They found that expression of toxins and other virulence factors is influenced by cues such as proximity to host phagocytic cells or the concentration of secreted molecules such as NO. These results showed that only a subset of cells within a community of pathogenic bacteria need to express virulence factors. The lab uses genetic… Continue Reading. Your email address will not be published. Home » Research Talks » Microbiology. Audience: Student Researcher Educators of Adv.
In this context, scientists refer to the human body as the host. A positive host-microbe relationship is usually described as either mutualistic or commensalistic.
In mutualism both the host and the microbe benefit. Which is in contract to commensalisms, where one partner of the relationship benefits usually the microbe and the other partner usually the host is neither benefited nor harmed. In many cases it may be difficult to establish whether a particular host-microbe relationship should be considered mutualistic or commensalistic, since scientists are only beginning to understand the role of normal flora in human health.
In other words, individual microbes may be carrying out important functions within our bodies that we have not yet discovered. Just as host-microbe relationships can be positive or neutral, they can also be negative. Such a host-microbe relationship is usually described as parasitic or pathogenic. In a parasitic relationship the microbe benefits at the expense of the host and similarly in a pathogenic relationship the microbe causes damage to the host.
In both cases the cost to the host can vary from slight to fatal. And in most cases the relationship will actually remain positive. The host provides a niche and nutrition for the colonizing microbe and the microbe occupies a space that a potential parasite or pathogen might otherwise colonize.
In these cases microbial communities may even aid in digestion or synthesize nutrients for the host. However, life is not always perfect, and in certain situations good-standing members of your normal flora can cause disease or invading pathogens can displace them. The result will be disease. Human skin is not a particularly rich place for microbes to live. The skin surface is relatively dry, slightly acidic and the primary source of nutrition is dead cells.
This is an environment that prevents the growth of many microorganisms, but a few have adapted to life on our skin. Propionibacterium acnes is a Gram positive bacterium that inhabits the skin. As the name implies P. Although acne outbreaks can result in emotional and physical discomfort the infection is not life threatening. A point complemented by P. Another prominent member of the skin flora is Staphylococcus epidermidis. This is a highly adapted Gram positive bacterium that can survive at many sites throughout the body.
In such cases, S. Under this scenario S. Today, researchers and manufacturers are developing new approaches to designing catheters that prevent biofilm formation. The human nose is home to the infamous Gram positive bacterium Staphylococcus aureus , best known for its role in hospitals where it is a major cause of surgical wound and systemic infection. You may have heard of S. Infections of this bacterium are now a very serious threat to human health because it has become resistant to all commercially available antibiotics, including methicillin and vancomycin.
It is often carried in the noses of health care workers and transmitted from patient to patient. Why some people carry S. A predominant member of this community is the Gram positive bacterium Streptococcus mutans.
It grows on biofilms on the surface of teeth plaque where it consumes sugar and converts it to lactic acid. Lactic acid erodes the enamel on the surface of teeth, which leads to the formation of cavities. Interestingly, a group of researchers have developed a strategy to combat dental decay by using a genetically modified strain of bacteria that produces a toxin that specifically kills S. The trick is that this genetically modified strain of bacteria will only survive in your mouth if you provide it with specific nutrients.
Basically, you brush the new strain of bacteria onto your teeth and they produce a toxin that prevents the growth of S. To maintain the strain of bacteria in your mouth you provide the essential nutrient by swishing daily with a mouthwash—just remember to feed your bacteria! Whether or not tooth decay is a disease serious enough to warrant the use of a new strain of genetically modified bacteria is debatable.
The effects of altering the populations of bacteria in the mouth may have unpredictable consequences. For example, Streptococcus pneumoniae is a much more threatening bacteria that can colonize the mouth. Under normal circumstances the growth of S. Would the removal of S. What kind of organism would live in a highly acidic pH environment like the stomach? One organism that has been discovered living in the human stomach is the Gram negative bacterium called Helicobacter pylori [4].
How can it survive? Well, it creates a less acidic microenvironment. In addition, H. Share This Flashcard Set Close. Please sign in to share these flashcards. We'll bring you back here when you are done. Sign in Don't have an account? Set the Language Close.
Flashcards » Normal Flora vs Pathogens. Add to Folders Close. Please sign in to add to folders. Upgrade to Cram Premium Close. Upgrade Cancel. Shuffle Toggle On. Card Range To Study through. Normal Flora. Some important microorganisms of the normal flora and our interaction with these organisms. What are the advantages and disadvantages of the normal flora. What are nosocomial infections and some of the major microorganisms causing nosocomial infections.
Infection 2. Etiologic Agent 3. Pathogenesis 4.
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