The bacteria they are a large group of prokaryotic microorganisms. They are generally only a few microns in size. They have different shapes ranging from cylindrical to spiral to cane shapes..
They are practically ubiquitous organisms and can be located in the soil, marine and freshwater bodies of water, inhabiting the intestinal flora and saliva of many vertebrates, and as parasites of animals and plants. They have also been found in extreme environments such as acidic hot springs, hydrothermal vents, and radioactive waste..
These microbes are an essential part of many nutrient cycles. They are the basic component of the microbiota of all trophic chains and their biomass can be calculated at approximately 5 × 10 30 bacteria on planet earth.
Another interesting figure is that of the amount of bacteria that inhabit the human body: it is thought that in an average human there are around 39 billion bacterial cells and most of these are part of the intestinal flora.
The traditional classification of bacteria comprised a polyphyletic taxonomic group. Today that group has been divided into two domains bacteria and archea. Bacteria is recognized as the prokaryotic group with membrane lipids composed of diacyl diesters of glycerol.
On the other hand, archea is the group of prokaryotes whose membrane is composed of isoprenoid lipids (glycerol diether or glycerol tetraether). They also present differences in their ribosomal RNA, being called bacterial rRNA and archaean rRNA, respectively..
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Bacteria have a great morphological variety and size. These unicellular organisms can measure from 0.3 microns to 0.5 millimeters, however, in general, their measurements are between 0.3 and 5.0 microns..
The shape called cocci (spherical) is the most common among bacteria. However, other forms such as bacilli (shaped like a stick or rod) are also relatively common..
Other morphs not so frequent among bacteria are: commas, also called vibrios (shaped like a slightly curved rod or like the punctuation mark ","), and spirilias or spirochetes (with spiral shapes). Some more unusual are still shaped like stars.
The representatives of the bacterium domain, being prokaryotic unicellular organisms, do not present a defined nucleus or complex membranous organelles. The cell wall of these have a pectidoglycan that contains muramic acid and the membrane lipids contain straight chain fatty acids with ester bonds..
They present gas vesicles. The transfer RNA has thymine (in most tRNAs) and N-formylmethionine (carried by the initiator tRNA). They present polycistronic mRNA, that is, it encodes more than one protein.
Ribosomes are 70s in size. They are sensitive to chloramphenicol and kanamycin, do not show sensitivity to the antibiotic anisomycin.
Bacterial RNA polymerase is a large molecule. It has five subunits of approximately 410 kilodaltons each. Additionally, in its structure the RNA polymerase has a groove 55 Å in length and 25 Å in width. You are sensitive to rifampicin. Does not present type II polymerase promoters.
Bacteria fix nitrogen, perform photosynthesis based on chlorophyll, and also perform chemolithotrophy (oxidation of inorganic compounds). They do not produce methane or present the enzyme ATPase.
The identification and classification of bacteria is one of the most complex issues in the biology of microorganisms. There are numerous characteristics and methods that are used for the identification and subsequent classification of these individuals..
Classical characteristics include morphology, physiology and metabolism, biochemistry, ecological relationships and functions, and genetics..
The most commonly used analyzes are: fermentation products, type of nutrition, carbon and nitrogen sources, storage inclusions, motility, osmotic tolerance, optimal physical-chemical conditions, photosynthetic pigments, among many others..
Other non-classical features are found at the molecular level. In recent decades, the use of nucleic acids and proteins in the taxonomy of bacteria has gained great momentum..
Comparisons between genes (proteins and nucleic acids) provide vast information on kinship and, of course, similarity between organisms.
Bacteria, was a term traditionally used to designate all unicellular prokaryotes. However, molecular systematics showed that this ancient group of organisms (prokaryote) diverged into 2 groups or domains.
These two groups were called eubacteria and archebacteria. Later they were renamed as bacteria and archea. The Archea are a group most closely related to members of a third domain, called the Eukarya..
This last group is made up of eukaryotic organisms. Together, the 3 domains (bacteria, archea and eukarya) make up the current classification of life.
Bacteria can be classified following various criteria such as:
Bacteria are generally unicellular, however, depending on the cellular organization, they can be classified as "unicellular and multicellular".
Depending on the environment in which they are found and the way in which they carry out their processes to obtain energy and nutrients, bacteria are classified into:
Depending on the composition of the cell wall of the bacteria, they react to the Gram stain, either with a dark blue or violet color, or on the other hand with a pink or red color and their classification is as follows:
Depending on the temperatures where these micro-organisms develop, they can be classified into:
Bacteria have long been identified according to their shape, and their classification is as follows:
Following the revolutionary classification by Carl Woese and colleagues in 1990, the classification of bacteria radically changed. Currently, according to the LPSN or list of prokaryotic names with standing in the nomenclature (List of Prokaryotic names with Standing in Nomenclature), the bacterium domain is divided into 34 phyla. Among these phyla are:
Elongated and helical bacteria. Gram negative. They have an outer cell envelope. They move by means of axial filaments.
Group of Gram-positive bacteria, mainly with thickened cell wall and low content or percentage of GC. Firmicutes are primarily rod-shaped and sometimes coconut-shaped. Many species produce endospores.
Gram-negative bacteria, with varied morphology and a cell wall formed by lipopolysaccharides. Mainly heterotrophic, although some species can photosynthesize. They are very abundant in the oceans and other bodies of water.
Bacterial organisms that have chlorophyll and phycocyanin. They are called blue-green algae. They are Gram-negative and capable of oxygenic photosynthesis.
Bacteria adapted to a great diversity of habitats. Anaerobic metabolism. Gram negative. Some species are opportunistic pathogens.
Group of bacteria that carry out anoxygenic photosynthesis. Anaerobic metabolism. Gram negative. They are called green sulfur bacteria.
Monodermal bacteria, that is, they have a single cell membrane. They have a very thin outer cell wall of peptidoglycan. The group has thermophilic and mesophilic representatives. Some photosynthesize. Mainly aerobic. Gram positive.
They are bacteria adapted to living in extreme environments. They are considered hyperthermophilic organisms. Anaerobic metabolism and can process carbohydrates. They are gram negative.
The main mechanism of reproduction of bacteria is binary fission or bipartition. It is a type of asexual reproduction, where the bacterial cell needs to double in size and then divides, giving rise to two daughter cells..
This type of asexual reproduction allows bacteria to have an exponential population growth rate. In this way, the growing population can make better and faster use of available resources and also broaden the possibility of generating organisms or strains resistant to the different environments in which they develop..
It is a type of cell division in which the nucleus is divided into several equal parts and then the division of the cytoplasm occurs, giving rise and simultaneously to several daughter cells.
This type of asexual bacterial reproduction occurs in a nonspecific location of the parent bacterium. It begins with a bulge in the cytoplasm called a bud, which then doubles the size of the parent and separates as a new individual (daughter cell). This type of reproduction has been observed in the phyla Planctomycetes, Firmicutes and Cyanobacteria.
This type of reproduction, also called atypical binary fission, consists of a small circular cell (baeocyte), which subsequently increases in mass or size, forming a vegetative cell..
During the increase in size this vegetative cell replicates its DNA multiple times, later it goes on to the reproductive phase where it undergoes cytoplasmic fissions, which will later become tens or even hundreds of baeocytes. This type of reproduction has been studied in cyanobacteria.
Bacteria have multiple types of nutrition:
Bacteria that use inorganic substrates such as nitrites, nitrates, iron or sulfates for biosynthesis or energy preservation through anaerobiosis or aerobiosis.
Bacterial organisms that obtain hydrogen or electrons from organic sources such as carbohydrates, hydrocarbons, or lipids. These organisms can be aerobic or anaerobic, even heterotrophic or autotrophic..
Organisms that develop synthesizing inorganic substances that could be carbon, but inorganic such as carbon dioxide.
Those organisms that synthesize chemical substances whose carbon source is organic, such as polysaccharides.
Bacteria that require synthesizing inorganic substances for the conservation and obtaining of energy, but also require organic compounds to meet their biosynthetic metabolic needs.
Of the great diversity of bacteria known to man, only a few (in proportion) cause disease. The pathologies caused by these microorganisms in humans can be classified according to their origin, that is, according to the mechanism of transmission or acquisition of this:
Bacteria that cause airborne diseases usually affect the respiratory tract or respiratory system, and in other cases can cause skin conditions. Here are some airborne diseases:
In most cases this disease is transmitted, by Corynebacterium diphtheriae, even if C. ulcerans can produce similar clinical manifestations.
The disease is transmitted from a sick person to a healthy person by means of particles transmitted during respiration. It can also occur through contact with the secretion of skin lesions. Diphtheria can affect almost any mucous membrane and the most common clinical forms are:
The disease is caused by an aerobic Gram-negative bacterium native to soil and aquatic ecosystems called Legionella pneumophila. This bacterium has also been isolated in air conditioning systems and shower enclosures..
The disease is the result of the spread of the bacteria via the air from a reservoir to the human respiratory system. Men over the age of 50 who are compromised with smoking, alcoholism, or immunodeficiencies are more likely to contract the disease.
The bacterium is housed in the phagosomes of alveolar macrophages, from where it multiplies and causes tissue damage. The symptoms of this disease are: cough without expulsion of respiratory secretions, fever, severe bronchopneumonia and neurological problems may manifest.
This disease consists of an inflammation of the meninges of the brain and spinal cord. It can have an aseptic or bacterial origin. The pathology of bacterial origin comes from the respiratory secretions of carriers of the disease or from active cases.
The bacteria that cause meningitis initially colonize the nasopharynx, from where they cross the mucosa and enter the bloodstream, and from there to the cerebrospinal fluid from where they inflame the meninges..
Symptoms of this infection are: a respiratory illness or sore throat, followed by confusion, vomiting, headache (in some cases severe), stiff neck and back.
Several species of bacteria are related to pneumonia, however the species Mycobacterium avium Y M. intracellulare they are the main causes of this disease. These bacteria have a worldwide distribution and infect not only man but other vertebrates and insects.
It is thought that the respiratory and digestive systems are the entry point for these bacilli for the colonization of patients. The disease manifests in people as a lung infection, much like that caused by tuberculosis.
Many other diseases are transmitted by airway bacteria, among which we can mention: tuberculosis, produced by the Koch bacillus (Mycobacterium tuberculosi); whooping cough, caused by the bacteria Bordetella pertussis, and diseases caused by streptococci.
Bacterial diseases caused by these invertebrates are considered rare, however they are the subject of much interest. Some of these diseases are:
Pathology caused by bacteria Ehrlichia chaffeensis, that is transmitted by animal reservoirs such as the tick. Once the bacteria enter the bloodstream, it causes a nonspecific febrile illness called Human Monocytic Ehrlichiosis (HEM). The disease is characterized by symptoms such as: fever, chills, headache and myalgia.
Bacterial disease transmitted to man by lice. The bacillus that causes this disease is Rickettsia prowasekii. When the louse feeds on an infected person, the bacteria infect the arthropod's gut and spread.
In a short time, large amounts of rickettsiae appear in the lice feces, and when the louse sucks the blood of another healthy individual they defecate.
When the irritation from the bite causes the individual to scratch, it contaminates the damaged site and allows the rickettsiae to enter their bloodstream, where they later cause inflammation of the blood vessels by infection of their endothelial cells. The symptoms of this disease are fever, severe headache and myalgia..
Lyme disease is a bacterial infection transmitted to man by a tick bite whose natural hosts are voles and deer. The causative bacteria are spirochetes of the genus Borrelia.
Clinically the disease has three stages: first it usually begins with skin lesions that expand like rings. This stage is often accompanied by fever, chills, fatigue, malaise, and headaches..
The second stage is characterized by bouts of arthritis, heart inflammation, and neurological problems. The third and last stage, can be observed years later, and is characterized in that individuals develop demyelination of neurons and present symptoms similar to Alzheimer's or multiple sclerosis..
Although arthropod-transmitted bacterial infections are considered rare, some have caused massive deaths in mankind, such as the Black Death or the bubonic plague, caused by Yersinia pestis.
Another disease not as deadly as the black plague is Q fever caused by the bacteria Coxiella burnetii and that infects livestock, domestic animals and man.
These bacterial diseases are mainly associated with skin infections and underlying tissue. Some of these pathologies are:
Disease transmitted by being in direct contact with infected farm animals or their products. The bacteria causing the disease is the Bacillus anthrasis and its endospores can remain viable for many years in the soil or in animals.
Infection in humans occurs mainly due to damage or cuts to the skin (cutaneous affection), it can also affect the respiratory (pulmonary anthrax) and gastrointestinal (gastrointestinal anthrax) systems.
An eschar (an ulcerated skin papule) forms on the skin and accompanying symptoms include fever, headache, and nausea..
It is a polymicrobial STD (sexually transmitted disease), that is, produced by several bacteria. Such bacteria are Gardnerella vaginalis, species of the genus Mobiluncus Y Mycoplasma hominis.
It is a disease considered mild but very contagious and its symptoms are: foamy, copious vaginal discharge with odors similar to fish, there is no pain, burning or itching.
Another bacterial sexually transmitted disease. It is caused by Neisseria gonorrhoeae. This diplococcus, once it enters the body, attaches itself to mucous cells through pili and protein II. This adhesion prevents it from being expelled from the vagina by normal secretions or urine..
Symptoms in men are: discharge from the urethra of a yellow to green pus, with frequent urination, accompanied by pain and a burning or burning sensation. Only 10-20% of those exposed to the bacteria develop in women, and if they develop the disease, it can cause ectopic pregnancies and even sterility.
Bacterial diseases by direct contact are very diverse both in their origin and in their development, the most mentioned are STDs and of these we can mention: genitourinary diseases caused by mycoplasmas Ureaplasma urealyticum Y Mycoplasma hominis; and chancre, produced by Haemophilus lucreyi.
Other diseases of non-sexual contact and caused by bacteria are: inclusion conjunctivitis, leprosy, cat scratch disease, gas gangrene and many others.
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