Microbiology

Question 1

Prokaryotes

Answer 1

-single cell organisms (or groups of cells) that lack nuclear membranes, chloroplasts, mitochondria, endoplasmic reticulum
-abundant in soil, marine and fresh waters & essential for ecosystems to function
-oldest organisms on earth
-includes Cyanobacteria, Archaea, Eubacteria

Question 2

Archaea

Answer 2

-originally thought to exist only in extreme environments; one in thermal hot springs (110 °C)
-others produce methane from digestion of organic matter in anaerobic conditions
-studies find many more that exist in more “normal” environments

Question 3

Cyanobacteria

Answer 3

-formally called “blue-green algae”
-have pigment phycocyanin which mixes with other pigments to give various shades of blue-green
-like many prokaryotes, able to carry out photosynthesis, but only ones to use chlorophyll a (like all higher plants)
-all use light as energy source and CO2 as carbon source
-some can assimilate organic substances or fix nitrogen
* Some create toxic algal blooms in lakes

Question 4

Eubacteria

Answer 4

-“true” bacteria, grouped according to cell shape, cell-wall chemistry, aerobe/anaerobe, spore formation
-by far most abundant organisms in water: millions to hundreds of millions/mL
-most are free-living decomposers
-some in water are harmful to humans, presence usually due to sewage
contamination

Question 5

Eukaryotes

Answer 5

-most visible to naked eye
-well-developed cell organelles bound by membranes
-typically divided into photosynthetic primary producers (plants, algae) and consumers (animals and protozoa)

Question 6

Chlorophytes (green algae)

Answer 6

-generalists; some with heterotrophic capabilities, many thrive in high nutrient conditions
-highly diverse; small unicellular (~ 2 µm) to large colonial forms (> 35 µm); up to 50% species richness, but usually not abundant
-motile/non-motile

Question 7

Chrysophytes (golden-brown algae)

Answer 7

-coldwater, low nutrient specialists
-unicellular and colonial
-autotrophic, but mixotrophy (consume bacteria) occurs under nutrient-poor or low-light conditions
-most diverse and abundant in oligotrophictemperate and boreal lakes with low phytoplankton biomass

Question 8

Diatoms (Bacillariophyceae)

Answer 8

-diverse overturn bloomers
-very diverse autotrophs (often specialized)
-require dissolved silica (Si) to construct glass-like frustules.
-heavy, non-flagellated cells, sink under calm conditions
-sedimentary resting structures->rapid recolonization (& dominance) during mixing periods
-many are benthic (periphyton)

Question 9

Cryptophytes

Answer 9

-deep/cold water specialists
-small, unicellular with 2 flagella
-often comprise deepwater clorophyll maxima (oligotrophic lakes)
-deepwater species can be heterotrophic (absorb DOC, potential phagotrophy)
-mmajor component of zooplankton diet (palatable, size)

Question 10

Dinoflagellates

Answer 10

-stress-tolerant specialists
-mixotrophic flagellates: consume bacteria, algae and even microzooplankton
-can endure periods of extreme resource-limitation (e.g. winter and late summer)
-many are inedible, large-celled species with spines
-sedimentary resting stages
-can tolerate acidification and eutrophication and co-exist with Cyanobacteria
-produce toxins (red tide)