lecture 8 - fiber degradtion
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What are fibrolytic bacteria?
Bacteria that degrade cellulose and hemicellulose
What conditions do rumen fibrolytic bacteria require?
Anaerobic conditions
What are Hungate roll tubes used for?
Culturing and isolating anaerobic bacteria
Why must oxygen be excluded when culturing many rumen bacteria?
They are anaerobic and may be oxygen-sensitive
What is the glycocalyx?
A polysaccharide coating that helps bacteria attach to fiber
Why is attachment to fiber important?
It keeps bacteria near their substrate for digestion
How can attachment help bacterial enzymes work?
It keeps enzymes close to the fiber they break down
What can expose new attachment sites on plant fiber?
Chewing and physical breakdown
What energy source do fibrolytic bacteria need?
Fermentable carbohydrates
What nitrogen source do fibrolytic bacteria need?
Ammonia
Why do fibrolytic bacteria need carbon skeletons?
To build cellular components
Which branched-chain VFAs can support fibrolytic bacteria?
Isobutyrate, isovalerate, and 2-methylbutyrate
Which vitamins do fibrolytic bacteria need?
B vitamins
Name the three major fibrolytic bacteria.
Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus
Which bacterium is a major cellulolytic species and has a strong attachment ability to fiber?
Fibrobacter succinogenes
About how long does Fibrobacter succinogenes take to colonize fiber?
~30 mins
Which major fibrolytic species colonizes fiber fastest?
Ruminococcus flavefaciens
About how quickly can Ruminococcus flavefaciens colonize fiber?
About 1 minute
What structure does Ruminococcus flavefaciens produce?
cellulosome
What does albus mean in Ruminococcus albus and why did it get that name?
White; it forms white colonies
About how long does Ruminococcus albus take to colonize fiber?
About 5 minutes
Which minor fibrolytic bacterium acts on hemicellulose and pectin?
Butyrivibrio fibrisolvens
What shape and motility feature are associated with Butyrivibrio fibrisolvens?
It is a flagellated rod
Below what rumen pH can fiber digestion begin to decline?
About pH 6.7
At what rumen pH is fiber digestion severely impaired?
About pH 6.0
Why are fibrolytic bacteria sensitive to low pH?
Low pH interferes with their activity, attachment, and survival