Lecture 15 - Microbial Communication Flashcards Preview

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What must bacteria be able to do in order to survive due to the fact that the environments they inhabit are complex and subject to rapid change?

must adapt by being able to sense and respond to the rapid changes


What are the 6 functions of bacterial communication?

coordination of gene expression within a single or unrelated population(s) | evade host immune response | coordinate virulence gene expression | inhibit a competitor | inhibit/stimulate host colonization


What are the 3 different kinds of bacterial communication?

intraspecies, interspecies, and inter-kingdom


What is intraspecies signaling?

communication within a population of same species


What is interspecies signaling?

communication between populations of different species


What is inter-kingdom signaling?

abusing signal pathways by signaling molecules of one organism (bacteria) to change behavior of another organism (animal) from a different kingdom


What are bacterial pheromones?

signals that alter bacterial behavior


What are the characteristics of communication signals that bacteria use to communicate?

small molecules released from cell (active transport or passive diffusion)


What must cells – that a bacteria is attempting to communicate with – must possess?

the ability to recognize the signaling molecules = receptors = can be within cells or on surface of cell


What is quorum sensing?

type of bacterial communication that regulates gene expression due to signaling molecules


What is quorum sensing dependent on?

population dependent <> population density increases = quantity of signaling molecules increases


Which type of bacteria uses quorum sensing?

both gram+ and gram– but use different signal molecules


What are the 4 ecological roles of quorum sensing?

coordinate gene expression (within one species or between different species), evade host immune responses, direct signaling between bacterium and host


What is AHL?

N-acyl homoserine lactone = best studied diffusible signal, many bacterial species can produce this


What are the structural components of AHL? Which part stays consistent?

homoserine lactone ring and fatty-acyl side chain | the homoserine lactone ring stays consistent


Which bacterium uses AHL? Which one can't and why?

gram– | gram+ can't use AHL because they lack a porous outer membrane (like seen in gram– cells) instead they have a thick peptidoglycan cell wall


What is specificity determined by within the AHL molecule?

length and modifications of side chain


What is vibrio fischeri? Where are they found on?

marine bacteria capable of bioluminescence found free-living within the ocean OR attached on the light organ of an animal


What is the population density of Vibrio fischeri when it is in the open ocean? What is the consequence of this in terms of cell signaling? What operon transcription depends on this signaling pathway?

low density = low chemical signaling activity | the Lux operon = won't be transcribed


What is the population density of Vibrio fischeri when it is on the light organ of a marine animal? What is the consequence of this in terms of cell signaling?

high population density because they are more concentrated within one area = high chemical signaling activity >>> signals diffuse into cells and bind to transcription factor for Lux-operon = luminescence


What is the Lux operon expression dependent on?

amount of AHL molecules


What do the signal molecules function closely as?

transcription factors that can inhibit or enhance gene expression


Where are the genes, that these signaling molecules control, usually located at?

on an operon


What is another name for interspecies signaling?



What was the example discussed in class to explain how interspecies signaling works?

Pseudomonas species produce phenazines


What are phenazines?

three-pigmented antibiotics


What is positive cross-talk?

species A restores the ability of an activity in species B | beneficial type of communication


What is negative cross-talk?

species A inhibits the ability of an activity in species B | detrimental type of communication


What causes Crown galls disease in plants?

A. tumefaciens


What are the symptoms of Crown galls disease?

development of "galls" at the soil surface or "crown" of the plant