Procaryotic Cell Division with Respect to Wall and Membranes

Higgins, M. L.; Shockman, Gérald D.; Ryter, A

doi:10.3109/10408417109104477

Cited by 172 publications

(121 citation statements)

References 147 publications

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“…Many mutants with altered shape have been described previously in both gram-negative and in gram-positive bacteria, but in all cases the mutants were isolated from rod-shaped species and mutations led to the formation of cocci instead of normal rods (1, 8, 22, 25-27, 31, 40, 42, 50). In contrast, the possibility of obtaining the rod shape as a consequence of a mutation occurring in wild-type cocci has never even been considered before, probably because since the rod shape involves a higher organizational complexity than does the coccal shape, it was thought that additional genes not carried by cocci were needed to obtain rod-shaped bacteria (20). In contrast, as described above, the TCS model also considers the possibility that wild-type bacteria may ordinarily grow as cocci even when they carry the site for lateral wall elongation, provided that the activity of the site is relatively low (34).…”

Section: Discussionmentioning

confidence: 99%

“…What we did find surprising, however, was the fact that the authors ascribed to a hypothesis other than the TCS model (5) the concept whereby the activity of the sites for lateral wall elongation and for septum formation alternates during the cell cycle. No trace of this concept can be found in the paper cited (20), and it cannot be taken for granted that such activity alternates, as documented by the fact that some This is the first report describing mutants isolated from wild-type cocci that undergo transition from coccal to rod shape. Many mutants with altered shape have been described previously in both gram-negative and in gram-positive bacteria, but in all cases the mutants were isolated from rod-shaped species and mutations led to the formation of cocci instead of normal rods (1, 8, 22, 25-27, 31, 40, 42, 50).…”

Section: Discussionmentioning

confidence: 99%

“…that in rod-shaped bacteria two separate functions may exist, one responsible for lateral wall elongation and the other responsible for septum formation (38). This suggestion was taken up by Higgins and Shockman (20), who proposed that in contrast to rods, cocci expand their surfaces only through cross wall formation and that rods must carry additional genetic information for the production of lateral walls. Others (13,18,23,28,39,(41)(42)(43)(44)46) have supported these proposals.…”

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confidence: 93%

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Bacterial cell shape regulation: testing of additional predictions unique to the two-competing-sites model for peptidoglycan assembly and isolation of conditional rod-shaped mutants from some wild-type cocci

1990

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The two-competing-sites model for peptidoglycan assembly for bacterial cell shape regulation suggests that in rods, bacterial cell shape depends on the balance between two reactions (sites), one responsible for lateral wall elongation and the other responsible for septum formation. The two reactions compete with each other so that no lateral wall can be formed during septum formation and vice versa. When the site for lateral wall elongation overcomes that for septum formation, long rods or filaments are formed and cell division may be blocked. When the reaction leading to septum formation is hyperactive compared with the other, coccobacilli or cocci are formed. Other bacteria carry only one site for peptidoglycan assembly and can grow only as cocci. The two-competing-sites model predicts that two different types of cocci exist (among both morphology mutants and wild-type strains); one carries only the site for septum formation, whereas the other also carries the site for lateral wall elongation, the former site predominating over the latter. As a consequence of the inhibition (by antibiotics or by mutations) of septum formation in wild-type cocci of various species and in coccoid morphology mutants, some cocci are expected to undergo transition to rod shape and others are not. We have evaluated these predictions and show that they are in agreement. In fact, we found that among wild-type cocci belonging to 13 species, those of 6 species formed rods, whereas the remaining organisms maintained their coccal shape when septa were inhibited by antibiotics. Some coccoid morphology mutants of rod-shaped bacteria underwent coccus-to-rod transition after septum inhibition by antibiotics, whereas others maintained their coccal shape. When a mutation that causes septum inhibition was expressed in a morphology mutant of Klebsielia pneumoniae grown as a coccus, transition to rod shape was observed. A total of 914 mutants unable to form colonies at 42TC were isolated from the coccoid species mentioned above. Between 75 and 95% of the mutants isolated from the species that formed rods when septum formation was inhibited by antibiotics but none of those isolated from the others underwent coccus-to-rod transition upon incubation at the nonpermissive temperature.In previous papers, we proposed a model for shape regulation in bacteria and presented a large body of experimental data in support of it (33,34,37). In this study, we have extensively tested predictions concerning the effects on cell shape of septum inhibition by antibiotics and mutations in various wild-type and mutant coccoid bacteria (see predictions 6 and 7 of Table 1, which have previously been evaluated only preliminarily). We show that all predictions are fulfilled and demonstrate that some coccoid species but not others undergo transition to rod shape when septa are specifically blocked by antibiotics and that mutants undergoing coccus-to-rod transition can be isolated in some coccoid species but not in others.The two-competing-sites (TCS) model for peptidoglycan ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 93%

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Bacterial cell shape regulation: testing of additional predictions unique to the two-competing-sites model for peptidoglycan assembly and isolation of conditional rod-shaped mutants from some wild-type cocci

1990

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“…The cell division in grampositive cocci begins with centripetal penetration of the wall followed by the appearance of wall bands [25]. Subsequently, the new wall bands are separated by a nascent cross-wall.…”

Section: Discussionmentioning

confidence: 99%

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

et al. 2006

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Background and Objectives: A reliable method to eradicate the bacteria of residual carious dentin has not yet been developed. The aim of this study was to evaluate the antibacterial effect of a diode laser on Streptococcus mutans through different thickness (500, 1,000, and 2,000 mm) of human dentin. The thermal effect of laser irradiation was also investigated. Study Design/Materials and Methods: Dentin specimens were inoculated with 2 ml of S. mutans on one side and irradiated by a diode laser on the other side with a power output ranging from 0.5 to 7 W. The laser tip was swept with the whole irradiation area of 7 mmÂ3 mm at a speed of about 10 mm/second with a total irradiation time of 30 seconds. Cooling with distilled water (30 ml/minute) was applied simultaneously during laser irradiation. After laser irradiation, the bacteria was removed from the dentin surfaces and cultured for 48 hours at 378C anaerobically to assess the colony forming units (CFU) per ml. The morphology of the lased bacteria and the temperature rise during laser irradiation were observed by scanning electron microscope (SEM) and measured by thermocouple, respectively. Results: The results revealed that 7 W of laser power could kill 97.7% of CFU through 500 mm thickness of dentin. However, the bactericidal efficiency was significantly reduced as the dentin thickness was increased. The morphological changes of lased bacteria ranged from less affected such as loss of their wall bands and existence of minicells to more severely degenerated, such as disintegration and fusion of cells with pores on the cell wall. Only the dentin specimens with a thickness of 500 mm exhibited a temperature rise greater than 5.58C after receiving 5 or 7 W of laser irradiation. Conclusions: A diode laser can eliminate the Streptococcus mutans of the residual carious dentin without inducing high pulpal temperature rise when the remaining dentin thickness is greater than 1 mm.

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“…Cell shape is maintained by the covalently bonded murein layer of the cell envelope (35). Higgins and Shockman (15) postulated the existence of two different systems for murein synthesis: the cell elongation system would produce only cylindrical murein required for cell growth, and the septation system would be periodically activated to synthesize the polar caps during cell division. Penicillin-binding protein 3 (PBP 3), a protein encoded by the pbpB gene (33), is a transpeptidase needed only during septum formation (17).…”

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confidence: 99%

Identification, cloning, and expression of bolA, an ftsZ-dependent morphogene of Escherichia coli

et al. 1988

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A newly found morphogene of Escherichia coli, boLA, mapping at min 10 of the genetic map, was cloned in a 7.2-kilobase BamHI fragment and identified by its ability to produce osmotically stable spherical cells when overexpressed. This gene codes for a polypeptide of 13 kilodaltons. Overexpression of boUl+ was achieved in low-copy-number vectors with operon fusions to the tet and lac promoters, indicating a clockwise direction of transcription. While no modification of any of the penicillin-binding proteins was observed, morphological effects due to overexpression of boUl+ were shown to be dependent on the presence of an active ftsZ gene product. Our results suggest the existence of a mechanism mediated by FtsZ for modifying the conformation of nascent murein in the early steps of septum formation.

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Procaryotic Cell Division with Respect to Wall and Membranes

Cited by 172 publications

References 147 publications

Bacterial cell shape regulation: testing of additional predictions unique to the two-competing-sites model for peptidoglycan assembly and isolation of conditional rod-shaped mutants from some wild-type cocci

Bacterial cell shape regulation: testing of additional predictions unique to the two-competing-sites model for peptidoglycan assembly and isolation of conditional rod-shaped mutants from some wild-type cocci

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

Identification, cloning, and expression of bolA, an ftsZ-dependent morphogene of Escherichia coli

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