lecture 15 (ch 20: eukaryotic microbial diversity)

importance of eukaryotic microbes (3)?

1. Medicine: make antibiotics and cause infections

2. Food & industrial production: help with fermentation (bread, cheese) and enzyme production

3. Key part of food webs: do photosynthesis and serve as consumers in aquatic food webs

What nutritional modes do eukaryotic microbes use?

photoautotrophs and organoheterotrophs (lithotrophy extremely rare)

How does eukaryotic diversity compare in terms of size and complexity?

• Greater variation in size & complexity

  • Range from unicellular, colonial, to multicellular

  • All have DNA inside a nucleus and membrane-bound organelles

What does it mean that fungi are absorptive heterotrophs?

They secrete degradative enzymes to break down complex materials and absorb small molecules for nutrition.

Saprophytes

organisms that decompose dead organic matter; most fungi are saprophytes.

What is the key component of fungal cell walls?

chitin: a polymer of N-acetylglucosamine (NAG), a building block of peptidoglycan

yeast

unicellular fungus

How does yeast reproduce ?

• Reproduces asexually by budding or by fission

• Can also reproduce sexually by mating

components of mold

• Made of thread-like filaments called hyphae

• Can have septa or not (division between “cells”)

• Hyphae form networks called mycelium

mushroom

• spore-bearing structure (fruiting body) produced by some kinds of fungi

• Arises from mycelium, so not really a separate morphology

• Spread spores to new environments

ecological roles of fungi

1. saprophytes (decomposers)

2. beneficial symbionts

3. harmful symbionts

4. parasites/pathogens 

draw and describe asexual fungal life cycle

• Spore germinates into mycelium

• Mitosis in mycelium produces (mito)spores

• Spores are disseminated to new location

draw sexual fungal life cycle

chytridiomycota

• aquatic environment, moist soil

• Have motile spores (zoospores)

• Saprophytic, occasionally parasitic 

Zygotmycetes

mainly saprophytes that grow on decaying organic matter. Their habitats include soil, rotting fruits and vegetables, bread, and other decomposing plant material.

basidiomycetes

• Terrestrial — forests, grasslands, soil, plants

• Mainly decomposers

• Their fruiting bodies (such as mushrooms) are often visible above ground in these habitats. Some species are also plant pathogens and can be found on crops

protist

unicellular or colonial eukaryotes that aren’t fungi (ex. protozoa, algae, slime molds)

Protozoa

• heterotrophic single-celled protists

algae

• Algae: uni or multicellular, phototrophic protists.

  • Found in soil, water, and symbiotic with other organisms 

slime molds

heterotrophic spore-formers

primary algae

derived from a eukaryote that engulfed a cyanobacterium

secondary algae 

derived from a protozoan that engulfed a primary algae

Are Blue-Green Algae actually algae?

No, they are Cyanobacteria, the only photosynthetic prokaryotes (i.e., with PS I & PS II)

plasmogamy

cells fuse w/o nuclei merging

karyogamy

nuclear fusion

mycorrhizae

a symbiotic relationship between fungi and plant roots

zoospore

motile spores

sporangium

bulbous membrane on top of aerial hypha

australia’s great barrier reef

• (home to 10% of all Earth’s corals) has a problem 

  • Since 1995, half the corals have died off by “bleaching”

  • Loss of algal symbionts that conduct photosynthesis and feed their coral hosts

• Causes are complex, but important factor is increase in ocean temperature

harmful algal blooms

• Bloom = large concentration of algal cells 

• Usually caused by increased nutrient availability (mostly N & P)

• Can produce harmful toxins → fish, bird & mammal die-off