FcgRMediated Phagocytosis
The binding of IgG-opsonized targets to their cognate receptors, FcgR, leads to their rapid internalization by a process driven by a remarkable actin-dependent rearrangement of the phagocyte plasma membrane. Actin remodeling is a biphasic event, with initial polymerization during pseudopod extension followed by rapid depo-lymerization during or immediately after sealing of the nascent vacuole 76 . The signals triggering this response will be described next. Particle binding induces clustering...
Gene Transfer in Intracellular Symbionts
Unlike intracellular bacterial parasites, intracellular symbionts have a mutual or commensal relationship with their hosts 6 . Mutualism describes a relationship where both species receive a fitness gain, and commensalism is where one gains but the other is not significantly harmed 86 . However, living together allows symbiotic species to genetically coevolve in a way that can benefit both 87 . Thus, symbiosis is regularly referred to as mutualism 88, 89 . Given that many organisms share...
Dictyostelium a Surrogate Host for Legionella Mycobacterium and Other Pathogens
Different bacterial species are taken up with different efficiencies and not all phagocytosed bacteria are killed by D. discoideum. In recent years D. discoideum has been established as a host model for several pathogens, including Pseudomonas aeruginosa 24, 25 , Mycobacterium avium, M. marinum 26, 27 , Vibrio cholerae 28 , Klebsiella pneumoniae 29 and Legionella pneumophila 30, 31 . The research areas presently pursued include the use of Dictyostelium wild-type cells as screening system for...
Come On In Get Killed Death in the Shredder
Phagocytosis is defined as the ingestion of a particle by a cell see Chapter 3 . Phagocytosis in vertebrates is typically carried out by professional phagocytic cells, that is, polymorphonuclear cells particularly neutrophils , dendritic cells, monocytes and macrophages, but is not unique to them. Most ingested particles are apoptotic cells, microorganisms and denatured protein complexes larger than some 0.4 mm in diameter. Their surface molecules are recognized by a variety of phagocyte...
Naraporn Somboonna
Children's Hospital Oakland Research University of California at Berkeley University of California at San Francisco National Center for Genetic Engineering and Biotechnology National Science and Technology Development Agency Pathumthani 12120 Thailand
Gene Transfer in Intracellular Bacterial Parasites
Trafficking for intracellular bacteria can be categorized into intraphagosomal and intracytoplasmic pathways, in which different relationships with the host cell compartment may involve different modes ofgene transfer and different types ofacquired genes. Intraphagosomal pathogens include Afipia, Brucella, Burkholderia, Chlamydia, Coxiella, Ehrlichia, Francisella, Legionella, Mycobacterium, Rhodococcus, Nocardia and Salmonella, while intracytoplasmic pathogens include Listeria, Rickettsia and...
Burkholderia pseudomallei
Joanne M. Stevens and Mark P. Stevens 22.1 Burkholderia pseudomallei and Melioidosis 393 22.2 An Overview of the Intracellular Life of B. pseudomallei 394 22.3 Genome Structure and Diversity of B. pseudomallei 395 22.4 Cell Contact and Adherence 396 22.9 Intracellular Replication 405 22.10 Immunology of B. pseudomallei-Host Cell Interactions 406 22.11 Concluding Remarks 407 References 408
Dictyostelium a Professional Phagocyte at the Border of Multicellularity
Dictyostelium cells are so-called social amoebae which live in the forest soil, feed on bacteria by phagocytosis and proliferate by binary fission 6 . As the food supply diminishes, the haploid cells stop growing and enter the social phase oftheir life cycle by assembling into multicellular aggregates. In a complex developmental process, approximately 105 cells form a migrating slug and finally a fruiting body, consisting of dead stalk cells and spores. The phagocytic potential of Dictyostelium...
The Whole Animal Model Drosophila melanogaster
D. melanogaster mount both cellular and humoral immune responses to pathogens. The innate immune response of the fruit fly D. melanogaster is characterized by a cellular immune response which depends on circulating phagocytic cells, a melanization response which produces reactive oxygen species at sites of infection, and the production ofantimicrobial peptides in the fat body. D. melanogaster lacks an antibody-mediated adaptive immune response 52 , but can react to different kinds of infections...
Phagosome Maturation
After a foreign particle is taken up, the recently formed phagosome undergoes a process of maturation. In essence, phagosomes mature through a series of fusion and fission events with the endocytic pathway. The result of this process is the gradual modification of the phagosomal membrane and contents, ultimately yielding a hybrid organelle known as the phagolysosome. The content of the phagolysosome is recognized by its very low pH, the presence of hydrolytic enzymes and bactericidal peptides...
A Look Through the Microscope of Evolution
Now, here, you see, it takes all the running you can do, just to keep in the same place. The Red Queen in Lewis Carroll's Alice in Wonderland. The Origin of Species by the Means of Natural Selection, 1859 According to Darwin, life may have started in some warm little pond. Rather than in warm ponds, it is believed today that primitive Bacteria and Archaea arose in the vicinity of hot vents in the ancient oceans some 4 billion years ago and microbes still rule the earth today. It was only after...
Legionelladirected Phagosome Biogenesis
Phagocytosis in D. discoideum and macrophages is known to be regulated by a heterotrimeric G protein-linked signal transduction Table 4.1 . By using pharmacological inhibitors and Dictyostelium mutants it has been demonstrated that L. pneumophila uptake occurs by conventional phagocytosis which requires hetero-trimeric G proteins and the PLC pathway. Moreover, these experiments revealed that cytoplasmic calcium levels, the cytoskeleton proteins coronin, villidin and a-actinin filamin as well as...
References Emc
1 Hayward, R.E., Derisi, J.L., Alfadhli, S., Kaslow, D.C. etal. 2000 Mol Microbiol, 35, 6-14. 2 Monahan, I.M., Betts, J., Banerjee, D.K. and Butcher, P.D. 2001 Microbiology, 147, 459-471. 3 Molestina, R.E., Klein, J.B., Miller, R.D., Pierce, W.H. et al. 2002 Infect Immun, 70, 2976-2981. 4 Florens, L., Washburn, M.P., Raine, J.D., Anthony, R.M. et al. 2002 Nature, 419, 520-526. 5 Heuer, D., Kneip, C., Maurer, A.P. and Meyer, T.F. 2007 Int J Med Microbiol, 297, 569-576. 6 Eyles, J.E., Unal, B.,...
Quantification of Phagosome pH
The first probe developed to explore the intraphagosome environment was a pH sensor. Taking advantage of an assay developed to measure endosome pH 8, 9 , particles were surface labeled with a pH-sensitive fluor, usually fluorescein, whose emission at 520 nm quantifies the intracellular pH due to its exquisite sensitivity when excited at 490 nm 10, 11 . Fluorescein's maximum utility is in the pH range from 5.0 to 7.5, but pH-sensitive fluors with different pH ranges e.g., Oregon Green are also...
A Short History of Theories and Discoveries
The complex mutual relationship between intracellular microbes and their host cells is a challenging field of research and requires the perspective of evolution biology. The individual host-microbe interactions covered in this book all raise the following questions how do microbes enter, survive and proliferate in, and how do they exit host cells And how can intracellular niches be characterized and what are the benefits of intracellular life for the microbes and its consequences for the host...
ParticleInduced Impact on Phagosome Isolation
The phagocytic cell encounters a large diversity of particles that vary in size, shape, stiffness and surface properties. For example, red blood cells are round, deformable and between 6 and 40 mm in size bacteria are rather stiff, round, spiral- or rod-shaped, 1 mm in size but can often be found in grapes or strings, like staphylococci or streptococci respectively. Dead cells and most bacteria are negatively charged while mycobacteria are hydrophobic 48 . Accordingly, particles are recognized...
Quantification of Lysosome Components in Phagosomes
Fusion of phagosomes with lysosomes is central to the destruction and killing of ingested materials and microorganisms see Chapter 10 . Phagosome-lysosome fusion is likely to occur in two ways, both of which may act on the same phagosome i complete fusion of preexisting lysosomes with the maturing phagosome and ii transient fusion events between lysosomes and phagosomes, during which only some lysosome contents are transferred into phagosomes and possibly vice versa . The latter has been termed...
Evolution of Intracellular Parasitism
Many microorganisms of diverse phylogenetic beginnings have adapted to intracellular life, each in its own unique way, and sometimes remarkable resemblances in behaviour among intracellular parasites are best ascribed to convergence in similar intracellular habits rather than to divergence from a common origin. Finally it should be remembered that adaptation to intracellular life, although by no means rare, is not easy. After all, most parasites still live extracellularly. James W. Moulder 1985...