Genetic Analysis of Legionella pneumophila Intracellular Multiplication in Human and Protozoan Hosts

Legionella ◽  
2014 ◽  
pp. 90-96
Author(s):  
Gil Segal ◽  
Howard A. Shuman
Keyword(s):  
Genetic Analysis ◽  
Legionella Pneumophila ◽  
Intracellular Multiplication

scholarly journals The Legionnaires' disease bacterium (Legionella pneumophila) inhibits phagosome-lysosome fusion in human monocytes.

1983 ◽  
Vol 158 (6) ◽  
pp. 2108-2126 ◽  
Author(s):  
M A Horwitz
Keyword(s):  
Acid Phosphatase ◽  
Legionella Pneumophila ◽  
Thorium Dioxide ◽  
Live Bacteria ◽  
Phosphatase Cytochemistry ◽  
Legionnaires Disease ◽  
Intracellular Multiplication ◽  
Erythromycin A ◽  
Secondary Lysosomes ◽  
Bacterial Protein Synthesis

The interactions between the L. pneumophila phagosome and monocyte lysosomes were investigated by prelabeling the lysosomes with thorium dioxide, an electron-opaque colloidal marker, and by acid phosphatase cytochemistry. Phagosomes containing live L. pneumophila did not fuse with secondary lysosomes at 1 h after entry into monocytes or at 4 or 8 h after entry by which time the ribosome-lined L. pneumophila replicative vacuole had formed. In contrast, the majority of phagosomes containing formalin-killed L. pneumophila, live Streptococcus pneumoniae, and live Escherichia coli had fused with secondary lysosomes by 1 h after entry into monocytes. Erythromycin, a potent inhibitor of bacterial protein synthesis, at a concentration that completely inhibits L. pneumophila intracellular multiplication, had no influence on fusion of L. pneumophila phagosomes with secondary lysosomes. However, coating live L. pneumophila with antibody or with antibody and complement partially overcame the inhibition of fusion. Also activating the monocytes promoted fusion of a small proportion of phagosomes containing live L. pneumophila with secondary lysosomes. Acid phosphatase cytochemistry revealed that phagosomes containing live L. pneumophila did not fuse with either primary or secondary lysosomes. In contrast to phagosomes containing live bacteria, the majority of phagosomes containing formalin-killed L. pneumophila were fused with lysosomes by acid phosphatase cytochemistry. The capacity of L. pneumophila to inhibit phagosome-lysosome fusion may be a critical mechanism by which the bacterium resists monocyte microbicidal effects.

scholarly journals Molecular mechanism of elongation factor 1A inhibition by a Legionella pneumophila glycosyltransferase

2010 ◽  
Vol 426 (3) ◽  
pp. 281-292 ◽  
Author(s):  
Ramon Hurtado-Guerrero ◽  
Tal Zusman ◽  
Shalini Pathak ◽  
Adel F. M. Ibrahim ◽  
Sharon Shepherd ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Binding Sites ◽  
Substrate Recognition ◽  
Elongation Factor ◽  
Negative Bacterium ◽  
Glucose Binding ◽  
Legionnaires Disease ◽  
Organelle Trafficking ◽  
Intracellular Multiplication ◽  
Positively Charged

Legionnaires' disease is caused by a lethal colonization of alveolar macrophages with the Gram-negative bacterium Legionella pneumophila. LpGT (L. pneumophila glucosyltransferase; also known as Lgt1) has recently been identified as a virulence factor, shutting down protein synthesis in the human cell by specific glucosylation of EF1A (elongation factor 1A), using an unknown mode of substrate recognition and a retaining mechanism for glycosyl transfer. We have determined the crystal structure of LpGT in complex with substrates, revealing a GT-A fold with two unusual protruding domains. Through structure-guided mutagenesis of LpGT, several residues essential for binding of the UDP-glucose-donor and EF1A-acceptor substrates were identified, which also affected L. pneumophila virulence as demonstrated by microinjection studies. Together, these results suggested that a positively charged EF1A loop binds to a negatively charged conserved groove on the LpGT structure, and that two asparagine residues are essential for catalysis. Furthermore, we showed that two further L. pneumophila glycosyltransferases possessed the conserved UDP-glucose-binding sites and EF1A-binding grooves, and are, like LpGT, translocated into the macrophage through the Icm/Dot (intracellular multiplication/defect in organelle trafficking) system.

Importance of theicmNgene in the growth ofLegionella pneumophilain amoebic cells at low temperature

2012 ◽  
Vol 58 (4) ◽  
pp. 490-501
Author(s):  
Tian Qin ◽  
Ken-ichiro Iida ◽  
Zhenyu Piao ◽  
Susumu Shiota ◽  
Hongyu Ren ◽  
...  
Keyword(s):  
Low Temperature ◽  
Legionella Pneumophila ◽  
Gene Replacement ◽  
Gene Products ◽  
Intracellular Growth ◽  
Bacterial Proliferation ◽  
Intracellular Multiplication ◽  
Type Ivb Secretion ◽  
Type Ivb Secretion System

Legionella pneumophila grows in amoebae and has achieved the ability to grow at various temperatures, although the mechanisms controlling this ability remain poorly understood. The Icm/Dot type IVB secretion system is composed of more than 25 proteins and is known to be essential for intracellular growth. The role of the icmN gene in intracellular multiplication and the effects of culture temperatures on it are not precisely understood. We conducted our investigation using an icmN mutant made by gene replacement mutagenesis. Intracellular growth of the mutant was impaired both in mammalian macrophages and amoeba at 37 °C. In particular, intracellular growth in amoebae was completely impaired at 25 °C. It was found that genes from icmN to icmC formed an operon, i.e., icmN, -M, -L, -E, -G, -C,, and the promoter activity of the icmN operon was stronger at 25 than at 37 °C. It was suggested that icmM and its downstream genes had a secondary promoter that enables icmN mutant grow in amoebae at lower temperatures and macrophages at 37 °C. These results show that the icmN promoter has a low temperature inducible nature, and gene products of the icmN operon require high expression for bacterial proliferation at low temperatures within amoeba.

The intracellular multiplication of Legionella pneumophila in protozoa from hospital plumbing systems

1991 ◽  
Vol 142 (6) ◽  
pp. 677-685 ◽  
Author(s):  
K Nahapetian ◽  
O Challemel ◽  
D Beurtin ◽  
S Dubrou ◽  
P Gounon ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Plumbing Systems ◽  
Intracellular Multiplication

scholarly journals sciS, an icmF Homolog in Salmonella enterica Serovar Typhimurium, Limits Intracellular Replication and Decreases Virulence

2005 ◽  
Vol 73 (7) ◽  
pp. 4338-4345 ◽  
Author(s):  
Duncan A. Parsons ◽  
Fred Heffron
Keyword(s):  
Legionella Pneumophila ◽  
Salmonella Enterica ◽  
Wild Type Strain ◽  
Salmonella Enterica Serovar Typhimurium ◽  
The Body ◽  
Wild Type ◽  
Serovar Typhimurium ◽  
Intracellular Multiplication ◽  
Late Stages ◽  
Made In

ABSTRACT Salmonella enterica serovar Typhimurium utilizes macrophages to disseminate from the intestine to deeper tissues within the body. While S. enterica serovar Typhimurium has been shown to kill its host macrophage, it can persist intracellularly beyond 18 h postinfection. To identify factors involved in late stages of infection, we screened a transposon library made in S. enterica serovar Typhimurium for the ability to persist in J774 macrophages at 24 h postinfection. Through this screen, we identified a gene, sciS, found to be homologous to icmF in Legionella pneumophila. icmF, which is required for intracellular multiplication, is conserved in several gram-negative pathogens, and its homolog appears to have been acquired horizontally in S. enterica serovar Typhimurium. We found that an sciS mutant displayed increased intracellular numbers in J774 macrophages when compared to the wild-type strain at 24 h postinfection. sciS was maximally transcribed at 27 h postinfection and is repressed by SsrB, an activator of genes required for promoting intracellular survival. Finally, we demonstrate that an sciS mutant is hypervirulent in mice when administered intragastrically. Taken together, these data indicate a role for SciS in controlling intracellular bacterial levels at later stages of infection and attenuating virulence in a murine host

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