My Operasalmonella intracelularni parazit?
Monday, May 24, 2010 11:09:56 AM
prevzate ze Science
Microbiology:
Salmonella's Safety Catch
R. John Collier
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.
E-mail: john_collier@hms.harvard.edu
Many pathogenic bacteria disable their host's immune system and thereby protect themselves from destruction by delivering "effector proteins" into the inner, cytosolic compartment of the eukaryotic host cells. Gram-negative bacteria, in particular, have evolved an elaborate "needle complex"—the type III secretion system (T3SS), consisting of more than 20 proteins—to convey an arsenal of effector proteins from their own cytosolic compartment across three membranes directly into the cytosol of the host cell (1). These bacteria spend much of their lives in transit between eukaryotic hosts, however, and it would be a potentially catastrophic waste of their resources to secrete effector proteins continuously into their environment. On page 1040 of this issue, Yu et al. (2) describe a system to regulate the secretion process in Salmonella enterica, an important intracellular pathogen of humans and animals.
The authors show that after the bacterium enters the host cell within a membrane-bound vacuole, it detects its arrival there by sensing the pH sequentially in two locations: first the acidic pH within the vacuole and then, once the T3SS has penetrated the vacuolar membrane, the neutral pH of the cytosol outside the vacuole. Only then does the bacterium allow its effector proteins to proceed through the T3SS needle into the host cell cytosol to control selected metabolic processes of that cell.
Microbiology:
Salmonella's Safety Catch
R. John Collier
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.
E-mail: john_collier@hms.harvard.edu
Many pathogenic bacteria disable their host's immune system and thereby protect themselves from destruction by delivering "effector proteins" into the inner, cytosolic compartment of the eukaryotic host cells. Gram-negative bacteria, in particular, have evolved an elaborate "needle complex"—the type III secretion system (T3SS), consisting of more than 20 proteins—to convey an arsenal of effector proteins from their own cytosolic compartment across three membranes directly into the cytosol of the host cell (1). These bacteria spend much of their lives in transit between eukaryotic hosts, however, and it would be a potentially catastrophic waste of their resources to secrete effector proteins continuously into their environment. On page 1040 of this issue, Yu et al. (2) describe a system to regulate the secretion process in Salmonella enterica, an important intracellular pathogen of humans and animals.
The authors show that after the bacterium enters the host cell within a membrane-bound vacuole, it detects its arrival there by sensing the pH sequentially in two locations: first the acidic pH within the vacuole and then, once the T3SS has penetrated the vacuolar membrane, the neutral pH of the cytosol outside the vacuole. Only then does the bacterium allow its effector proteins to proceed through the T3SS needle into the host cell cytosol to control selected metabolic processes of that cell.
