lecture 2: microbiomes and fungal ways of life

Question 1

endosymbiosis/endosymbiotic theory

Answer 1

◆ 1.8 billion ya
◆ how mitochondria was gained by bacteria

Question 2

microbiome

Answer 2

◆ refers to all microorganisms found in a given well-defined habitat
◆ includes bacteria and archaea, fungi, algae, other unicellular eukaryotes
◆ dynamic, environment-dependent
◆ v important for development, nutrition, health, and more

Question 3

horizontal/vertical transmission

Answer 3

◆ horizontal transmission = acquired from environment
◆ vertical transmission = passed down directly from parent to offspring

Question 4

heterocysts

Answer 4

in some cyanobacteria, some cells in chain will differentiate, becoming heterocysts
◆ allows spatial separation of nitrogen fixation (anaerobic) from photosynthesis (aerobic)
◆ “filamentous chains”

Question 5

metabolite cross-feeding

Answer 5

(prokaryotes)

interaction between bacterial strains in which molecules resulting from the metabolism of one strain are further metabolized by another strain

Question 6

biofilm

Answer 6

a surface coating colony of one or more species of prokaryotes. engage in metabolic cooperation

◆ mats of cells that secrete and become stuck to each other in a matrix of polysaccharides and protein
◆ ex: stromatolies, plaque/tartar, antibiotic resistance

Question 7

quorum sensing

Answer 7

◆ if enough other microbes of the same type nearly, new density-dependent activity is induced
◆ population density detected by concentration of secreted autoinducer molecules
◆ triggers by high cell density
◆ ex: food poisoning, infections

Question 8

absorptive nutrition

Answer 8

a way of obtaining energy and nutrients in which digestive enzymes are secreted into a substrate, then smaller, easily assimilated molecules are absorbed through the cell membrane

Question 9

hypha (hyphae) vs mycelium

Answer 9

hypha = single filament
- can be specialized
- ex: arbuscular mycorrhizal fungi, ectomycorrhizal fungi
mycelium = network of hyphae

Question 10

indeterminate growth

Answer 10

no defined end structure

◆ in context of mycelial networks (fungi)
◆ huge and ancient, complex

Question 11

mycorrhizal fungi (arbuscular, ecto-)

Answer 11

(a) arbuscular mycorrhizal fungi
◆ penetrate root cells and create structures called arbuscules
◆ type of specialized hyphae

(b) ectomycorrhizal fungi
◆ form nets around the whole root and cell surfaces within root but do not enter cells
◆ type of specialized hyphae

Question 12

fungi

Answer 12

Role: decomposer/fermenters
- convert sugars to CO2 and alcohol
- breaking down lignin (a substance most bacteria cannot)

◆ play a crucial role in agriculture, biotech, and health
◆ formed basis of terrestrialization and life on land today
◆ general characteristics
- unicellular or multicellular (non-motile, filamentous)
- chitin-rich cell walls
- are heterotrophs (absorptive nutrition)
- mycelial networks

Question 13

short history of life

Answer 13

1. first eukaryotes appear, limited nutrients in oceans
2. unicellular euk. radiate
3. post-thaw, landmass breaks up = more nutrients
4. life sprouts on land