Global Influences of Microbes Flashcards
What are the main protagonists of climate change?
CO2, methane and N2O
Which organisms can fix carbon?
- Photoautotrophs (e.g. Cyanobacteria)
- Lithoautotrophs
- Facultative anaerobic purple bacteria
What do photoautotrophs do?
Use energy from sunlight to convert CO2 and water into organic materials to be used in cellular functions such as biosynthesis and respiration
Bind and convert Co2 into biomass
What are the 2 parts to Co2 fixation by photoautrotrophs?
- Generation of energy
- Assimilation of Co2 through the Calvin cycle
How does cyanobacteria generate energy for part 1 of Co2 fixation?
Through the light dependent reaction
Describe the light dependent reaction
- Uses light energy to make energy storage molecule ATP and the reduced electron carrier NADPH
- Takes place in the thylakoid membranes of organelles (chloroplasts)
- Light is absorbed by pigments in PSII and passed between pigments to the reaction center
- Energy is transferred to P680, boosting an electron to a high energy level
- The high energy electron is passed to an acceptor molecule and replaced with an electron from water
- The splitting of water releases O2
- The high energy electron travels down an ETC, losing energy
- Some released energy drives the pumping of H+ ions from the stroma into the thylakoid interior, building a gradient
- As H+ ions flow down their gradient into the stroma, they pass through ATP synthase, driving ATP production (this is known as chemiosmosis)
Describe the light independent (dark) reaction
- The electron from PSII arrives at PSI and joins the P700 special pair of chlorophylls in the reaction center
- Light energy absorbed by the pigments and passed into the reaction center boosts the electron in P700 to a very high energy level and it is transferred to an acceptor molecule
- The special pair’s missing electron is replaced by a new electron from PSII
- The high energy electron travels down a short second leg of the ETC where it is passed to NADP+ to make NADPH
What are some impacts of climate change on oceans?
- influences composition, location and existence of carbon fixing microbes
- increased temperatures affects water salinity (ice cap melting) and wind
- may increase/decrease phytoplankton growth
- increase in surface runoff of nutrients (can lead to cyanobacterial blooms)
What are cyanobacterial blooms?
Huge mat-like structures of organisms
What are the 2 major consequences of cyanobacterial blooms?
- Biochemical O2 debt
- creation of anoxic regions
What is biochemical O2 debt?
A decrease in O2 in the water due to microbial proliferation
How are anoxic regions created?
- organisms sink to the floor when they die and are degraded by bacteria
- decaying plankton consume O2
How does facultative anaerobic purple bacteria fix CO2?
Using the Calvin cycle
How do Lithoautotrophs fix carbon?
Mostly under anaerobic conditions, generating their energy through the use of compounds (eg. hydrogen sulphide)
True or False, both lithoautotrophs and facultative anaerobic purple bacteria use RuBisCo
True
Describe the process of carbon cycling
- Primary fixers are consumed by grazers and decomposers
- Grazers are consumed by predators which are then consumed by higher predators
- Decomposers consume predators and higher predators
Describe the role of the ocean as a carbon sink
- Co2 is absorbed by phytoplankton which sink to the ocean floor when they die
- These are not degraded fully as O2 is scarce
- This carbon has been compressed over millions of years => FOSSIL FUELS
What are some ways carbon is released into the environment?
- Fossil fuels
- Respiration
- Methanogenesis
- Melting ice caps releases undecomposed organisms which then release carbon upon decomposition
What are methanogens?
They are obligate anaerobes and chemoautotrophs
How are methanogens chemoautotrophs?
They use H2 as a terminal electron acceptor during anaerobic respiration
(Generate energy by reducing Co2 to methane)
Where do methanogens live?
In anoxic environments such as swamps and marshes, and the guts of most mammals
What is the role of termites in relation to methanogens?
- Their gut contains a protist called Mixtricha paradoxa which degrades lignin to form acetate and organic acids
- ## The Co2 and H2 produced using fermentation are consumed by methanogens to make methane
How can microbes be used as biofuels?
- A by-product of microbial fermentation is the production of alcohol
- Co2 is still produced but is carbon neutral (carbon fixed by plants = carbon used as fuel)
Advantages of bioethanol production
- Renewable energy source
- Carbon neutral
- Can be used alone or mixed with other liquid fuels
Disadvantages of bioethanol production
- Uses land to grow fuel crops that could have been used to feed people
- Production requires energy input
- Bioethanol can be damaging in non-compatible fuel systems
Rank the following feedstocks for ethanol production in order of easiest, harder, and hardest:
Sugar crops, Lignocellulosic material, Starch crops
Easiest = sugar crops
Harder = Starch crops
Hardest = Lignocellulosic material
Name the 4 diseases of cattle
- Bovine Tuberculosis (TB)
- Nagana
- Rinderpest
- Ringworm
What was the economic impact of Foot and Mouth disease?
- 6 million animals culled
- consequences to tourism, transport
- loss of £8 billion to economy
- Changes in food security practices
What are the symptoms of TB in cattle?
- Infected lymph nodes in head
- tubercles in the chest cavity and lungs
- weakness
- coughing
- weight loss
How is a mycobacterium killed by the immune system?
- Is phagocytosed into a phagosome (vacuole)
- The phagosome fuses with the lysosome
- Need activated macrophages to kill mycobacteria (activate by immune molecules to change the phenotype)
- T cell response produces cytokines which activate macrophages and eliminate bacteria
How does mycobacterium evade the immune system?
- They secrete protein and lipid factors that block phagosome maturation and prevent phagolysosome fusion
- Mycobacteria are resistant to acidification and reactive oxygen species
- Inhibits apoptosis and autophagy
How does TB evade the immune system long term?
Infected macrophages are phagocytosed by other macrophages and accumulate, forming lesions. This continues until death.
How is TB spread?
- Many potential reservoirs exist: deer, fox, rodents
- Badgers thought to transmit directly to cows
- Difficult to monitor and control spread from wildlife to cattle
Which strain of TB is used to vaccinate humans?
The Bacillus Calmette-Guerin (BCG) strain
What TB vaccines are available to cattle?
Vaccines are not successful in cattle, however injectable badger BCG vaccine has been working well so far in badgers
Which animals are affected by African animal trypanosomes (Trypanosomiasis)?
Cattle and other livestock
What are the symptoms of Trypanosomiasis in cattle?
- Swelling
- Fever
- Reduced milk production
- Fertility issues
- Weight loss
Which trypanosomes are responsible for Trypanosomiasis?
- T. congolense
- T. vivax
- T. brucei spp.
How do trypanosomes evade the immune response?
Antigenic variation
How does antigenic variation allow immune evasion of trypanosomes?
- Variant surface glycoprotein (VSG) switching alloes trypanosomes to change their coat protein, making it difficult to find one vaccine that will recognise all.
- Trypanosomes first induce an immune response and then change their antigen coat to prevent clearing
How is Trypanosomiasis treated?
Using drugs like diminazene aceturate, homidium bromide/chloride, isometamidium chloride
What are some measures used to prevent Trypanosomiasis?
- Breed trypanotolerant cattle
- Control vectors: remove fly using traps, bush clearing and insecticide
What is Rinderpest?
An acute, highly contagious viral disease of cattle, water buffalo and other wildlife
What virus is responsible for Rinderpest?
Morbillivirus
How is Rinderpest spread?
Through close contact - breath, secretions, excretions
What are some symptoms of Rinderpest?
Fever, diarrhoea, oral lesions
What is the long lasting effects of infection with Rinderpest?
Infected individuals develop a long lasting specific immune response to morbilliviruses:
- Reduced B cells, monocytes, neutrophils and some T cell types
Is Rinderpest eradicated?
Yes
What is ringworm?
It is a fungal infection of hair and keratinised layers of the skin (also known as dermatophytosis) (is a cattle infection)
Can zoonosis occur in ringworm from cattle to humans?
Yes, theough direct contact/bites
What is the name of the Ringworm fungi?
Trichophyton verrucosum
How do you treat ringworm?
Vaccines are available
What is the Foot and Mouth disease virus?
A picornavirus of cloven hoofed livestock (pigs, cows, sheep, goats)
How many serotypes of Foot and Mouth disease are there?
7, with serotype O responsible for 70% of global outbreaks
Describe how Foot and Mouth disease virus enters the cell
- The virus capsid protects the RNA genome while outside of the host cel and also allows entry into cells by binding to specific receptors
- RNA genome is then released into the cytoplasm of the cell
- Translation occurs to produce viral proteins, including non-structural proteins
- +ve sense RNA are packaged by capsid proteins to generate new virus particles
