Diff: Bacteria

'''Bacteria''' are single-celled prokaryotic microorganisms. They are found in soil, water, air, animals, plants, extreme environments, and the human body. Some bacteria cause disease, many are harmless, and many are essential to ecosystems, digestion, biotechnology, and industry.

Bacteria are not animals, plants, or fungi. They lack a membrane-bound nucleus and are usually much smaller than human cells. Their simplicity does not make them primitive in a practical sense. Bacteria are highly diverse, adaptable, and successful forms of life.

== Cell Structure ==

Bacterial cells are prokaryotic. Their DNA is usually found in a nucleoid region rather than inside a nucleus. Many bacteria also contain plasmids, which are smaller DNA molecules that can carry useful traits such as antibiotic resistance genes.

Common bacterial structures include:

* A cell membrane.

* A cell wall, often containing peptidoglycan.

* Cytoplasm containing ribosomes and other cell components.

* A nucleoid containing the main chromosome.

* Plasmids in some species.

* Capsules, flagella, fimbriae, or pili in some species.

Gram staining is a laboratory method that helps divide many bacteria into Gram-positive and Gram-negative groups. Gram-positive bacteria have a thicker peptidoglycan wall. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane.

== Shapes ==

Bacteria have several common shapes. Cocci are roughly spherical. Bacilli are rod-shaped. Vibrios are comma-shaped. Spirilla and spirochaetes are curved or spiral forms.

Shape is useful for description, but it is not enough to identify a bacterium by itself. Identification may involve staining, growth conditions, biochemical tests, genetic tests, microscopy, and clinical or environmental context.

== Reproduction and Genetic Change ==

Most bacteria reproduce by binary fission. In this process, the cell copies its DNA and divides into two daughter cells. Under favourable conditions, some bacterial populations can grow very quickly.

Bacteria can also gain genetic variation through mutation and horizontal gene transfer. Horizontal gene transfer can occur through transformation, transduction, or conjugation. These processes help bacteria adapt and can spread traits such as antibiotic resistance.

== Metabolism ==

Bacterial metabolism is extremely varied. Some bacteria use oxygen, while others grow without it. Some obtain energy from organic compounds. Others use inorganic chemicals or light.

This metabolic diversity is one reason bacteria are important in nature. They contribute to decomposition, nitrogen cycling, sulphur cycling, carbon cycling, and other processes that keep ecosystems functioning.

Bacteria are central to nutrient cycling. Decomposer bacteria break down dead material. Nitrogen-fixing bacteria convert atmospheric nitrogen into forms that plants can use. Other bacteria take part in soil formation, water treatment, marine food webs, and symbiotic relationships.

The human microbiome also contains many bacteria. Bacteria in and on the body can help digest food, train the immune system, compete with harmful microbes, and produce useful compounds. A healthy relationship between humans and their microbes is complex and varies by body site.

== Disease ==

Some bacteria are pathogens. They can cause infections such as tuberculosis, cholera, bacterial pneumonia, meningitis, urinary tract infections, sepsis, wound infections, and foodborne illness.

Bacterial disease depends on the organism, the host, the route of infection, and the environment. Not every exposure leads to illness, and not every bacterium found in a patient is necessarily the cause of disease.

== Antibiotics and Resistance ==

Antibiotics are medicines used to treat bacterial infections. They may kill bacteria or stop them growing. They do not treat viral infections such as colds or influenza.

Antimicrobial resistance occurs when bacteria and other microbes survive drugs designed to kill them or stop their growth. Resistance can spread through bacterial populations and can make infections harder to treat. Good prescribing, infection control, vaccination, sanitation, diagnostics, and surveillance all matter in reducing the problem.

== Uses ==

Bacteria are used in food production, medicine, agriculture, environmental management, and research. Fermentation uses bacteria to make foods such as yoghurt, cheese, vinegar, and some fermented vegetables.

In biotechnology, bacteria can be engineered or selected to make proteins, enzymes, medicines, fuels, and chemicals. They are also used in wastewater treatment, bioremediation, composting, and laboratory research.

== Classification ==

Bacterial classification has changed as genetic methods have improved. Older systems relied heavily on shape, staining, growth, and metabolism. Modern classification uses DNA and RNA sequence data as well as other evidence.

Major bacterial groups include Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Spirochaetes, Chlamydiae, and Cyanobacteria. The names and boundaries of groups can change as taxonomy is revised.

== See Also ==

* [[Virus]]

* [[Medicine]]

== References ==

* [https://www.ncbi.nlm.nih.gov/books/NBK8477/ NCBI Bookshelf: Bacterial structure]

* [https://www.ncbi.nlm.nih.gov/books/NBK470553/ NCBI Bookshelf: Gram-positive bacteria]

* [https://www.britannica.com/science/bacteria Encyclopaedia Britannica: Bacteria]

* [https://www.britannica.com/science/binary-fission Encyclopaedia Britannica: Binary fission]

* [https://www.cdc.gov/antibiotic-use/data-research/facts-stats/index.html CDC: Antibiotic use facts]

* [https://www.cdc.gov/antimicrobial-resistance/about/index.html CDC: About antimicrobial resistance]

* [https://openstax.org/books/biology-2e/pages/22-2-structure-of-prokaryotes-bacteria-and-archaea OpenStax Biology 2e: Structure of prokaryotes]

[[Category:Biology]]

[[Category:Microbiology]]

[[Category:Medicine]]