, the structure of which is species-specific and also depends on light intensity.

Bacteria that carry out anoxygenic photosynthesis have pigment centers of only one type; cyanobacteria and other oxygenic microorganisms have two centers connected in series. The reaction center of light-harvesting pigment antennas is chlorophyll A or bacteriochlorophylls A, B and G. Cyanobacteria, like higher plants, use the first pigments.

A characteristic feature of phycobilins is that they form complexes with specific proteins that penetrate membranes.

Autotrophs without chlorophyll

Such unusual autotrophs were discovered among archaebacteria from the Dead Sea. Their cells lack green chlorophylls - instead, so-called halobacteria contain bacteriorhodopsin located on the surface of cell membranes. Its structure is very interesting - it is a complex of retinal pigment and a special protein.

Photosynthetic halobacteria are heterotrophs that live in high-salt environments. Their colonies are orange-yellow in color due to the large amount of carotenoids they contain in their cells. Photosynthesis in these organisms begins only in conditions of low oxygen concentration. They cannot exist in low-salinity conditions and exhibit positive chemotaxis (movement) towards places with high salt content.