Intracellular Bacteria Survival Strategies

Intracellular Bacteria Survival Strategies Survival strategies of intracellular bacteria to amoeba grazing Free living amoebae are unicellular protozoan that are ubiquitous in various environments. They mainly feed on bacteria through phagocytosis, and kill them in phagosome, which is a harsh acidic environment that contains different antimicrobial weapons. Amoebae grazing has been suggested to be one of the major forces that shaping bacterial abundance and diversity. However, some bacteria have developed strategies to survive phagocytosis by free-living amoebae and are able to exploit host cell resources. Below we try to summarize our current knowledge on the diverse mechanisms that are used by intracellular pathogens to overcome amoebae defenses. The most obvious strategy is to escape from the phagosome so that intracellular pathogens can avoid amoebae killing. Because phagosome is generally viewed as a harsh environment where ingested bacteria are confronted with acidification, oxidative burst, nutrient deprivation, and various antimicrobial small molecules. For instance, some members of the genus Mycobacterium, such as Mycobacterium marinum and M. tuberculosis, have evolved the ability to escape from phagosome into the host cytosol. This process requires the mycobaterial type VII secretion system ESX-1. In addition, both M. marinum and M. tuberculosis can be ejected from the cell through an F-actin structure ejectosome to spread cell to cell [1,2]. In general, cytosol is considered as permissive for bacterial growth, as it provides nutrients and is protected from host immune killing [3]. Therefore it is an ideal place for bacteria to thrive after escaping from phagosome. However, some intracellular pathogens can invade more unusual intracellular niches such as the eukaryotic nucleus. This includes in the free living amoebae Naegleria clarki [4] and more recently in another amoeba strain Hartmannella sp. [5]. These so called intranuclear bacteria are relatively rare and current studies suggest an independent evolutionary origin of an intranuclear life style. Taken together, after escaping intracellular bacteria can live in either cytosol or nucleus. The second strategy is to stay within the phagosomal vacuole, but subvert its antimicrobial mechanisms. These include preventing phagosome-lysosome fusion, modulating phagosomal pH, damaging phagosomal membranes, and/or quenching oxidative bursts [6]. Intracellular pathogens can utilize a combination of these approaches. For instance, Legionella pneumophila has evolved a complex system which allows the bacteria to hijack the phagocytic vacuole [7]. It can evade the endocytic pathway and the subsequent phagosome-lysosome fusion, delays its acidification and establishes a safe intracellular niche called Legionella containing vacuole (LCV), which allows intracellular replication [7,8]. Further studies suggest that L. pneumophila uses the Icm/Dot type IV secretion system (T4SS) and the Lsp type II secretion system (T2SS) to avoid killing and exploit host resources [7,9]. There are plenty of other bacteria using similar strategies [10]. However, a very special case is that some intracellu lar pathogens can exploit the complex cycle of the social amoeba. In the amoeba farming symbiosis, our lab group has found that some wild Dictyostelium discoideum clones stably associate with different bacterial partners and use them as food and weapons [11-14]. These clones are called farmers because they can seed and harvest their crops in new environments [14]. In addition, two clades of inedible Burkholderia bacteria have been found to induce farming, causing the amoeba host to carry them, along with edible crop bacteria [11]. Another recent case shows that Bordetella bronchiseptica can also exploit the complex life cycle of D. discoideum. Interestingly, B. bronchiseptica resides outside the D. discoideum spores, while the carried Burkholderia localize both inside and outside of spores, indicating these two bacteria have different exit strategies. Overall, the majority of intracellular pathogens occupy phagosomal vacuole, while only some are able to escape the phagosome [6]. This is possibly due to the fact that specialized mechanisms are needed to escape from phagosome [3,6]. There is no clear relationship between the type of survival strategies and whether the microbe is an obligate or facultative intracellular pathogen [6]. References 1. Hagedorn M, Rohde KH, Russell DG, Soldati T (2009) Infection by Tubercular Mycobacteria Is Spread by Nonlytic Ejection from Their Amoeba Hosts. Science 323: 1729-1733. 2. Gerstenmaier L, Pilla R, Herrmann L, Herrmann H, Prado M, et al. (2015) The autophagic machinery ensures nonlytic transmission of mycobacteria. Proceedings of the National Academy of Sciences of the United States of America 112: E687-E692. 3. Ray K, Marteyn B, Sansonetti PJ, Tang CM (2009) Life on the inside: the intracellular lifestyle of cytosolic bacteria. Nature Reviews Microbiology 7: 333-340. 4. Schulz F, Horn M (2015) Intranuclear bacteria: inside the cellular control center of eukaryotes. Trends in Cell Biology 25: 339-346. 5. Schulz F, Lagkouvardos I, Wascher F, Aistleitner K, Kostanjsek R, et al. (2014) Life in an unusual intracellular niche: a bacterial symbiont infecting the nucleus of amoebae. ISME Journal 8: 1634-1644. 6. Casadevall A (2008) Evolution of Intracellular Pathogens. Annual Review of Microbiology 62: 19-33. 7. Hoffmann C, Harrison CF, Hilbi H (2014) The natural alternative: protozoa as cellular models for Legionella infection. Cellular Microbiology 16: 15-26. 8. Escoll P, Rolando M, Gomez-Valero L, Buchrieser C (2013) From amoeba to macrophages: exploring the molecular mechanisms of Legionella pneumophila infection in both hosts. Curr Top Microbiol Immunol 376: 1-34. 9. Hubber A, Kubori T, Nagai H (2014) Modulation of the Ubiquitination Machinery by Legionella. Molecular Mechanisms in Legionella Pathogenesis 376: 227-247. 10. Steinert M (2011) Pathogen-host interactions in Dictyostelium, Legionella, Mycobacterium and other pathogens. Seminars in Cell Developmental Biology 22: 70-76. 11. DiSalvo S, Haselkorn TS, Bashir U, Jimenez D, Brock DA, et al. (2015) Burkholderia bacteria infectiously induce the proto-farming symbiosis of Dictyostelium amoebae and food bacteria. Proceedings of the National Academy of Sciences of the United States of America 112: E5029-E5037. 12. Stallforth P, Brock DA, Cantley AM, Tian XJ, Queller DC, et al. (2013) A bacterial symbiont is converted from an inedible producer of beneficial molecules into food by a single mutation in the gacA gene. Proceedings of the National Academy of Sciences of the United States of America 110: 14528-14533. 13. Brock DA, Read S, Bozhchenko A, Queller DC, Strassmann JE (2013) Social amoeba farmers carry defensive symbionts to protect and privatize their crops. Nature Communications 4. 14. Brock DA, Douglas TE, Queller DC, Strassmann JE (2011) Primitive agriculture in a social amoeba. Nature 469: 393-396.

Magnetic Resonance Imaging Essay -- Medical Technology Medicine Essays

Magnetic Resonance Imaging Magnetic resonance imaging has the potential of totally replacing computed tomography. If history was rewritten, and CT invented after MRI, nobody would bother to pursue CT. --Philip Drew (Mattson and Simon, 1996) WHAT IT IS Magnetic Resonance Imaging, or commonly known as MRI, is a technique used in medicine for producing images of tissues inside the body. It is an important diagnostic tool because it enables physicians to identify abnormal tissue without opening the body through surgery. MRI lets physicians see through bones and organs. MRI does not expose the patient to radiation, unlike tests that use X-rays. MRI provides an unparallel view inside the human body. It is the method of choice for the diagnosis of certain diseases, disorders, and injuries. MRI is safe for most people, but it uses a powerful magnet and so cannot be used on people with metal implants, such as pacemakers or artificial joints (World Book, 2000). WHAT IT IS LIKE INSIDE Three main components make up an MRI unit: a magnet, devices for transmitting and receiving radio waves, and a computer. The patient is placed inside a machine that has a huge magnet. There is a horizontal tube running through the magnet from front to back. This tube is known as the bore of the magnet. The patient, lying on his or her back, slides into the bore on a special table. Once the body part to be scanned is in the exact center or isocenter of the magnetic field, the scan can begin (www.howstuffworks.com). The magnetic field causes the nuclei of certain atoms inside the body to line up. The machine then sends out a radio signal, which causes the nuclei to change direction. The change create signals that a computer translates to produce ... ...ams are also very expensive. (www.howstuffworks.com) For most patients, the numerous benefits of MRI far outweigh the drawbacks. MRI can provide you with an abundant amount of information about your health.MRI is a tool to diagnose, visualize, amd evaluate parts of our body. MRI can help prevent the spread of diseases by catching them in their early stages, and so still treatable. Staying healthy is probably the most important thing that we can do. Medical technology, such as MRI, can help us do that. Sources: Lauterbur, Paul C., and Liang, Zhi-Pei, Principles of Magnetic Resonance Imaging, IEEE Press, New York, 2000, p. 2-4. Mattson, James, and Simon, Merrill,The Story of MRI, Bar-Ilan University Press, New York, 1996, p. 1. World Book Encyclopedia, Magnetic Resonance Imaging, World Book Inc., Chicago, Vol 13, 2000, p. 56-57. www.howstuffworks.com

National Identity Cards

Identity (ID) cards are known for their utility and integrity, which led to the adoption of its use by many countries all over the world. Some countries even have national IDs, which are officially released and which use is mandatory to all who sojourn in said territories. Examples of these countries that have a national ID system are France, Germany, Belgium, Luxemburg, Spain, and Greece. On the other hand, many developed countries such as Australia, Sweden, Canada, and the United States, did not adopt such an identification system. National ID systems are established to serve two main purposes. The first one is to increase the police powers of the State. Consequently, ID cards can help the State reduce crime rate, conduct social engineering, and reduce the threat of insurgents or political extremists. The second purpose is to establish a comprehensive and useful administration of government services. The technology behind modern ID systems, such as the magnetic stripes and the microprocessor technology, ID cards offer a valuable towards the more efficient delivery of government services. However, while it appears that having a National ID system may offer many advantages, such a system could also pave the way for abuses on civil rights, invasion of privacy, and discrimination. In addition, the establishment of such a comprehensive registration system, would entail a huge amount in costs, which is an important consideration to make. All of these considerations should be weighed in order to reach at an intelligent decision on the issue of whether citizens of the United States should be required to carry National IDs. Â   Â   Â   Â  

Different Cultures Outlook On Death - 859 Words

Human beings differ in their beliefs and behaviors because of culture. Culture is the way someone experience life events such as birth, death, and how they seek food, water, and shelter. As humans we create our own world, emotions, events, and we are control in our everyday life. Every culture has a different way they view things, and that’s simply because of the way they were raised and brought into this world. Different cultures outlook on death can be completely opposite. One culture thinks that death marks a passage of a person from one world to another. Others think death is an ending. Some fear death and others do not. Personally I fear death, I’m scared of the unknown, but that’s just how I was raised. Another example of how cultures differ is food. As an American I personally would never think twice about drinking milk. I’ve been drinking milk sense I was born, but people in china think milk is â€Å"undrinkable†. In America we have dogs for pets, and in other countries they raise dogs for meat. We just need to be able to accept and understand the fact that everyone’s different, everyone has there own beliefs and behaviors. If someone doesn’t have the same morals as you, we are usually quick to judge and not understand their perspective. As humans we are so trapped in our own little worlds, the idea of our beliefs and behaviors are always right and true and others are always wrong and immoral, that’s called ethnocentric fallacy. Relativism says that no culture can beShow MoreRelatedThe Culture Of The Family983 Words   |  4 PagesEvery family has a different culture. Whether the culture is about religion, or within the immediate family, every family has a different outlook. Laney and her family have discussed what their culture is. Culture includes what the family does on a daily basis and traditions. On a daily basis Laney keeps in touch with her family. 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