Bacteria – Definition, Types, and Structure of Bacteria

Bacteria are microorganisms of single cells, renowned for their tremendous capacity to adapt and multiply as well as for their ancient history. Some of the earliest recognized fossils are those of bacteria-like organisms— nearly 3.5 billion years old. While some bacteria cause disease and mortality, others are useful or even useful, breaking down or generating antibiotics. Classified by form, there are three types of bacteria: spherical, cylindrical and curved.

Types of bacteria

The Cocus

The coccus bacteria, like a berry, are spherical. The name is actually obtained from the Greek term “kokkos,” meaning berry. These are some of the lowest and easiest bacteria with an average diameter of approximately 0.5 to 1.0 micrometers. (A micrometer is approximately 1/1,000,000 per meter.) This classification includes an amount of pathogenic (disease-causing) organisms. 

Some instances of cocci are streptococcus, which may trigger strep throat and scarlet fever. Staphylococcus, specifically Staphylococcus aureus, which may trigger food poisoning and toxic shock syndrome; and meningococcus, which may trigger a number of meningococcal illnesses, including epidemic bacterial meningitis.  

Browse more Topics under Microorganisms

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• Heterotrophs
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The Bacillus

The form of the bacillus bacteria is rod-like. These bacteria are a little more complicated than the class of coccus and are 0.5 to 1.0 microns broad by 1.0 to 4.0 microns long on average.

Some of these bacteria are pathogenic, such as Yersinia pestis, which can trigger bubonic and pneumonic plague or the anthrax-causing Bacillus anthracis. But beneficial bacteria, like those used to create antibiotics, as well as those that colonize the human intestinal tract, also belong to this community, helping with digestion.

The Spirochete 

The bacteria of spirochete are in the form of a spiral. They appear almost worm-like when regarded under a microscope, wiggling wildly and shifting about. Two of the spirochete family’s most well-known representatives are Treponema pallidum, the syphilis-causing bacteria, and Leptospira, which produces leptospirosis.

Beneficial spirochetes include symbiotic spirochetes that enter the stomachs of ruminants such as sheep, cattle, and goats where cellulose and other hard-to-digest plant polysaccharides are converted into nourishing meat and fiber for their host. Beneficial spirochetes also reside in termites intestines and assist in wood and plant fiber digestion. This enables termites to help remove rotted and diseased wood and discharge organic matter into the soil to enrich its value.

Structure of Bacteria

Bacteria (unique: bacteria) are categorized as prokaryotes, which are single-celled organisms with a straightforward inner framework that lacks a nucleus, and contain DNA that either flows loosely in a bent, thread-like mass called the nucleoid or indistinct, linear parts called plasmids. Ribosomes are the spherical units in the bacterial cell that use the data stored in ribosomal RNA to assemble proteins from specific amino acids.

Two protective covers usually surround bacterial cells: an external cell wall and an internal cell membrane. Some bacteria, like mycoplasmas, have no cell wall whatsoever. Some bacteria may even have the capsule called a third, ultimate protective layer. Whip-like extensions often contain bacteria surfaces— lengthy ones known as flagella or brief ones known as pili— that assist bacteria to move around and connect to a host.

Practice Questions on Types of Bacteria 

Q. Name the bacteria form that utilizes Co2 as the sole source of living carbon.

1. Organotrophs
2.  Heterotrophs
3. Autotrophs
4. Lithotrophs

Answer: C. Autotrophs

Q. Name the sort of bacteria used as a source of the electron by decreased inorganic materials?

1. Organotrophs
2. Heterotrophs
3. Autotrophs
4. Lithotrophs

Answer: D. Lithotrophs