Common Cell Shape Evolution of Two Nasopharyngeal Pathogens

Abstract

Respiratory infectious diseases are the third cause of worldwide death. The nasopharynx is the portal of entry and the ecological niche of many microorganisms, of which some are pathogenic to humans, such as Neisseria meningitidis and Moraxella catarrhalis. These microbes possess several surface structures that interact with the actors of the innate immune system. In our attempt to understand the past evolution of these bacteria and their adaption to the nasopharynx, we first studied differences in cell wall structure, one of the strongest immune-modulators. We were able to show that a modification of peptidoglycan (PG) composition (increased proportion of pentapeptides) and a cell shape change from rod to cocci had been selected for along the past evolution of N. meningitidis. Using genomic comparison across species, we correlated the emergence of the new cell shape (cocci) with the deletion, from the genome of N. meningitidis ancestor, of only one gene: yacF. Moreover, the reconstruction of this genetic deletion in a bacterium harboring the ancestral version of the locus together with the analysis of the PG structure, suggest that this gene is coordinating the transition from cell elongation to cell division. Accompanying the loss of yacF, the elongation machinery was also lost by several of the descendants leading to the change in the PG structure observed in N. meningitidis. Finally, the same evolution was observed for the ancestor of M. catarrhalis. This suggests a strong selection of these genetic events during the colonization of the nasopharynx. This selection may have been forced by the requirement of evolving permissive interaction with the immune system, the need to reduce the cellular surface exposed to immune attacks without reducing the intracellular storage capacity, or the necessity to better compete for adhesion to target cells.

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

“…These observations imply that coccoid cells result from rods that have lost the ability to elongate. Moreover, examples of rods changing into spheres have been demonstrated both genetically and biochemically with the use of antibiotics, thus lending support to this model (28)(29)(30)(31)(32). Indeed, a recent paper describing the possible evolutionary steps that might have driven the bacillus-to-coccoid shape transition in Neisseria meningitidis provides evidence that the process happened in two distinct genetic steps.…”

“…Indeed, a recent paper describing the possible evolutionary steps that might have driven the bacillus-to-coccoid shape transition in Neisseria meningitidis provides evidence that the process happened in two distinct genetic steps. The authors further argue that convergent evolution in Moraxella catarrhalis resulted in a similar shape transition for a pathogen that occupies the same niche as N. meningitidis, suggesting that environmental selective pressure was the driving force behind this shape change (32).…”

Characterization in Helicobacter pylori of a Nickel Transporter Essential for Colonization That Was Acquired during Evolution by Gastric Helicobacter Species

“…pylori strains analyzed in [22]). The MycoHIT program [60,61] was used to search for NixA, subunits of NiuBDE, NikABCDE, NikZYXWV, urease (UreB) and hydrogenase (HydA). The identified proteins were then mapped onto a previously-determined phylogenetic tree of Helicobacter species [22] (Fig 8).…”

Amidase Activity of AmiC Controls Cell Separation and Stem Peptide Release and Is Enhanced by NlpD in Neisseria gonorrhoeae

“…In E. coli, AmiA is more active on intact sacculi than AmiC, as AmiA is present throughout the periplasm and capable of remodeling activity throughout the sacculi, whereas AmiC is septally restricted and shows a preference for septal PG over sidewall PG (14,18). GC is coccal in shape and lacks components of the PG elongation machinery (58,59), making it unlikely to have sidewall PG. It may be that a single broad specificity, cell separation amidase is sufficient when there is no need for multiple amidases that differentiate between septal and sidewall PG.…”