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Flashcards in Chapter 23 Deck (19)

What is an ecosystem

The sum total of all organisms and abiotic factors in a particular environment


What is a habitat

Portion of an ecosystem where a community could reside. An ecosystem contains many habitats


What is symbioses

Relationships that microbes can establish with other organisms


What is parasitism

A relationship where one member in the relationship is harmed and the other benefits


What is mutualism

A relationship where both members benefit


What is commensalism

A relationship where one species benefits and the other is neither harmed nor helped


What is the microenvironment

The immediate environmental surrounding microbial cells. Ex. your mouth contains many microenvironments. Physiochemical conditions vary spatially and temporally


Describe the microbes feast-or-famine existence

Resources in natural environments are high variable. Bacteria on your teeth can be in the famine state most of the time because they have to wait for food to come to it. Once food is ingested and they can use it, they will feast and proliferate quickly before returning to their famine state


How do natural environments compare to laboratory environments

Growth rates in nature are usually well below maximum growth rates in laboratories. Competition and cooperation occur between microbes in natural systems


Why are surfaces important microbial habitats

Because nutrients adsorb to surfaces and microbial cells attach to surfaces


What are biofilms

Assemblages of bacterial cells that adhere to a surface and enclosed in an adhesive matrix excreted by the cells. Energy is required to form a biofilm


What is the matrix in biofilms made of

The matric is typically a mixture of polysaccharides


What are biofilms useful for

Biofilms trap nutrients for microbial growth and help prevent detachment of cells in flowing systems


What intiates biofilm formation

Biofilm formation is initiated by ATTACHMENT of a cell to a surface followed by expression of biofilm specific genes


What are biofilm specific genes

Could encode proteins that synthesize intercellurlar signalling (quorom sensing) molecules and initiate matrix formation


What is quorum sensing

Intercellular communication is critical in the development and maintenance of a biolfilm


What are AHLs

AHLs are major intracellular signaling molecules


Why do bacteria form biofilms

Self defense, allows cells to remain in favorable niche and bacterial symbioses


What is biofilm self-defense

Biofilms resist physical forces that sweep away unattached cells, phagocytosis by immune system cells, and penetration of antibiotics