A Francisella tularensis L,D‐carboxypeptidase plays important roles in cell morphology, envelope integrity, and virulence

2021 ◽  
Author(s):  
Briana Zellner ◽  
Dominique Mengin‐Lecreulx ◽  
Brenden Tully ◽  
William T. Gunning ◽  
Robert Booth ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Cell Morphology

scholarly journals A Single Mechanosensitive Channel ProtectsFrancisella tularensissubsp.holarcticafrom Hypoosmotic Shock and Promotes Survival in the Aquatic Environment

2017 ◽  
Author(s):  
David R. Williamson ◽  
Kalyan K. Dewan ◽  
Tanmay Patel ◽  
Catherine M. Wastella ◽  
Gang Ning ◽  
...  
Keyword(s):  
Fresh Water ◽  
Francisella Tularensis ◽  
Cell Morphology ◽  
Mechanosensitive Channel ◽  
Mammalian Host ◽  
Average Cell Size ◽  
Average Cell ◽  
Hypoosmotic Shock ◽  
Water Borne

AbstractFrancisella tularensissubspeciesholarcticais found throughout the northern hemisphere and causes the disease tularemia in humans and animals. An aquatic cycle has been described for this subspecies, which has caused water-borne outbreaks of tularemia in at least 10 countries. In this study, we sought to identify mechanosensitive channel(s) required for the bacterium to survive the transition from mammalian hosts to freshwater, which is likely essential for transmission of the bacterium between susceptible hosts. A singlemechanosensitivechannel MscS (FTL_1753), among the smallest members of the mechanosensitive channel superfamily, was found to protect subsp.holarctiafrom hypoosmotic shock. Deletion of this channel did not affect virulence within the mammalian host, howevermscSwas required to survive the transition from the host niche to fresh water. Deletion ofmscSdid not alter the sensitivity ofF. tularensissubspeciesholarcticato detergents, H2O2, or antibiotics, suggesting that the role of MscS is specific to protection from hypoosmotic shock. Interestingly, deletion ofmscSalso led to reduced average cell size without altering gross cell morphology. The small mechanosensitive channel identified and characterized in this study likely contributes to the transmission of tularemia between hosts by allowing the bacterium to survive the transition from mammalian hosts to fresh water.

scholarly journals A Francisella tularensis L,D-carboxypeptidase plays important roles in cell morphology, envelope integrity, and virulence

2019 ◽  
Author(s):  
Briana Zellner ◽  
Dominique Mengin-Lecreulx ◽  
Brenden Tully ◽  
William T. Gunning ◽  
Robert Booth ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Cell Morphology ◽  
Membrane Integrity ◽  
Infection Model ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
Virulent Type ◽  
Endopeptidase Activity ◽  
Altered Cell

SummaryFrancisella tularensis is a Gram-negative, intracellular bacterium that causes the zoonotic disease tularemia. Intracellular pathogens, including F. tularensis, have evolved mechanisms to survive in the harsh environment of macrophages and neutrophils, where they are exposed to cell membrane-damaging molecules. The bacterial cell wall, primarily composed of peptidoglycan (PG), maintains cell morphology, structure, and membrane integrity. Intracellular Gram-negative bacteria protect themselves from macrophage and neutrophil killing by recycling and repairing damaged PG – a process that involves over 50 different PG synthesis and recycling enzymes. Here, we identified a PG recycling enzyme, L,D-carboxypeptidase A (LdcA), of F. tularensis that is responsible for converting PG tetrapeptide stems to tripeptide stems. Unlike E. coli LdcA and most other orthologs, F. tularensis LdcA does not localize to the cytoplasm and also exhibits L,D-endopeptidase activity, converting PG pentapeptide stems to tripeptide stems. Loss of F. tularensis LdcA led to altered cell morphology and membrane integrity, as well as attenuation in a mouse pulmonary infection model and in primary and immortalized macrophages. Finally, an F. tularensis ldcA mutant protected mice against virulent Type A F. tularensis SchuS4 pulmonary challenge.

Cell morphology, volume, and surface area determinations from multilevel contouring within HVEM micrographs of serial sections and whole-cell mounts

1987 ◽  
Vol 45 ◽  
pp. 588-589
Author(s):  
M. Marko ◽  
A. Leith ◽  
D. Parsons
Keyword(s):  
Surface Area ◽  
Electron Micrographs ◽  
Cell Morphology ◽  
Individual Variation ◽  
Serial Section ◽  
Stereo Pair ◽  
Complex Structures ◽  
Serial Sections ◽  
Surface Areas ◽  
Computer Based

The use of serial sections and computer-based 3-D reconstruction techniques affords an opportunity not only to visualize the shape and distribution of the structures being studied, but also to determine their volumes and surface areas. Up until now, this has been done using serial ultrathin sections.The serial-section approach differs from the stereo logical methods of Weibel in that it is based on the Information from a set of single, complete cells (or organelles) rather than on a random 2-dimensional sampling of a population of cells. Because of this, it can more easily provide absolute values of volume and surface area, especially for highly-complex structures. It also allows study of individual variation among the cells, and study of structures which occur only infrequently.We have developed a system for 3-D reconstruction of objects from stereo-pair electron micrographs of thick specimens.

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