I. Basic concepts
1. Bacterial classification is based on the characteristics of each bacterium and their genetic relationship.
Class, organized into different levels of system. There are two kinds of classification: ① phenotypic classification based on the morphological, physiological and biochemical characteristics of bacteria, including traditional classification and numerical classification; ② Chemical analysis and nucleic acid analysis are classified according to the structural homology of bacterial macromolecules (nucleic acid, protein), which is called taxonomic classification or natural classification.
2. Naming of Bacteria On the basis of classification, each bacterium is given a scientific name, which makes it possible to communicate with each other in production practice, clinical practice and scientific research. According to the laws and regulations of bacteria naming, it can be guaranteed that all researchers name bacteria the same.
3. Identification of bacteria: put the unknown bacteria into a proper position in the system according to the classification principle, compare their similarities with the known bacteria, and determine the classification status of bacteria through comparative analysis. If it is the same as the known bacteria, the name of the known bacteria is adopted; if it is different, the new name is determined according to the naming principle.
Second, the classification level.
The classification of bacteria, like other organisms, is in turn kingdom, family, class, order, family, genus and species. Bacteria belong to monera, including bacteria, actinomycetes, mycoplasma, chlamydia, rickettsia and spirochetes.
Latin suffixes of classification levels are relatively fixed, and their expressions are as follows: order-order, subfamily-subfamily, subfamily-subfamily, subfamily-subfamily.
Strain is the basic unit of bacterial classification, which classifies bacterial groups with basically the same biological characteristics into one strain; Several strains with similar characters and close genetic relationship form a genus; Similar genera belong to one family; And so on. Between these two levels, two taxonomic units can be added, such as subphylum, subclass, subgenus and subspecies. Groups and groups are not formal classification levels, but refer to collectives with certain characteristics and can be borrowed at any level.
The bacteria of the same strain are still different in some aspects, which can be subdivided into subspecies, and the classification level below subspecies is type to distinguish some special characteristics. E.g., serotype); Have different antigenic structures; Phage); Have different sensitivities to phage; Bacteriocin types with different sensitivities to bacteriocin, and biotypes with different biochemical reactions and some biological characteristics.
Bacteria of the same species, subspecies or isotype separated from different sources are called strains. The establishment of the strain is a pure culture subcultured from a single original colony of a single isolate, such as Mycobacterium tuberculosis 10 strain isolated from sputum of 10 tuberculosis patients. A strain with typical characteristics of a certain bacterium is called a typical strain or a standard strain, and it is the reference strain of this strain. The classification, identification and naming of bacteria are based on model bacteria and can also be used as quality control standards.
Three. Naming of bacteria
The revised edition of 1990 of the International Code of Bacteriology (published by ASM in 1992) is a currently recognized naming code, which has been published in 1975 for many years. A code adopted by the Third International Conference on Microbiology confirmed the bacterial nomenclature legally published by the International Journal of Systematic Bacteriology (IJSB) after 1980 1.
The biological binomial method of bacterial scientific names has two characteristics: one is the Latin word form, and the other is a clear classification level, that is, a generic name and a species name. The genus name comes first, it is a noun, and the first letter is capitalized; After the name is an adjective, whether it is a person's name or a place name, it should be lowercase; Both are indicated in italics. The Chinese translation of the scientific name of bacteria comes before the generic name. For example, Mycobacterium tuberculosis and Salmonella typhi. Genus names can also be expressed by initials, such as Mycobacterium tuberculosis and Stiffi. Sometimes some common bacteria can also use common names, such as mycobacterium tuberculosis and typhoid Bacillus. Sometimes it refers to a certain genus of bacteria in general, but not to any one of them in particular. sp can be added after the name of the genus, such as Mycobacteriumsp and Salmonellasp, which means Mycobacterium and Salmonella (sp stands for species, plural uses SPP); If 1 subspecies name is used, add subspecies name after the species name, such as Klebsiella pneumoniae subspecies pneumonia.
Naming specification stipulates that the new bacterial name must be published after IJSB, published by the internationally recognized international bacterial naming adjudication committee, and published in the approved bacterial name list. All academic papers related to bacterial research must use the above officially named bacterial scientific names.
Bacterial classification method
The classification of bacteria is based on the identification and comprehensive analysis of a large number of classification marks of bacteria. Classification markers used for bacteria include morphological, physiological, biochemical, immunochemical and genetic characteristics. In recent years, the application of various modern technologies and equipment to study the chemical structure and composition of cells and analyze their source relationship has opened up a prospect for the development of bacterial taxonomy.