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Considering typical eukaryotic cell organelles, heterotrophic bacteria have ribosomes, essential for protein synthesis.

The bacterial cell wall is made of peptidoglycans.

There are three peculiar types of archaebacteria. The halophile archaebacteria only survive in salt-rich environments (even salinity of the sea is not enough for them). Thermoacidophile archaebacteria are characterized by living under high temperatures and low pH. The methanogen archaebacteria are those that liberate methane gas (CH₄), they are found in swamps.

Bacteria reproduce by binary fission (scissiparity). Some bacteria however present a kind of sexual reproduction (transformation, transduction or conjugation) with a combination of genetic material from different individuals.

Obligate anaerobes are those living beings that do not survive in the presence of oxygen. For example, the bacteria Clostridium tetani, agent of tetanus is an obligate anaerobe.

In superficial wounds, it is common to use hydrogen peroxide to expose anaerobic microorganisms to oxygen and kill them.

According to their necessity of oxygen bacteria are classified into anaerobic (those that survive without oxygen) and aerobic (those that do not survive without oxygen).

Most bacteria are heterotroph, they do not produce their own food. There are also autotroph bacteria: chemosynthetic bacteria or photosynthetic bacteria.

Some photosynthetic bacteria, like cyanobacteria, make photosynthesis like plants do, using water. Others, the sulfur photosynthetic bacteria, use hydrogen sulfide (H₂S) instead of water.

Bacteria can be found in various environments throughout the planet. There are bacteria in the air, in fresh water, on the surface, in the intermediate depth and on the bottom of the sea, in soils, in our skin and practically in all terrestrial environments through which air circulates freely. Some bacteria can be found in volcanic craters under extremely high temperatures.

Bacteria are prokaryotic and unicellular beings. Bacteria have simple organization, they present an external cell wall, plasma membrane, circular DNA within the cytoplasm and ribosomes for protein synthesis. Some bacteria are encapsulated, i.e., they have a polysaccharide capsule outside the cell wall.

Prokaryotic beings are classified into two big groups: archaebacteria and bacteria (this last also known as eubacteria).

Compared to bacteria, archaebacteria have basic differences, like the chemical compositions of their plasma membrane and cell wall and different enzymes related to DNA and RNA metabolism.

Some human diseases caused by bacteria are tuberculosis, pertussis, diphtheria, bacterial meningitis, gonorrhea, syphilis, bubonic plague, leptospirosis, cholera, typhoid fever, Hansen’s disease, trachoma, tetanus, anthrax.

Bacteria are used by industry in various ways. There are vaccines made of attenuated pathogenic bacteria or of antigens present in bacteria. One of the most ancient uses of bacteria is the fermentation of milk to produce yogurt, cheese and curd (even before the knowledge of the existence of bacteria these microorganisms were already used in the making of those products). Some methods of antibiotic production involve bacteria. The recombinant DNA technology (genetic engineering) allows the industrial production and commercialization of human proteins, like insulin for diabetics, synthesized by mutant bacteria. Some bacteria can produce fuel, like methane gas.

Them to parasite their host. Some bacteria have fimbriae, cilium-like structures that attach the bacterial cell to the host tissue. There are bacteria specialized in intracellular parasitism. Other bacteria secrete toxins, molecules that cause disease; in some cases, the bacterial population growth causes food contamination by toxins. Generally, bacterial disease is caused by bacterial population growth with invasion and destruction of tissues or by bacterial toxins that contaminate the organism.