Chapter 22b Flashcards
Only microbes have genes for glycoside hydrolases and polysaccharide lyases that can
degrade cellulose, hemicellulose, and other insoluble polysaccharides
Cellulose is the mos
abundant component of plant fibers
Two digestive plans
Foregut fermentation –Hindgut fermentation–
Rumen
pecial digestive organ in some herbivorous mammals (cows, sheep, elk)
Site of cellulose digestion
anaerobic microbes-rumen
Biochemical reactions in the rumen
1010–1011 microbes/g of rumen
•Cellulolytic microbes that hydrolyze cellulose to free glucose that is then fermented, producing volatile fatty acids (VFAs) and CH4 and CO2
Rumen microbes
Synthesize VFAs • Directly digested and serve as protein
Anaerobic microbes
–Bacteria –Protists –Fungi –Archaea
Rumen microbes continued
• Cellulose decomposers • Starch decomposers • Lactate decomposers • Succinate decomposer • Pectin decomposer • Methanogens
All sites on a human that contains microorganisms are part of the
microbiome
Human Microbiome Project
Humans are monogastric and omnivorous
•1014 cells present in microbiome (= 10× more
bacterial cells than human cells)
The Human Gut Microbial Community
Microbes in gut affect early development, health, and predisposition to disease
•High variability in gut communities between
different individuals
Colonization of gut begins at birth-responsible for “maturing” of gastrointestinal tract
Triggering expression of human genes responsible
for nutrient uptake and metabolism –Recognition of gut microflora as nonforeign –Development of mucosal barrier
Human gut microorganisms produce
Enzymes –Amino acids –Vitamins
•Firmicutes (64%) •Bacteroides (23%) •Proteobacteria (8%) •Actinobacteria (3%)
Human gut microorganisms may play a role in
obesity