Chapter 22b Flashcards

1
Q

Only microbes have genes for glycoside hydrolases and polysaccharide lyases that can

A

degrade cellulose, hemicellulose, and other insoluble polysaccharides

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2
Q

Cellulose is the mos

A

abundant component of plant fibers

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3
Q

Two digestive plans

A

Foregut fermentation –Hindgut fermentation–

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4
Q

Rumen

A

pecial digestive organ in some herbivorous mammals (cows, sheep, elk)

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5
Q

Site of cellulose digestion

A

anaerobic microbes-rumen

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6
Q

Biochemical reactions in the rumen

A

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

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7
Q

Rumen microbes

A

Synthesize VFAs • Directly digested and serve as protein

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8
Q

Anaerobic microbes

A

–Bacteria –Protists –Fungi –Archaea

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9
Q

Rumen microbes continued

A

• Cellulose decomposers • Starch decomposers • Lactate decomposers • Succinate decomposer • Pectin decomposer • Methanogens

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10
Q

All sites on a human that contains microorganisms are part of the

A

microbiome

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11
Q

Human Microbiome Project

A

Humans are monogastric and omnivorous
•1014 cells present in microbiome (= 10× more
bacterial cells than human cells)

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12
Q

The Human Gut Microbial Community

A

Microbes in gut affect early development, health, and predisposition to disease
•High variability in gut communities between
different individuals

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13
Q

Colonization of gut begins at birth-responsible for “maturing” of gastrointestinal tract

A

Triggering expression of human genes responsible

for nutrient uptake and metabolism –Recognition of gut microflora as nonforeign –Development of mucosal barrier

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14
Q

Human gut microorganisms produce

A

Enzymes –Amino acids –Vitamins

•Firmicutes (64%) •Bacteroides (23%) •Proteobacteria (8%) •Actinobacteria (3%)

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15
Q

Human gut microorganisms may play a role in

A

obesity

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16
Q

Mouth and skin are also heavily colonized by microorganisms

•Mouth:

A

At least 750 species of aerobic and anaerobic

bacteria –Methanogenic Archaea and yeast

17
Q

Mouth and skin are also heavily colonized by microorganisms: skin:

A

19 bacterial phyla (over 200 genera)
•Corynebacterium (moist sites) •Propionibacterium (oily sites) •Staphylococcus (oily sites)
–Fungi (mainly yeast)

18
Q

Heritable Symbionts of Insects

A

•Microbial symbionts can be acquired from :
–Environmental reservoir (horizontal transmission) –Parent (vertical or heritable transmission) –Heritable symbionts of insects are obligate (lack a
free-living replicative stage)

19
Q

Primary

A

Primary symbionts—required for host reproduction
–Restricted to bacteriome, bacterial cells found in bacteriocytes
•Ex: Buchnera supplies amino acids to aphids

20
Q

Secondary

A

Not required for reproduction –Not always present in every individual –Can invade different cells and live extracellularly –Must provide a benefit
•Nutritional •Protection from environment •Protection from pathogens

21
Q

Some insects exploit the metabolic potential of the symbiont

•Primary symbionts exhibit extreme gene reduction

A

Genome of insect symbiont ~160 to 800 kbp –Genome of related free-living bacteria ~2 to 8 Mbp –Retain only genes needed for host fitness
•Lose catabolic genes •Pathogens normally lose anabolic genes

22
Q

Termites

A

Decompose cellulose and hemicellulose

23
Q

Termite gut consists of foregut, midgut, and hindgut

A

Posterior alimentary tract of higher termites
•Diverse community of anaerobes including cellulolytic
anaerobes
–Lower termites
•Anaerobic bacteria and cellulolytic protists

24
Q

Aquatic Invertebrates as Microbial Habitats: Hawaiian Bobtail Squid

A

Aliivibrio fischeri and the Hawaiian bobtail squid
•A. fischeri bioluminesce in light organ
•camouflages the squid from predators

25
Q

Aquatic Invertebrates as Microbial Habitats: Hawaiian Bobtail Squid continued

A

Highly specific •Benefits both partners •Horizontal transmission of
bacterial cells—colonization shortly after juvenile squid hatch
•Bioluminescence is controlled by quorum sensing
•A. fischeri is supplied with nutrients by the squid

26
Q

Marine Invertebrates at Hydrothermal Vents and Gas Seeps

A

Primary producers in hydrothermal vents are chemolithotrophic microbes
•Diverse invertebrate communities develop near hydrothermal vents, including large tube worms, clams, mussels

27
Q

Chemolithotrophic prokaryotes that utilize reduced

A

inorganic materials emitting from the vents form endosymbiotic relationships with vent invertebrates

28
Q

Vent tube worms

A

Trophosome contains symbionts –Hemoglobin binds H2S and O2 –CO2 in blood

29
Q

Leeches

A

Leeches are parasitic annelids (segmented worms)
•Feed on vertebrate blood and secrete anticoagulants and vasodilators
•Crop has Aeromonas and a Rikenella-like bacterium •Intestinum has complex community
•Bladder—Ochrobactrum

30
Q

Reef-building corals

A

Coral skeleton very efficient light-gathering structure

•Phototrophic symbionts include cyanobacterium, rhodophytes, chlorophytes, dinoflagellates, and diatoms

31
Q

Reef-Building Corals

A

Most ecologically significant between stony coral and the dinoflagellate Symbiodinium
•Reef-building corals reproduce sexually by releasing gametes into the seawater
•Algal symbionts are typically found in the egg
•Developing coral can also ingest dinoflagellates
•Cnidarians receive fixed carbon
•Dinoflagellate receives inorganic nutrients

32
Q

Reef-Building Corals: Coral bleaching

A
  • Loss of color caused by lysis of symbiont

* High temperature and high light impair the photosynthetic apparatus of dinoflagellate