Diversity of Firmicutes peptidoglycan hydrolases and specificities of those involved in daughter cell separation

ABSTRACT As one of the final steps in the bacterial growth cycle, daughter cells must be released from one another by cutting the shared peptidoglycan wall that separates them. In Escherichia coli, this delicate operation is performed by several peptidoglycan hydrolases, consisting of multiple amidases, lytic transglycosylases, and endopeptidases. The interactions among these enzymes and the molecular mechanics of how separation occurs without lysis are unknown. We show here that deleting the endopeptidase PBP 4 from strains lacking AmiC produces long chains of unseparated cells, indicating that PBP 4 collaborates with the major peptidoglycan amidases during cell separation. Another endopeptidase, PBP 7, fulfills a secondary role. These functions may be responsible for the contributions of PBPs 4 and 7 to the generation of regular cell shape and the production of normal biofilms. In addition, we find that the E. coli peptidoglycan amidases may have different substrate preferences. When the dd-carboxypeptidase PBP 5 was deleted, thereby producing cells with higher levels of pentapeptides, mutants carrying only AmiC produced a higher percentage of cells in chains, while mutants with active AmiA or AmiB were unaffected. The results suggest that AmiC prefers to remove tetrapeptides from peptidoglycan and that AmiA and AmiB either have no preference or prefer pentapeptides. Muropeptide compositions of the mutants corroborated this latter conclusion. Unexpectedly, amidase mutants lacking PBP 5 grew in long twisted chains instead of straight filaments, indicating that overall septal morphology was also defective in these strains.

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Role of theN-Acetylmuramoyl-l-Alanyl Amidase, AmiA, ofHelicobacter pyloriin Peptidoglycan Metabolism, Daughter Cell Separation, and Virulence

Microbial Drug Resistance ◽

10.1089/mdr.2016.0070 ◽

2016 ◽

Vol 22 (6) ◽

pp. 477-486 ◽

Cited By ~ 10

Author(s):

Catherine Chaput ◽

Chantal Ecobichon ◽

Nadine Pouradier ◽

Jean-Claude Rousselle ◽

Abdelkader Namane ◽

...

Keyword(s):

Cell Separation ◽

Daughter Cell ◽

Daughter Cell Separation

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Fast Mechanically Driven Daughter Cell Separation Is Widespread in Actinobacteria

mBio ◽

10.1128/mbio.00952-16 ◽

2016 ◽

Vol 7 (4) ◽

Cited By ~ 17

Author(s):

Xiaoxue Zhou ◽

David K. Halladin ◽

Julie A. Theriot

Keyword(s):

Cell Division ◽

Cell Separation ◽

Daughter Cell ◽

Bacterial Species ◽

Video Microscopy ◽

Model Organisms ◽

Gram Positive ◽

Wide Range ◽

Cell Shapes ◽

Daughter Cell Separation

ABSTRACT Dividing cells of the coccoid Gram-positive bacterium Staphylococcus aureus undergo extremely rapid (millisecond) daughter cell separation (DCS) driven by mechanical crack propagation, a strategy that is very distinct from the gradual, enzymatically driven cell wall remodeling process that has been well described in several rod-shaped model bacteria. To determine if other bacteria, especially those in the same phylum ( Firmicutes ) or with similar coccoid shapes as S. aureus , might use a similar mechanically driven strategy for DCS, we used high-resolution video microscopy to examine cytokinesis in a phylogenetically wide range of species with various cell shapes and sizes. We found that fast mechanically driven DCS is rather rare in the Firmicutes (low G+C Gram positives), observed only in Staphylococcus and its closest coccoid relatives in the Macrococcus genus, and we did not observe this division strategy among the Gram-negative Proteobacteria . In contrast, several members of the high-G+C Gram-positive phylum Actinobacteria ( Micrococcus luteus , Brachybacterium faecium , Corynebacterium glutamicum , and Mycobacterium smegmatis ) with diverse shapes ranging from coccoid to rod all undergo fast mechanical DCS during cell division. Most intriguingly, similar fast mechanical DCS was also observed during the sporulation of the actinobacterium Streptomyces venezuelae . IMPORTANCE Much of our knowledge on bacterial cytokinesis comes from studying rod-shaped model organisms such as Escherichia coli and Bacillus subtilis . Less is known about variations in this process among different bacterial species. While cell division in many bacteria has been characterized to some extent genetically or biochemically, few species have been examined using video microscopy to uncover the kinetics of cytokinesis and daughter cell separation (DCS). In this work, we found that fast (millisecond) DCS is exhibited by species in two independent clades of Gram-positive bacteria and is particularly prevalent among the Actinobacteria , a diverse group that includes significant pathogens as well as bacteria that generate medically important antibiotics.

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