62 terms

Microbial Ecology and Diseases

Define ecology
the study of the relationship of organisms to each other and their environment
What is a population?
all the members of a particular species that live in a defined geographic area
Define ecological community.
The various populations within a defined region
Define biota
The sum of living organisms
Define habitat.
The physical space/location where a species lives
Define ecosystem
A dynamic complex of plant, animal, and microbial communities and their non-living environment interacting as a functional unit
What is an example of an ecosystem?
A herd of cattle alters the soil chemistry. Mushrooms, which require high level of soil nitrogen, thrive where there are cows.
What are the two major elements of an ecosystem?
Energy flow and nutrients
Define producers
Crucial organisms that introduce biological molecules into a food chain or a food web
What are the three categories of contributing agents to an ecosystem?
Producers, consumers, decomposers
In an ecosystem, the cycle flows between which worlds?
Biotic and abiotic
What nutrients can be recycled through the environment indefinitely?
Iron or phosphorous but not energy
Why is energy gradually lost between levels in the ecosystem?
The energy is transferred
What does the width of the arrow represent in the diagram?
The relative quantity of energy lost during each transfer (most is lost as heat)
Who conducted an iron enrichment experiment and what was his purpose?
Atsushi Tsuda of the University of Tokyo in 2003. He believed he might increase fish population and might even help reduce the problem of global warming
How many pounds of iron were dumped in the North Pacific Ocean?
770 pounds over 20,000 acres
What were the iron enrichment experimental results after 2 weeks?
1. The phytoplankton populations increased
2. The levels of CO2 in the air immediately over the iron-fertilized water fell
How exactly would the addition of iron to sea water increase phytoplankton populations, and possibly those of fish as well?
In the iron-poor environment, iron is the limiting factor for phytoplankton growth. The North Pacific is noteworthy for its iron limitation. Adding iron will increase the growth of phytoplankton and may increase the phytoplankton biomass consumed by fish, increasing the fish population.
Would iron-fertilization work in other marine environments too?
In the Atlantic Ocean, it is nitrogen rather than iron that limits the phytoplankton growth. The impact of added iron would not be significant. The tropical parts of the Pacific Ocean are not iron-poor either.
Define photosynthesis
The major process by which CO2 is incorporated into organic matter
Define respiration
Accounts for the return of CO2 to the atmosphere
What is the most abundant microorganism in the ocean?
Prochlorococcus (Penny Chisholm)
What role do producers play in the carbon cycle?
They remove CO2 from the atmosphere and convert it into biological molecules through photosynthesis
What role do consumers play in the carbon cycle?
They obtain carbon compounds in their diet and release CO2 as a respiration waste product.
How do microorganisms return carbon to the environment?
As they decompose organic matter
How do some marine organisms use CO2?
They form calcium carbonate (CaCO3) skeletons that can release CO2 back into the environment when exposed to the atmosphere
Combustion of ____ adds to the atmospheric CO2 pool
fossil fuel
What does it mean that CO2 is what kind of gas?
A "green house" gas that traps heat in the atmosphere and contributes to climate change
What do many researchers believe is an important piece of the global warming problem?
The imbalance in the carbon cycle
What happens to some of the excess CO2?
It is absorbed by the ocean which stores large amounts of CO2 in dissolved form
How does the iron enrichment experiment effect CO2 levels?
Increased phytoplankton biomass, increases amounts of CO2 being removed. Some of the CO2 might remain in the marine environment as the phytoplankton die or are eaten by consumers leading to a decrease in atmospheric CO2
Could Tsuda's technique reduce global warming?
It's hard to tell. The amount of iron required and the area of the ocean that would need fertilization might be far too large to cause any meaningful reduction in atmospheric warming
Might there be other unforeseen consequences of such iron supplementation?
No one knows the consequence of introducing so much extra CO2 into the ocean. We know very little about the RATE at which the ocean absorbs CO2 and releases it back into the atmosphere.
What causes the smell of mudflats?
Hydrogen sulfide released by anaerobic bacteria as a respiration waste product
What causes the black color of mudflats?
The H2S reacting with metallic ions in the mud
What does sulfur oxidizing bacteria do?
Converts H2S to SO4(-2). Hydrogen sulfide cannot be used so the bacteria converts it to the sulfate usable form.
How is sulfate used?
It is absorbed by plants, where it is converted into organic molecules such as amino acids
How does sulfur enter the food chain?
In the form of organic molecules or by being reduced to H2S by bacteria
What does sulfur reducing bacteria do?
Converts SO4(-2) to H2S
What does nitrogen fixing bacteria do?
Converts N2 (gas) into ammonia (NH4+)
What does nitrifying bacteria do?
Converts some of the NH4+ into nitrite (NO2-) and nitrate (NO3-)
Which compounds can be used by plants to produce nitrogen containing organic molecules?
NH4+, NO2-, and NO3- (ammonia, nitrite, and nitrate)
Plants are consumed by _____
Define decomposers.
They decompose dead plants and animals via ammonification (back to ammonium)
Can ammonium be recycled?
What do denitrifying bacteria do?
Convert NO3- (nitrate) back to N2 (gas)
Phosphorus in what enters the cycle?
In rocks or guano
How does phosphorus enter the cycle?
As phosphate (PO4 (-3)) by erosion or by the dissolving power of bacterial acids
What happens to phosphorus when it enters the food chain?
It is incorporated into organic molecules such as nucleic acid, ATP, or phospholipids
What returns organic phosphates to the environment?
What happens to most phosphate in the soil?
It is leached from the soil to oceans because it is soluble
How do deposits of guano come about?
Marine birds, feed on marine animals and deposit their feces on the land with some guano
How does most phosphorus from the seas return to the Earth's landmasses?
Only by geological uplift of the ocean floors- very slow process.
What was the solution attempted to control the rabbit population in Australia?
The myxoma virus, common in South American rabbits, was introduced into the Australian rabbit population
What was the immediate effect in Australian rabbits?
Immediate and severe. Over 99% of all rabbits were dead in a few years
What was the later effect in Australian rabbits?
Within a few more years, rabbit populations once again began to increase because 1) the rabbits had begun to evolve resistance to myxoma virus and 2) the virus had become less deadly
What happened to the rabbits in England?
The virulence of the virus remained extremely high and exposed rabbits still rabidly succumbed to infection
Why were the South American rabbits unaffected by myxoma virus?
Rabbits which developed resistance reproduced more successfully than non-resistant rabbits. Less virulent virus strains are better able to persist (long enough to reach the next host.)
Why did myxoma virus, so deadly initially for rabbits in Australia, become progressively less pathogenic?
Rabbits in Australia had never been exposed to myxoma virus so there had never been any selection for resistance. Then the rabbits with some resistance were the ones that survived and reproduced. The less virulent viral strains did better than more virulent ones, because they allowed an infected rabbit to live long enough for the virus to get to a new rabbit.
Why didn't this reduction in pathogenicity occur in England also? What is different about the situation in Australia and England?
The ENVIRONMENT. In Australia, myxoma virus is transmitted between rabbits by mosquitos through mosquitos feeding on an infected rabbit and transmitting the virus to another rabbit. In England, fleas are the vector.
What is the difference between mosquitos or fleas being the vector?
Adult mosquitos die when the weather turns cold so there is no vector in the winter. Fleas survive the winter months so they are always working to find more hosts and the virulent virus wins. Also, fleas live on animals so they have easy access.
Why was the virus more virulent in England than Australia?
Since there was no viral transmission in the winter months the mild virus won because the virulent strain killed their rabbit hosts quickly and were left with a dead host. In England, the virus was transmitted year round so there was never any difficulty getting to the next rabbit. Consequently, less virulent viral strains did not enjoy a reproductive advantage.