Question

Define the term normal flora. Discuss its role in immunity

• List and describe the following types of symbiotic relationships.
  • Mutualism
  • Commensalism
  • Parasitism
• Define virulence factors. Speculate how these factors help the organism avoid the immune system and cause disease.

Answer 1

noraml flora is the normal organism that live on the surface of body. For example streptococci, E.coli etc

Mutualism, association between organisms of two different species in which each benefits. Mutualistic arrangements are most likely to develop between organisms with widely different living requirements.

Commensalism is a relationship between two organisms in which one organism benefits, and one is unaffected ex. birds living in holllow trees

Parasitism is a relationship between 2 organism where one is benifited while other is harmed ex. lice living on head

Virulence is described as an ability of an organism to infect the host and cause a disease. Virulence factors are the molecules that assist the bacterium colonize the host at the cellular level. These factors are either secretory, membrane associated or cytosolic in nature. The cytosolic factors facilitate the bacterium to undergo quick adaptive—metabolic, physiological and morphological shifts. The membrane associated virulence factors aid the bacterium in adhesion and evasion of the host cell. The secretory factors are important components of bacterial armoury which help the bacterium wade through the innate and adaptive immune response mounted within the host. In extracellular pathogens, the secretory virulence factors act synergistically to kill the host cells. In this review, we revisit the role of some of the secreted virulence factors of two human pathogens: Mycobacterium tuberculosis—an intracellular pathogen and Bacillus anthracis—an extracellular pathogen. The advances in research on the role of secretory factors of these pathogens during infection are discussed.