Bacterial genome research strategies are mainly divided into six parts: DNA extraction and sequencing, genome assembly, genome finishing (Genome finishing), gene prediction, gene annotation and genome comparison analysis.

Bacterial genome structure

1. The chromosomal genome of a bacterium usually consists of only one circular double-stranded DNA molecule, and the chromosomes of the bacteria are relatively clustered together to form a denser region called a nucleoid. The nuclear-free membrane is separated from the cytoplasm. The central part of the nucleus is composed of RNA and scaffold proteins, and the periphery is a double-stranded closed-loop DNA supercoil. Chromosomal DNA is usually linked to the cell membrane, and the number of junctions varies with bacterial growth and different life cycles. The signal region involved in DNA replication and transcription on the DNA strand preferentially binds to the cell membrane, such as the origin of replication (OriC) of E. coli chromosomal DNA, the end of replication (TerC), and the like. The role of the cell membrane here may be to fix the chromosomes. In addition, the replicated chromosomes are evenly distributed to the two progeny bacteria during cell division. Details on the nuclear-like structure are currently unclear.

1.  It has an operon structure. The structural gene is polycistronic, that is, several functionally related structural genes are connected in series and regulated by the same regulatory region. . Several operons can also be regulated by a common regulatory gene, the regulon.

1. In most cases, the structural gene is a single copy in the bacterial chromosomal genome, but the gene rrn encoding rRNA is often multi-copy, which may facilitate the rapid assembly of ribosomes, so that cells can be easily used when protein synthesis is urgently needed. There is a large amount of ribosome formation in a short time.

1. Similar to the genome of the virus, the proportion of unencoded DNA is much less than that of the eukaryotic genome.

1. Isogene having an isoenzyme encoding. For example, in the E. coli genome, there are two genes encoding chorismic acid mutase, and two genes encoding acetolactate synthase.

1. Unlike the viral genome, the coding sequences in the bacterial genome generally do not overlap, i.e., there is no overlap of genes.

(7) Recognition regions having various functions in a DNA molecule such as an origin of replication OriC, a replication termination region TerC, a transcription initiation region, and a termination region. These regions tend to have a special order and contain an inverted repeat order.

(8) At the end of a gene or operon, there is often a special termination sequence that allows transcription termination and RNA polymerase to detach from the DNA strand. For example, the tail of the E. coli tryptophan operon contains a 40 bp GC-rich region followed by an AT-rich region, which is the structure of the transcription terminator. The terminator has strong and weak points, and the strong terminator contains an inverted repeat sequence, which forms a stem-loop structure followed by a polyT structure. Such a terminator can terminate transcription without the need to terminate protein participation. The weak terminator, although it also has an inverted repeat, has no polyT structure and requires termination of protein participation to terminate transcription.

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