Microbiomes Flashcards
(33 cards)
Microbes roles in environment
- Decompose
- Recycle nutrients
- Provide nutrients for plants
- They create fossil fuels
- Marine phytoplankton perform
half of the global
photosynthetic CO2 fixation
and half of the oxygen
production despite amounting
to only ~1% of global plant
biomass
Role of microbes in soil formation
- Association of Ascomycete fungus and
green algae and/or cyanobacteria - Fungus obtains carbon and O2 from its
partner - Fungus provides a firm substrate,
protection from high light intensity, water,
and minerals - They are very diverse and can be found in
all types of ecosystems - They grow on soil, rock, bark, wood,
barnacles, and buildings
Role of microbes in soil formation - lichens
- Deterioration of the rock via
excretion of acids - Physical penetration of rock crevices
between mineral grains - Nitrogen fixation by cyanobacteria
Soil organic matter…
- Retains nutrients
- Maintains soil structure
- Holds water for plant use
- Levels change depending on environmental conditions and agricultural
management practices - Mineral soils contain less than 20% organic carbon (most soils)
- Organic soils contain more than 20% organic carbon
Depletion of soil organic matter leads to…
- soil degradation and nutrient depletion
- decline in agronomic and biomass productivity
- decline in environmental quality (emissions of CO2 and other gases, hipoxia and situation of reservoirs)
- food insecurity, malnutrition and hunger
Microorganisms and the nitrogen cycle
Nitrogen fixing bacteria
* Azotobacter, Rhizobium convert N2 to NH3/NH4
Nitrifying bacteria
* Nitrosomas convert NH3 to NH4 to NO2
* Nitrobacter convert NO2 to NO3
Denitrifying bacteria
* Pseudomonas convert NO3 to N2
Microorganisms and the phosphorus cycle
Microbial immobilization and
mineralization of P ensures cycling
of P
* Aerobic and anaerobic bacteria
and fungi
Interactions in the rhizosphere
- Plants influence the
composition of their
rhizosphere microbiome - Microbes may improve
plants’ tolerance to stress
Diazotrophs (2 main groups)
- Endosymbionts (i.e. rhizobia
that live in root nodules) - Plant growth promoting
rhizobacteria (PGPR) (i.e. free-
living nitrogen fixing bacteria)
Mycorrhizal roots
Plants gain access to nutrients and water in a bigger volume of soil
Locked up nutrients may be
solubilized by Mycorrhiza and thereby become accessible to the root
Climate change
a change in the average temperature and cycles of weather over a long period of time
- If the climate changes quickly, organisms don’t have enough time to adapt to new conditions and may
no longer be able to survive
Effect of climate change - Malaria
- If mosquito habitats becomes warmer, then their rate of reproduction increases, as does the number of bites and
consequently blood meals they take - Warmer weather also extends their breeding season
- As more locations get warmer, mosquitoes can travel further
- It is predicted that a 2–3°C rise in temperature would increase the number of people affected by malaria by approximately 3–5% (several hundred million people).
What is the built environment?
- Any part of your external environment that is not a natural environment
- The built environment encompasses all manufactured structures, including any buildings,
transportation systems, public spaces, and other physical surroundings constructed by
humans - It is estimated that humans in developed nations spend about 90% of their time in built
environments (homes, workplaces, schools, cars, hospitals, etc.) - Built environments have unique microbial communities that are unlike those found
elsewhere on Earth
Differences between the developed urban environment and developing rural environment..
Developed Urban:
- small family size
- low helminth exposure
- few infections
- high antibiotic exposure
- low farming exposure
- low microbial exposure
- allergy and autoimmune disease is common
Developing Rural:
- large family size
- high helminth exposure
- many infections
- low antibiotic exposure
- high farming exposure
- high microbial exposure
- allergy and autoimmune disease is uncommon
Different sources of microorganisms (influencing indoor microbiomes)
- humans - movement, respiration, touching surfaces, skin shedding
- pets
- outdoor air
- materials and surfaces
- moisture and humidity
- ventilation and air filtration
porous materials
(e.g. wood, many types of stone, fabrics) absorb moisture and organic matter,
creating microhabitats for microbial growth
non-porous materials
(e.g. plastic, metal) are much less likely to support microbial growth long
term (but can still act as transfer points)
hard surfaces
(e.g. countertops, stainless steel, glass) tend to have fewer microorganisms due to reduced moisture retention and easier cleaning
soft surfaces
(e.g. carpets, upholstery, curtains) can have more diverse microbial communities
because they trap moisture, organic matter, skin flakes, and are cleaned less often
high-touch surfaces
Door handles, computer keyboards, lift buttons, handrails are considered microbial hotspots due to
frequent human contact
- Studies show that microbes from hands can persist for hours or even days on certain materials
wet areas
(bathrooms, kitchens) encourage microbial growth, so the density of microorganisms in these
areas is likely to be greater than a drier area
Amplicon sequencing (metataxonomics)
- Sequencing of one gene amplified from the DNA extracted from a sample, most commonly
16S/18S rRNA (targeted)
Metagenomics
- Sequencing all of the DNA extracted from a sample (untargeted)
