Importance of Normal Flora
Prevent colonization by pathogens as they occupy space which would have been occupied by pathogens and also compete for nutrients.
They stimulate antibody mediated immune response that may cross react with future pathogens thus preventing diseases.
Lactobacilli a normal flora in the vagina produce acid which maintains acidic ph thus preventing growth of micro organisms like over growth of Candida albicans.
Normal floras in gut secrets vit k and B12 enteric bacteria and other vit b by lactic acid bacteria by e into food which help in food supplementation and others produce antimicrobial substances which kill or inhibit pathogen growth eg intestinal bacterias produce avariety of substances ranging from relatively non specific fatty acids and peroxides to highly specific bacteriocins which inhibit or kill other bacteria.

Disadvantages of Normal Floras

• In case of immune suppression can act as opportunistic pathogens

• May be a source of infection to other persons

• They may share nutrients with pathogens leaving the host with nothing hence leading to infections

Mechanisms that can Disrupt Normal Floras

• Suppression of the normal flora by antibiotics allowing overgrowth of resistant species

• Changes in the general health of the person such as immunity suppression

• Local trauma such as skin breakage due to accident or surgery

• Introduction to a new site e.g. migration of E. coli from anus to vagina leads to urinary tract infections

• Hormonal changes especially during pregnancy and menstruation

Symbiotic Relationships
Symbiosis: is a close interaction between two organisms of different species that is to say host and symbiot living together. Host is usually the larger organism and symbiot is the small one in the relationship. Symbiotic relationships may be classified as below:

• Mutualism: an association in which both organisms benefit from the relationship eg E.coli in the colon produces vit k for the host while the host provides nutrients and shelter to it

• Commensalism: association in which one organism benefits and the other is left an affected eg most of the normal floras

• Parasitism: an association in which one organism benefits and the other is harmed eg the worms in our bodies