Mckayla Burns Samantha Jackson. Key Words Diel- A 24 hour period Cytoskeleton- A structural support...
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Transcript of Mckayla Burns Samantha Jackson. Key Words Diel- A 24 hour period Cytoskeleton- A structural support...
The Diel Rhythm that underlies the symbiotic relationship between
Euprymna scolopes and Vibrio fischeri
Mckayla BurnsSamantha Jackson
Key WordsDiel- A 24 hour periodCytoskeleton- A structural support system
made of microtubules and microfilamentsMicroarray-A technique used for
biochemical, genetic analysisChitin-a nitrogen-containing polysaccharideG3P-is a chemical compound used for the
anaerobic respiration of glycerolBlebbing- a blistering or swelling that
occurs in the cytoskeleton
About the AuthorsAndrew M. Wier• Associate professor at Pace University• Uses Euprymna scolopes and Vibrio fischeri as a general model to
study the effects of beneficial bacteria on animal host tissues.
Spencer V. Nyholm• Previous research: Dominance of Vibrio fischeri in secreted mucus
outside the light organ of Euprymna scolopes: the first site of symbiont specificity. Appl. Environ. Microbiol., 69(7), 3932-3937.
• Professor at the University of Connecticut• Also studies the symbiosis between tubeworm and sulfur oxidizing
bacteria in hydrothermal vents
Background InformationHorizontal Transmission:• Every generation of Euprymna scolopes and
Vibrio fischeri must establish the symbiosis, which is different from vertical transmission where the symbiosis is passed from parent to offspring
Mutualistic Relationship:• The squid provides nutrients for the bacteria
and the bacteria provides the squid with bioluminescence which is used for the squid’s protection
Background Information
Figure 1: The diel cycle of the squid/Vibrio symbiosis
A: Shows the position of the light organ within the squid, the expulsion of bacteria from the light organ, and crypt where bacteria symbionts resides
B: The blue line symbolizes the population of the bacteria throughout a 24 hour period. Bacteria’s populations are the highest when the nocturnal host is the most active.
- During expulsion the squid releases 95% of it’s bacteria symbionts, keeping only 5% to regenerate
General Gene ExpressionThe greatest changes in gene expression of
the host cells and symbiont cells occurred before and after dawn
The highest up regulation of host genes occurred before dawn
The highest percentage of up regulated genes in the symbionts occurred after dawn
During some intervals both partners changed the expression of genes specifically used for signaling and metabolism
PurposeTo describe the
transcriptional, metabolic, and physiological aspects of the symbiosis between Euprymna scolopes and Vibrio fischeri and determine if they follow a diel pattern
PhysiologicalMethods:• Used TEM (Transmission Electron Microscopy)• Examined the epithelium cells within the light organ of
Euprymna scolopes over 4 different time periods within 24 hours Results:• Major change in the morphology of the epithelial cells• Directly after dawn, the epithelial cells of the light organ are
obliterated• Following this there was an increase in the number of host
vesicles anticipating the creation of new bacterial symbionts• A few hours later the microvillar border is restored within the
epithelial cells• Next, the light organ is colonized by new bacteria cells and it is
ready for night fall and bioluminescence
How do the Bacteria Repopulate the light organ?Metabolize the lipid vesicles the host cells creates
after dawnHost changes its tissue organization in order to
provide the symbiont with glycerol and fatty acidsBacteria incorporate fatty acids from host lipids into
its membrane
Fatty Acid Composition of Bacterial Symbionts
Regulation of cytoskeleton genes
Up regulated just before dawn
Down regulated just after down
TEMS of the host crypt epithelia
Transcriptional Analysis Reveals Patterns in Symbiont MetabolismMethods:Examined changes in bacterial gene expression
during the day and nightMicroarray analysis of the RNA in the central cores of
the E. scolopes light organsResults:Diel Pattern of Symbiont MetabolismJust before expulsion there is an increase in the
expression of genes for the fermentation for chitinJust after dawn there is an increase in the expression
of genes for the anaerobic respiration of glycerol
Why do the symbionts shift their metabolism?At night during bioluminescence symbionts
use chitin fermentation to generate ATPAfter dawn and throughout the day the
symbionts use anaerobic respiration of glycerol to generate ATP
The form of anaerobic metabolism may be dependent on the substrates available at the time
When chitin is available 12% more energy is produced using fermentation
When glycerol is available more energy is produced using anaerobic respiration
Evidence of a diel pattern of symbiont metabolism.
Wier A M et al. PNAS 2010;107:2259-2264
©2010 by National Academy of Sciences
Conclusions:
There is a transformation of host tissue anatomy
There is a change in gene expression by both partners
These changes are controlled by a daily rhythm
Bioluminescence is maintained by daily interactions between the squid and the bacteria
Strengths/WeaknessesStrengths:• Results for anatomical changes are consistent
with diel rhythm hypothesis• Results support metabolic changes occur on a
diel rhythm Weaknesses:• The source of the nitrate for anaerobic
respiration is still unknown
Further Study:1. “Although the nutritional conditions within the light organ remain unknown, taken together, these calculations support the possibility that over the course of a 24 hour period, the host provides different substrates to its symbionts to optimize their performance under changing physiological conditions present in its tissue over the day-night cycle.” ^(Page 2262)
2. Do changes in the anatomy and gene expression present in other mammalian systems follow a diel rhythm?Tissues in Mouse Colon are believed to follow a circadian
rhythm 3. Parallels between beneficial and pathogenic bacteria induced effacement