cyanobacteria(Cyanobacteria) is a type of bacteria that obtains the energy they need through photosynthesis. They are also sometimes called blue-green algae, referring to the appearance and ecological niche of these organisms, but now the term "algae" is usually limited to eukaryotic members of the group. Bench or traces of cyanobacteria (stromatolites) are believed to be up to 2.8 billion years old, although recent evidence casts doubt on this claim. Immediately after their emergence, they became the dominant group of photosynthetic organisms, producing oxygen, hydrocarbons and other organic compounds. It was thanks to these organisms that the qualitative composition of the Earth's atmosphere changed, in which oxygen gradually accumulated and carbon dioxide became less. Also, it was the representatives of this group that were captured as a result of endosymbiosis, becoming the chloroplasts of plants and other eukaryotes, allowing them to carry out photosynthesis. Cyanobacteria are the largest and most important group of living organisms on Earth in terms of their impact on the biosphere, accounting for 90% of the live mass of the entire biosphere.

life forms

Cyanobacteria include unicellular, colonial and filamentous forms. Some filamentous cyanophytes form differentiated nitrogen-fixing cells known as heterocysts and dormant cells or spores called akinetes. Each cell usually has thick, gelatinous cell walls that stain negatively for Gram. The average cell size is 2 µm. They are distinguished by the ability to adapt the composition of photosynthetic pigments to the spectral composition of light, so that their color varies from bright green to dark blue.

Traffic

Cyanobacteria do not have flagella, but some of them are able to move along surfaces using bacterial gliding. Many others also have the ability to move, but the mechanism of this phenomenon still has no explanation.

Environment and ecology

Most species are found in fresh water, while others live in the seas, in moist soil, or even on temporarily wet rocks in arid areas. Some enter into symbiotic relationships with lichens, plants, resists or sponges, and provide their symbiont with the products of photosynthesis. Some live in sloth furs, providing camouflage color. Cyanobacteria make up a significant proportion of oceanic phytoplankton. Capable of forming thick bacterial mats. Some species are toxic (the most studied toxin is microcystin, produced for example by the species Microcystis aeruginosa) or conditionally pathogenic (Anabaena sp.) The main participants in water blooming cause massive fish kills and poisoning of animals and people, for example, when water blooms in Ukrainian reservoirs. Cyanobacteria are a unique ecological group that combines the ability to produce oxygen photosynthetically and fix atmospheric nitrogen (in 2/3 of the studied species).

Physiology

Photosynthesis in cyanobacteria typically uses water as an electron donor and produces oxygen as a by-product, however some may also use hydrogen sulfide, as occurs among other photosynthetic bacteria. Carbon dioxide is reduced, creating carbohydrates through the Calvin cycle. In most forms, the photosynthetic organs are found in folds of the cell membrane called the thylakoids. A large amount of oxygen in the atmosphere was created by the actions of ancient cyanobacteria. Due to their ability to bind under aerobic conditions, they are often found as symbionts with a number of other groups of organisms such as fungi (lichens), corals, ferns (Azolla), flowering plants (Gunnera), etc. Cyanobacteria are the only group of organisms that can fix nitrogen and carbon under aerobic conditions, a fact that may be responsible for their evolutionary and ecological success.

Cyanobacteria possess a full-fledged photosynthetic apparatus, characteristic of the acid-seeing photosynthetics. The photosynthetic electron transport chain includes the photosystem (PS)-II b6f-cytochrome complex and PS-I. Ferredoxin serves as the final electron acceptor, water is the electron donor; it is split in the water oxidation system, similar to such a system of higher plants. Svitlazbiruchi complexes are represented by special pigments - phycobilins, collected (as in red algae) in phycobilisomes. When switched off, PS-II is capable of using exogenous electron donors other than water: reduced sulfur compounds, organic substances in the framework of cyclic electron transfer with the participation of PS-I. However, the efficiency of this way of photosynthesis is low, and it is used mainly to survive adverse conditions.

Cyanobacteria are distinguished by an extremely developed system of intracellular folds of the cytoplasmic membrane (CPM) - tildakoidiv; assumptions have been made about the possible existence of a system of thylakoids not associated with a membrane, which until recently was considered impossible in prokaryotes. The stored energy from photosynthesis is used in the dark processes of photosynthesis to produce organic matter from atmospheric CO2.

Most cyanobacteria are obligate phototrophs, which, however, are capable of a short existence due to the breakdown of glycogen accumulated in the light in the oxidative pentose phosphate cycle and in the process of glycolysis (the sufficiency of glycolysis alone to maintain vital activity is questioned). The tricarboxylic acid cycle (TCA) cannot be used for energy in the absence of α-ketoglutarate dehydrogenase. The "broken" TCA, in particular, leads to the fact that cyanobacteria are characterized by an increased level of export of metabolites to the environment.

Nitrogen fixation is provided by the enzyme nitrogenase, which is highly sensitive to molecular oxygen. Since oxygen is released during photosynthesis, two strategies have been implemented in the evolution of cyanobacteria: spatial and temporal separation of these processes. In unicellular cyanobacteria, the peak of photosynthetic activity is observed in the light, and the peak of nitrogenase activity is observed in the dark. The process is genetically regulated at the level of transcription; cyanobacteria are the only prokaryotes in which the existence of circadian rhythms has been proven (and the duration of the daily cycle can exceed the duration of the life cycle!) In filamentous cyanobacteria, the process of nitrogen fixation is localized in specialized terminal differentiated cells - heterocysts, which are distinguished by thick cell stunkas that prevent the penetration of oxygen. With a lack of bound nitrogen in the environment in the colony, there are 5-15% heterocysts. PS-II is reduced in heterocysts. Heterocysts obtain organic matter from photosynthetic members of the colony. The accumulated bound nitrogen accumulates in cyanophycin granules or is exported as glutamic acid.

Relationships in chloroplasts

Chloroplasts are found in eukaryotes (algae and higher plants), more likely to be reduced endosymbiotic cyanobacteria. This endosymbiotic theory is supported by structural and genetic similarities. Primary chloroplasts are found among green plants, where they contain chlorophyll b, and among red algae and glaucophytes, where ions contain phycobilins. It is now believed that these chloroplasts probably had a common origin. Other algae probably took their chloroplasts from these forms through secondary endosymbiosis or food.

Meaning

Cyanobacteria, according to the generally accepted version, were the "creators" of the modern oxygen-containing atmosphere on Earth (according to another theory, atmospheric oxygen has a geological origin), which led to the first global ecological catastrophe in natural history and a dramatic change in the biosphere. Now, being a significant component of oceanic plankton, cyanobacteria are at the beginning of most of the food chains and produce most of the oxygen (more than 90%, but not all researchers recognize this figure). The cyanobacterium Synechocystis became the first photosynthetic organism whose genome was completely decoded (in 1996, Kazusa Research Institute, Japan). Currently, cyanobacteria are the most important model objects of research in biology. In South America and China, bacteria of the genera Spirulina and Nostoc are used for food, drying and preparing flour, due to the lack of other types of food. They are credited with healing and healing properties, which, however, have not yet been confirmed. The possible use of cyanobacteria in the creation of closed life support cycles or as a mass feed / food additive is considered.
Certain cyanobacteria produce cyanotoxins, such as toxoid-a, toxoid-as, aplysiatoxin, domoic acid, microcystin LR, noduralin R (from Nodularia), or saxitoxin. At least one secondary metabolite, cyanovirin, has anti-HIV activity. See hypoliths for an example of cyanobacteria living in extreme environments.

Cyanobacteria include a large group of organisms that combine the prokaryotic structure of the cell with the ability to carry out photosynthesis, accompanied by the release of O 2, which is characteristic of different groups of algae and higher plants. The combination of traits inherent in organisms belonging to different kingdoms or even superkingdoms of living nature made cyanobacteria an object of struggle for belonging to lower plants (algae) or bacteria (prokaryotes).

The question of the position of cyanobacteria (blue-green algae) in the system of the living world has a long and controversial history. For a long time they were considered as one of the groups of lower plants, and therefore the taxonomy was carried out in accordance with the rules of the International Code of Botanical Nomenclature. And only in the 60s. XX century, when a clear distinction between prokaryotic and eukaryotic types of cellular organization was established and on the basis of this, K. van Niel and R. Steinier formulated the definition of bacteria as organisms with a prokaryotic cell structure, the question arose of revising the position of blue-green algae in the system living organisms.

The study of the cytology of blue-green algae cells using modern methods has led to the undeniable conclusion that these organisms are also typical prokaryotes. As a consequence of this, R. Steinier proposed to abandon the name "blue-green algae" and call these organisms "cyanobacteria" - a term that reflects their true biological nature. The reunification of cyanobacteria with the rest of the prokaryotes has forced researchers to revise the existing classification of these organisms and subordinate it to the rules of the International Code of Nomenclature for Bacteria.

For a long time, about 170 genera and more than 1000 species of blue-green algae have been described by algologists. Currently, work is underway to create a new taxonomy of cyanobacteria based on the study of pure cultures. More than 300 pure strains of cyanobacteria have already been obtained. For classification, constant morphological features, patterns of culture development, features of cellular ultrastructure, size and nucleotide characteristics of the genome, features of carbon and nitrogen metabolism, and a number of others were used.

Cyanobacteria are a morphologically diverse group of gram-negative eubacteria, including unicellular, colonial and multicellular forms. In the latter, the unit of structure is a thread (trichome, or filament). Threads are simple or branching. Simple filaments consist of a single row of cells (single-row trichomes) that have the same size, shape and structure, or cells that differ in these parameters. Branching trichomes arise as a result of various reasons, and therefore distinguish between false and true branching. The ability of trichome cells to divide in different planes leads to true branching, resulting in multi-row trichomes or single-row filaments with single-row lateral branches. False branching of trichomes is not associated with the peculiarities of cell division within the filament, but is the result of attachment or connection of different filaments at an angle to each other.

During the life cycle, some cyanobacteria form differentiated single cells or short filaments that serve for reproduction (baeocytes, hormogonia), survival under adverse conditions (spores, or akinetes), or nitrogen fixation under aerobic conditions (heterocysts). A more detailed description of the differentiated forms of cyanobacteria is given below when describing their taxonomy and the process of nitrogen fixation. A brief description of the akinetes is presented in Ch. 5. For different representatives of this group, the ability to slide is characteristic. It is characteristic of both filamentous forms (trichomes and/or hormogonia) and unicellular forms (baeocytes).

There are various ways of reproduction of cyanobacteria. Cell division occurs by equal binary division, accompanied by the formation of a transverse septum or constriction; unequal binary fission (budding); multiple division (see Fig. 20, A–D). Binary fission can occur only in one plane, which in unicellular forms leads to the formation of a chain of cells, and in filamentous forms to an elongation of a single-row trichome. Division in several planes leads in unicellular cyanobacteria to the formation of clusters of regular or irregular shape, and in filamentous bacteria, to the emergence of a multi-row trichome (if almost all vegetative cells of the filament are capable of such division) or a single-row trichome with lateral single-row branches (if the ability to divide in different planes reveal only individual cells of the thread). Reproduction of filamentous forms is also carried out with the help of fragments of trichomes, consisting of one or more cells, in some - also by hormogonia, which differ in a number of features from trichomes, and as a result of germination of akinetes in favorable conditions.

The work begun on the classification of cyanobacteria in accordance with the rules of the International Code of Nomenclature for Bacteria led to the identification of 5 main taxonomic groups in the rank of orders that differ in morphological characters (Table 27). To characterize the identified genera, data obtained from the study of cellular ultrastructure, genetic material, and physiological and biochemical properties are also used.

The Chroococcales order includes unicellular cyanobacteria that exist as single cells or form colonies (Fig. 80). Most representatives of this group are characterized by the formation of sheaths surrounding each cell and, in addition, holding groups of cells together, i.e., participating in the formation of colonies. Cyanobacteria, whose cells do not form sheaths, easily disintegrate to single cells. Reproduction is carried out by binary fission in one or more planes, as well as by budding.

Table 27. Main taxonomic groups of cyanobacteria

People most often intuitively understand the world that surrounds them. But there are also microscopic creatures on Earth that are not visible to the naked eye. In the process of studying them, questions arise: what are these bacteria and cyanobacteria? How are they different from viruses?

Let's remember the basics

Bacteria is a group of unicellular microorganisms that lack an enveloped cell nucleus. Bacteria come in different shapes. They are divided into types such as:

• cocci (spherical);
• bacilli (rod-shaped);
• spirochetes (spiral);
• convoluted: vibrios (in the form of a comma).

According to the methods of nutrition, heterotrophic and autotrophic organisms can be distinguished. The latter live off the inorganic substances that they produced themselves with the help of the energy of chemical reactions.

Other classifications can also be distinguished. For example, they are separated on the basis of staining or non-staining according to the Gram method. To do this, the bacteria are treated with special dyes, then it is checked whether they discolor after washing or not. If they do not discolor, then they are called gram-positive, otherwise - gram-negative. The first group includes most pathogenic bacteria. To the second - for example, cyanobacteria.

archaebacteria

Archaebacteria (or archaea, Archaebacteria) stand out separately. These are prokaryotes (they lack a nucleus). Archaebacteria and bacteria have some similarities. For example, they are brought together by similar size and shape of cells. However, despite the outward resemblance to bacteria, in some ways (part of the genes), archaebacteria are more reminiscent of eukaryotes. There are more than 40 types of archaebacteria.

Bacteria and viruses

In everyday life, these concepts are often not distinguished. Although in reality the difference is huge:

It is important to distinguish viruses from bacteria, if only because the diseases caused by the action of these organisms are treated differently. For example, antibiotics do not work for viral infections.

Cyanobacteria and their features

Cyanobacteria are a group of gram-negative bacteria capable of photosynthesis with the release of oxygen. In Latin, the name is written as Cyanobacteria. Cyanobacteria are blue-green algae.

According to modern science, cyanobacteria arose about 3 billion years ago. They are cells with multilayered walls, consisting of insoluble polysaccharides. These cells do not have nuclei or chloroplasts. There are both solitary and colonial forms.

Cyanobacteria are photoautotrophs, they are capable of synthesizing carbohydrates. Like green plants, they can break down water molecules using light energy. In the process, hydrogen and free oxygen are formed. In addition, a sufficiently large number of cyanobacteria are able to fix atmospheric nitrogen, which is subsequently consumed by animals and plants, that is, they are capable of chemosynthesis.

The color of cyanobacteria is determined by the pigments in the cells:

• chlorophyll - green;
• phycocyanin - blue;
• phycoerythrin - red;
• carotenoids are yellow.

The color can vary from blue-green to brownish.

The main difference from bacteria is photosynthesis with the release of oxygen.

Reproduction and sporulation

In most cases, cyanobacteria reproduce by simple cell division. The life cycle of unicellular forms under favorable conditions is about 6-12 hours.

If adverse environmental conditions occur, some types of cyanobacteria can form spores. At the same time, the amount of water in the cell decreases, the shell becomes thicker. Spores can stay in unfavorable conditions for a long time and without water due to reserve substances. When favorable conditions occur, a dormant cell emerges from the spore.

habitats

Most often, cyanobacteria can be found in water bodies rich in organic matter. Some species also live in highly saline lakes. They are also found on the soil, as participants in symbioses (for example, in lichens)

Notable Representatives

• Oscillatoria. Lives in fresh water.
• Nostoc. The colonial form also lives in fresh water. In China and Japan it is eaten.

1

Differences from bacteria

Unable to absorb organic
exogenous compounds
The presence of two photosystems located on
membranes of specialized structures -
thylakoids.
The possibility of two
mutually exclusive processes - oxygen
photosynthesis and anaerobic nitrogen fixation
Absence of flagella or flagellar stages.
2

Morphologically, they are represented by the following forms:

Unicellular. Separate
cells function like
independent organisms.
Colonial. individual cells
united in colonies in which
binding material is
slime.
Unicellular and
colonial
forms have
coccoid type
organizations for
whom
characteristic
motionless,
dressed
shells
cells.
3

single cells
Synechocystis
(Chroococcales)
Microcystis colonies
(Chroococcales)
4

Multicellular.
They have a filamentous type of organization.
The morphological unit of these cyanides
is a trichome - a filamentous formation,
consisting of several rows of symplasts
(via plasmodesmata -
microscopic plasma bridges)
connected cells. Trichomes can be
branched and unbranched.
5

Trichomes in multicellular forms

Forked, for example,
Fischielopsis (Stigonematales)
Unbranched, for example,
Anaebena (Nostocales)
6

Types of trichomes by cell differentiation

Homocytic - all
cells are the same
form and function
heterocytic - cells
different in shape and
functions
7

Cells of heterocytic trichomes

Vegetative (same as in homocytic
trichomes)
Akinetes (resting spores) - required
for breeding
Heterocysts - responsible for fixation
atmospheric nitrogen.
top cells. Only in morphological
progressive forms. Growth is at their expense
most difficult to differentiate
thalli.
8

cell wall

From 35 to 50 nm. The thickest in akineta and
heterocyst. Similar in structure to that of
gram-negative bacteria.
Murein is a specific peptidoglycan. At
some species have calcium deposits. At
many - mucous membranes and covers.
9

10. Murein

10

11. Spare substances

Glycogen-like polysaccharide
Cyanophycin is a nitrogen-containing polypeptide.
Found only in blue-green algae
11

12. Cyanobacteria do not have:

Complete chloroplasts
Mitochondria
Nuclei
12

13. Pigments

Chlorophyll a (in prochlorophyll algae
chlorophyll b is found.
carotenoids (beta-carotene and zeaxanthin,
specific carotenoids -
mixoxanthophyll, oscillaxanthin,
caxanthin and echinenone).
Phycobilins (not found in prochlorophyll
algae): phycocyanin, allophycocyanin and
phycoerythrin. Works only in conjunction with
proteins.
Scytomin (not everyone) - absorbs into
ultraviolet part of the spectrum (212 - 300 nm).
13

14. Reproduction

Cell division.
With the help of gonidia (endospores - if inside
mother cell, exospores (baeocytes) - if
outside).
Filamentous - with the help of hormogonia. Usually the decay is
by heterocysts (heterocysts themselves are not capable of
reproduction!)
Akinetami - disputes.
There is no typical sexual reproduction. There is
parasexual processes in which there is an exchange
genomes in different cells.
14

15. Chroococcal order (Chroococcales)

15

16.

16

17.

17

18. Pleurocapsal order (Pleurocapsales)

18

19. Order Oscilatorium (Oscillaroriales)

19

20. Nostocales order

20

21. Nostoc paludosum

21

22. Nodularia spumigena

22

23.

23

24. Order Stigonematales

24

25. The value of blue-green algae in nature and in human life:

The appearance of oxygen and the ozone layer.
Played a role in the creation of rocks and
soil formation.
They are components of the lichen thallus.
primary producers.
"Water Bloom"
Grown as a source of

They are used as test objects.
Application for farmland fertilizer as
25
source of nitrogen.

26. Habitats of blue-green algae

fresh water
Seas
soil, rocks
Symbionts of some flagellates,
roots, etc.
26

27.

Blooming microcystis
Cyanobacterial mat (synechocystis)
Sectional view of cyanobacterial mat
27

28. EUGLEN ALGAE - EUGLENOPHYTA

Pigments:
Chlorophylls "a" and "b"
carotenoids
Spare material:
paramylon
Many euglena chloroplasts
No
About 1000 species.
Most are monadic, there are both coccoid and
amoeboid.

29.

The body is covered with a pellicle - an elastic protein
protoplast layer under the plasmalemma - this allows
make crawling movements

30. cell structure of euglenoids

31. Euglena

32. Phacus

33. Trachelomonas

34. SIGNIFICANCE OF EUGLENIC ALGAE

Participate in the process of self-purification of water
Water pollution indicators
Objects for the study of photosynthesis, structures
chromatophores, phototaxis, movement of flagella
They study the effect of antibiotics, herbicides,
growth substances
They are used to quantify
vitamin B12

35. Green Algae (Chlorophyta)

35

36. Types of organization of green algae thallus

Monadic
palmelloid
cocoid
filamentous
Multifilamentous (heterotrichal)
Parenchymal
Pseunoparenchymal
Siphon. Mostly green, some yellow-green
Charophytic.
Siphonocladal. Only the green
Sarcinoid.
!!! The rhizopoidal organization of the thallus in green algae is not
discovered!!!
36

37. Features of the structure

The cell membrane is rigid, most often cellulose. It happens and
peptidoglycan; spropropellic (product of degradation
carotenoids, in higher plants - is part of the shell
pollen).
The reserve product, starch, is deposited inside the chloroplast (around
pyrenoid and in the stroma). However, not all. Dasikladovy - inulin. At
some (for example, representatives of the genus Dunaliella - lipids).
There is usually only one chloroplast. located in the center of the cell. But there is
exceptions both in number and location of chloroplasts in
cell. Chloroplasts are green.
Stigma (light-sensitive eye) is located inside the chloroplast and is not
associated with the flagellar apparatus.
Most species have a large intracellular vacuole with
cell sap.
Motile species have flagella, their number varies.
37

38. Photosynthetic pigments

Chlorophyll a
Chlorophyll b
carotenoids (alpha and beta carotene,
lutein, neoxanthin, zeaxanthin and others)
38

39. Reproduction

Asexual (cell division in two,
immobile aplanospores,
mobile zoospores).
Vegetative (rupture of threads).
Sexual (isogamy, heterogamy, oogamy)
most often, conjugation).
Life cycles: zygotic reduction,
sporic reduction (with heteromorphic
generation change).
39

40. What is the difference between subdivisions of Chlorophyta?

Features of the flagellar apparatus.
features of mitosis.
features of cytokinesis.
metabolic features.
40

41.

41

42. Subdivision Chlorophytina

Prasinophyte class (Prasinophyceae)
Class proper green algae
(Chlorophyceae)
Class trebouxiaceae (Trebouxiphyceae)
Ulva class (Ulvophyceae)
42

43. Class Prasinophytes (Prasinophyceae)

Free-living inhabitants of the seas and
freshwater reservoirs
Tetraselmis sp.
The class includes forms: monadic,
rarely palmellodes and coccoides
forms
43

44. Class proper green algae (Chlorophyceae)

Types of organization of thalli: monadic,
palmelloid, coccoid, filamentous,
heterotrichial.
During mitosis, the telophase body is not preserved, the filaments
spindles always shorten in anaphase.
Cell division always occurs with a furrow
or the formation of a plate with the participation
phycoplast (plates of microtubules). because of
the presence of such a structure, it is assumed that
this class is a dead end branch of evolution.
Life cycles haploid with zygotic
44
reduction.

45. Order Volvox (Volvocales)

Unicellular, colonial and coenobial monadic forms.
Under unfavorable conditions - palmelloid state.
45
Reproduction: vegetative, asexual, sexual - isogamy (less often hetero- and oogam

46.

Dunaliella salina
46

47.

Haematococcus pluvialis
Chlamydomonas reinhardtii
47

48. Chlorococcal order (Chlorococcales)

Coccoid forms as unicellular,
as well as colonial.
Chloroccocum acidum
Asexual reproduction - flagellated
zoospores and autospores. sexual process
isogamous, oogamous and heterogamous.
Hydrodiction sp.
48

49.

Scenedesmus quadricauda
Pediastrum
49

50. Oedogoniales order

Filamentous type of organization of the thallus.
The threads are often branching.
asexual reproduction -
zoospores. The sexual process is oogamous.
50

51. Chaetophorales order

Miscellaneous thalli
Fritschiella tuberosa
Iso-, hetero- and oogamy
51

52.

52

53. Class trebouxiaceae (Trebouxiphyceae)

Eremosphaera viridis
Coccoid, filamentous and lamellar.
Asexual reproduction - autospores, cell division
. The sexual process is oogamous.
Prasiola stiputata
53

54. Class ulvae (Ulvophyceae) Order ulotrix (Ulothricales)

.
Ulva class (Ulvophyceae)
Order ulotrix
(ulothricales)
Thallus coccoid, filamentous, lamellar.
Asexual reproduction is by autospores, the sexual process is isogamous.
54

55. Order Ulvae (Ulvales)

Thallus lamellar or tubular
Asexual reproduction - by zoospores, vegetative - by sections of the thallus.
The sexual process is isogamous and heterogamous.
55

56. Bryopsidal order (Bryopsidales)

Caulerpa
Bryopsis
Siphon thallus.
No radial symmetry.
Asexual reproduction is almost non-existent.
The sexual process is heterogamous, less often isogamous.
Codium
56

57. Order Dasicladales (Dasicladales)

The sexual process is isogamous.
Siphon thallus.
with radial symmetry.
57

58. Siphonocladal order (Siphonocladales)

Thallus siphonocladal
Cladophora
Asexual reproduction - zoospores
The sexual process is heterogamous.
58

59. Subdivision Charophytina

Class Trentepoliaceae (Trentepohliophyceae)
Klebsormidia class (Klebsormidiophyceae)
Conjugate or coupler class
(Zygnematophyceae, Conjugatophyceae)
Class Characeae (Charophyceae)
59

60. Class Trentepoliaceae (Trentepohliophyceae)

Thallus heterotrichous, but reduced
Asexual reproduction is by zoospores.
Vegetative - the main one.
60

61. Class Klebsormidia (Klebsormidiophyceae) Order Klebsormidia

Cocoid, sarcinoid and filamentous thalli.
Asexual reproduction - zoospores.
Vegetative.
61

62. Coleochaetal order (Coleochaetales)

Filamentous thallus.
Asexual reproduction - zoospores
The sexual process is oogamous.
62

63. Class of conjugates or couplings (Zygnematophyceae, Conjugatophyceae) Zygnematales order

Unicellular and filamentous forms.
Vegetative.
The sexual process is conjugation.
63

64. Desmidial order (Desmidiales)

Vegetative.
Unicellular and filamentous forms.
Cosmarium
The sexual process is conjugation.
Straurastum
64

65. Charophyceae class

The thallus is heterotrichial, complicated.
Vegetative with the help of nodules, the sexual process is complicated.
65

66. The value of green algae in nature and human life

primary producers. The basis of food
chains.
oxygen producers.
Test objects.
Cultivated for
biologically active substances.
serve as food for humans and
farm animals.
66

67. Habitats

Seas
fresh water
On trees, buildings.
The soil

Viruses, bacteria, cyanobacteria

Viruses in modern biology are considered as one of the five kingdoms of wildlife. They were discovered in 1892 by the Russian scientist D.I. Ivanovsky. The term was proposed by M. Beijerink in 1899. Viruses are non-cellular forms of life, occupying an intermediate position between living and non-living matter. They are made up of DNA (or RNA) and protein and are not capable of protein synthesis on their own. They exhibit the properties of living organisms only when they are in the cells of pro- or eukaryotes and use their metabolism for their own reproduction.

The sizes of viruses are from 15 to 2,000 nm. The core contains the genetic material (DNA or RNA). By structure and size, viruses are divided into simple (adenoviruses) and complex (smallpox, herpes, influenza). There are actually viruses and bacteriophages - bacterial viruses (described in 1917 by F. D "Erelle). Lytic and latent viruses are found by their effect on host cells. Outside, the virus is covered with a protein coat - a capsid that performs protective, enzymatic and antigenic functions. Viruses are more complex structure may additionally include carbohydrate and lipid fragments.

The virus genome enters the bacterium as a result of specific (or nonspecific) absorption of the bacteriophage on the host cell. The viral nucleic acid is “injected” into the cell, while the protein remains on the cell wall.

DNA-containing viruses (smallpox, herpes) use the metabolism of the host cell to synthesize their mRNA and proteins. RNA-containing viruses (AIDS, influenza) either initiate the synthesis of the RNA of the virus and its protein, or, thanks to enzymes - reverse transcriptase or reverse transcriptase, synthesize DNA first, and then the RNA and protein of the virus. Thus, the virus genome, integrating into the hereditary apparatus of the host cell, changes it and directs the synthesis of viral components. The newly synthesized viral particles leave the host cell and invade other (neighboring) cells.

Protecting themselves from viruses, cells produce a protective protein - interferon, which inhibits the synthesis of new viral particles. Interferon is used to treat and prevent certain viral diseases. The human body resists the action of viruses by producing antibodies. However, for some viruses, such as oncogenic or the AIDS virus, there are no specific antibodies. This circumstance complicates the development of vaccines.

Bacteria are the most ancient prokaryotic cellular organisms, the most widespread in nature. They play an important role as decomposers of organic matter, nitrogen fixers, and are causative agents of diseases in animals and humans. In medicine, bacteria are used to produce antibiotics (streptomycin, tetracycline, gramicidin), in the food industry - to produce lactic acid products, alcohols. Bacteria are also objects of genetic engineering.

The bacterial cell is covered with a murein membrane. Some types of bacteria form a mucous capsule that prevents the cell from drying out. The cell wall can form outgrowths - pili, which contribute to the association of bacteria into groups, as well as their conjugation. The bacterial membrane is folded. Enzymes or photosynthetic pigments (in photoautotrophic bacteria) are localized on the folds. The role of membrane organelles is performed by mesosomes - large invaginations of membranes. The cytoplasm contains ribosomes and inclusions (starch, glycogen, fats). Some bacteria have flagella. The hereditary material of bacteria is contained in the nucleoid in the form of a circular DNA molecule.

According to the shape of a bacterial cell, they are distinguished:

Cocci (spherical): diplococci, streptococci, staphylococci;

Bacilli (rod-shaped): solitary, chained, bacilli with endospores;

Spirilla;

Vibrios;

Spirochetes.

According to the way they use oxygen, bacteria are aerobic and anaerobic.

Bacteria reproduce by cell division without spindle formation. The sexual process in some of them is associated with the exchange of genetic material during conjugation. Bacteria are spread by spores.

Pathogenic bacteria: vibrio cholerae, diphtheria bacillus, dysentery bacillus, etc.

Cyanobacteria (incorrectly referred to as blue-green algae) arose over 3 billion years ago. They are cells with multilayered walls, consisting of insoluble polysaccharides. There are their unicellular and colonial forms. Cyanobacteria are structurally similar to bacteria. They are photoautotrophs. Chlorophyll is located on free-lying membranes in the cytoplasm. Cyanobacteria reproduce by dividing or breaking up colonies; have the ability to spore formation; widely distributed in the biosphere; able to purify water by decomposing decay products; enter into symbiosis with fungi, forming some types of lichens; are the first settlers on volcanic islands and rocks.