chapter 20 - microbial ecosystems Flashcards
Ecosystem
sum of all organisms and abiotic properties
Habitat
where community could reside in ecosystem
Population
group of microorganisms of the same species
Community
consists of populations living with other populations
Microbial diversity
richness vs. abundance
Species richness
total number of different species
Species abundance
proportion of each species in an ecosystem
Resources
carbon, nitrogen, oxygen
Conditions
temperature, pH, O2 levels, light
Guilds
metabolically related microbial populations
Niche
habitat shared by a guild
Biogeochemistry
study of biologically mediated chemical transformations
Biochemical cycle
defines transformation of key element by biological/chemical agents
Fundamental niche
full range of environmental conditions where organism can exist
Prime/realized niche
each organism has at least one, where it is most successful
Microenvironment
immediate environment surrounding of microbial cell
is always changing, hence wide range of conditions
When can metabolic cooperation be seen?
when organisms carry out complementary metabolisms (syntrophy)
Why are surfaces important for microbial habitats?
- offer great access to nutrients
- protection from predators
- offers cell to stay in favourable habitat, not get washed away
Biofilms
- assemblage of bacterial cells on surface, in adhesive matrix
- helps trap nutrients for microbial growth
What is the matrix made up of in biofilms?
mixture of polysaccharides
What are the implications of biofilms?
- self defense: resists antibodies
- medical/dental conditions: kidney stones, strep, plaques on teeth
- slow flow of liquids
Microbial Mats
simply thick biofilms built by phototropic bacteria, containing filamentous cyanobacterias.
Mineral soil
rock weathering and inorganic material
Organic soil
sedimentation in bogs/marshes
O Horizon
undecomposed plant material
A Horizon
most microbial growth, rich organic mat with lots of nutrients
B Horizon
little microbial activity, subsoil with a tad of nutrients from A horizon
C Horizon
directly above bedrock
What is the soil mainly composed of in microenvironment?
water and air: 50%
inorganic matter: 40%
organic matter: 5%
micro/macroorganisms: 5%
How is soil formed?
- CO2 formed by respiring organisms
- freezing + thawing breaks apart rocks, allowing roots to penetrate
Rhizosphere
area around plant roots where secrete sugars
Arid soils
dry, limited plant growth
in extreme temepratures, of low water and variable temperatures will slowly form
Biological soil crust
made up of cyanobacteria
use 16s rRNA gene sequencing to see phylogenetic samplings
Terrestrial subsurfaces
lower than cell surface, grows in extremely nutrient-limited environments
microbial diversity is seen in shallow subsurface areas
Freshwater
highly variable in resources and conditions since photosynthesis and respiration work together to control O2 and CO2
What are the oxygenic phototrophs in freshwater and what do they produce?
algae and cyanobacteria
produce: oxygen and organic material
Planktonic
free floating
Benthic
attached to bottom or sides
What depends on activity of primary producers?
heterotrophic microbes in aquatic systems
Does water have limited solubility in water?
yes
What are the three stratification of water columns in lake, what temperature do they have as well as oxygen and sulfur levels?
- Epilimnion: warm, not dense, 24-20ºC, O2: 12-10mg/l, H2S: 0mg/l
- Hypolimnion: cooler, dense, 8-4ºC, O2: 4-0mg/l, H2S: 6-5 mg/l
- Thermocline: zone separating both, 20-8ºC, O2: 10-4mg/l, H2S: 0mg/l
Biochemical oxygen demand
microbial oxygen consuming capacity
(when NO3 goes up, cyanobacteria go up, they bring NO3 levels down)
Phylogenetic sampling
16s rRNA gene sequencing
What are the differences between marine and freshwater environments?
- saline
- low in nutrients
- cooler
- lower in microbial activity
Oxygen minimum zone
regions where oxygen-depleted waters at intermediate depth
Marine dead zone
a reduced level of oxygen in the water
What is seen on top layer of ocean but not bottom?
Phototrophs and nutrients
What is the major marine phototroph and what does it account for?
Prochlorococcus, accounts for >40% of biomass and 50% of net primary production.
What happens to pelagic bacteria?
The deeper you go, bacteria levels will decrease, and archaea levels will rise, resulting in equal amounts of bacteria and archaea.
Pelagibacter
Most abundant marine heterotroph
Proteorhodopsin
captures light energy to drive ATP synthesis
What is most abundant in pelagic marine
viruses, bacteriophages
How must viruses/bacterias be in deep sea?
must be chemotrophic since there is low temp, and nutrient levels, and high pressure and no light
How are deep sea sediments harvested?
by drilling ocean floor
What are the two types of hydrothermal vents?
warm vents: cold water under, smoke less hot
hot vents: extremely hot, black smoke
What dominates in vents?
Chemolithotrophic bacteria
as they use inorganic materials from vents
(thermophiles and hyperthermophiles also present)
more diversity in bacteria than archaea.
