The CcdB toxin is an efficient selective marker for CRISPR-plasmids developed for genome editing in cyanobacteria

Menestreau, Martin; Rachedi, Raphaël; Risoul, Véronique; Foglino, Maryline; Latifi, Amel

doi:10.17912/micropub.biology.000512

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…There is some evidence to support a role of both plasmid and integrated TA systems as competing with other MGEs, providing a protective advantage to host cells from invading genetic material [41,42,70] with specific examples for this TA system [63,71]. The strong toxicity mediated by CcdB has been co-opted for use in multiple biotechnology applications including plasmid selection and screening for CRISPR activity [72][73][74][75]. CcdB has also been formulated into a potent treatment by combining the toxin with intein sites, allowing controllable targeting of the CcdB activity in selected bacterial cells [76] or in other approaches by the direct administration of a peptide derived from the CcdB sequence [77].…”

Section: Ccdb Toxin Proteins From Ccdab Type II Ta Systemsmentioning

confidence: 99%

Friend or Foe: Protein Inhibitors of DNA Gyrase

Ruan,

Tu,

Bourne

2024

Biology

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DNA gyrase is essential for the successful replication of circular chromosomes, such as those found in most bacterial species, by relieving topological stressors associated with unwinding the double-stranded genetic material. This critical central role makes gyrase a valued target for antibacterial approaches, as exemplified by the highly successful fluoroquinolone class of antibiotics. It is reasonable that the activity of gyrase could be intrinsically regulated within cells, thereby helping to coordinate DNA replication with doubling times. Numerous proteins have been identified to exert inhibitory effects on DNA gyrase, although at lower doses, it can appear readily reversible and therefore may have regulatory value. Some of these, such as the small protein toxins found in plasmid-borne addiction modules, can promote cell death by inducing damage to DNA, resulting in an analogous outcome as quinolone antibiotics. Others, however, appear to transiently impact gyrase in a readily reversible and non-damaging mechanism, such as the plasmid-derived Qnr family of DNA-mimetic proteins. The current review examines the origins and known activities of protein inhibitors of gyrase and highlights opportunities to further exert control over bacterial growth by targeting this validated antibacterial target with novel molecular mechanisms. Furthermore, we are gaining new insights into fundamental regulatory strategies of gyrase that may prove important for understanding diverse growth strategies among different bacteria.

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Section: Ccdb Toxin Proteins From Ccdab Type II Ta Systemsmentioning

confidence: 99%

Friend or Foe: Protein Inhibitors of DNA Gyrase

Ruan,

Tu,

Bourne

2024

Biology

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Unravelling HetC as a peptidase-based ABC exporter driving functional cell differentiation in the cyanobacterium Nostoc PCC 7120

Rachedi,

Risoul,

Foglino

et al. 2024

Microbiol Spectr

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The export of peptides or proteins is essential for a variety of important functions in bacteria. Among the diverse protein-translocation systems, peptidase-containing ABC transporters (PCAT) are involved in the maturation and export of quorum-sensing or antimicrobial peptides in Gram-positive bacteria and of toxins in Gram-negative organisms. In the multicellular and diazotrophic cyanobacterium Nostoc PCC 7120, the protein HetC is essential for the differentiation of functional heterocysts, which are micro-oxic and non-dividing cells specialized in atmospheric nitrogen fixation. HetC shows similarities to PCAT systems, but whether it actually acts as a peptidase-based exporter remains to be established. In this study, we show that the N-terminal part of HetC, encompassing the peptidase domain, displays a cysteine-type protease activity. The conserved catalytic residues conserved in this family of proteases are essential for the proteolytic activity of HetC and the differentiation of heterocysts. Furthermore, we show that the catalytic residue of the ATPase domain of HetC is also essential for cell differentiation. Interestingly, HetC has a cyclic nucleotide-binding domain at its N-terminus which can bind ppGpp in vitro and which is required for its function in vivo . Our results indicate that HetC is a peculiar PCAT that might be regulated by ppGpp to potentially facilitate the export of a signaling peptide essential for cell differentiation, thereby broadening the scope of PCAT role in Gram-negative bacteria. IMPORTANCE Bacteria have a great capacity to adapt to various environmental and physiological conditions; it is widely accepted that their ability to produce extracellular molecules contributes greatly to their fitness. Exported molecules are used for a variety of purposes ranging from communication to adjust cellular physiology, to the production of toxins that bacteria secrete to fight for their ecological niche. They use export machineries for this purpose, the most common of which energize transport by hydrolysis of adenosine triphosphate. Here, we demonstrate that such a mechanism is involved in cell differentiation in the filamentous cyanobacterium Nostoc PCC 7120. The HetC protein belongs to the ATP-binding cassette transporter superfamily and presumably ensures the maturation of a yet unknown substrate during export. These results open interesting perspectives on cellular signaling pathways involving the export of regulatory peptides, which will broaden our knowledge of how these bacteria use two cell types to conciliate photosynthesis and nitrogen fixation.

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The CcdB toxin is an efficient selective marker for CRISPR-plasmids developed for genome editing in cyanobacteria

Cited by 2 publications

References 11 publications

Friend or Foe: Protein Inhibitors of DNA Gyrase

Friend or Foe: Protein Inhibitors of DNA Gyrase

Unravelling HetC as a peptidase-based ABC exporter driving functional cell differentiation in the cyanobacterium Nostoc PCC 7120

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