What is an essential part of proteins, amino acids, DNA, etc in cell?
Where is the reservoir for nitrogen in the atmostphere?
Nitrogen gas (N2)
How do eukaryotic organisms obtain their nitrogen?
They depend on certain bacteria to fix nitrogen gas and convert it to useable forms like ammonia (nh3) and nitrate (no3-), plants use the ammonia and nitrate, and the nitrogen gets passed up the food chain from there
What bacteria is primarily responsible for nitrogen fixation?
Rhizobium and cyanobacteria
Where do Rhizobium live? What is its relationship with its habitat?
nodules in the roots of legumes (peas, beans, etc) - mutually beneficial, plants provide shelter and nutrients, and the Rhizobium provides ammonia
What are the nodules that Rhizobium live in caused by?
infection of the roots by the Rhizobium
Where do cyanobacteria usually reside? Where else can they live?
They are aquatic, so deep ocean depths, but they can be found anywhere with enough moisture.
All bacteria that fix nitrogen use what enzyme? What does that enzyme do?
Nitrogenase, it converts nitrogen gas to ammonia (N2 --> NH3)
How do nitrogen-fixing bacteria benefit soil?
They make it more nutritious. Plants can use the ammonia or nitrate they produce.
What species of bacteria is bad for soil. Why?
Psuedomonas. They convert nitrate back to nitrogen gas, making the soil less nutritious and increasing the need for fertilizers on cropland.
How much bacteria does groundwater usually contain? Why?
few, because most microbes become trapped in soil as water seeps through
When does the risk of groundwater contamination increase?
when human activities bypass or overwhelm the filtering action of the soil (eg: wells, feedlots, broken septic tank systems)
When is surface water most highly contaminated? Why?
after rainfall, large numbers of soil microbes get washed into lakes and rivers
How long does it take for surface water to return to normal after rainfall?
It's estimated that more than how much of the oxygen in our atmosphere is produced by what?
1/2, oceanic phytoplankton
What are oceanic phytoplankton?
free floating, photosynthetic organisms, including algae and cyanobacteria
What is the most numerous photosynthetic organism on Earth?
What is Prochlorococcus?
Large increases in photosynthetic activity happens how often in the North Atlantic Ocean? Why?
annually, spring thawing of polar ice cuases mixing of ocean water, which brings nutrients up from the ocean floor, population blooms and photosynthesis increases
What are some ocean depth barriers for life?
cold, pressure, salt concentration, lack of oxygen
There's still an active community in the deep ocean depths, what percentage of all life on Earth lives down there? And where at the depths do they live?
1/3, sediment at the bottom of the ocean
What percent of infections are caused by contaminated water?
How many deaths result worldwide each year from infections caused by contaminated water?
Who are most effected by water quality? Why?
children under five - their immune systems aren't developed enough and they're more susceptible to dehydration and shocks that can occur due to diarrheal diseases
What is the definition of coliform?
facultatively anaerobic, gram negative, non endospore forming rod that ferment lactose to acid and gas within 48 hours at 37 degrees celsius
What are some examples of coliforms?
E. coli, Proteus, etc
Where are most coliforms found? What does their presence in food/water mean?
intestinal tracts of mammals; is has been contaminated with fecal material
What kind of testing is used to detect contamination of food/water?
coliform testing, it's the single most common test used to determine microbial quality of food/water
Are coliforms pathogenic?
no, many human pathogens live in the intestinal tract so if they are in water/food, then other microbes could be too
What is eutrophication?
a natural process of increased growth of organisms as bodies of water slowly become more nutritious over time
What happens if nutrients in bodies of water increase too quickly?
sudden increase in algal population may occur, when they die they release alot of nutrients and bacterial populations will suddenly increase, then sudden increase in bacterial metabolism depleted the water of oxygen and results in an oxy-gen deprived dead zone where fish and animals can't live
What nutrients contribute most to europhication?
nitrogen and phosphorus (low quantities in water which prevents rapid growth)
How can humans contribute to eutrophication?
fertilizer run-off and dumping sewage, they are rich in nitrogen and phosphorus
How many continuous dead zones exist in the world? Where do they occur?
more than 400, where coastal cities dump sewage into the ocean
Where is the largest dead zone in the world?
Where the Mississippi River runs into the Gulf of Mexico and covers more than 8,000 square miles
What is bioremediation?
use of microbes to degrade pollutants
Where are bioremediations being used currently?
How is bioremediation being used on oil spills?
workers spray nitrogen, phosphorus, and other minerals (fertilizers) onto the spill area which encourages the growth of bacteria already present and they degrade petroleum hydrocarbons
What species is especially good at bioremediation?
What is the goal of municipal water treatment?
produce water free of pathogens
What are the three steps required for water treatment?
flocculation, filtration, and disinfection
What is flocculation?
raw water is mixed with a flocculant which binds to the contaminant in water (soil particles, clay, mineral, microbes) and forms clumps, water is transferred to a tank where the clumps of floc drop out of solution
What is an example of a flocculant?
What is filtration (water treatment)?
water is passed through a filter of sand or crushed coal, which removes more contaminants (it's not a microbiological filter, but microbes will become trapped in passageways through sand)
What microbe is usually filtered through filtration? Why is that good?
Cysts of protozoa, they are difficult to kill with chlorine
What is disinfection (water treatment)?
water is disinfected by adding chlorine
What is the ppm of chlorine?
What is Arkadelphia's source of water?
What are most microbes (like humans)? What does that mean?
Chemoheterotrophs, the food we eat for carbon and energy aand other nutrients are also foods that microbes can use as carn and energy sources
What must microbes be able to tolerate in food to use them as carbon sources?
temperature, pH, osmotic pressure, and moisture content
When is a food considered spoiled?
when enough changes in taste, appearance, or smell of the food makes it unpalatable
What are some causes of change in food?
the natural ripening process of food; microbes: metabolic waste products of microbes (acids, ammonia), degradation of food caused by microbial exoenzymes, sliminess (biofilm production), visible microbial growth on food
Most spoilage organisms are NOT what?
pathogenic, they just make food distasteful
What number of spoilage organisms must be present to change food (smell, taste, look)?
10^6-10^7 per gram or mL
What is the most common bacteria responsible for spoilage of milk and raw meat?
Metabolically, what is Psuedomonas fragi?
What are spoiled odors and flavors due to?
metabolism of proteins and the production of ammonia, hydrogen sulfide, and other foul-smelling compounds
A foodborne illness is not a foodborne illness if what?
the food itself is poisonous (mushrooms, fish)
What is a common foodborne illness? What is it caused by? What is it called? What are its symptoms?