Metabolism (metabolism) of bacteria is aggregate two interconnected opposing processes of catabolism and anabolism.
Catabolism (dissimilation) - decay of substances in the process of enzymatic reactions and the accumulation of the energy released during this in ATP molecules.
Anabolism (assimilation) - synthesis of substances with energy consumption.
Features of metabolism in bacteria are that:
Its intensity has enough high level, which is possibly due to a much larger ratio of surface to unit mass than that of multicellular organisms;
Processes dissimilation prevail over processes assimilation;
substrate spectrum the substances consumed by bacteria are very wide - from carbon dioxide, nitrogen, nitrites, nitrates to organic compounds, including anthropogenic substances - environmental pollutants (thereby ensuring its self-purification processes);
Bacteria have very a wide range of different enzymes- it also contributes to the high intensity of metabolic processes and the breadth of the substrate spectrum.
Bacterial enzymes by localization are divided into 2 groups:
exozymes- bacterial enzymes released into the external environment and acting on the substrate outside the cell (for example, proteases, polysaccharides, oligosaccharidases);
endozymes- bacterial enzymes acting on substrates inside the cell (for example, enzymes that break down amino acids, monosaccharides, synthetases).
Enzyme synthesis genetically determined, but regulation their synthesis is through direct and feedback, that is, for some it is repressed, and for others it is induced by the substrate. Enzymes, the synthesis of which depends on the availability of an appropriate substrate in the environment (for example, beta-galactosidase, beta-lactamase) are called inducible .
Another group of enzymes whose synthesis does not depend on the presence of a substrate in an environment called constitutive (for example, glycolysis enzymes). Their synthesis always takes place, and they are always contained in microbial cells in certain concentrations.
Study the metabolism of bacteria using physicochemical and biochemical methods research in the process of culturing bacteria under certain conditions on special nutrient media containing one or another compound as a substrate for transformation. This approach makes it possible to judge the metabolism by a more detailed study of the processes of various types of metabolism (proteins, carbohydrates) in microorganisms.
Protein metabolism in bacteria - this, on the one hand, - the process of synthesis of own amino acids and proteins by assimilating the necessary components from the external environment, and on the other, - extracellular protein breakdown under the influence of various enzymes. If protein breakdown occurs under anaerobic conditions, then this process is called putrefaction and if it goes in aerobic conditions - smoldering.
In the presence of proteases in bacteria, proteins are cleaved by them to intermediate decay products - peptones, and in the presence of peptidases in bacteria, peptones are cleaved by them to amino acids and their decay products (ammonia, hydrogen sulfide, indole). Proteolytic(the ability to break down proteins) and peptolytic(the ability to break down peptones) properties are not expressed in all bacteria, therefore, their study in conjunction with other enzymatic properties helps to identify bacteria.
Carbohydrate metabolism in bacteria it is also twofold - it is the process of synthesis and breakdown of carbohydrates... Breakdown of carbohydrates by bacteria (saccharolytic properties) under aerobic conditions with the formation of carbon dioxide and water is called burning , a split by them carbohydrates under anaerobic conditions - fermentation.
Depending on the nature of the end products of the decomposition of carbohydrates in anaerobic conditions, fermentation is distinguished:
Alcohol,
Lactic acid,
Propionic acid,
Formic acid,
Butyric acid,
Acetic acid.
Molecular oxygen does not participate in fermentation processes. Most fermenting bacteria are obligate anaerobes... However, some of them are - facultative anaerobes, are able to carry out the fermentation process in the presence of oxygen, but without its participation. Moreover, this oxygen inhibits the fermentation process. And it is replaced by combustion (breathing - the ultimate acceptor of hydrogen - oxygen). This effect was named the Pasteur effect and is one of classic examples of the change in metabolism in bacteria depending on environmental conditions.
Synthesis of biopolymers a bacterial cell requires energy. It is formed during biological oxidation and is stocked in the form macroerg molecules- ATP and ADP.
Respiratory organelles in most bacteria are derivatives of the cytoplasmic membrane - mesosomes , on which special respiratory enzymes are localized such as cytochrome oxidase. Biooxidation type is one of the key features to differentiate between different microorganisms. On this basis there are three groups of bacteria:
The first group - obligate aerobes , which are able to receive energy only through breathing and need molecular oxygen as the final electron acceptor. For them, as a type of redox processes, oxidation is characteristic, in which oxygen is the final acceptor of electrons.
The second group - obligate anaerobes - bacteria, able to grow only in an oxygen-deprived environment... For them, as a type of redox processes, fermentation is characteristic, in which there is a transfer of electrons from the donor substrate to the acceptor substrate.
The third group - facultative anaerobes - bacteria, able to grow in the presence and absence of oxygen, and use both molecular oxygen and organic compounds as terminal electron acceptors.
Among them there may be facultative anaerobic bacteria capable of switching from oxidation to fermentation (enterobacteria), and aerotolerant facultative anaerobic bacteria, which can grow in the presence of atmospheric oxygen, but do not use it, but receive energy exclusively through fermentation (for example, lactic acid bacteria).
For microbiological diagnostics, the study of microorganisms and in biotechnological purposes microorganisms are cultivated on artificial X nutrient media.
Under bacterial growth understand an increase in the mass of cells without changing their number in the population as a result of the coordinated reproduction of all cellular components and structures.
Increase in the number of cells in the population microorganisms are designated by the term "Reproduction" ... It is characterized by the generation time (the time interval during which the number of cells doubles) and by such a concept as the concentration of bacteria (the number of cells in 1 ml).
Unlike the mitotic division cycle in eukaryotes, the reproduction of most prokaryotes (bacteria) follows the path binary fission, a actinomycetes - by budding... Moreover, all prokaryotes exist in haploid state, since the DNA molecule is presented in the cell in the singular.
When studying the process of reproduction of bacteria, it must be borne in mind that bacteria always exist in the form of more or less numerous populations, and the development of a bacterial population in a liquid nutrient medium in a batch culture can be considered as a closed system. In this process, 4 phases are distinguished.:
1st - initial, or lag phase , or the phase of delayed reproduction, it is characterized by the onset intensive cell growth, but the rate of their division remains low;
2nd - logarithmic, or log phase , or exponential phase, it is characterized by a constant maximum rate of cell division and a significant increase in the number of cells in the population;
3rd - stationary phase , it occurs when the number of cells in the population ceases to increase. This is due to what comes balance between the number of newly formed and dying cells... The number of living bacterial cells in the population per unit volume of the nutrient medium in the stationary phase is denoted as M-concentration ... This indicator is characteristic for each type of bacteria;
4th - withering phase (logarithmic death), which is characterized by a predominance in the population of the number of dead cells and progressive a decrease in the number of viable cells in the population.
The cessation of growth in the number (reproduction) of the population of microorganisms occurs in connection with depletion of the nutrient medium and / or accumulation in it metabolic products microbial cells. Therefore, by removing metabolic products and / or replacing the nutrient medium, regulating the transition of the microbial population from the stationary phase to the phase of withering away, it is possible to create an open biological system striving to eliminate the dynamic equilibrium at a certain level of population development. This process of growing microorganisms is called flow-through cultivation(continuous culture). Growth in continuous culture makes it possible to obtain large masses of bacteria during flow-through cultivation in special devices (chemostats and turbidistats) and is used in the production of vaccines, as well as in biotechnology to obtain various biologically active substances produced by microorganisms.
To study metabolic processes throughout the cycle of cell division, it is also possible to use synchronous cultures. Synchronous cultures - cultures of bacteria, all members of the population of which are in the same phase of the cycle. This is achieved using special cultivation methods, however, after several simultaneous divisions, the synchronized cell suspension gradually switches back to asynchronous division, so that the number of cells subsequently increases not step by step, but continuously.
When cultured on solid nutrient media, bacteria form colonies ... This is an accumulation of bacteria of the same species visible to the naked eye, which is most often the offspring of one cell. Colonies of bacteria of different species differ:
The value
Transparency,
Height,
The nature of the surface
Consistency.
The nature of the colonies is one of taxonomic traits of bacteria.
The most important feature of living organisms are variability and heredity... The basis of the hereditary apparatus of bacteria, like all other organisms, is DNA (in RNA viruses - RNA ).
Along with this, the hereditary apparatus of bacteria and the possibilities of studying it have a number of peculiarities. First of all, bacteria - haploid organisms i.e. they have one chromosome... In this regard, with the inheritance of traits, there is no phenomenon dominance... Bacteria have a high reproduction rate, and therefore several tens of generations of bacteria are replaced in a short period of time (day). This makes it possible to study huge populations and it is quite easy to detect even rare mutations in frequency.
Hereditary apparatus bacteria is represented chromosome... Bacteria have only one. If there are cells with two or four chromosomes, then they are the same. Bacterial chromosome - it DNA molecule... The length of this molecule reaches 1.0 mm and, in order to "fit" in a bacterial cell, it is not linear, as in eukaryotes, but supercoiled into loops and rolled into a ring. This ring is attached at one point to the cytoplasmic membrane.
On the bacterial chromosome, there are separate genes... Escherichia coli, for example, have more than 2 thousand of them. but genotype (genome) bacteria is represented not only by chromosomal genes. The functional units of the bacterial genome, in addition to chromosomal genes, are IS sequences, transposons and plasmids.
IS sequences - short fragments of DNA. They do not carry structural (coding for a particular protein) genes, but contain only genes responsible for transposition(the ability of IS-sequences to move along the chromosome and integrate into its various parts). The IS sequences are the same in different bacteria.
Transposons ... These are DNA molecules - larger than IS sequences. In addition to the genes responsible for transposition, they contain a structural gene encoding this or that feature. Transposons move easily along the chromosome. Their situation affects expression both their own structural genes and neighboring chromosomal genes. Transposons can also exist outside the chromosome, autonomously, but are not capable of autonomous replication.
Plasmids - it circular supercoiled DNA molecules... Their molecular weight varies widely and can be hundreds of times greater than that of transposons. Plasmids contain structural genes that endow the bacterial cell with different, very important properties for her:
R-plasmids - drug resistance,
Col-plasmids - to synthesize colicins,
F-plasmids - to transfer genetic information,
Hly plasmid - to synthesize hemolysin,
Tox plasmid - to synthesize a toxin,
Plasmids of biodegradation - to destroy one or another substrate and others.
Plasmids can be integrated into the chromosome(unlike IS sequences and transposons, to strictly defined areas), and there may be offline... In this case, they have the ability to autonomously replicate, and that is why there can be 2, 4, 8 copies of such a plasmid in a cell.
Many plasmids contain genes transmissibility and are able to be transmitted from one cell to another during conjugation (exchange of genetic information). Such plasmids are called transmissible.
The presence of an F-plasmid ( fertility factor, sex factor ) gives bacteria the function of a donor, and such cells are able to transfer their genetic information to others, F-cells... In this way, the presence of an F-plasmid is a genetic expression of sex in bacteria... Not only donor function is associated with the F-plasmid, but also some other phenotypic traits. This is, first of all, the presence of F-saws ( genital cilia), with the help of which contact is established between donor and recipient cells. Through their channel donor DNA is transferred during recombination. On the genital cilia, receptors for male fi-phages are located. F cells lack these receptors and are insensitive to such phages.
Thus, the presence of F-cilia and sensitivity to fi-phages can be considered as phenotypic expression (manifestation) of sex in bacteria.
Bacteria distinguish two types of variability - phenotypic and genotypic.
Phenotypic variability – modifications- does not affect the genotype... Modifications affect most individuals in the population. They not inherited and they fade over time, that is, they return to the original phenotype after more (long-term modifications) or fewer (short-term modifications) number of generations.
Genotypic variability affects the genotype... It is based on mutations and recombinations.
Mutations bacteria do not fundamentally differ from mutations of eukaryotic cells. The peculiarities of mutations in bacteria are relative ease of identification, since it is possible to work with large populations of bacteria ... By origin, mutations can be:
spontaneous,
induced.
By length:
Spot,
Chromosomal mutations.
By focus:
Reverse mutations.
Recombinations in bacteria differ from recombinations in eukaryotes:
First, bacteria have multiple mechanisms recombinations (exchange of genetic material).
Secondly, during recombinations in bacteria, not a zygote is formed, as in eukaryotes, but merozygote (carries completely the genetic information of the recipient and part of the genetic information of the donor in the form of an addition).
Third, during recombinations in a bacterial recombinant cell not only the quality but also the amount of genetic information changes.
Transformation introduction of a ready-made DNA preparation into the recipient bacterial cell(specially prepared or directly isolated from the donor cell). Most often, the transfer of genetic information occurs when the recipient is cultivated on a nutrient medium containing the donor's DNA.
For the perception of donor DNA during transformation, the recipient cell must be in a certain physiological state ( competence), which is achieved by special methods of processing the bacterial population. During transformation, single (more often one) signs are transmitted. Transformation is the most objective evidence of the relationship of DNA or its fragments with one or another phenotypic trait, since a pure DNA preparation is introduced into the recipient cell.
Transduction Is the exchange of genetic information in bacteria by transmission her from donor to recipient with moderate(transducing)bacteriophages.
Transducing phages can carry one or more genes (traits). Transduction happens:
Specific (always the same gene is transferred),
Nonspecific (different genes are transmitted).
It's connected with localization transducing phages in the donor's genome. In the first case, they are always located in one place on the chromosome, in the second, their localization is not constant.
Conjugation Is the exchange of genetic information in bacteria by transferring it from donor to recipient at their direct contact.
After education between donor and recipient conjugation bridge one strand of donor DNA enters the recipient cell through it. The longer the contact, the more of the donor DNA can be transferred to the recipient. Based on the interruption of conjugation at regular intervals, it is possible to determine the order of the genes on the chromosome of bacteria - to build chromosome maps bacteria (to arming bacteria). F + cells have a donor function.
Normal microflora accompanies its owner throughout his life. Its essential importance in maintaining the vital activity of the organism is evidenced by observations of gnotobiont animals(deprived of their own microflora), whose life is significantly different from that of normal individuals, and sometimes it is simply impossible. In this regard, the doctrine of normal human microflora and its disorders is a very important section of medical microbiology.
It is now firmly established that organism a person and the microorganisms inhabiting it are single ecosystem... From modern positions normal microflora should be seen as set of many microbiocenoses , characterized by a certain species composition and occupying a particular biotype in the body. In any microbiocenosis it is necessary to distinguish between constantly occurring types of microorganisms - characteristic (indigenous, autochthonous flora), additional and random - transit (allochthonous Flora). The number of characteristic species is relatively small, but numerically they are always the most abundant. The species composition of transient microorganisms is diverse, but they are few in number.
The surfaces of the skin and mucous membranes of the human body are abundantly populated with bacteria. Moreover, the number of bacteria inhabiting the integumentary tissues (skin, mucous membranes) is many times greater than the number of the host's own cells. The quantitative fluctuations of bacteria in the biocenosis can reach several orders of magnitude for some bacteria and, nevertheless, fit into the accepted standards. Formed microbiocenosis exists as a whole as a community of united food chains and related microecology species.
The totality of microbial biocenoses found in the body of healthy people constitutes the normal human microflora. Currently, the normal microflora is considered as an independent extracorporeal organ. It has a characteristic anatomical structure ( biofilm) and it has certain functions. It was found that the normal microflora has a fairly high species and individual specificity and stability.
Constructive metabolism is aimed at the synthesis of four main types of biopolymers: proteins, nucleic acids, polysaccharides, and lipids.
Below is a generalized schematic diagram of the biosynthesis of complex organic compounds, where the following main stages are highlighted: the formation of organic precursors from the simplest inorganic substances (I), from which "building blocks" (II) are synthesized at the next stage. Subsequently, the building blocks, binding to each other by covalent bonds, form biopolymers (III): Applications (Fig. No. 3)
The presented scheme of biosynthetic processes does not reflect the entire complexity of the transformation of low-molecular-weight precursors into building blocks with a large molecular weight. In fact, the synthesis proceeds as a series of successive reactions with the formation of various intermediate metabolic products. In addition, the levels of development of the biosynthetic abilities of microorganisms are very different. In some microbes, constructive metabolism includes all the stages shown in the diagram, in others it is limited to the second and third or only the third stage. That is why microorganisms differ sharply from each other in their nutritional needs. However, the elemental composition of food is the same for all living organisms and must include all the components that make up the cellular substance: carbon, nitrogen, hydrogen, oxygen, etc.
Depending on the carbon sources used in constructive exchange, microorganisms are divided into two groups: autotrophs and heterotrophs.
Autotrophs (from the Greek "autos" - itself, "trophe" - food) use carbon dioxide as the only source of carbon and from this simple inorganic precursor compound they synthesize all the necessary biopolymers. Autotrophs have the highest biosynthetic ability.
Heterotrophs (from the Greek “heteros” - other) need organic carbon sources. Their nutritional needs are extremely varied. Some of them feed on the waste products of other organisms or use dead plant and animal tissues. Such microorganisms are called saprophytes (from the Greek "sapros" - rotten and "phyton" - a plant). The number of organic compounds they use as carbon sources is extremely large - these are carbohydrates, alcohols, organic acids, amino acids, etc. Almost any natural compound can be used by one or another type of microorganism as a source of nutrition or energy.
For the synthesis of cellular proteins, microorganisms need nitrogen. In relation to the sources of nitrogen nutrition among microorganisms, autoaminotrophs and heteroaminotrophs can be distinguished. The former are able to use inorganic nitrogen (ammonium, nitrate, molecular) or the simplest forms of organic (urea) and from these compounds build a variety of proteins in their body. In this case, all forms of nitrogen are first converted into the ammonium form. This most reduced form of nitrogen is easily transformed into an amino group. Heteroaminotrophs need organic forms of nitrogen - proteins and amino acids. Some of them require a complete set of amino acids, others create the necessary protein compounds from one or two amino acids by converting them.
Many microorganisms heterotrophic with respect to carbon are autoaminotrophs. These include the bacteria involved in wastewater treatment.
The need for oxygen and hydrogen for constructive metabolism is met by microorganisms at the expense of water and organic nutrients. The sources of ash elements (P, S, K, Mg, Fe) are the corresponding mineral salts. The need for these elements is small, but the presence in the environment is mandatory. In addition, microelements - Zn, Co, Cu, Ni, etc. are necessary for the normal functioning of microbes. Part of them is part of the natural nutrition of microbes, part is assimilated by them from mineral salts.
Methods for obtaining food, that is, methods for feeding microorganisms, are very diverse. There are three main ways of feeding: holophytic, saprozoic, and holozoic.
Holophytic nutrition (from the Greek "holo" - as a whole, "fit" - a plant) occurs according to the type of photosynthesis of plants. Such nutrition is inherent only in autotrophs. Among microorganisms, this method is characteristic of algae, colored forms of flagellates and some bacteria.
Heterotrophic microorganisms either feed on solid food particles or absorb dissolved organic matter.
Holozoic nutrition predetermines the development of special organelles in microorganisms for digesting food, and in some - for capturing it. For example, uncolored ciliated and ciliated ciliates have a mouth opening, to which food is adjusted by flagella or cilia, respectively. The most highly organized ciliates form a stream of water in the form of a funnel directed by the narrow end into the mouth by the perioral cilia. Food particles settle at the bottom of the funnel and are swallowed by the ciliates. Such ciliates are called sedimentators. Amoebas feed by phagocytosis.
Microorganisms with a holozoic way of feeding for constructive metabolism mainly use the cytoplasm of other organisms - bacteria, algae, etc. and have special organelles for digestion. The digestive process in protozoa is carried out in the digestive vacuoles.
Digestion consists in the hydrolytic breakdown of complex organic substances into simpler compounds. In this case, carbohydrates are hydrolyzed to simple sugars, proteins to amino acids, and during lipid hydrolysis, glycerol and higher fatty acids are formed. Digestion products are absorbed into the cytoplasm and undergo further transformation.
Bacteria, microscopic fungi, yeast do not have special organelles to capture food, and it enters the cell through the entire surface. This way of eating is called saprozoic.
To enter a cell, nutrients must be in a dissolved state and have the appropriate molecular size. For many high-molecular compounds, the cytoplasmic membrane is impermeable, and some of them cannot even penetrate the cell membrane. However, this does not mean that high molecular weight compounds are not used by microorganisms as nutrients. Microorganisms synthesize extracellular digestive enzymes that hydrolyze complex compounds. Thus, the process of digestion, which occurs in protozoa in vacuoles, in bacteria is carried out outside the cell (Appendix Fig. 4).
The size of the molecules is not the only factor that determines the penetration of nutrients into the cell.
The cytoplasmic membrane is capable of passing some compounds and retaining others.
Several mechanisms of the transfer of substances through the cell membrane are known: simple diffusion, facilitated diffusion, and active transfer (Appendices Fig. 5).
Simple diffusion is the penetration of molecules of a substance into a cell without the help of any carriers.
In the saturation of the cell with nutrients, simple diffusion does not matter much. However, it is in this way that water molecules enter the cell. An important role in this process is played by osmosis - the diffusion of solvent molecules through a semipermeable membrane in the direction of a more concentrated solution.
The role of the semipermeable membrane in the cell is played by the cytoplasmic membrane. A huge number of molecules of various substances are dissolved in the cell sap, therefore the cells of microorganisms have a rather high osmotic pressure. Its value in many microbes reaches 0.5-0.8 MPa. In the environment, the osmotic pressure is usually lower. This causes water to flow into the cell and creates a certain tension in it called turgor.
With facilitated diffusion, solutes enter the cell with the participation of special carrier enzymes called permeases. They seem to capture the molecules of solutes and transfer them to the inner surface of the membrane.
Simple and facilitated diffusion are variants of passive transport of substances. In this case, the driving force of the transfer of substances into the cell is the concentration gradient on both sides of the membrane. However, most substances enter the cell against the concentration gradient. In this case, energy is expended on such a transfer, and the transfer is called active. Active transfer proceeds with the participation of specific proteins, is coupled with the energy metabolism of the cell and allows the accumulation of nutrients in the cell in a concentration many times greater than their concentration in the external environment. Active transfer is the main mechanism for the entry of nutrients into cells with saprozoic nutrition.
Consider the first group of genes. Ethanol is oxidized in two steps, and there are two key enzymes at work in those two steps. First, under the action of the enzyme alcohol dehydrogenase, ethanol is converted into acetaldehyde ...
Genetics and biochemistry of alcoholism
Ethyl alcohol catabolism occurs mainly in the liver. Here, from 75% to 98% of the ethanol introduced into the body is oxidized. Alcohol oxidation is a complex biochemical process ...
Hydrophilic hormones, their structure and biological functions
Biosynthesis. Unlike steroids, peptide and protein hormones are the primary products of biosynthesis. The corresponding information is read from DNA (DNA) at the stage of transcription ...
Study of the seasonal biorhythm of bacillary-coccal transformation of the bacterium Helicobacter pylori
The Helicobacter pylori bacterium has very successfully adapted to life in the extreme conditions of the human stomach. It is gram negative, which already implies a powerful impenetrable cell wall. She is able to live in microaerophilic conditions ...
Yeast morphology and metabolism
Regulation of primary metabolic processes
A living cell is a highly organized system. It contains various structures, as well as enzymes that can destroy them. It also contains large macromolecules ...
The role of peptides in the functioning of the nervous system
As noted above, three protein molecules are known that include enkephalin sequences in their structure: proopiomelanocortin, preproenkephalin A (proenkephalin), preproenkephalin B (prodinorphin). Sequences ...
More than 2/3 of the amino nitrogen of amino acids is accounted for by glutamate and its derivatives; these amino acids are quantitatively dominant in the brain of all studied animal species. A similar picture is observed in the spinal cord ...
Free amino acids of the nervous system
Aromatic amino acids - tryptophan, phenylalanine and tyrosine - are important as precursors of 5-hydroxytrilamine and catecholamines, which play an extremely important role in neuronal processes ...
The structure and transport of androgens
In target organs there are separate, specific cytoreceptors of sex hormones. These hormone receptors are, obviously, the tissue component of every endocrine function - including the gonadal one ...
Physiology and biochemistry of plant components
The Hatch and Slack cycle has also been found in succulent plants. But if in C4 plants cooperation is achieved due to the spatial separation of two cycles (inclusion of CO2 into organic acids in the mesophyll, reduction in the sheath) ...
All listed in table. 1 photosynthetic microorganisms are adapted to the use of light in the visible (wavelength 400-700 nm) and the near-infrared part of the spectrum (700-1100 nm) ...
Energy metabolism of microorganisms
Of the three pathways for the formation of ATP, substrate phosphorylation is the simplest. This type of energy metabolism is typical for many bacteria and yeast that carry out various types of fermentation ...
Energy metabolism of microorganisms
Most heterotrophic organisms receive energy in the process of respiration - the biological oxidation of complex organic substrates that are hydrogen donors. Hydrogen from the oxidized substance enters the respiratory chain of enzymes ...
Energy metabolism of microorganisms
Oxidation of reduced mineral compounds of nitrogen, sulfur, iron serves as an energy source for chemolithotrophic microorganisms ...
Despite the fact that organic life as a whole is a very complex and multifaceted phenomenon, the individual mechanisms that support its existence can be disassembled into completely simple components that are understandable even for neophytes who are first interested in microbiological issues. Bacterial metabolism belongs to such conditionally complex, but in fact very simple mechanisms.
In microbiology, the general picture of metabolism in any organism is a cycle of reactions, some of which provide the body with energy, while others constantly replenish the body with matter (supply building material).
In this respect, the metabolism of a bacterial cell is no different from general biological principles. Moreover, bacteria were the founders of the still functioning mechanism for ensuring the vital activity of a living cell.
Depending on the metabolic products, there are two types of it:
The presence of a strict gradation does not imply that somewhere in the organism of a bacterial cell, energy is separately synthesized, but organic matter is separately built with the consumption of already accumulated energy. No.
The overwhelming majority of metabolic processes occur in a prokaryotic cell simultaneously and represent a closed cycle. So, in the process of catabolism, products are formed that are immediately picked up by cellular structures, and the reaction of biosynthesis of certain enzymes is triggered, which, in turn, regulate the processes of energy synthesis.
In relation to the substrate, metabolism in bacteria is divided into several stages:
These steps are important for microbiologists to identify prokaryotes by the enzymes they produce at different stages of metabolism.
The peculiarities of the metabolism of bacteria are that prokaryotic cells can use not only oxygen, but also other organic and inorganic compounds as oxidants (sources of energy and carbon). Of the organics present on planet Earth, only bacteria have such wide access to the initial resources to maintain their vital activity.
Such features of metabolism in bacteria are due to the presence of two types of enzymes (protein molecules that accelerate reactions in living cells):
Some enzymes are constantly produced by the cellular organism (constitutive), and there are those that are produced as a reaction to the appearance of a particular substrate (inducible).
Energy metabolism in representatives of the bacterial kingdom can be carried out in two different biological ways:
Chemotrophic respiration (transfer of an electron from a substrate to intracellular substances) in bacteria occurs in three ways:
The peculiarities of metabolism in bacteria include the richness of choice of receivers of free electrons, which is released in the process of substrate oxidation, which is inherent only in the world of prokaryotes.
So, depending on what substance is the final acceptor of electrons, the following types of anaerobic respiration differ:
The use of ATP energy to build cellular material is nothing more than biosynthetic reactions to create:
The reactions take place in several stages. As a result of the initial stages, protein molecules-monomers are formed from the decomposition products of glucose (pentose phosphates, pyruvate, acetyl CoA, etc.), which are assembled into macromolecules at the next stages.
Amino acids are the main building blocks of protein. The protein contains 20 amino acids, and all of them are synthesized by the bacterium itself. This synthesis occurs as a result of 7 main biosynthetic reactions:
The amino group of amino acids gets its nitrogen from nitrates, nitrites, molecular nitrogen and ammonia (depending on the type of bacteria). It is into these organic compounds that inorganic nitrogen is converted before becoming part of the polymer macromolecules of a particular amino acid.
Nucleotides are the building blocks for DNA and RNA, as well as for coenzymes (non-protein molecules that are protein activation centers).
If the bacterium has access to the residues of nucleic acids or nucleotides are present in the substrate, the bacterial cell will consume the ready-made nucleotides, and only in the absence of the finished product does the bacterium carry out a complex synthesis of the nucleic polymer.
Lipids are organic substances consisting of fats and fat-like substances, synthesized by bacteria from the intermediate metabolite acetyl-CoA. As a result of complex reactions using enzymes, fatty acids are synthesized, from which the bacterium builds cell walls and forms electronic transport chains.
The life of the human body is a very complex and unique phenomenon, however, it has such mechanisms that support its existence and at the same time they can be disassembled down to the simplest components that are accessible to everyone. Here, first of all, it is necessary to say about the metabolism of bacteria, which is complex only conditionally, in fact, such a process as the metabolism of bacteria is quite simple. To get acquainted with the metabolic process of microorganisms in detail, the science of microbiology helps. The processes under study help to form new forms of treatment for a wide variety of ailments.
If we talk about the general picture of the metabolic bacterial process, then we are talking about a certain reaction cycle, and on some reactions the task is to provide the human body with energy, and as for others, they are ways to replenish the body with matter, that is, in fact, they are a kind of building material ... If we talk about the metabolism of bacterial cells, then it is impossible to find differences from the biological principles of the general type. It is bacteria that are the basis of the provisional mechanism of the life process of living cells.
There are 2 types of such a process, which depend on metabolic products:
Most of the metabolic-type processes take place in a prokaryotic-type cell, and this process is of a one-time nature, all this has the form of a closed-type cycle. When the metabolic process takes place, products begin to form, which are accompanied by structures of the cellular type, then a biosynthetic reaction begins, in which certain enzymes take part, they carry out the process of synthesis of an energetic nature. These types of metabolism of microorganisms are not the only ones, there are others.
The metabolism of microorganisms refers to the substrate, here we are talking about several stages:
All the features of this process are due to the fact that there are two types of enzymes (we are talking about protein-type molecules that can accelerate reactions in the cellular structure:
It should be noted that there are a number of enzymes that are ways to be produced by the cellular structure on an ongoing basis (constitutive nature), and there are those that produce in the form of a reaction when a certain substrate appears.
Such a process in bacteria is carried out by certain methods of a biological type:
If we talk about how bacteria breathe in a chemotrophic way, then there can be 3 ways:
It should be noted that growth is a process when an individual increases in size, and as for the reproduction process itself, this is when the population begins to increase.
It is noteworthy that bacteria are able to multiply in such a way that binary division is simply carried out, but this method is far from the only one, there is also budding. If the bacteria have a gram-positive form, then there is the formation of a septum from a cell-type wall and a cytoplasmic-type membrane that can grow inward. If the bacteria are gram-negative, then a constriction begins to form, after which the cell splits into a pair of individuals.
The speed of the reproduction process is noteworthy; it can be different. If we talk about the overwhelming majority of bacteria, then they divide every half hour. And there are tuberculous mycobacteria, the division process of which is slower, suffice it to say that one division may take at least 18 hours. Spirochetes also do not divide quickly, about 10 hours, so you can see how the metabolism of microorganisms differs.
If you sow bacteria in a liquid nutrient medium, taking a certain volume, and then taking a sample every hour, then the bacterial growth has the shape of a curved line.
Such substances grow in several phases:
In conclusion, it should be noted that the metabolism of all bacteria and microbes may have certain differences, there may be a variety of factors. The individual characteristics of the human body are of great importance. And as for such a process as the regulation of metabolism, they began to study it even in prokaryotes, and specifically in prokaryotes (these are the operons of the intestinal stick).
To date, there are various methods of study. If sulfur bacteria are studied, then the study has its own characteristics, and other methods can be used to study bacterial changes. Iron bacteria, which have a unique feature of oxidizing ferrous iron, deserve special attention.
