Chapter 20 - Microbial Symbioses

Question 1

Symbiosis

Answer 1

intimate relationship between two organisms

Question 2

mutualistic relationship

Answer 2

one in which both partners benefit

Question 3

commensalistic relationship

Answer 3

one partner benefits, other does not

Question 4

pathogenic relationship

Answer 4

one partner benefits at the expense of the other

Question 5

Where are most human microbes found?

Answer 5

In the hut, particularly about 1-4 hours after eating a meal

Question 6

Gut Microbes importance?

Answer 6

Essential for host digestion and nutrition, aiding in digestion by breaking down carbohydrates, liberating short chain fatty acids. Produce vitamins

Question 7

Gut Microbes and Obesity

Answer 7

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

Question 8

Human Microbiome and Disease

Answer 8

microbiota changes have been seen to be associated with diseased states or dysbiosis

Question 9

Human Microbiome Project (HMP)

Answer 9

International research program focused on functions of guy microbiota.

Question 10

Biofilms

Answer 10

complex aggregation of cells that are encased w/in an extracellular matrix and attached to a surface

Question 11

Biofilm Development 1

Answer 11

Cell disposition and attachment - free floating cells must collide with surface - surface typically preconditioned w/ environmental proteins

Question 12

Biofilm Development 2

Answer 12

Colonization - cell-to-cell signaling occurs, leads to expression of biofilm specific genes.

Question 13

Biofilm Development 3

Answer 13

Maturation - the EPS matrix fully encases all the cells, as biofilm continues to thicken and grow - water channels throughout the structure

Question 14

Biofilm Development 4

Answer 14

Detachment and sloughing - individual cells released to the environment 0 this can be triggered by environmental factors

Question 15

Why do biofilms develop?

Answer 15

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

Question 16

Biofilm Impacts

Answer 16

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

Question 17

Quorum Sensing

Answer 17

The ability of some bacteria to communicate in a density-dependent fashion, allowing them to delay activation of specific genes until it is advantageous

Question 18

what does quorum sensing require?

Answer 18

cell-to-cell communication, using small diffusible substances known as autoinducers

Question 19

What happens as cell population increases in regards to quorum sensing

Answer 19

The concentration of autoinducer increases as well, causing the molecule to diffuse back into individual cells where it triggers activation of specific genes