An agar plate streaked with microorganisms
Rod-shaped Bacillus subtilis
Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.
Phylogenetic tree of Bacteria, Archaea and Eucarya. The vertical line at bottom represents the last universal common ancestor.
Louis Pasteur in his laboratory, painting by A. Edelfeldt in 1885
Bacteria display many cell morphologies and arrangements
Statue of Koch in Berlin
The range of sizes shown by prokaryotes (Bacteria), relative to those of other organisms and biomolecules.
Structure and contents of a typical Gram-positive bacterial cell (seen by the fact that only one cell membrane is present).
An electron micrograph of Halothiobacillus neapolitanus cells with carboxysomes inside, with arrows highlighting visible carboxysomes. Scale bars indicate 100 nm.
Helicobacter pylori electron micrograph, showing multiple flagella on the cell surface
Bacillus anthracis (stained purple) growing in cerebrospinal fluid
Many bacteria reproduce through binary fission, which is compared to mitosis and meiosis in this image.
A culture of ''Salmonella
A colony of Escherichia coli
Helium ion microscopy image showing T4 phage infecting E. coli. Some of the attached phage have contracted tails indicating that they have injected their DNA into the host. The bacterial cells are ~ 0.5 µm wide.
Transmission electron micrograph of Desulfovibrio vulgaris showing a single flagellum at one end of the cell. Scale bar is 0.5 micrometers long.
The different arrangements of bacterial flagella: A-Monotrichous; B-Lophotrichous; C-Amphitrichous; D-Peritrichous
Streptococcus mutans visualised with a Gram stain.
Phylogenetic tree showing the diversity of bacteria, compared to other organisms. Here bacteria are represented by three main supergroups: the CPR ultramicrobacterias, Terrabacteria and Gracilicutes according to recent genomic analyzes (2019).
Overview of bacterial infections and main species involved.
Colour-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells
In bacterial vaginosis, beneficial bacteria in the vagina (top) are displaced by pathogens (bottom). Gram stain.
Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.

Bacteriology is the branch and specialty of biology that studies the morphology, ecology, genetics and biochemistry of bacteria as well as many other aspects related to them.

- Bacteriology

The study of bacteria is known as bacteriology, a branch of microbiology.

- Bacteria

3 related topics

Alpha

Scanning electron microscope image of Vibrio cholerae. This is the bacterium that causes cholera.

Germ theory of disease

Currently accepted scientific theory for many diseases.

Currently accepted scientific theory for many diseases.

Scanning electron microscope image of Vibrio cholerae. This is the bacterium that causes cholera.
A representation by Robert Seymour of the cholera epidemic depicts the spread of the disease in the form of poisonous air.
Louis Pasteur's pasteurization experiment illustrates the fact that the spoilage of liquid was caused by particles in the air rather than the air itself. These experiments were important pieces of evidence supporting the idea of germ theory of disease.

"Germ" refers to not just a bacterium but to any type of microorganism, such as protists or fungi, or even non-living pathogens that can cause disease, such as viruses, prions, or viroids.

Eventually, a "golden era" of bacteriology ensued, during which the germ theory quickly led to the identification of the actual organisms that cause many diseases.

An agar plate streaked with microorganisms

Microbiology

Scientific study of microorganisms, those being unicellular , multicellular (cell colony), or acellular (lacking cells).

Scientific study of microorganisms, those being unicellular , multicellular (cell colony), or acellular (lacking cells).

An agar plate streaked with microorganisms
Avicenna hypothesized the existence of microorganisms.
Antonie van Leeuwenhoek (1632–1723)
Van Leeuwenhoek's microscopes by Henry Baker
Martinus Beijerinck is often considered as a founder of virology
Innovative laboratory glassware and experimental methods developed by Louis Pasteur and other biologists contributed to the young field of bacteriology in the late 19th century.
A university food microbiology laboratory
Fermenting tanks with yeast being used to brew beer

Microbiology encompasses numerous sub-disciplines including virology, bacteriology, protistology, mycology, immunology, and parasitology.

Eukaryotic microorganisms possess membrane-bound organelles and include fungi and protists, whereas prokaryotic organisms—all of which are microorganisms—are conventionally classified as lacking membrane-bound organelles and include Bacteria and Archaea.

A Gram stain of mixed Staphylococcus aureus (S. aureus ATCC 25923, Gram-positive cocci, in purple) and Escherichia coli (E. coli ATCC 11775, Gram-negative bacilli, in red), the most common Gram stain reference bacteria

Gram stain

A Gram stain of mixed Staphylococcus aureus (S. aureus ATCC 25923, Gram-positive cocci, in purple) and Escherichia coli (E. coli ATCC 11775, Gram-negative bacilli, in red), the most common Gram stain reference bacteria
Gram stain of Candida albicans from a vaginal swab. The small oval chlamydospores are 2–4 µm in diameter.
Purple-stained gram-positive (left) and pink-stained gram-negative (right)

Gram stain or Gram staining, also called Gram's method, is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria.

Gram staining is a bacteriological laboratory technique used to differentiate bacterial species into two large groups (gram-positive and gram-negative) based on the physical properties of their cell walls.