Chapter 20 - Microbial Symbioses Flashcards
Symbiosis
intimate relationship between two organisms
mutualistic relationship
one in which both partners benefit
commensalistic relationship
one partner benefits, other does not
pathogenic relationship
one partner benefits at the expense of the other
Where are most human microbes found?
In the hut, particularly about 1-4 hours after eating a meal
Gut Microbes importance?
Essential for host digestion and nutrition, aiding in digestion by breaking down carbohydrates, liberating short chain fatty acids. Produce vitamins
Gut Microbes and Obesity
Hypothesized that microbes may play a part in obesity as seen in mice. More Firmicutes bacteria and methanogenic archaea that may be more efficient at absorbing nutrients
Human Microbiome and Disease
microbiota changes have been seen to be associated with diseased states or dysbiosis
Human Microbiome Project (HMP)
International research program focused on functions of guy microbiota.
Biofilms
complex aggregation of cells that are encased w/in an extracellular matrix and attached to a surface
Biofilm Development 1
Cell disposition and attachment - free floating cells must collide with surface - surface typically preconditioned w/ environmental proteins
Biofilm Development 2
Colonization - cell-to-cell signaling occurs, leads to expression of biofilm specific genes.
Biofilm Development 3
Maturation - the EPS matrix fully encases all the cells, as biofilm continues to thicken and grow - water channels throughout the structure
Biofilm Development 4
Detachment and sloughing - individual cells released to the environment 0 this can be triggered by environmental factors
Why do biofilms develop?
Offer cells increased protection from harmful conditions or substances such as UV light. Also allows for cells to “put down roots” to remain close to one another. Also allows for cells to grow in microbial populations and benefit from cell-to-cell communication
Biofilm Impacts
Responsible for many types of chronic infections as the group is resistent to antibiotic- dental plaque is another example - also affect any industry relying on pipes to convey water, food, oild
Quorum Sensing
The ability of some bacteria to communicate in a density-dependent fashion, allowing them to delay activation of specific genes until it is advantageous
what does quorum sensing require?
cell-to-cell communication, using small diffusible substances known as autoinducers
What happens as cell population increases in regards to quorum sensing
The concentration of autoinducer increases as well, causing the molecule to diffuse back into individual cells where it triggers activation of specific genes
