Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters. Bacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow.
Naming rules
The current nomenclature for bacterial species requires a capital letter for the genus name and an epithet beginning by a lowercase letter for the species name [7]. Genera and epithet should be Latin or Latinized; the specific epithet is an adjective that must agree with the gender of the generic name [7].Bacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow. Some live in or on other organisms including plants and animals including humans. There are approximately 10 times as many bacterial cells as human cells in the human body.
Bacteria are examples of the prokaryotic cell type. In general, prokaryotic cells are those that do not have a membrane-bound nucleus. In fact "pro-karyotic" is Greek for "before nucleus". Besides bacteria, the cyanobacteria (blue-green algae) are a major group of prokaryotes.
Are Bacteria Animals or Plants? Bacteria are neither animals nor plants. Bacteria are single-celled, prokaryotic organisms in comparison to animals and plants which are multicellular, eukaryotic organisms. Because bacteria are prokaryotic, they do not have a nucleus and no membrane-bound organelles.
Only the single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes—pro means before and kary means nucleus. Animals, plants, fungi, and protists are all eukaryotes—eu means true—and are made up of eukaryotic cells.
Prokaryotic organisms belong either to the domain Archaea or the domain Bacteria; organisms with eukaryotic cells belong to the domain Eukarya.
Gram-positive bacteria can be divided into two major subdivisions: the phylum Actinobacteria, also described as the high-G+C gram-positives, and the phylum Firmicutes, also known as the low-G+C gram-positives, a group that includes such well-known genera as Bacillus and Clostridium (21).
Examples of Bacteria. Bacteria are the plural of bacterium, which are microscopic one-celled organisms. They are found everywhere and can be harmful, as in infections; or they can be beneficial, as in fermentation or decomposition. Five types of bacteria are: Coccus, Bacillus, Spirillum, Rickettsia, and Mycoplasma.
A strain is a genetic variant or subtype of a microorganism (e.g., virus or bacterium or fungus). For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. These flu strains are characterized by their differing isoforms of surface proteins.
Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter, and Salmonella.
Whereas specie refers to organisms that are related based on genetic, biochemical and phenotypic criteria, a strain refers to isolates of a given species based on a number of characteristics including serotyping, enzyme type, functional traits and protein plasmid characterization etc.
The core genome represents the genes present in all strains of a species. It typically includes housekeeping genes for cell envelope or regulatory functions. The variable or accessory genome (also: flexible, dispensable genome) refers to genes not present in all strains of a species.
The Proteobacteria are further divided into five classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, and Epsilonproteobacteria (see Taxonomy of Clinically Relevant Microorganisms).
The order Neisseriales comprises morphologies including cocci, curved rods, spirillae, rods, multicellular ribbons and filaments. Most organisms are heterotrophs with some facultative methylotrophs and chemolithoheterotrophs.
The Betaproteobacteria are highly metabolically diverse and contain chemolithoautotrophs, photoautotrophs, and generalist heterotrophs. The type order is the Burkholderiales, comprising an enormous range of metabolic diversity, including opportunistic pathogens.
Akkermansia muciniphila (phylum Verrucomicrobia) is a mucin-degrading bacteria, believed to contribute to intestinal health and glucose homeostasis [56,57]. It could represent 3%–5% of the bacterial community [58], mainly residing in the intestinal mucosa, an interface between the gut microbiome and host tissues [59].
Gram-Positive and Gram-Negative Bacteria. The gram-positive bacteria retain the crystal violet colour and stains purple whereas the gram-negative bacteria lose crystal violet and stain red. Thus, the two types of bacteria are distinguished by gram staining.
Medical Definition of Gram-negative
Gram-negative: Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram's method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (called peptidoglycan).A variety of genera, which are not closely related to each other, convert energy from light through photosynthesis. "Proteobacteria" are associated with the imbalance of microbiota of the lower reproductive tract of women. These species are associated with inflammation.
