Chromosomal Replication, Plasmid Replication, and Cell Division

Hiroaki Takeuchi; Teruko Nakazawa

doi:10.1128/9781555818005.ch23

Chapter 23 : Chromosomal Replication, Plasmid Replication, and Cell Division

Authors: Hiroaki Takeuchi, Teruko Nakazawa¹

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Affiliations: 1: Department of Microbiology, Yamaguchi University School of Medicine, Ube, Yamaguchi 755-8505, Japan

Content Type: Monograph

Publication Year: 2001

Category: Bacterial Pathogenesis

Book DOI: 10.1128/9781555818005

Chapter DOI: 10.1128/9781555818005.ch23

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Abstract:

The study of chromosomal replication and cell division of bacteria has extended beyond Escherichia coli, and important insights have emerged recently from studies in other species, especially Bacillus subtilis and Caulobacter crescentus. Cell division is coordinated with other cell cycle events such as genomic DNA synthesis that leads to chromosomal replication and partition, increase of cell mass, and cell expansion by cell wall synthesis. This chapter reviews the information about predicted genes related to chromosomal replication, plasmid replication, and cell division in Helicobacter pylori, and a plausible replication machinery of the bacterium is discussed in light of the current understanding of bacterial organization and function of replication and cell division. The DnaA protein is essential for the initiation of chromosomal replication and is highly conserved among different bacteria. Clinical isolates of H. pylori have been reported to carry plasmids ranging in size from 1.5 to 40 kb. Three cryptic plasmids, pHPK225 (1.5 kb), pHPM180 (3.5 kb), and pHell (2.9 kb), have been completely sequenced. Cell division of gram-negative bacteria proceeds through nucleoid segregation, partitioning of the cytoplasm into two compartments each containing a copy of the cell's genetic information, and invagination of the three layers of the cell envelope between the chromosome. Chromosomal replication and cell division of bacteria are well-organized and coordinately regulated processes operated by a complex genetic machinery. H. pylori seems to possess almost all the components known to be involved in chromosomal replication and cell division in E. coli.

Citation: Takeuchi H, Nakazawa T. 2001. Chromosomal Replication, Plasmid Replication, and Cell Division, p 259-267. In Mobley H, Mendz G, Hazell S (ed), Helicobacter pylori. ASM Press, Washington, DC. doi: 10.1128/9781555818005.ch23

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Chromosomal Replication, Plasmid Replication, and Cell Division

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Figure 1

Regions including the putative origin of replication (oriC) of H. pylori 26695 and J99. Numbers at each end of the scale represent the position in nucleotides in the genome. Open boxes without gene names represent hypothetical genes with unknown functions. Genes in this region are folB (dihydroneopterin), frpB3 (iron-regulated outer membrane protein aldolase), selA (selenocysteine synthase), nusA (transcription termination factor), eco571R (type II restriction enzyme R and M protein), res (type III restriction enzyme R protein), mod (adenine-specific DNA methyltransferase), recG (ATP-dependent DNA helicase), and dnaA (chromosomal replication initiator protein). JHP1409 is for type II DNA modification enzyme (methyltransferase) ( 17 ). Numbers under the boxes represent HP and JHP numbers of strains 26695 and J99, respectively. Horizontal arrows above the boxes represent the direction of transcription. The DnaA-box sequences with exact matches (•) and a single mismatch (O) are indicated.

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Figure 1

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Figure 2

Localization of cell division-related genes on the H. pylori 26695 genome. Boxes with numbers below represent ORF of strain 26695. Horizontal arrows above the boxes represent the direction of transcription. Boxes are not drawn to scale and are separated when the genes are more than 20 bp apart. Closed boxes represent putative genes involved in cell division listed in Table 2 . Other genes in these regions are ilvC (acetohydroxy acid isomeroreductase), dprA (DNA processing chain A), prmA (ribosomal protein L11 methyltransferase), pssA (phosphatidylserine synthase), proC (pyrroline-5-carboxylate reductase), tsf (translation elongation factor EF-Ts), fliE (flagellar basal-body protein), flgC (flagellar basal-body rod protein), flgB (flagellar basal-body rod protein), and ceuE (ferric iron ABC transporter, periplasmic iron-binding protein). Vertical-striped and open boxes represent conserved hypothetical and hypothetical genes, respectively.

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Figure 2

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Figure 3

H. pylori HPK5 (wild type, left) and HPKT510 (cdrA-disrupted mutant, right) micrographs. 4′, 6′-diamidino-2-phenylindole (DAP)-stained micrographs (A) and shadowed electron micrographs (B) of H. pylori HPK5 (wild type) and HPKT510 (cdrA-disrupted mutant) from exponential-phase cultures. Cells were grown in brucella broth supplemented with 5% horse serum under a microaerobic condition ( 62 ). Bars indicate 10 μm in A and 1 μm in B.

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Figure 3

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Tables

Chromosomal Replication, Plasmid Replication, and Cell Division

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Table 1

Proteins involved in chromosomal replication of E. coli and their homologs recognized in H. pylori a

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Table 1

Proteins involved in chromosomal replication of E. coli and their homologs recognized in H. pylori a

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Table 2

Proteins involved in cell division of E. coli and their homologs identified in H. pylori strains 26695 a and J99 b

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Table 2

Proteins involved in cell division of E. coli and their homologs identified in H. pylori strains 26695 a and J99 b