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Purdue scientists reveal how bacteria build homes inside healthy cells

Public release date: 20-Dec-2011
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Contact: Elizabeth K. Gardner
ekgardner@purdue.edu
765-494-2081
Purdue University

WEST LAFAYETTE, Ind. - Bacteria are able to build camouflaged homes for themselves inside healthy cells - and cause disease - by manipulating a natural cellular process.

Purdue University biologists led a team that revealed how a pair of proteins from the bacteria Legionella pneumophila, which causes Legionnaires disease, alters a host protein in order to divert raw materials within the cell for use in building and disguising a large structure that houses the bacteria as it replicates.

Zhao-Qing Luo, the associate professor of biological sciences who headed the study, said the modification of the host protein creates a dam, blocking proteins that would be used as bricks in cellular construction from reaching their destination. The protein "bricks" are then diverted and incorporated into a bacterial structure called a vacuole that houses bacteria as it replicates within the cell. Because the vacuole contains materials natural to the cell, it goes unrecognized as a foreign structure.

"The bacterial proteins use the cellular membrane proteins to build their house, which is sort of like a balloon," Luo said. "It needs to stretch and grow bigger as more bacterial replication occurs. The membrane material helps the vacuole be more rubbery and stretchy, and it also camouflages the structure. The bacteria is stealing material from the cell to build their own house and then disguising it so it blends in with the neighborhood."

The method by which the bacteria achieve this theft is what was most surprising to Luo.

The bacterial proteins, named AnkX and Lem3, modify the host protein through a biochemical process called phosphorylcholination that is used by healthy cells to regulate immune response. Phosphorylcholination is known to happen in many organisms and involves adding a small chemical group, called the phosphorylcholine moiety, to a target molecule, he said.

The team discovered that AnkX adds the phosphorylcholine moiety to a host protein involved in moving proteins from the cell's endoplasmic reticulum to their cellular destinations. The modification effectively shuts down this process and creates a dam that blocks the proteins from reaching their destination.

The bacterial protein Lem3 is positioned outside the vacuole and reverses the modification of the host protein to ensure that the protein "bricks" are free to be used in creation of the bacterial structure.

This study was the first to identify proteins that directly add and remove the phosphorylcholine moiety, Luo said.

"We were surprised to find that the bacterial proteins use the phosphorylcholination process and to discover that this process is reversible," he said. "This is evidence of a new way signals are relayed within cells, and we are eager to investigate it."

The team also found that the phosphorylcholination reaction is carried out at a specific site on the protein called the Fic domain. Previous studies had shown this site induced a different reaction called AMPylation.

It is rare for a domain to catalyze more than one reaction, and it was thought this site's only responsibility was to transfer the chemical group necessary for AMPylation, Luo said.

"Revealing that this domain has dual roles is very important to identify or screen for compounds to inhibit its activity and fight disease," he said. "This domain has a much broader involvement in biochemical reactions than we thought and may be a promising target for effective treatments."

During infection bacteria deliver hundreds of proteins into healthy cells that alter cellular processes to turn the hostile environment into one hospitable to bacterial replication, but the specific roles of only about 20 proteins are known, Luo said.

"In order to pinpoint proteins that would be good targets for new antibiotics, we need to determine their roles and importance to the success of infection," he said. "We need to understand at the biochemical level exactly what these proteins do and how they take over natural cellular processes. Then we can work on finding ways to block these activities, stop the infection and save lives."

A paper detailing their National Institutes of Health-funded work is published in the current issue of the Proceedings of National Academy of Sciences. In addition to Luo, Purdue graduate student Yunhao Tan and Randy Ronald of Indiana University co-authored the paper. Luo next plans to use the bacterial proteins as a tool to learn more about the complex cellular processes controlled by phosphorylcholination and to determine the biochemical processes role in cell signaling.

Writer: Elizabeth K. Gardner, 765-494-2081, ekgardner@purdue.edu Source: Zhao-Wing Luo, 765-496-6697, luoz@purdue.edu

Related website:
Luo lab: http://bilbo.bio.purdue.edu/luolab/

Related news release:
Purdue biologists identify new strategy used by bacteria during infection: http://www.purdue.edu/newsroom/research/2011/110712LuoNature.html

PHOTO CAPTION:
Purdue associate professor of biological sciences Zhao-Qing Luo, at right, and graduate student Yunhao Tan look at the growth of Legionella pneumophila bacteria in a petri dish. (Purdue University photo provided by Laurie Iten and Rodney McPhail)

A publication-quality photo is available at http://news.uns.purdue.edu/images/2011/luo-legionella.jpg

Abstract on the research in this release can be found at: http://www.purdue.edu/newsroom/research/2011/111220LuoPNAS.html

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How Legionnaires' bacteria proliferate, cause disease

ScienceDaily (Nov. 17, 2011) — A University of Louisville scientist has determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs.

The results are published online on Nov. 17 in Science.

Yousef Abu Kwaik, Ph.D., the Bumgardner Endowed Professor in Molecular Pathogenesis of Microbial Infections at UofL, and his team believe their work could help lead to development of new antibiotics and vaccines.

"It is possible that the process we have identified presents a great target for new research in antibiotic and vaccine candidates, not only for Legionnaires' disease but in other bacteria that cause illness," he said.

According to the Centers for Disease Control and Prevention, Legionnaires' disease is a lung infection caused by the bacterium called Legionella. The bacterium got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of pneumonia of unknown causes that was later determined to be caused by the bacterium. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. There is no vaccine currently available for it.

For two years, the researchers examined Legionella which is an intracellular bacterium that exists in amoebae in the water systems; it is transmitted to humans through inhalation of water droplets. Cooling towers and whirlpools are the major sources of transmission. The bacterium uses the amoeba's cellular process to "tag" proteins, causing them to degrade into their basic elements of amino acids. These amino acids are used by the bacteria as the main source of energy to grow and cause disease.

"The bacteria live on an 'Atkins diet' of low carbs and high protein, and they trick the host cell to provide that specialized diet," Abu Kwaik said.

The same process occurs in a host -- animal or human -- who inhales the bacterium and is diagnosed with Legionnaires' disease. However, the bacteria do not tag the proteins, but rather trick the host into tagging the proteins for degradation to generate the amino acids.

In the laboratory, Abu Kwaik and his team saw that by inactivating the bacterial virulence factor responsible for tricking the cell into tagging proteins for degradation in mice models, the pulmonary disease was totally prevented. This was totally due to disabling the bacteria from generating amino acids, he said.

The process was then reversed, and the disease became evident when the mice, infected by the disabled bacteria, were injected with amino acids to compensate for the inability of the altered bacteria.

"Bacteria need to live on high protein and amino acids as sources of nutrition and energy in order to replicate in a host. This is what causes pulmonary disease," Abu Kwaik said. "No one has known how they generate sufficient sources of nutrients from the host to proliferate. Our work is the first to identify this process for any bacteria that cause disease."

He added that the type of host infected does not appear to affect the process. "Whether in a single-cell amoeba or a multi-cellular mammal, Legionella seems to know what to do; the process is the same, and is highly conserved through evolution. By interfering with the bacterium's sources of nutrients, we can stop it from thriving and causing disease."

Examining nutrient sources for organisms with the goal of stopping them from acquiring nutrients is a relatively new arena of basic research that deserves further study, he said. "We went after the basics -- the food and energy source -- which are prerequisite for the bacteria to grow and cause disease. It is not a process that is well understood yet, but by first discovering how an organism gets nutrients by tricking the host into degrading proteins, and then interfering with that process, we can, in effect, starve it to death and prevent or treat the disease."

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Journal Reference:

Christopher T. D. Price, Tasneem Al-Quadan, Marina Santic, Ilan Rosenshine, and Yousef Abu Kwaik. Host Proteasomal Degradation Generates Amino Acids Essential for Intracellular Bacterial Growth. Science, 17 November 2011 DOI: 10.1126/science.1212868

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How Legionnaires' bacteria cause disease

Published: Nov. 18, 2011 at 11:05 PM

LOUISVILLE, Ky., Nov. 18 (UPI) -- A bacterium that causes Legionnaires' disease manipulates cells to generate amino acids it needs to grow and infect the lungs, U.S. researchers say.

Yousef Abu Kwaik of the University of Louisville and his team said their work could help lead to development of new antibiotics and vaccines for the disease.

"It is possible that the process we have identified presents a great target for new research in antibiotic and vaccine candidates, not only for Legionnaires' disease but in other bacteria that cause illness," Abu Kwaik said in a statement.

For two years, the researchers examined Legionella, which is an intercellular bacterium that exists in amoebae in the water systems; it is transmitted to humans through inhalation of water droplets. Cooling towers and whirlpools are the major sources of transmission.

The study, published in the journal Science, said the bacterium uses the amoeba's cellular process to "tag" proteins, causing them to degrade into their basic elements of amino acids, which are used by the bacteria as the main source of energy to grow and cause disease.

"The bacteria live on an 'Atkins diet' of low carbs and high protein and they trick the host cell to provide that specialized diet," Abu Kwaik said.

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UofL researcher determines how Legionnaires' bacteria proliferate, cause disease

Public release date: 17-Nov-2011
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Contact: Jill Scoggins
jill.scoggins@louisville.edu
502-852-7461
University of Louisville

LOUISVILLE, Ky. ? A University of Louisville scientist has determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs. The results are published online today (Nov. 17) in "Science."

Yousef Abu Kwaik, Ph.D., the Bumgardner Endowed Professor in Molecular Pathogenesis of Microbial Infections at UofL, and his team believe their work could help lead to development of new antibiotics and vaccines.

"It is possible that the process we have identified presents a great target for new research in antibiotic and vaccine candidates, not only for Legionnaires' disease but in other bacteria that cause illness," he said.

According to the Centers for Disease Control and Prevention, Legionnaires' disease is a lung infection caused by the bacterium called Legionella. The bacterium got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of pneumonia of unknown causes that was later determined to be caused by the bacterium. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. There is no vaccine currently available for it.

For two years, the researchers examined Legionella which is an intercellular bacterium that exists in amoebae in the water systems; it is transmitted to humans through inhalation of water droplets. Cooling towers and whirlpools are the major sources of transmission. The bacterium uses the amoeba's cellular process to "tag" proteins, causing them to degrade into their basic elements of amino acids. These amino acids are used by the bacteria as the main source of energy to grow and cause disease.

"The bacteria live on an 'Atkins diet' of low carbs and high protein, and they trick the host cell to provide that specialized diet," Abu Kwaik said.

The same process occurs in a host ? animal or human ? who inhales the bacterium and is diagnosed with Legionnaires' disease. However, the bacteria do not tag the proteins, but rather trick the host into tagging the proteins for degradation to generate the amino acids.

In the laboratory, Abu Kwaik and his team saw that by inactivating the bacterial virulence factor responsible for tricking the cell into tagging proteins for degradation in mice models, the pulmonary disease was totally prevented. This was totally due to disabling the bacteria from generating amino acids, he said.

The process was then reversed, and the disease became evident when the mice, infected by the disabled bacteria, were injected with amino acids to compensate for the inability of the altered bacteria.

"Bacteria need to live on high protein and amino acids as sources of nutrition and energy in order to replicate in a host. This is what causes pulmonary disease," Abu Kwaik said. "No one has known how they generate sufficient sources of nutrients from the host to proliferate. Our work is the first to identify this process for any bacteria that cause disease."

He added that the type of host infected does not appear to affect the process. "Whether in a single-cell amoeba or a multi-cellular mammal, Legionella seems to know what to do; the process is the same, and is highly conserved through evolution. By interfering with the bacterium's sources of nutrients, we can stop it from thriving and causing disease."

Examining nutrient sources for organisms with the goal of stopping them from acquiring nutrients is a relatively new arena of basic research that deserves further study, he said. "We went after the basics ? the food and energy source ? which are prerequisite for the bacteria to grow and cause disease. It is not a process that is well understood yet, but by first discovering how an organism gets nutrients by tricking the host into degrading proteins, and then interfering with that process, we can, in effect, starve it to death and prevent or treat the disease."

With Abu Kwaik, authors of the paper are Christopher T.D. Price, Ph.D. and Tasneem Al-Quadan, a doctoral student, in UofL's Department of Microbiology and Immunology; Marina Santic, Ph.D., of the University of Rijeka, Croatia; and Ilan Rosenshine, Ph.D., of the Hebrew University Medical School in Jerusalem, Israel.

The work was funded by a grant from the National Institute of Allergy and Infectious Diseases.

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View the original article here

Researcher Determines How Legionnaires' Bacteria Proliferate, Cause Disease

Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Respiratory / Asthma
Article Date: 21 Nov 2011 - 0:00 PST

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A University of Louisville scientist has determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs. The results are published online in Science.

Yousef Abu Kwaik, Ph.D., the Bumgardner Endowed Professor in Molecular Pathogenesis of Microbial Infections at UofL, and his team believe their work could help lead to development of new antibiotics and vaccines.

"It is possible that the process we have identified presents a great target for new research in antibiotic and vaccine candidates, not only for Legionnaires' disease but in other bacteria that cause illness," he said.

According to the Centers for Disease Control and Prevention, Legionnaires' disease is a lung infection caused by the bacterium called Legionella. The bacterium got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of pneumonia of unknown causes that was later determined to be caused by the bacterium. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. There is no vaccine currently available for it.

For two years, the researchers examined Legionella which is an intercellular bacterium that exists in amoebae in the water systems; it is transmitted to humans through inhalation of water droplets. Cooling towers and whirlpools are the major sources of transmission. The bacterium uses the amoeba's cellular process to "tag" proteins, causing them to degrade into their basic elements of amino acids. These amino acids are used by the bacteria as the main source of energy to grow and cause disease.

"The bacteria live on an 'Atkins diet' of low carbs and high protein, and they trick the host cell to provide that specialized diet," Abu Kwaik said.

The same process occurs in a host - animal or human - who inhales the bacterium and is diagnosed with Legionnaires' disease. However, the bacteria do not tag the proteins, but rather trick the host into tagging the proteins for degradation to generate the amino acids.

In the laboratory, Abu Kwaik and his team saw that by inactivating the bacterial virulence factor responsible for tricking the cell into tagging proteins for degradation in mice models, the pulmonary disease was totally prevented. This was totally due to disabling the bacteria from generating amino acids, he said.

The process was then reversed, and the disease became evident when the mice, infected by the disabled bacteria, were injected with amino acids to compensate for the inability of the altered bacteria.

"Bacteria need to live on high protein and amino acids as sources of nutrition and energy in order to replicate in a host. This is what causes pulmonary disease," Abu Kwaik said. "No one has known how they generate sufficient sources of nutrients from the host to proliferate. Our work is the first to identify this process for any bacteria that cause disease."

He added that the type of host infected does not appear to affect the process. "Whether in a single-cell amoeba or a multi-cellular mammal, Legionella seems to know what to do; the process is the same, and is highly conserved through evolution. By interfering with the bacterium's sources of nutrients, we can stop it from thriving and causing disease."

Examining nutrient sources for organisms with the goal of stopping them from acquiring nutrients is a relatively new arena of basic research that deserves further study, he said. "We went after the basics - the food and energy source - which are prerequisite for the bacteria to grow and cause disease. It is not a process that is well understood yet, but by first discovering how an organism gets nutrients by tricking the host into degrading proteins, and then interfering with that process, we can, in effect, starve it to death and prevent or treat the disease."

Article adapted by Medical News Today from original press release. Click 'references' tab above for source.
Visit our infectious diseases / bacteria / viruses section for the latest news on this subject. With Abu Kwaik, authors of the paper are Christopher T.D. Price, Ph.D. and Tasneem Al-Quadan, a doctoral student, in UofL’s Department of Microbiology and Immunology; Marina Santic, Ph.D., of the University of Rijeka, Croatia; and Ilan Rosenshine, Ph.D., of the Hebrew University Medical School in Jerusalem, Israel.
The work was funded by a grant from the National Institute of Allergy and Infectious Diseases.
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View the original article here

How Legionnaires' bacteria proliferate, cause disease

Scientist have determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs. (Source: ScienceDaily Headlines)

MedWorm Sponsor Message: Please support the DoctorsInChains.org campaign for the health workers in Bahrain. #FreeDoctors

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How Legionnaires' bacteria cause disease

LOUISVILLE, Ky., Nov. 18 (UPI) -- A bacterium that causes Legionnaires' disease manipulates cells to generate amino acids it needs to grow and infect the lungs, U.S. researchers say. (Source: Health News - UPI.com)

View the original article here

UofL researcher determines how Legionnaires' bacteria proliferate, cause disease

(University of Louisville) A University of Louisville scientist has determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs. The results are published online today (Nov. 17) in Science. (Source: EurekAlert! - Medicine and Health)

View the original article here

Researcher Determines How Legionnaires' Bacteria Proliferate, Cause Disease

A University of Louisville scientist has determined for the first time how the bacterium that causes Legionnaires' disease manipulates our cells to generate the amino acids it needs to grow and cause infection and inflammation in the lungs. The results are published online in Science. Yousef Abu Kwaik, Ph.D., the Bumgardner Endowed Professor in Molecular Pathogenesis of Microbial Infections at UofL, and his team believe their work could help lead to development of new antibiotics and vaccines... (Source: Health News from Medical News Today)

View the original article here

ScotRail finds legionella bacteria in train toilet systems

TRACES of potentially fatal bacteria have been found in the toilet water systems of trains in Scotland. (Source: Scotsman.com News - Health)

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Study Shows Automatic Faucets Carry High Levels Of Bacteria, Unsafe For Use In High-Risk Patient Hospital Settings

Researchers at The Johns Hopkins University School of Medicine have determined that electronic faucets are more likely to become contaminated with unacceptably high levels of bacteria, including Legionella spp., compared with traditional manually operated faucets. The study will be presented on Saturday at the annual meeting of the Society for Healthcare Epidemiology of America (SHEA). Electronic-eye, non-touch faucets have been increasingly utilized in healthcare settings to lower water consumption and in an attempt to reduce recontamination of the hands of healthcare personnel... (Source: Health News from Medical News Today)

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Epidemiology of Respiratory Infections Caused by Atypical Bacteria in Two Kenyan Refugee Camps

Abstract   Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella spp. are common causes of atypical pneumonia; however, data about these atypical pathogens are limited in the refugee setting. Paired nasopharyngeal and oropharyngeal specimens were collected from patients with respiratory illness presenting to healthcare centers in two refugee camps in Kenya. The specimens were tested for C. pneumoniae, M. pneumoniae, and Legionella spp. as well as eight respiratory viruses. Atypical pathogens were detected in 5.5% of the specimens of which 54% were co-infected with at least one of the eight viruses tested. Patients positive for atypical bacteria co-infected with virus were significantly more likely to have severe acute respiratory illness than patients infected with onl...

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Biologists discover new way in which bacteria hijack healthy cells during infection

Purdue University biologists identified a new way in which bacteria hijack healthy cells during infection, which could provide a target for new antibiotics.

Zhao-Qing Luo, the associate professor of biological sciences who led the study, said the team discovered a new enzyme used by the bacterium Legionella pneumophila - which causes Legionnaires' disease - to control its host cell in order to take up residence.

"Legionnaires' disease is a severe form of pneumonia, and this finding could lead to the design of a new therapy that saves lives," Luo said. "At the same time it also provides great insight into a general mechanism of both bacterial infection and cell signaling events in higher organisms including humans."

Successful infection by Legionella pneumophila requires the delivery of hundreds of proteins into the host cells that alter various functions to turn the naturally hostile environment into one tailor-made for bacterial replication. These proteins tap into existing communication processes within the cells in which an external signal, such as a hormone, triggers a cascade of slight modifications to proteins that eventually turns on a gene that changes the cell's behavior, he said.

"Pathogens are successful because they know how information in our cells is relayed and they amplify some signals and block others in order to evade the immune system and keep the cell from defending itself," Luo said. "Despite our understanding of this, we do not know much about how the proteins delivered by the bacteria accomplish this - how they work. This time we were able to pinpoint an enzyme and see how it disrupted and manipulated a specific signaling pathway in order to create a better environment for itself."

The signaling pathway involved was only recently identified, and the discovery by Luo and graduate student Yunhao Tan also provides a key insight into its process. A paper detailing their National Institutes of Health-funded work is published online in the current issue of the journal Nature.

The signaling pathway involves a new form of protein modification called AMPylation in order to relay instructions to change cell behavior and has been found to be used by almost all organisms, Luo said.

The bacterial enzyme discovered by the Purdue team, named SidD, reverses or stops the AMPylation process, he said.

"It had not been known before if the AMPylation signaling process was reversible or if it was regulated by specific enzymes," Luo said. "Now we know that it is, and we have a more complete picture that will allow us to use it as a scientific tool to learn more about complex cellular processes. By being able to turn the signaling on and off, we can control different activities and detect mechanisms we wouldn't see under normal physiological conditions."

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