Bacteria are microscopic organisms formed by a single cell. There are bacteria all over the planet, whether in water, soil or highly hostile habitats, such as radioactive waste in deep areas of the earth's crust or in the highly acidic pH of our stomach.
Most of the bacteria do not cause disease, but a small number is responsible for infections in common clinical practice. The bacterium is one belonging to the kingdom Monera and is formed by a single prokaryotic cell, i.e., does not present any organelle or core surrounded by membranes, such as mitochondria. Organelles are "float" freely in bacteria interior, for example, their DNA.
As has been already mentioned, bacteria exist on the entire planet. In a drop of fresh water there are about 1 million bacteria. In our body there are 10 times more bacteria than our own cells, most of them located in the skin and gastrointestinal tract. Our body has a bacterial flora that does not cause disease itself, however, helps our digestion and protects us against invading bacteria.
There are bacteria in extreme locations of the land, however the vast majority live in wetlands and moderate temperature. Some bacteria can survive harsh environments because of its ability to transform into Endospore, an inactive hard and tough coated cell, but that the genetic material remains protected for many years, in some cases for centuries. The coating resists Endospore extremes of pH, temperature, pressure, lack of water, radiation, and some chemical disinfectants. When the environment becomes habitable again, the Endospore becomes a metabolically active bacteria and able to reproduce.
Each bacterium is transmitted in a different way. Diseases such as meningitis, tuberculosis and whooping cough are transmitted through respiratory secretions, such as cough or spit. Sexually transmitted diseases like gonorrhea and syphilis are, as the name implies, transmitted by sexual intercourse.
There are also bacteria acquired through poorly maintained food, causing food poisoning, as in cases of Salmonella and Shigella.
There are infections caused by bacteria that live normally in our body. These infections occur when bacteria that normally inhabit a given location in the body can migrate to another. For example: urinary infection usually occurs when natural bacteria of the intestinal tract accidentally hit women genitals. Most strains of E.coli bacteria in the intestines cause no problems, but the bladder can cause irritation causing cystitis. The same occurs in the skin colonized by billions of bacteria, mainly of the genus staphylococcus and streptococcus. When there is a wound, it exposes the inner region of the body for these bacteria, which can penetrate it to cause serious infections.
To learn how each bacterium causes a disease, follow the links to the matters that are provided throughout this text.
To combat bacterial infections it is necessary to release the hands of antibiotics. As will be explained later in this text, there are several types of bacteria, some completely different from other. Therefore, different types of antibiotics are indicated for different types of bacteria and infections. Urinary tract infection is most often caused by the bacterium E.coli and antibiotics commonly used in these cases are Bactrim or ciprofloxacin, drugs that are not intended, for example, to treat pneumonia and meningitis caused by various bacteria.
In this part a few technical terms will be used so that the text can serve as a source for school biology. Most bacteria are heterotrophic, i.e., they cannot produce their own food and have to obtain it in the environment or in other organisms. There are also autotrophic bacteria, which can produce their own food, usually through photosynthesis.
The simplest method for the classification of bacteria is the following. There are three major groups:
Coconuts: spherical bacteria that have a tendency to cluster.
There are different kinds of nuts, classified according to the form of cluster. When pods are grouped in pairs they are called diplococci; cocci are bacteria of the genus Staphylococcus that are grouped in clusters, streptococci (Streptococcus) is a genus of cocci that are usually grouped in a row.
Coconuts are responsible for a wide variety of diseases, some of them already covered in other texts on this site, such as:
Neisseria gonorrhoeae, a bacterium that causes gonorrhea
Neisseria meningitidis, a bacterium that causes meningitis
Streptococcus pneumoniae, a bacterium that causes pneumonia
Streptococcus pyogenes, a bacterium that causes tonsillitis, Scarlet and rheumatic fever
Staphylococcus aureus, a bacterium that causes various infections, usually initiated in the skin, such as cellulitis, sty and multidrug-resistant infections
Rods or bacilli
Rods or bacilli: rod-shaped bacteria. They may or may not have flagella that help them get around. Examples of pathogenic bacilli are Bacillus anthracis, which causes anthrax, Corynebacteriumdiphtheriae causes diphtheria and Salmonella typhi, which causes typhoid fever.
Spiraled: bacteria are spiral-shaped, generally divided into two groups: espirilos and spirochetes. Among the spirochetes the most common is Treponemapallidum, which causes syphilis.
This division into formats that are not very useful because there are several bacteria with different formats such as comma (vibrio), rod-shaped bacteria that are not considered bacilli, the presence or absence of flagella, and even bacteria with hybrid forms, such as coccobacilli.
Relying only on the form can cause much confusion. Therefore, there are several ways to characterize and classify bacteria, an example is the Gram method.
The Gram is a special violet dye used in laboratories to recognize some types of bacteria. The method of Gram bacteria divided into two major groups: those, which cell wall becomes purple when exposed to the dye, are referred to as gram-positive bacteria and those that remain with pink wall, are called gram-negative bacteria.
Shapes of bacteria
The gram is a very useful test in clinical practice because of high speed of the result. While the identification of culture takes 48 to 72 hours for identifying a bacteria, gram is completed in several minutes.
Examples of gram positive bacteria:
Examples of gram negative bacteria:
Importantly, the method of Gram does not identify which bacteria are present, it only tells us that there is a gram-positive or gram-negative one causing an infection. This information, however, is often sufficient to direct the initiation of an antibiotic regimen while the culture is not ready. For example, if a patient with fever, reaps a urine test which indicates presence of gram-negative bacteria, we can choose an antibiotic for urinary tract infection before the identification of bacteria by culture, as doctors know beforehand which gram negatives cause most urinary tract infections.
We can also differentiate between aerobic and anaerobic bacteria. The first group consists of bacteria that need oxygen to live, the second are those that cannot survive in environments with oxygen. There are also facultative anaerobic bacteria that can live both in non- and oxygenated environments.