Did you know that once upon a time microbes were considered worms? Seriously. The Swedish naturalist Carl Linnaeus, who created a unified system of classification of the vegetable and animal worlds, brought together all the organisms in one genus under the name of Chaos and took to the worms. It was in the first half of the XVIII century, when almost nothing was known about microbes. Even the word “microbe” did not exist, it appeared only in 1878.
The existence of microbes was discovered in the XVII century by the Dutchman Antony van Leeuwenhoek (1632-1723), who is undeservedly considered the inventor of the microscope. This is one of those myths, which is so rich in the history of mankind. Leeuwenhoek did not invent a microscope, he improved it, turned the “magnifying” system of two lenses into a full-fledged optical scientific device. Microscopes Leeuwenhoek (he has designed a lot of them) allowed to obtain at least tristatetrue increase. “At least”, because according to some information Leeuwenhoek was able to create a microscope that increases five hundred times, but to our time this device has not survived. The most powerful of the nine extant microscopes Leeuwenhoek can get an increase of two hundred and seventy-five times, rounded – three hundred.
The germs nearly undermined the scientific authority of man. The fact is that he described the results of his observations in a microscope and sent these notes to the Royal society for the development of knowledge about nature. Some observations were published in the journal of the Society. Pretty soon, Leeuwenhoek had a reputation as an outstanding naturalist, but when he in 1676 sent to London a description of single-celled organisms discovered in the course of their observations, he did not believe. The existence of such “crumbs”seemed too improbable. To check in the Dutch city of Delft, where he lived Leeuwenhoek, from London, was directed to the whole Commission – a group of highly respected members of Society. Leeuwenhoek showed his London colleagues “crumbs” in the microscope, after which the credibility of his reports was restored. And if the meticulous British did not come to the Commission, the topic of microorganisms could be “closed” for a long time and someone would later have to open them again.
Leeuwenhoek was a naturalist – he opened, sketched and described, but did not study in detail. Yes, and he did not have that opportunity. Based on the information obtained by Leeuwenhoek, Carl Linnaeus combined all microorganisms in the genus Chaos. With all the desire (and it is inquisitive scientist was clearly) Linnaeus could not add anything significant to what Leeuwenhoek did. Microbiology science began to develop only in the NINETEENTH century. Yes, since the beginning, still can not stop all developing Yes developing. Microbiologists do not joke when they say that the secrets of the microscopic Universe, that is, the secrets of microorganisms, are more difficult to reveal than the secrets of the “big” Universe. So it is. And the further you plunge into the microscopic Universe, the more secrets are revealed to you.
Chaos is a prophetic name. Indeed, if you collect all the microorganisms in one genus, you get exactly chaos and nothing but chaos. However, despite the fact that almost three hundred years have passed since Linnaeus created his classification and much has changed during this time, the myth of the universal equality of microbes still lives in the minds of the General public. People believe that all microbes are similar to each other and still consider the words “microbe” and “bacterium” synonyms.
All the microbes are similar to each other? Yes, they can all be different, these primitive single-celled creatures?
Lots of things. First of all – the presence of the kernel.
Each cell, whether it is a cell of a multicellular organism or an independent unicellular organism, contains hereditary information encoded in the form of a certain sequence of fragments of deoxyribonucleic acid molecules (abbreviated – DNA). The portion of the DNA molecule in which one single trait is encoded is called the genome. The number of DNA molecules in different organisms varies greatly – from one to several tens, and sometimes hundreds. For example, Siberian sturgeon has two hundred and forty of them!
DNA molecules can be compactly Packed into the cell nucleus, in which case the cell will be called eukaryotic or eukaryotic. If the DNA molecules are in the cytoplasm – semi-fluid internal environment of the cell – in the “unpackaged” form, such a nuclear-free cell is called prokaryotic or prokaryotic.
Prokaryotes include bacteria and archaea, which differ significantly in a number of physiological and biochemical properties from bacteria. Eukaryotes include fungi, plants, animals and protists. Prokaryotic cells are very small – from 0.5 to 5 microns in diameter.
In evolutionary terms, prokaryotic cells are considered to be more ancient than eukaryotic, that is, eukaryotes descended from prokaryotes. Evolution goes from the simple to the complex, so eukaryotic cells are more complex than prokaryotic, they have more cellular organs, called organelles or organoids. But, on the other hand, the cells, which are a single-celled organism, arranged more complex than the cells of a multicellular organism. The fundamental difference between unicellular organisms from the cells of multicellular organisms is the presence of unicellular special-purpose organoids that help them perform all the necessary functions. Movement and capture of food provide outgrowths – false legs, flagella and cilia. Excretory function is provided by contractile bubbles-vacuoles, and digestive – other vacuoles containing substances that can cleave “swallowed” nutrients. There are specialized intracellular structures that provide irritability and so on.
Please note that a Paramecium has a more complex structure than an amoeba. The “Shoe” has a mouth with a throat, there is a powder – an analogue of the rectum, and in addition to the main core there is also a small one.
Is this similar to each other, the amoeba and the Shoe? Not really, right?
And now – about synonyms.
Consider the words “microbe” and “bacteria” interchangeably, it is still something to consider synonyms for the word “bird” and “Sparrow”. Yes, a bacterium is a microbe, and a Sparrow is a bird, but not every microbe is a bacterium, just as not all birds are sparrows.
Bacteria are just one type of prokaryotic microorganism. Besides bacteria the prokaryotes include the archaea. Has anyone heard this name before? Hardly.
Archaea are single-celled microorganisms that do not have a nucleus and any other membrane organelles. Membrane organelles, as it is easy to guess by name, called cellular “organs”, limited by the cytoplasm of the membrane, that is, the shell. The vacuoles mentioned above are an example of membrane organelles.
We will not delve into the cellular structure, because we do not need it. Figuratively speaking, this book is devoted not so much to the analysis of “microbial anatomy” as “microbial sociology”. Be aware that there are most simply arranged by microorganisms, like archaea, and know that every tenth of prokaryotes in our digestive tract belongs to the archaea. By the way, the name “archaea” translates as “ancient”. This is clear – the most simply organized microorganisms must have ancient origins.
Why bacteria is known to all, and archaea – only the biologists? The answer is simple – the archaea have no such scandalous glory, as have bacteria. Archaea do not cause diseases in humans (at least, those are not yet described), sit quietly in the intestine, do not harm. Someone, please tell me, interested in the decent quiet ones? Quite another thing – shocking scandalists-bacteria! In the world of microbes everything is arranged in the same way as in the world of people, the only difference is in the size of the inhabitants.
In the text flashed another obscure word – “protists”.
All eukaryotic microorganisms, with the exception of unicellular fungi, belong to protists (that is, to the first). Amoebas and infusoria, with whom we recently met, belong to protists. Among the amoebas with infusoria there are pathogenic, that is, those that cause disease. For example, dysentery amoeba, settling in the cells of the colon, causes amoebic dysentery, and infusion of Balantidium coli, penetrating into the cells of the small intestine, causes balantidiasis or infusory dysentery.
Have you heard about malaria? Its causative agent is another protist – malarial Plasmodium, which prefers to live in human erythrocytes (red blood cells). Malaria is characterized by regular attacks of fever, which occur with the mass destruction of red blood cells by plasmodia that have multiplied in them.
All small protists, ranging in size from two to four micrometers, are intracellular parasites. Among the protists and the giants who, for all their odnocletocnami, the micro-organisms do not apply. For example, xenophyophores living on the bottom of the World ocean (including the bottom of the Mariana trench) can reach up to ten centimeters in diameter. It turns out a biological paradox – single-celled xenophyophores are the habitat of various multicellular organisms.
To fungi-microorganisms, and if scientifically, then to unicellular fungi, are well-known to all yeast – beer, wine and others. Some yeast can cause disease. For example, yeast genus Candida, which is a component of normal human microflora, with the weakening of immunity or prolonged use of antibiotics, can cause a disease called candidiasis.
What’s the connection between antibiotics and candidiasis? The fact is that normally in any ecological system  there is a certain balance, an established ratio of various microorganisms. Antibiotics work on bacteria but have no effect on fungi. If bacteria begin to die EN masse, their place in the ecological niche is occupied by other microorganisms, in particular – mushrooms. As they say, “a Holy place is never empty.”
This begs the question – why yeast is considered a unicellular fungi, not protists? The fact that yeast has a number of features inherent in fungi. For example – can reproduce by budding, in which daughter cells are formed from the outgrowths of the mother cell, called kidneys. The protists (and bacteria archaea too) propagated by dividing the parent cell into two daughter.
In your opinion, what problem is the main “stumbling block” in Microbiology today? Even not only in Microbiology, but in biology as a whole. Why do biologists keep crossing imaginary swords and spears? Who is to blame for the discord that split the scientific biological community into two camps?
Blame viruses that do not have a cellular structure and this is different from all other organisms.
The virus is not a cell! The most simply organized viruses are genetic material – deoxyribonucleic or ribonucleic acid – Packed in a protein shell called a capsid.
Capsid performs not only a protective function. It also ensures that the virus attaches to the surface of the cell membranes. The capsid is attached to the membrane, but does not penetrate the cell. Only nucleic acid is introduced into the cell, which forces the cell to “replicate” it, that is, in fact, to produce new viruses. Viruses do not have a cell membrane and cytoplasm with organoids, do not have their own metabolism, and there is only Packed in a capsid genetic material – a matrix for the synthesis of new viruses. Virus “subdues” his cage and only the cage he is living “a full life”. Outside the cell, the virus is inactive.
The most complex viruses – bacteria parasitic bacteriophages (which translates as “bacteria eaters”), have a device for transporting their genetic material into bacteria. The body of the bacteriophage has a head, which is nucleic acid, tail – protein tube, which is a continuation of the protein shell of the head, and tail processes. By means of the tail, the genetic material of the virus contained in the bacteriophage head is pushed into the host cell. This process is called injection and it really resembles a medical injection made with a syringe.
To date, several thousand viruses are known, but this “list” is far from complete, new species are constantly added to it. It is believed, that is, it is assumed that viruses are the most numerous biological form on our planet and that their species account for millions.
The size of viruses is very small, they are expressed in nanometers (one nanometer is 10-9 m). “Fine” the virus of poliomyelitis has a size of about twenty nanometers, and a “giant” virus jaundice beet was grown up to a thousand nanometers. Bacteriophages are on average about a hundred nanometers long. Due to such small size, several dozen viruses of the same species can live in one cell at the same time, there is enough space for everyone.
Viruses affect all living things – animals, plants, microorganisms. Parasitizing in cells, viruses disrupt the normal functioning of organisms, causing disease. Influenza, various hepatitis, AIDS are all viral diseases.
Each virus has a strictly defined range of hosts, whose organisms are its environment. There are bacteriophages-“fussy”, parasitic only on one kind of bacteria, but the rabies virus affects all mammals (and humans including) without exception.
Even very far from medicine, people know that viral diseases are difficult to treat, and some are now considered incurable.
It would seem – a paradox. How much do these small viruses need to die? Logically rid the body of such simple pests should be very simple. But nature has its own logic. Viruses are very small and have a simple structure, so it is very difficult to cause their death. Outside the cell, the virus is in an inactive state, it does not occur any biological processes. And what are the same antibiotics? These are substances that disrupt the normal course of vital processes in bacteria or, say, protists. The process is broken – the body dies. And that can be disrupt have virus? And it is very difficult to destroy it – chalk Yes dodgy. In addition, the fight against viruses is greatly complicated by the fact that they live inside the cells and it is necessary to act on them in such a way as not to cause additional damage to the cells.
Modern antiviral drugs on the principle of action are divided into two groups: stimulating the immune system to fight viruses and affecting viruses directly (preventing the penetration of the virus into the cell, the reproduction of the virus in the affected cell and the exit of copies of the virus from the cell).
Jokingly biologists say about viruses: “they are alive, but not really.”
Speaking seriously, it is impossible to be “not quite” alive – either you are alive or inanimate.
Some biologists refer viruses to living beings with the proviso that it is a non-cellular form of life. Can viruses reproduce? Capable! Are viruses able to adapt to environmental conditions? Capable! Viruses are hereditary? Have! That’s it! So, they are alive and they can be attributed to microorganisms.
Opponents argue – well, what are they live? Viruses are not a form of life, but complexes of organic  molecules interacting with living organisms. Independently, without the use of other people’s resources, viruses can not be reproduced? They can’t! Own metabolism and energy do not have? You do not have! Means live they can not be considered!
Well suited to viruses poetic definition of “organisms on the edge of life.”
The author of this book shares the opinion of those biologists who believe viruses are a special form of life. “Complex organic molecules” is a vague concept. Broth is also a complex of organic molecules, and when you eat broth, it interacts with your body – is not it? Like it or not, from any side or look, and the main feature of all life is the ability to reproduce. Let inside the “foreign” cells. If something has such power, it should be considered alive.
But prions are organic molecules that interact with living organisms. Nothing more. Or, to put it another way – infectious agents of protein nature.
Prions do not belong to microorganisms and are mentioned here only for comparison with viruses. Prions are protein molecules capable, like viruses, to increase their number, using the functions and resources of living cells. Nucleic acid, that is, genetic information, prions do not contain. Prion is a single molecule, and nothing but molecules. The molecule can not be considered a living organism, for this it is too simple.
Few have heard of prions, but almost all have heard of the disease they can cause. This is “mad cow”, and if scientifically, then spongiform encephalopathy of cattle. In humans, a similar disease is called Creutzfeldt-Jakob disease. The causative agents of “mad cow” are not microbes, and prions.
From a biological point of view, prions are interesting as the only agents (to call them living organisms does not dare), the reproduction of which occurs without the participation of genetic material contained in nucleic acids. The genetic code of the prion to reproduce itself is not necessary, a copy of their molecules in the cells occurs without the matrix. Just some miracles! Yes, really – miracles. All that science has not yet explained can be considered miracles.
Some prions, safe, do not cause diseases, exist in our body normally. Prions have started to be studied recently, and therefore very little is known about the normal functions of prions. And to be honest, almost nothing is known, there are only hypotheses. For example, scientists suggest that “normal” prions may be involved in providing long-term memory.
This concludes our General Microbiology course. Now you have an idea of the diversity of the microbial Universe and even know what prions are.
“How is it finished?! – some readers were surprised now. – Why didn’t they say anything about cocci?” Streptococci, staphylococci, gonococci, pneumococci, meningococci… It’s a whole group of “pests”!»
Yes, “pests”, i.e., infectious agents, among cocci enough. But the cocci are bacteria. So called bacteria spherical shape, and the name comes from the Greek word “coconut”, meaning “grain”. We’ll talk about them in the next Chapter, which will be devoted to bacteria and some myths associated with them.
Our course of private Microbiology consists of three chapters – “bacterial”, “viral” and a Chapter about how microorganisms “fight” with each other.