Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hide and seek: Researchers discover a new way for infectious bacteria to enter cells

23.08.2005


French scientists have learned how Listeria monocytogenes, which causes a major food-borne illness, commandeers cellular transport machinery to invade cells and hide from the body’s immune system. They believe that other infectious organisms may use the same mechanism.

The Listeria bacterium, found in soil and water, can be transmitted to humans via undercooked and unpasteurized food, causing flu-like symptoms or gastrointestinal distress. For individuals with weakened immune systems, listeriosis can be fatal, and infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or infection of the newborn.

The research was conducted by Pascale Cossart, a Howard Hughes Medical Institute international research scholar, and her colleague Esteban Veiga at the Institut Pasteur in Paris, and will be published in the August 21, 2005, issue of Nature Cell Biology. Cossart and Veiga detailed how Listeria invades cells by activating cellular machinery that transports viruses, small molecules, and proteins. Once it has safely entered a cell, the microbe can replicate and continue the process of infection.



The body usually deals with bacteria and other large, foreign microbes through a process called phagocytosis. Specialized cells engulf the invading microbe and destroy it. Scientists long believed that cells use a second process, called endocytosis, to deal with smaller molecules or viruses. In endocytsosis, a cell’s outer membrane pinches inward around the target to form a pocket that’s brought inside the cell, creating a structure called a vesicle.

"Phagocytosis and endocytosis may, in fact, be more similar than past research suggests. This is a totally new concept," Cossart says.

Cossart’s lab had observed that Listeria – which is 20 times the size of the largest particle scientists believed a cell could take in by endocytosis – could invade non-phagocytic cells. Other labs had made similar observations with other bacteria. Cossart and Veiga investigated the underlying machinery behind this uncommon invasion strategy, which they knew depended on an interaction between a protein on the surface of the bacteria, known as InlB, and a protein called Met on the surface of the cell it was invading.

They discovered that when InlB interacts with Met, the cell responds by adding a chemical tag to Met that flags it for protein recycling or degradation. Since Met is on the outside surface of the cell and the recycling and degradation machineries are inside, the cell must bring Met inside through endocytosis in order to dispose of it. As the cell creates the vesicle that will transport tagged Met, Listeria stows away and invades the cell.

By manipulating the gene expression of the cells Listeria was invading, the researchers showed that specific molecules known to be involved in endocytosis were essential for successful invasion by Listeria. Similarly, they found that an enzyme that tags proteins for recycling was also required.

Listeria’s use of receptor-mediated endocytosis to infect hosts, according to Cossart, suggests that other bacteria may exploit the same mechanism to gain entry into non-phagocytic cells. "This mechanism of cell entry may be used by several different kinds of bacteria, which is a major deviation from the belief that endocytosis is strictly for importing small molecules into cells," she says.

Cindy Fox Aisen | EurekAlert!
Further information:
http://www.hhmi.org

More articles from Life Sciences:

nachricht Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>