1
Q
what is generalised transduction?
A
when a piece of degraded host genome is put into a viral capsid instead of the virus genome. this takes a large chunk of genetic information to another cell and only occurs in the lytic cycle
2
Q
what is specialised / restricted transduction?
A
when virus takes a small piece of host DNA when it leaves the bacterial genome to form a loop in the cytoplasm. this is then passed on to other cells, and only occurs in the lysogenic cycle
3
Q
what is conjugation?
A
transfer of genetic information via plasmids
4
Q
what organelle is used for conjugation?
A
pili
5
Q
what type of virulence factor is a plasmid?
A
fertility factor
6
Q
what is an HFR cell?
A
a high frequency recombinant cell which has the plasmid bind into the host genome
7
Q
why do HFR cells transfer so much genetic information?
A
the plasmid is bound into the host genome, so when it replicates the plasmid picks up a lot of host genetic information, which is then transferred to another bacterial cell
8
Q
what are the three symbiotic associations?
A
commensalism, mutualism, and parasitism
9
Q
what is mutualism?
A
when both species benefit eg humans and gut microbes
10
Q
what is commensalism?
A
when one species benefits and the other is not significantly affected eg humans and skin microbes (we benefit)
11
Q
what is parasitism
A
when one species benefits and the other one is harmed eg humans and opportunistic parasites
12
Q
why are there exceptions to Koch’s postulates?
A
- can’t be grown in pure culture
- can’t deliberately infect a healthy person to test it
- caused by multiple pathogens
- caused by virulent strains of normal microbes
13
Q
what are some examples of exceptions to Koch’s postulates?
A
- leprosy and siphilus, because neither can be grown in the lab and you can’t deliberately infect healthy people with them
- liver cancer and peridontal disease are both caused by multiple pathogens. liver disease is caused by a combination of Hepatitis A and B
- some E. coli strains are pathogenic
14
Q
what is pathogenicity?
A
the ability of a microbe to cause disease
15
Q
what is virulence?
A
the ability to infect, spread disease, and be transmitted
16
Q
what are opportunistic pathogens?
A
microbes which are part of our normal microflora which can become virulent and cause disease under different conditions
17
Q
what causes opportunistic microbes to become pathogenic?
A
- immune system suppression (HIV, cancer, transplant therapy)
- depletion of normal microbes from antimicrobial therapy
- displacement of microbes to a different tissue within the body
18
Q
what type of toxins do gram negative bacteria release?
A
endotoxins / lipopolysaccharides which are embedded in the cell wall
19
Q
what type of toxins do gram positive bacteria release?
A
exotoxins
20
Q
what are the features of endotoxins?
A
- poor antigens
- heat stable
- weak toxins
- all have similar structures
21
Q
how are endotoxins released?
A
- phagocytosis
- released from dead bacteria
22
Q
what do endotoxins cause?
A
- fever
- inflammation
23
Q
what are the features of exotoxins?
A
- heat labile
- potent toxins
- varied structures
- tissue specific
24
Q
what are the two types of exotoxins?
A
- neurotoxins
- cytotoxins
25
what do exotoxins cause?
- destroy any cells they come into contact with
| - can kill
26
how are exotoxins released?
secreted from the cell
27
what is selective toxicity?
targeting features of the pathogen which are different from the host cell so that the host is not harmed by the antibiotic
28
what are some bacterial structures which are targeted by selective toxicity?
- cell wall (targets peptidoglycan in bacteria)
- cytoplasmic membrane (similar to host cell so is not ideal)
- protein synthesis (bacterial ribosomes are different to eukaryote ribosomes)
- metabolic processes (targets bacterial processes which humans dont use)
- DNA / RNA synthesis
29
what are the virulence factors of the cell?
- adhesions
- motility
- siderophores
- capsules
- toxins
30
how do adhesions work?
- physical adhesions work by fimbriae and pili binding to the host cell
- chemical adhesions work by chemical reactions binding the bacteria to the host cell
31
how is motility a virulence factor?
it allows the bacteria to move through mucus
32
what do siderophores do?
take up iron from the host to the pathogen, weakening the host and strengthening the bacteria
33
how does penicillin work?
- active site is a lactum ring
- binds to the penicillin binding protein in the cell wall
- affects transpeptidase, an enzyme which links chains of peptidoglycan in the cell wall
- enters through porins in the cell wall
34
what effect on the bacterial cell does penicillin have?
- cell wall degrades and becomes porous
| - cell bursts from osmotic pressure
35
what techniques are used to create resistance to penicillin?
- degradation of active site
- change binding protein
- change target enzyme
- decreased uptake of penicillin
36
how does degradation of the active site produce penicillin resistance?
the bacteria produces an enzyme which degrades the lactum ring on penicillin, meaning that the penicillin can't work properly. makes the host allergic to penicillin
37
how does changing the target protein produce penicillin resistance?
mutating the penicillin binding protein means that penicillin can't bind to it, and therefore can't produce an antibiotic effect
38
how does changing the target enzyme produce penicillin resistance?
mutating the transpeptidase enzyme means that penicillin no longer has an effect on it
39
how does decreased uptake produce penicillin resistance?
no longer making or altering porins restricts the amount of penicillin taken up by the cell, so reduces the effect it can have
40
what is an antibiotic?
a substance produced by one microorganism which is strongly antagonistic to other microbes in strong concentration
41
what are the three types of antibiotic?
- bacteriocidal
- bacteriolysic
- bacteriostatic
42
what do bacteriostatic antibiotics do?
- prevent the growth of bacteria
- dont kill them
- dont destroy their cells
43
what do bacteriocidal antibiotics do?
- kill bacteria
| - dont destroy their cells
44
what do bacteriolysic cells do?
- kill bacteria
| - destroy their cells
45
what is a zone of inhibition?
a zone around an antibiotic on an agar plate where all the bacteria have been killed
46
what does a small zone of inhibition indicate?
that the antibiotic is not very effective
47
what does a large zone of inhibition indicate?
that the antibiotic is effective
48
what is the minimal inhibitory concentration?
the smallest amount of antibiotic needed to kill the microbes
49
what amount of antibiotic is used in treatment?
four times more than the minimal inhibitory concentration
50
what do virulence factors assist in?
- colonisation
- invasion
- growth
- survival
51
what is the best target of selective toxicity? why?
peptidoglycan in the cell wall, because only bacteria have this and it is not present in eukaryotes so there is no risk of the host cell being affected
52
what is the worst target of selective toxicity? why?
cell membranes, because the eukaryote and prokaryote cell membranes are very similar so there is a significant risk that the host will also be affected by the antibiotic
53
how do you prevent antibiotic resistance?
- test the sensitivity of the target antibiotic
- use the correct antibiotic concentration
- treat for long enough
- complete the antibiotic regime
- use multiple antibiotics for chronic infections
- dont add antibiotics to animal food
54
how long should antibiotic treatment last for?
5 - 10 days
55
what should be considered when choosing antibiotics?
- source of infection
- site of infection
- nature of the microbe (eg Gram positive or negative)
56
how can antibiotics be administered?
- topically (skin or eye)
- suppository
- orally
- intravenously
- intramuscular
57
what is the fastest way to administer antibiotics?
intravenously
58
what is the slowest way to administer antibiotics?
intramuscularly
59
what are the possible infection sources?
- nosocomal
- animal reservoir
- non-living reservoir (eg soil, water)
- human carriers
60
where are nosocomal infections contracted?
in healthcare facilities
61
Describe the properties of the bacterial genome
- few duplicated genes
- high number of genes compared to genome size
- DNA loop in cytoplasm, not membrane bound
62
How many genes do bacteria have?
200 - 800
63
what does a small bacterial genome indicate?
that the bacteria is a parasite, as it only needs the genes for survival in one constant environment
64
what does a large bacterial genome indicate?
that the bacteria lives in a range of environments, as it has the genes necessary to survive in many conditions
65
what is vertical gene transfer?
when genes are passed on to off spring
66
what is horizontal gene transfer?
transfer of genes between two organisms in the same generation
67
why are many mutations observed in bacteria?
because they reproduce so rapidly
68
what is transformation?
uptake of genetic information from the environment
69
which experiment showed transformation?
Griffith's
70
how is the rate of transformation increased?
electroporatation
71
what is transduction?
transfer of genetic information via a bacteriophage vector
72
how many people enter healthcare facilities with infections?
73
how many people leave healthcare facilities with infections?
>60%
74
what is an exogenous nosocomal infection?
an infection contracted from a nurse or doctor
75
what is an endogenous nosocomal infection?
an infection created by opportunistic pathogens when microbes from the patients are moved to a different site
76
what is an iatrogenic nosocomal infection?
when an infection is contracted as a result of medical treatment
77
why do so many people get infections in hospitals?
- accumulation of primary pathogens
- accumulation of resistance microbes
- microbes are highly virulent when leaving hosts
- patients in hospital are more susceptible to infection
78
what are the five stages of infection?
- incubation
- prodromal period
- illness
- decline
- convalascence
79
describe the incubation period
- no signs or symptoms
| - low infectivity
80
what determines the length of the incubation period?
- site of infection
- immune defences
- virulence of pathogen
- characteristics of pathogen
- dose of pathogen
81
describe the prodromal period
- vague, general symptoms
- not usually infections
- short period
82
describe the illness period
- most severe signs and symptoms
- most infectious
- immune system has not yet developed specific defences
83
describe the decline period
- declining signs / symptoms
- immune response or medical intervention cause decrease in number of pathogens present
- pathogen could be latent within host
84
describe the convalescence period
- no signs or symptoms
- tissues repaired
- patient recovers
85
describe the cycle of infection
1. exposure to pathogen
2. adhesion to skin or mucus
3. invasion through epithelical cells
4. colonisation and growth
- production of virulence factors
5. a) toxicity with local or systematic effects
b) invasiveness with more growth at original and further sites
- results in more exposure to pathogen
6. tissue damage and disease
86
how can diseases be classified?
- effected system
- severity of infection
- taxonomic group of pathogen
87
what are acute infections?
rapid
88
what are chronic infections
slow and long
89
what are sub-acute infections?
infections which allow opportunistic pathogens to cause infections
90
what are latent infections?
infections which have no effect on the patient but the pathogen is in their body
91
what is the incidence rate?
the number of new cases
92
what is the prevalence of a disease?
the total number of cases of the disease
93
what is an endemic disease?
- always present in population
| - low incidence rate
94
what is a sporadic disease?
-a few scattered cases
95
what is an epidemic disease?
- large number of cases within a set population
| - small time frame
96
what is a pandemic disease?
-widespread disease (continental / global)
97
what causes seasonal incidence rates to peak?
animal vectors breeding / being more active at certain times of the year
98
what experimental approaches are used in epidemiology?
- reporting of clinical cases
- diagnostic followups to confirm incidence
- monitoring disease after therapy or vaccination
- monitoring case history over decades
99
what are the stages of microbial colony growth?
- lag phase
- exponential growth
- stationary phase
- decay
100
what is the lag phase?
the time taken for the colony to become established
101
what is the exponential phase?
- unlimited division of cells
- no limiting factors
- population doubles over given time intervals
102
what is the stationary phase?
- colony stops reproducing
| - cryptic growth observed
103
what is the decline phase?
-growth limiting factors cause the viable count of the colony to decline
104
what are growth limiting factors?
- environmental conditions which limit the growth of cells
- depletion of essential nutrients
- accumulation of waste products
105
what do bacteria need in order to grow in culture?
- energy source
- carbon source
- reducing power
106
why is an energy source needed?
organisms need a way to generate ATP because its needed for anabolic and catabolic reactions
107
why is a carbon source needed?
it provides the precursor metabolites for organic building blocks, allowing for the formation of macromolecules
108
why is a reducing power needed?
reducing powers (eg NADH and NADPH) are needed to power anabolic reactions and electron transport chains
they are especially important for photoautotrophs
109
what is catabolism?
energy generation, occurs when complex molecules are broken down into building blocks
-produces energy for anabolism
110
what is anabolism?
energy consumption, used when macromolecules are produced from monomers
-uses energy from catabolism
111
what is an autotroph?
an organism which uses an inorganic carbon source
112
what is a heterotroph?
an organism which organic carbon source
113
what is a chemotroph?
an organism which gains energy from organic or inorganic chemical compounds.
114
what is a phototroph?
an organism which gains energy from light
115
what is a photoautotroph? (and examples)
organisms which gain energy from sunlight and have inorganic carbon sources
eg plants, algae, cynobacteria
116
what is a photoheterotroph? (and examples)
organisms which gain energy from sunlight and have organic carbon sources
eg green and purple non-sulfur bacteria
117
what is a chemoautotroph? (and examples)
gains energy from inorganic chemical sources (eg H2S) and has inorganic carbon sources
eg hydrogen, sulfur, and nitrifying bacteria
118
what is a chemoheterotroph? (and examples)
organisms which gain energy from organic chemical sources (eg glucose) and has organic carbon sources
eg animals, bacteria, fungi, yeasts
119
what social abilities do myxobacteria have?
- social gliding motility (swarming)
| - fruiting bodies
120
how do myxobacteria swarm?
move forward or backwards by changing the polarity of the cell
121
what does the P engine do?
pulls the myxobacteria along using pili
122
what does the S engine do?
secretes slime for the myxobacteria to slide on
123
how do myxobacteria kill other microbes?
they pool the colonies hydrolytic enzymes, lysing other microbial cells
124
how do myxobacteria form fruiting bodies?
- a multicellular action
- aggregation formation towards the foci
- forms a spore
125
why do myxobacteria form fruiting bodies?
-survival mechanism against starvation
126
what is microbial ecology?
the study of the interrelationships between microorganisms and their environment
127
what is enrichment culture?
a culture which provides the specific temperature and chemical conditions needed to encourage groups of specific microbes. this replicates the specific environmental conditions needed for growth in a laboratory.
128
what is a mesocosm?
an experimental system which simulates real life conditions as closely as possible, showing the interaction of the four trophic groups in microbial communities.
129
what trophic group are colourless sulfur bacteria in?
chemoautotrophs
- energy from H2S
- carbon from CO2
130
what trophic group are sulfate reducing bacteria?
chemoheterotrophs
- energy and carbon source from acetate
- acetate acts as reducing agent in anaerobic respiration
131
what trophic group are coloured bacteria?
photoautotrophs
- carbon from CO2
- energy from photosynthesis
132
how is acetate produced in a Winogradsky column?
acetate (which is needed by the sulfate reducing bacteria) is produced when sulfate reducing bacteria carry out fermentation of cellulose
133
how is carbon dioxide produced in a Winogradsky column?
acetate is broken down into carbon dioxide. this also releases energy which the sulfate reducing bacteria use.
134
what trophic group are cynobacteria?
photoautotrophs
- energy from photosynthesis
- inorganic carbon source
135
what is the order of trophic groups in Winogradsky columns?
- photoautotrophs
- chemoautotrophs
- photoautotrophs
- chemoheterotrophs
136
what is the order of microbes in Winogradsky columns?
- cynobacteria
- colorless sulfur bacteria
- purple sulfur bacteria
- green sulfur bacteria
- sulfate reducing bacteria
- cellulose degrading bacteria
137
what is the energy source gradient in Winogradsky columns?
sunlight (photoautotrophs)
->
chemicals (chemoautotrophs)
138
what is the sulfide gradient in Winogradsky columns?
low -> high
139
what is the oxygen gradient in Winogradsky columns?
high -> low
140
what is the reducing agent of cynobacteria?
H2O being oxidised to form O2
141
what is the reducing agent of colourless sulfur bacteria?
H2S being oxidised to form SO4
142
what is the reducing agent of coloured bacteria?
H2S being oxidised to form S
143
what is the reducing agent of sulfate reducing bacteria?
SO4(2-) being oxidised to form H2S
144
what is the reducing agent of cellulose degrading bacteria?
cellulose being reduced to form lactate and other organic acids
145
what type of respiration do coloured bacteria do?
anoxygenic photosynthesis
146
what type of respiration do cynobacteria do?
oxygenic photosynthesis
147
what type of respiration do cellulose degrading bacteria do?
fermentation
148
how does anoxygenic photosynthesis work?
- H2S is oxidised, transferring electrons to NADP+ to produce NADPH
- NADPH reduces back to NADP+, donating an electron to CO2 so that is can form an organic molecule
149
how does cyclic phosphorylation work?
- an electron is excited by light, going from +0.5V to -1.0V
- the electron flows down the electron transport chain, generating ATP
- the same electron is reduced again, forming a cycle
150
how is non-cyclic phosphorylation different to cyclic phosphorylation?
- in cyclic phosphorylation the same electron is used over and over again
- in non-cyclic phosphorylation the electron is removed from the complex and replaced by the splitting of a water molecule
151
how do microbes in Winogradsky columns coexist while competing for light?
each species absorbs a different wavelength of light
152
what do cynobacteria use to capture light energy?
chlorophyll A
153
what do green and purple bacteria use to capture light energy?
bacteriochlorophyll
154
what wavelengths of light do cynobacteria absorb?
500 - 550nm
155
what wavelengths of light do algae absorb?
500 - 550nm
156
what wavelengths of light do purple bacteria absorb?
>800 nm
157
what wavelengths of light do green bacteria absorb?
550 - 850nm
158
what is produced in the decomposition of organic material?
- humus
- CO2
- CH4
159
what is the biochemical oxygen demand a measure of?
the cleanliness of water
160
what does the BOD measure?
the relative amount of dissolved oxygen consumed by microbes while aerobically decomposing organic and inorganic material in the water sample
161
what occurs in aerobic decomposition?
organic pollutants are oxidised to CO2. this process requires oxygen
162
why does polluted water have a higher BOD than clean water?
there are more materials in the water needing to be broken down, so more oxygen is required to aerobically decompose them
163
what is a dead zone?
an area where the oxygen concentration is too low for organisms to survive. this is called environmental hypoxia
164
why do dead zones occur?
bacteria decompose massive amounts of material in the water, causing all the oxygen in the area to be converted to carbon dioxide
165
what is an example of a dead zone?
The Gulf of Mexico
166
how did the Gulf of Mexico become a dead zone?
- Missisippi river carried industrial run off and fertiliser to the ocean
- caused massive algal blooms because of the large amounts of nitrogen and carbon
- the algae died and was decomposed, using all the oxygen in the area
167
what is a coliform?
a bacterial indicator of the sanitary quality of food and water. it indicates when pathogens from faeces are present
168
what is primary treatment?
physical process
169
what occurs in screening? (primary treatment)
screening of waste water is the first step in primary treatment. this removes indestructible objects from the water so that they can be destroyed
170
what occurs in the sedimentation tank? (primary treatment)
wastewater is sent to the sedimentation tank after screening. this separates it into sludge and liquid.
171
what happens to the sludge after the sedimentation tank? (primary treatment)
incinerated
172
what happens to the liquid after the sedimentation tank? (primary treatment)
- sent for marine disposal
| - may also be treated by UV or chlorination to reduce the number of pathogens
173
what is secondary treatment?
biological process
174
what is used in secondary treatment?
indigenous, water bourne microbes
175
what occurs in the aeration tank? (secondary treatment)
- microbes convert organic materials to carbon dioxide
| - oxygen is pumped through to ensure that this can occur
176
what occurs in the settling tank? (secondary treatment)
- clear effluent (very low BOD) leaves the tank
- flocs settle into an activated sludge
- flocs are either returned to the aeration tank (replenishing the microbes) or go to anoxic sludge digestion
177
what is tertiary treatment?
anything which occurs after primary and secondary treatments
178
what are some examples of tertiary treatments?
- filtration
- UV
- chloride disinfectant
- anoxic sludge digestion
179
what occurs in anoxic sludge digestion?
- anoxic anaerobes break down complex polymers in sludge via fermentation
- very slow processes
- produces organic acids eg lactic acid and methane
180
what are raw materials which can be used to produce biofuels?
- starch
- sucrose
- cellulose
181
what are the steps in biofuel production?
raw materials -> solubilise and hydrolyse -> fermentation -> distillation -> biofuels
182
what is used to carry out fermentation?
- bacteria
| - yeasts
183
what three things are needed to produce enough raw materials for biofuel production?
- vast landmass
- cheap labour
- favourable climate
184
which two gases can be used to produce biofuels?
- carbon dioxide
| - carbon monoxide
185
what can synthetic microbes be used for?
- optimise biofuel production
- produce food
- produce antibiotics
- degrade pollutants eg DDT
186
what is the human microbiome project?
a strategy to understand the microbial composition of humans in regards to metabolism and disease
187
what is a microbiome?
the complete collection of genes in the genomes of all bacterial species which have evolved with the human host
188
what is the microbiota?
individual bacterial species within the biome
189
what are the four most common bacterial phyla in humans?
- firmicutes
- bacteroidetes
- proteobacteria
- actinobacteria
190
what is the most common bacterial genus in the human gastrointestinal tract?
Bifidobacterium, from the actinobacteria phylum
191
describe the environment of the gastrointestinal tract
- anaerobic
- constant environment
- acidic pH in stomach, gets more neutral lower down
192
what can destabilise human gut microbes?
broad spectrum antibiotics
193
when is the adult microbiome established?
in the weaning stage
194
how do gut microbes benefit us?
- break down toxins, carcinogens, and xerobiotics
- synthesise micronutrients such as vitamins
- ferment indigestible food into short chain fatty acids
- protect us from pathogens
195
what is an Archaean gut microbe?
Methanobrevibactor smithii, from the Euryarchareota phylum
196
how are obese state gut microbes different to lean state gut microbes?
- harvest more energy
- 50% more firmicutes
- 50% less bacteroidetes
- more Methanobrevibacter
197
describe the mouse obesity experiment
- germ free and conventional mice were both fed a Western diet
- germ free mice gained less weight even though they ate more
- microbe transplant occured
- germ free mouse + conventional microbes = mouse got fat
- germ free mouse + germ free microbes = mouse stayed lean
198
what did the mouse obesity experiment show?
- obesity is transferable
| - obese state microbes have increased fermentation ability
199
what is a functional food?
a food which claims to have a health promoting or disease preventing benefit beyond supplying nutrients
200
what are probiotics?
food which contain live microbes which give a benefit to the host
201
what is an example of probiotics?
-yogurt which contains a strain of Bifideobacteria infantis which helps irritable bowel syndrome
202
what are two common microbes in probiotics?
- lactic acid bacteria
| - Bifideobacteria
203
what is a requirement of microbes in probiotics?
must be able to survive through the stomach to colonise the gut
204
what are prebiotics?
specialised plant fibres which beneficially nourish the good bacteria in the large intestine. they are not digested by the body, so can act as fertiliser for the bacteria
205
what are some examples of ruminants?
cows, goats, sheep
| -animals which have a rumen stomach
206
what are rumen microbes?
microbes which live in rumen stomachs
207
what is the relationship between rumens and ruminants?
they have a mutually dependant, symbiotic relationship
208
what are the four parts of the ruminant stomach?
- rumen
- reticulum
- omasum
- abomsum
209
how are the first three parts of the rumen stomach different to the last part?
- the first three chambers don't secrete any acid, digestive enzymes, or mucus so all digestion of cellulosic material is done by microbes
- the fourth chamber is the only "true" acidic stomach
210
what occurs in the rumen?
food is churned for 9 - 12 hours in a rotary mation while rumen microbes break down cellulose structures
211
what occurs in the reticulum?
food is regurgitated and re-chewed (chewing the cud) to increase the surface area of the food, increasing the rate of bacterial digestion
212
what happens in the omasum?
- partially digested food is filtered
| - regulates what enters the abomasum
213
what happens in the abomasum?
- denatures protein
- digests gastric juices
- site of bacterial protein assimilation, allowing the ruminant to gain protein and vitamins from dead microbes
214
what are the features of the rumen?
- large surface area = can hold more food for microbial fermentation
- 39 degrees, 6.5 pH = constant environment which selects for specialised bacteria
215
how is a balanced pH maintained?
carbonate from ruminant saliva offsets acid produced by bacterial fermentation
216
what is a syntrophic relationship?
- when one species lives off the waste products of another species
- a relationship which makes a reaction possible which is not energetically possible with only one species present
217
how is the rumen microbes an example of a syntrophic relationship?
there is crossfeeding of nutrients and end products, so one species lives off the waste products of another species
218
what are examples of cellulose degraders?
- Fiberobacter succinogenes
| - Ruminococcus albus
219
what are examples of starch degraders?
- Bacteroides ruminocola
| - Streptococcus bovis
220
what are examples of lactase degraders?
Megasphaera elsdenii
221
what is an example of a methanogen?
Methanobrevibactor rumniantium
222
what is cellulosis?
hydrolysis of cellulose
223
what is amylosis?
hydrolysis of starch
224
what occurs during rumen fermentation?
cellulose, starch, and sugars are hydrolysed and fermented. this produces short chain fatty acids, carbon dioxide, and methane
225
what are three types of short chain fatty acids produced during rumen fermentation?
- acetic acid
- propanoic acid
- butric acid
these acids act as a carbon source and an energy source for the ruminant
226
how do ruminants benefit from their relationship with rumen microbes?
- plant structures eg cellulose are broken down, giving the ruminant an additional energy and carbon source. they can't do this because they don't have the enzymes.
- get protein and vitamins from assimilation of dead microbes in the abomasum
227
how do rumen microbes benefit from their relationship with ruminants?
- constant food supply
- constant environment
- space to live
228
what is an example of a syntrophic relationship between rumen microbes?
interspecies hydrogen transfer
229
what produces hydrogen in the rumen?
Ruminococcus albus
230
what uses hydrogen in the rumen?
methanogens eg Methanobrevibacter rumniantium
231
how does Ruminococcus albus produce hydrogen?
- oxidises glucose to pyruvate
| - hydrogen is side product
232
why must hydrogen concentration in the rumen be kept balanced?
lactase forms if hydrogen is added to pyruvate. when concentration of lactase is too high fermentation stops
233
what do methanogens use hydrogen for?
use as an electron donor to convert carbon dioxide to methane
234
why are methanogens important to the rumen?
keeping hydrogen levels balanced so that fermentation remains directed towards acetate, not lactate or acetate.
235
how efficitant is methane at trapping greenhouse gasses?
21 times more efficient than carbon dioxide
236
how much have methane levels risen since 1750?
148% increase
237
how much have carbon dioxide levels risen since 1750?
36% increase
238
what must we do to our food production in order to keep up with demand?
double it in the next 30 years
239
how much does agriculture contribute to NZ's greenhouse gas emissions?
50%
240
which gases make up agricultural greenhouse gas emissions?
- nitrous oxide = 16%
- methane = 32%
* carbon dioxide is absorbed by grass so it does not accumulate in the atmosphere as much
241
what does the Kyoto pledge state?
that NZ will lower greenhouse gas emissions back to 1990 levels and pay a tax based on how much we exceed this by
242
what are four strategies to reduce methane production by ruminants?
- different microbes absorb methane produced by rumen microbes
- feeding ruminants a different diet
- controlling growth of methanogens so that the least possible amount of methane is produced
- researching wallaby gut microbes as they emit very little methane compared to other ruminants
Cells 191
flashcards
Decks in class (3)
# Cards
