Chemotype

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A chemotype (sometimes chemovar) is a chemically distinct entity in a plant or microorganism, with differences in the composition of the secondary metabolites. Minor genetic and epigenetic changes with little or no effect on morphology or anatomy may produce large changes in the chemical phenotype. Chemotypes are often defined by the most abundant chemical produced by that individual and the concept has been useful in work done by chemical ecologists and natural product chemists. With respect to plant biology, the term "chemotype" was first coined by Dr. Rolf Santesson and his son Johan in 1968, defined as, "...chemically characterized parts of a population of morphologically indistinguishable individuals." [1]

Plant multicellular eukaryote of the kingdom Plantae

Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, plants were treated as one of two kingdoms including all living things that were not animals, and all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts, mosses and the green algae, but excludes the red and brown algae.

Microorganism microscopic living organism

A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or in a colony of cells.

Genetics Science of genes, heredity, and variation in living organisms

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.

In microbiology, the term "chemoform" or "chemovar" is preferred in the 1990 edition of the International Code of Nomenclature of Bacteria (ICNB), the former referring to the chemical constitution of an organism and the latter meaning "production or amount of production of a particular chemical." Terms with the suffix -type are discouraged so as to avoid confusion with type specimens. [2] The terms chemotype and chemovar were originally introduced to the ICNB in a proposed revision to one of the nomenclatural rules dealing with infrasubspecific taxonomic subdivisions at the 1962 meeting of the International Microbiological Congress in Montreal. The proposed change argued that nomenclatural regulation of these ranks, such as serotype and morphotype, is necessary to avoid confusion. In proposed recommendation 8a(7), it was asked that "authorization be given for the use of the terms chemovar and chemotype," defining the terms as being "used to designate an infrasubspecific subdivision to include infrasubspecific forms or strains characterized by the production of some chemical not normally produced by the type strain of the species." The change to the Code was approved in August 1962 by the Judicial Commission of the International Committee of Bacteriological Nomenclature at the VIII International Microbiological Congress in Montreal. [3]

Type (biology) Specimen(s) to which a scientific name is formally attached

In biology, a type is a particular specimen of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralize the defining features of that particular taxon. In older usage, a type was a taxon rather than a specimen.

Taxonomic rank Level in a taxonomic hierarchy

In biological classification, taxonomic rank is the relative level of a group of organisms in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.

A good example of a plant with many polymorphic chemotypes is Thymus vulgaris . While largely indistinguishable in appearance, specimens of T. vulgaris may be assigned to one of seven different chemotypes, depending on whether the dominant component of the essential oil is thymol, carvacrol, linalool, geraniol, sabinene hydrate (thuyanol), α-terpineol, or eucalyptol. Such chemotypes may be indicated as Thymus vulgaris ct. thymol (red thyme), or Thymus vulgaris ct. geraniol (sweet thyme), etc. Such an indication has no taxonomic standing. [1]

Polymorphism (biology) Occurrence of two or more clearly different morphs or forms in the population of a species

Polymorphism in biology and zoology is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population.

<i>Thymus vulgaris</i> species of plant

Thymus vulgaris is a species of flowering plant in the mint family Lamiaceae, native to southern Europe from the western Mediterranean to southern Italy. Growing to 15–30 cm (6–12 in) tall by 40 cm (16 in) wide, it is a bushy, woody-based evergreen subshrub with small, highly aromatic, grey-green leaves and clusters of purple or pink flowers in early summer.

Essential oil hydrophobic liquid containing volatile aroma compounds from plants

An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetherolea, or simply as the oil of the plant from which they were extracted, such as oil of clove. An essential oil is "essential" in the sense that it contains the "essence of" the plant's fragrance—the characteristic fragrance of the plant from which it is derived. The term essential used here does not mean indispensable as with the terms essential amino acid or essential fatty acid which are so called since they are nutritionally required by a given living organism. In contrast to fatty oils, essential oils typically evaporate completely without leaving a stain or residue.

Because chemotypes are defined only by the most abundant secondary metabolite, they may have little practical meaning as a group of organisms sharing the same trait. Individuals of one chemotype may have vastly different chemical profiles, varying in the abundance of kind of the next most abundant chemical. This means two individuals of the same chemotype could have different impacts on herbivores, pollinators, or resistance to pests. A study by Ken Keefover-Ring and colleagues in 2008 cautioned that, "...this can be a very qualitative assessment of an individual's chemical profile, under which may be hiding significant chemical diversity." [1]

See also

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Thyme herb with culinary, medicinal and ornamental uses

Thyme is any member of the genus Thymus of aromatic perennial evergreen herbs in the mint family Lamiaceae. Thymes are relatives of the oregano genus Origanum. They have culinary, medicinal, and ornamental uses, the species most commonly cultivated and used for culinary purposes being Thymus vulgaris.

Subspecies taxonomic rank subordinate to species

In biological classification, the term subspecies refers to a unity of populations of a species living in a subdivision of the species' global range and varies from other populations of the same species by morphological characteristics. A subspecies cannot be recognized independently. A species is either recognized as having no subspecies at all or at least two, including any that are extinct. The term is abbreviated subsp. in botany and bacteriology, or ssp. in zoology. The plural is the same as the singular: subspecies.

In biology, a tribe is a taxonomic rank above genus, but below family and subfamily. It is sometimes subdivided into subtribes.

In botanical nomenclature, variety is a taxonomic rank below that of species and subspecies, but above that of form. As such, it gets a three-part infraspecific name. It is sometimes recommended that the subspecies rank should be used to recognize geographic distinctiveness, whereas the variety rank is appropriate if the taxon is seen throughout the geographic range of the species.

Type species term used in zoological nomenclature (also non-officially in botanical nomenclature)

In zoological nomenclature, a type species is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen(s). A similar concept is used for suprageneric groups called a type genus.

Pelagibacter, with the single species P. ubique, was isolated in 2002 and given a specific name, although it has not yet been described as required by the bacteriological code. It is an abundant member of the SAR11 clade in the phylum Alphaproteobacteria. SAR11 members are highly dominant organisms found in both salt and fresh water worldwide – possibly the most numerous bacterium in the world, and were originally known only from their rRNA genes, which were first identified in environmental samples from the Sargasso Sea in 1990 by Stephen Giovannoni's laboratory in the Department of Microbiology at Oregon State University and later found in oceans worldwide. P. ubique and its relatives may be the most abundant organisms in the ocean, and quite possibly the most abundant bacteria in the entire world. It can make up about 25% of all microbial plankton cells, and in the summer they may account for approximately half the cells present in temperate ocean surface water. The total abundance of P. ubique and relatives is estimated to be about 2 × 1028 microbes.

Thymol chemical compound

Thymol (also known as 2-isopropyl-5-methylphenol, IPMP) is a natural monoterpenoid phenol derivative of cymene, C10H14O, isomeric with carvacrol, found in oil of thyme, and extracted from Thymus vulgaris (common thyme) and various other kinds of plants as a white crystalline substance of a pleasant aromatic odor and strong antiseptic properties. Thymol also provides the distinctive, strong flavor of the culinary herb thyme, also produced from T. vulgaris.

Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis, and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many are able to move about through gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma.

In prokaryote nomenclature, Candidatus is a component of the taxonomic name for a bacterium or other prokaryote, that cannot be maintained in a microbiological culture collection. It is an interim taxonomic status for yet-to-be-cultured microorganisms. An example would be "Candidatus Phytoplasma allocasuarinae". This can be abbreviated to "Ca. Phytoplasma allocasuarinae". Candidatus status may be used when a species or genus is well characterized but yet-uncultured. With today's technology much information is obtained by 16S ribosomal RNA or even near-complete genomes with modern metagenomics techniques.

Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species are assignable to families, it may not be noticeable that there is more than one code, but beyond this basic level these are rather different in the way they work.

The bacterial order Chlamydiales includes only obligately intracellular bacteria that have a chlamydia-like developmental cycle of replication and at least 80% 16S rRNA or 23S rRNA gene sequence identity with other members of Chlamydiales. Chlamydiales live in animals, insects, and protozoa. The order Chlamydiales belongs to the class Chlamydiae, phylum Chlamydiae, domain Bacteria.

The International Code of Nomenclature of Prokaryotes (ICNP) formerly the International Code of Nomenclature of Bacteria (ICNB) or Bacteriological Code (BC) governs the scientific names for Bacteria and Archaea. It denotes the rules for naming taxa of bacteria, according to their relative rank. As such it is one of the nomenclature codes of biology.

Carvacrol, or cymophenol, C6H3(CH3)(OH)C3H7, is a monoterpenoid phenol. It has a characteristic pungent, warm odor of oregano.

The International Journal of Systematic and Evolutionary Microbiology is a peer-reviewed scientific journal covering research in the field of microbial systematics that was established in 1951. Its scope covers the taxonomy, nomenclature, identification, characterisation, culture preservation, phylogeny, evolution, and biodiversity of all microorganisms, including prokaryotes, yeasts and yeast-like organisms, protozoa and algae. The journal is currently published monthly by the Microbiology Society.

Bacterial phyla

The bacterial phyla are the major lineages, known as phyla or divisions, of the domain Bacteria.

Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.

This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see glossary of scientific names. Note that many of the abbreviations are used with or without a stop.

The International Committee on Systematics of Prokaryotes (ICSP), formerly the International Committee on Systematic Bacteriology (ICSB), is the body that oversees the nomenclature of prokaryotes, determines the rules by which prokaryotes are named and whose Judicial Commission issues Opinions concerning taxonomic matters, revisions to the Bacteriological Code, etc.

<i>Thymus zygis</i> species of plant

Thymus zygis is a type of flowering plant in the family Lamiaceae.

References

  1. 1 2 3 Keefover-Ring K, Thompson JD, and Linhart YB. 2009. Beyond six scents: defining a seventh Thymus vulgaris chemotype new to southern France by ethanol extraction. Flavour and Fragrance Journal, 24(3): 117-122. doi:10.1002/ffj.1921
  2. ↑ Lapage SP, Sneath PHA, Lessel EF, et al., editors. 1992. Appendix 10B. Infrasubspecific Terms. International Code of Nomenclature of Bacteria: Bacteriological Code, 1990 Revision. Washington (DC): ASM Press; 1992.
  3. ↑ Clark WA, and Seeliger HPR. 1963. Detailed minutes concerning actions taken in the emendation of the International Code of Nomenclature of Bacteria and Viruses during the meetings of the Judicial Commission of the International Committee of Bacteriological Nomenclature at the VIII International Microbiological Congress in Montreal August, 1962. International Bulletin of Bacteriological Nomenclature and Taxonomy , 13(1): 1-22.
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