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"molecular biology has led to a breakthrough in the study of intestinal microecology. The most studied at present is 16S rRNA. In recent years, foreign scholars have used different molecular biology methods to study the 16SrRNA of bacteria, and obtained a wide range of bacterial 16SrRNA sequence library. This method can be used to detect bacteria in the intestines that < not be allowed to > orslow-growing bacteria. rRNA molecules are common in organisms, and the first structure of biological cell rRNA molecules has both conservative fragments and changing base sequences.
Over the long course of biological evolution, rRNA molecules maintain relatively constant biological functions and conservative base sequences, as well as mutation rates consistent with evolutionary processes, which are structurally Divided into conservative zones (conserveddomain) and variable regions (variabledomain), conservative fragments reflect kinship between biological species, while high-variable fragments can indicate differences between species, and those conservative or highly variable characteristic nucleotide sequences are the molecular basis for the identification of organisms of different classification levels (e.g., genus, species). Studying rRNA gene sequences can reveal systemic occurrences between species.
bacteria rRNA is divided into three seort factors, 5S, 16S, and 23SrRNA, respectively. Among them, 16SrRNA on the small sub-base of primary nuclear cell RNA is about 1540bp long, the structure and base arrangement complexity is moderate, and it is easier to sequence determination and analysis comparison.
< DNA sequence of 16SrRNA encoded on the bacterial chromosome, which is found > in all bacterial chromosome genes, and its internal structure consists of conservative and variable regions<> Therefore, the corresponding rDNA fragments can be amplified by PCR to quickly and sensitively detect the presence of certain bacteria or pathogenic bacteria in the sample, or to perform bacterial diversity analysis, especially those that cannot be cultured by hand microorganisms |
Woese (1980) defined the ancient bacterial community after comparing the nucleotide sequences of 16S (or 18S) rRNA/rDNA of more than 200 primary and total nuclear organisms (Including methane-producing bacteria, extreme salt-eating bacteria and extreme heat-eating bacteria), the biological community was re-divided into three main six-sector systems, namely, the three trunks of paleontical bacteria, real bacteria and etony organisms, which also include protozoa, fill", plants and animals.
because the ancient bacteria although the cell structure is similar to the real bacteria, but there are large differences in lipids and cell wall molecular structure, 16SrRNA base sequence analysis results also show that the ogenosity difference between the ancient bacteria and the real bacteria is not less than the difference between the primary nucleus and the true nucleus. It has now been agreed that 16SrRNA/rDNA gene sequences can be used to evaluate genetic polymorphism (genetic-versity) and systemic relationships in living organisms (phylogenetrics-ship), which can be used as a scientifically reliable indicator in bacterial taxonomy.
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" text-align:left;"> When classifying microorganisms in some special environments, it is difficult to obtain their pure culture for physiological analysis due to the limitations of separation culture technology<
Recently, many researchers have isolated and sequenced 16SrRNAs/rDNA directly from environmental micro-ecosystems, studied the microbial composition of many complex systems, including mammalian intestines, marsh silt, and ruminant stomachs, and discovered new species not found in traditional culture studies.
Dnaturing Gradient Get Electrophoresis," an electrophoresis technique first proposed by Fischer and Lerman in 1979 to detect DNA mutations. It has a higher resolution accuracy than "">> agarose electrophoresis and polyacrylamide gel electrophoresis, and a difference in nucleotide levels can be detected.
Muzyers and others used "GC splints" and heterogeneity dual-chain technology in DGGE for the first time in 1985.
To avoid the tedious labor of building a gene library, Muyzer, etc. (1993) introduced genetic fingerprinting technology (geneticfingerprint-niques) into the microbial ecology In the study, after dna separation and PCR amplification of the sample to obtain 16SrDNA fragments, 16SrDNA fragment composition map (i.e. genetic fingerprint) was obtained directly by denaturation gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE), and the microbial composition information of the system to be studied was obtained.
(Responsible Editor: King Kunlun of Great Han)
