Role of AmiA in the Morphological Transition of Helicobacter pylori and in Immune Escape

Chaput, Catherine; Ecobichon, Chantal; Cayet, Nadège; Girardin, Stephen E.; Werts, Catherine; Guadagnini, Stéphanie; Prévost, Marie-Claude; Mengin‐Lecreulx, Dominique; Labigne, Agnès; Boneca, Ivo Gomperts

doi:10.1371/journal.ppat.0020097

Cited by 103 publications

(134 citation statements)

References 58 publications

Supporting

Mentioning

130

Contrasting

Unclassified

Order By: Relevance

“…H. pylori coccoid cells showed 50-fold reductions in adherence and induction of the proinflammatory cytokine interleukin-8 (IL-8) (147), both of which are phenotypes associated with increased pathogenicity. Studies with mutants of amiA, encoding the sole amidase in H. pylori required for septum cleavage, suggest that in addition to lower adherence, the lower IL-8 induction by coccoids may also result from the diminished levels of tripeptide in the sacculi of coccoids, since amiA mutants fail to show lower tripeptide levels upon extended culture (148). While VBNC cells may have lower virulence, they still can serve as reservoirs for infectious organisms and can maintain plasmids, in the case of E. coli (149), and vancomycin resistance, in the case of Enterococcus (142).…”

Section: To Be or Not To Bementioning

confidence: 99%

Staying in Shape: the Impact of Cell Shape on Bacterial Survival in Diverse Environments

Yang

Blair

Salama

2016

Microbiol Mol Biol Rev

233

192

View full text Add to dashboard Cite

SUMMARYBacteria display an abundance of cellular forms and can change shape during their life cycle. Many plausible models regarding the functional significance of cell morphology have emerged. A greater understanding of the genetic programs underpinning morphological variation in diverse bacterial groups, combined with assays of bacteria under conditions that mimic their varied natural environments, from flowing freshwater streams to diverse human body sites, provides new opportunities to probe the functional significance of cell shape. Here we explore shape diversity among bacteria, at the levels of cell geometry, size, and surface appendages (both placement and number), as it relates to survival in diverse environments. Cell shape in most bacteria is determined by the cell wall. A major challenge in this field has been deconvoluting the effects of differences in the chemical properties of the cell wall and the resulting cell shape perturbations on observed fitness changes. Still, such studies have begun to reveal the selective pressures that drive the diverse forms (or cell wall compositions) observed in mammalian pathogens and bacteria more generally, including efficient adherence to biotic and abiotic surfaces, survival under low-nutrient or stressful conditions, evasion of mammalian complement deposition, efficient dispersal through mucous barriers and tissues, and efficient nutrient acquisition.

show abstract

Section: To Be or Not To Bementioning

confidence: 99%

Staying in Shape: the Impact of Cell Shape on Bacterial Survival in Diverse Environments

Yang

Blair

Salama

2016

Microbiol Mol Biol Rev

233

192

View full text Add to dashboard Cite

show abstract

“…A difference that was growth dependent but strain independent involved the increase in the level of the G-M-dipeptide motif when H. pylori entered the stationary phase. This modification is discussed elsewhere (9).…”

Section: Vol 189 2007mentioning

confidence: 99%

Characterization ofHelicobacter pyloriLytic Transglycosylases Slt and MltD

2007

Self Cite

View full text Add to dashboard Cite

Peptidoglycan (PG) is a cell wall heteropolymer that is essential for cell integrity. PG hydrolases participate in correct assembly of the PG layer and have been shown to be required for cell division, cell daughter separation, and maintenance of bacterial morphology. In silico analysis of the Helicobacter pylori genome resulted in identification of three potential hydrolases, Slt, MltD, and AmiA. This study was aimed at determining the roles of the putative lytic transglycosylases, Slt and MltD, in H. pylori morphology, growth, and PG metabolism. Strain 26695 single mutants were constructed using a nonpolar kanamycin cassette. The slt and mltD mutants formed normal bacillary and coccoid bacteria in the exponential and stationary phases, respectively. The slt and mltD mutants had growth rates comparable to the growth rate of the parental strain. However, the mltD mutant exhibited enhanced survival in the stationary phase compared to the wild type or the slt mutant. PG was purified from exponentially growing bacteria and from bacteria in the stationary phase, and its muropeptide composition was analyzed by high-pressure liquid chromatography. This analysis revealed changes in the muropeptide composition indicating that MltD and Slt have lytic transglycosylase activities. Glycan strand analysis suggested that Slt and MltD have exo and endo types of lytic transglycosylase activity, indicating that Slt is involved mainly in PG turnover and MltD is involved mainly in rearrangement of the PG layer. In this study, we determined the distinct roles of the lytic transglycosylases Slt and MltD in PG metabolism.Resistance to antibiotics has increased dramatically in the last few decades. Helicobacter pylori, the etiological agent of gastric diseases such as gastroduodenal ulcers and adenocarcinoma, is becoming increasingly resistant to the few antibiotics effective in vivo against this infection.Hence, new therapeutic strategies are required to overcome resistance to known antibiotics. PG is an essential macromolecule that surrounds bacteria and is responsible for their shape and resistance to turgor pressure. Its central role in cell viability has made the biosynthesis of PG one of the most successful antibiotic targets in bacteria. However, little is known about PG metabolism in H. pylori. Detailed knowledge about the PG metabolism of H. pylori could lead to the development of new antibiotics. Based on genome sequences, H. pylori appears to have little redundancy of genes involved in PG metabolism (1,4,20). H. pylori has all of the genetic complement required for the synthesis of PG precursors. Assembly of these precursors in the periplasm requires synthetases and PG hydrolases. H. pylori has three synthetases, PBP1, PBP2, and PBP3, and three PG hydrolases, including two lytic transglycosylases, Slt (HP0645) and MltD (HP1572), and an N-acetylmuramoyl-L-alanyl amidase, AmiA (HP0772).The aim of this work was to characterize the two lytic transglycosylases, Slt and MltD. We constructed single and double mutants and studied t...

show abstract

“…Periplasmic amidases have been shown to play a critical role in the cleavage of septal PG (4)(5)(6)(7). These enzymes hydrolyze the amide bond between the N-terminal L-alanine residue of the peptide side chain and MurNAc.…”

mentioning

confidence: 99%

Cell Separation in Vibrio cholerae Is Mediated by a Single Amidase Whose Action Is Modulated by Two Nonredundant Activators

et al. 2014

View full text Add to dashboard Cite

Synthesis and hydrolysis of septal peptidoglycan (PG) are critical processes at the conclusion of cell division that enable separation of daughter cells. Cleavage of septal PG is mediated by PG amidases, hydrolytic enzymes that release peptide side chains from the glycan strand. Most gammaproteobacteria, including Escherichia coli, encode several functionally redundant periplasmic amidases. However, members of the Vibrio genus, including the enteric pathogen Vibrio cholerae, encode only a single PG amidase, AmiB. Here, we show that V. cholerae AmiB is crucial for cell division and growth. Genetic and biochemical analyses indicated that AmiB is regulated by two activators, EnvC and NlpD, at least one of which is required for AmiB's localization to the cell division site. Localization of the activators (and thus of AmiB) is dependent upon the cell division protein FtsN. These factors mediate septal PG cleavage in E. coli as well; however, their precise roles vary between the two organisms in a number of ways. Notably, even though V. cholerae EnvC and NlpD appear to be functionally redundant under most growth conditions tested, NlpD is specifically required for intestinal colonization in the infant mouse model of cholera and for V. cholerae resistance against bile salts, perhaps due to environmental regulation of AmiB or its activators. Collectively, our findings reveal that although the cellular components that enable cleavage of septal PG appear to be generally conserved between E. coli and V. cholerae, they can be combined into diverse functional regulatory networks.

show abstract

Role of AmiA in the Morphological Transition of Helicobacter pylori and in Immune Escape

Cited by 103 publications

References 58 publications

Staying in Shape: the Impact of Cell Shape on Bacterial Survival in Diverse Environments

Staying in Shape: the Impact of Cell Shape on Bacterial Survival in Diverse Environments

Characterization ofHelicobacter pyloriLytic Transglycosylases Slt and MltD

Cell Separation in Vibrio cholerae Is Mediated by a Single Amidase Whose Action Is Modulated by Two Nonredundant Activators

Contact Info

Product

Resources

About