Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Sem 2: Microbiology > Week 9 > Flashcards

Week 9 Flashcards

1
Q

What are examples of infections caused by acellular agents?

A

Viruses, (viroids, virusoids, satellite RNAs, prions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are viruses?

A

Virus = sub-microscopic particle (20–300 nm) that can infect the cells of a biological organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the relationship between viruses and being a pathogen?

A

Obligate and intracellular - cannot carry out any metabolic pathway neither grow nor respond to environment cannot reproduce independently => use host cells machinery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a viron?

A

Core of nucleic acid (DNA or RNA, never both)
Protein coat = capsid
Envelope (some virions) = phospholipid membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the function of the outer surface of the virion?

A

Outer surface of virion (capsid or envelope) allows interaction with target cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the potential genetic material of a virus?

A

dsDNA
ssDNA
dsRNA
ssRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the relationship between viruses and host cells?

A

Most viruses infect particular cell types e.g. HIV
Specific affinity of viral surface proteins or glycoproteins for complementary proteins or glycoproteins on cell surface
A few viruses are generalists – infect many cell types in
many hosts e.g. rabies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the stages of a ‘generic’ viral infection?

A

Attachment
Entry
Synthesis
Assembly
Release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens during attachment?

A

Chemical attraction of virus to host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How can a virus enter a cell?

A

Direct penetration (poliovirus), membrane fusion (measles and mumps viruses), phagocytosis (herpes virus) uncoating of capsid may be involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens during the synthesis of a virus?

A

The manufactoring of new viruses
Different viruses (ss, ds DNA or RNA) -> different strategies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens during the assmebley of viruses?

A

DNA viruses assembled in nucleus,
RNA viruses in cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens during the release of viruses?

A

Enveloped viruses often released by budding, naked viruses via exocytosis or lysis of cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are stealth viruses?

A

‘Stealth viruses’ – released groups of viruses within vesicles = newly identified infection route

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the rough life cycle of an animal enveloped virus?

A

(a) Adsorption or docking with the host receptor protein
(b) Entry into the host cytoplasm
(c) Biosynthesis of viral components
(d) Assembly of viral components into complete viral units
(e) Budding from the host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is evidence of viral disease impacting us for a long time?

A

Ancient Egyptians suffered polio and smallpox
Rabies, smallpox and yellow fever affected humans for centuries
Most diseases that still plague the industrialised world

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which viruses are common for human infection?

A

DNA - colds, chickenpox, warts
RNA - influenza

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are therapeutic approaches to viruses?

A

Immunisations
Treatments to alleviate symptoms
Anti-viral drugs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is an example of an early infection of a disease?

A

Ramses V believed to be the first known victim of smallpox - examined pustules on his cheek

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the overview of the history of smallpox?

A

Smallpox (poxviridae)
Middle ages around 80% European population contracted smallpox
18th century – European colonists introduced smallpox to native Americans; as many as 3.5 million died
First human disease to be globally eradicated in nature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is an overview of the work by Edward Jenner?

A

Demonstrated immunization using mild cowpox virus (Vaccinia) to protect against smallpox (antigens are similar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why was eradication of smallpox possible?

A

Inexpensive, stable vaccine
Specificity of infection (no animal reservoirs)
Quick + obvious signs of infection (allowed quarantine)
Lack of asymptomatic cases (no carriers)
Virus spread by close contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the current danger of smallpox?

A

Few vials in labs could be used for bioterrorism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the overview of smallpox?

A

Smallpox caused by either Variola major or Variola minor
V. major mortality rate of 3–35%
V. minor causes milder disease called alastrim and kills ~1%
Double stranded DNA linear genome ~ 200kb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How is smallpox transmitted?

A

Transmitted primarily through prolonged social contact or direct contact with body fluids or contaminated objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the cycle of a smallpox infecting a cell?

A

Enters cells mainly by cell fusion, receptor unknown
Three classes of genes: early, intermediate and late (transcribed by viral RNA polymerase and associated transcription factors)
Genome replicated in cytoplasm
Virion produced after late gene expression
Transported to Golgi - two additional membranes added
Transported along microtubules and fusion with plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the an overview of Polio?

A

Picornaviridae Enterovirus Poliovirus
Naked positive ssRNA virus (+RNA acts as mRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the polio lifecycle for infection?

A

Transmitted via faecal-oral route
Infect pharynx and intestine (mucosa and lymphatic tissue)
Spread round body via viremia paralytic polio - cells of spinal cord and motor cortex of brain cytolytic - kill host cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How can Polio be prevented?

A

Salk – inactivated polio vaccine (1955)
Sabin – live, attenuated, oral polio vaccine (1961)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How has the vaccine impacted Smallpox and Polio?

A

London - vaccine introduced 1796 deaths caused by smallpox declined
USA - Polio vaccine introduced in 1955 both paralytic cases and deaths plummated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is an overview of the common cold?

A

Common cold Acute viral nasopharyngitis
Rhinovirus (as well as coronavirus, reovirus, adenoviruses)
>100 serotypes of rhinovirus cause most colds
>100,000 virions / ml nasal mucous
RNA genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is an overview for the common cold infecting a cell?

A

Entry after attachment to intercellular adhesion molecule
(ICAM)–1, ( receptor in the nasal epithelium and adenoids)
Viral infection activates several inflammatory pathways => host response is believed to be the major cause of cold symptoms Interleukin (IL)-1, IL-6, IL-8 responsible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is an overview of Chicken Pox?

A

Varicella-Zoster virus HHV-3 Herpesviridae
member of large group of viruses with enveloped polyhedral
capsids and linear dsDNA similar to Simplexvirus, Varicellovirus, Lymphocryptovirus, Cytomegalovirus, Roseolovirus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

How can chickenpox infect a person?

A

Enter host via respiratory tract
Enter host cells by attaching to receptor and fusing envelope with cytoplasmic membrane
Replicate at site of infection, spread via blood stream
Often latent infection (within sensory nerves)
Can reactivate to produce shingles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is an overview of warts virus?

A

Papillomaviruses - Papillomaviridae
single molecule of dsDNA contained within a small, naked, icosahedral capsid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What happens with the infection of warts?

A

Papillomas – benign growths of epithelium = warts
Fingers, toes, soles of feet, body trunk, external genitalia
Transmitted via direct contact
Immune system will eventually clear infected cells, but some lesions should be dealt with

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What can be caused by human papiloma virus family 16 and 18?

A

Known to be direct cause of cerival carinoma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

How do they test for the presence of HPV and cervical cancer?

A

Used to only get cell sample and investigate under microscope to see if cells might develop into cancer
Now this is done after a PCR to look for HPV nucleic acids to check for infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is an overview of Paravoviridae?

A

Only human pathogens with ssDNA genome
Causes B19 disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the overview of the disease B19?

A

Erythema infectiosum (fifth disease)
Reddening of skin (cheeks, arms, thighs, buttocks and trunk) Slap cheek - does rounds of nurseries
No treatment available (typically a mild rash illness)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is causing an increase in emerging/reemerging viral diseases?

A

Infective agent’s evolution
Globalisation
Habitat modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the WHO pandemic phase descriptions?

A

WHO pandemic phase descriptions: phase 1-6, post-peak period, possible new wave, post-pandemic period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is an overview of HIV?

A

Enveloped + ssRNA viruses with reverse transcriptase
Retroviridae
Human Immunodeficiency virus (HIV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is the overview of HIV cell infection?

A

Recognition of host cell (CD4 receptor)
tRNA primes DNA synthesis = RNA / DNA hybrid
RNA degraded
Second strand of DNA synthesised
Integration into host genome
Transcription/translation, assembly of virions
Release and destruction of T helper cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Why have HIV cases stabilised since 2000?

A

The use of antivirals reducing spread meaning people have a good quality life
Some people with CCR5 are more resistance -> mutanted chemokine receptor HIV cant infect cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is the structure of HIV?

A

2 copie sof RNA genome surrounded by capsid and a matirx
The spike proteins are gp41 and gp120 which binds to CD4 and co-recpetors on t-lymphocyte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is a brief overview of influenza?

A

Zoonosis
1918-1919 - affected 50 million people
March 2009: new influenza virus A (H1N1) first isolated, initially disseminated in Mexico and US and then worldwide. Eight weeks later: 74 countries with ~30,000 cases and 145 deaths. June 11th 2009: “pandemic”. 2019-nCoV: Ten weeks, 118,000 cases, 4292 deaths, “pandemic” declared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What was the genesis of swine-origin influenza A/H1N1?

A

In pig, swine, avian and human flu mixed togther. This mega flu mixed with another swine flu then jumped into human. Creating A/H1N1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

How did infleuenza enter and leave cells?

A

Enter through endocytosis
Leaves through budding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is an overview of influenza spike proteins?

A

Hemagglutinin and neuraminidase spikes on viral surface – role in attachment
genome = 8 different -ssRNA molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What are the other function of Neuraminidase and hemagglutinin?

A

Neuraminidase (N) – hydrolyse mucous in lungs
Hemagglutinin protein (H1-16) – responsible for binding to
human receptors and trigger endocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What creates new strains of influenza?

A

Antigenic drift and antigenic shift responsible for new strains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

How does hemagluttin work?

A

1: HA binds to sialic acid of target cell
2: Acidification inside endosome causes HA conformational change => ‘fusion peptide’ grabs endosome membrane
3: membranes pulled together => fusion and release of viral RNA

54
Q

What is an overview of severe acute respiratory syndrome (SARS)?

A

very virulent strains of new Coronaviruses
enveloped, positive ssRNA viruses

55
Q

What is an overview of Sars outbreak?

A

SE China spring 2003-2004 (8096 cases; 774 deaths)
Some participants at conference in Hong Kong to discuss epidemic caught SARS and spread it to Canada
mortality 10-15%, 50% in >65yr old
person-to-person AND vie excreta and stagnant water
ACE2 (angiotensin-converting enzyme 2) = receptor?

56
Q

How wide spread was covid?

A

760 million cases
7 million deaths

57
Q

What are examples of pandemics?

A

Plague of Justinian - 30-50 million 735-737
Black death - 200 million 1347-1351
Small pox - 56 million 1520

58
Q

What is R0?

A

A measure of how many people each sick person will infect on average

59
Q

What are examples of r numbers?

A

SARS - 3.5
Measles - 16
Ebola - 2

60
Q

What happens in an immune repsonse to a virus?

A

1) The virus infects or is phagocytosed by macrophages, dendritic cells or other phagocytes. Phagocytes break down, process and present antigens from the virus and produce type 1 cytokines.
(2) Type 1 cytokines cause T cells to differentiate into TH1 cells and CD8 T cells.
(3) TH1 cells and CD8 T cells cause apoptosis of infected cells and activate processes such as the production of reactive oxygen species in phagocytes, which destroy the viruses. Antibody production is elevated, resulting in opsonisation, greater phagocytosis and destruction of viruses.
(4) Virus is cleared and memory T cells are produced, which can rapidly respond to future infections

61
Q

What are examples of antibodies and there greater function?

A

Antibody (especially secretory IgA) Blocks binding of virus to cell, thus preventing infection
IgG, IgM and IgA Blocks fusion of viral envelope with host cells plasma membrane
IgG and IgM Enhances opsonisation
IgM Agglutinates viral particles
Complement activated by IgG or IgM Mediates opsonisation by C3b and lysis of enveloped viral particles by membrane attack complex

62
Q

What are examples of cell mediated cellular responses?

A

Cell-mediated IFN-g secreted by TH or TC cells Has direct anti-viral activity
Cytotoxic T lymphocytes (CTLs) Kills virus-infected self-cells
NK cells and macrophages Kills virus-infected cells by ADCC

63
Q

Why is nitrogen production important?

A

Half the world’s population is fed by synthetic N fertiliser

64
Q

What are the large reservoirs of nitrogen and the amount of nitrogen stored?

A

Atmospheric N2 4 x 10^21 g
Plant N 3.5 x 10^15 g
Ocean N 6 x 10^15 g
Soil N 9.5 x 10^15 g
Total soil N flux 1.5 x 10^15 g year-1

65
Q

What is the nitrification pathway?

A

NH3 –> NO2- –> NO3-

66
Q

What is ammox?

A

Converison of either NH3 or NO2- to N2

67
Q

What is the denitrification pathway?

A

NO3- –> NO2- –> NO –> N2O –> N2

68
Q

How is N2 turned into NH3?

A

N2 undergoes nitrogen fixation to form organic N
Mineralisation turns organic N to NH3

69
Q

Why is nitrogen important?

A

Used as electron donors and acceptors, involved in various steps of N-cycling.
Electron donors can be used as energy sources
Electron acceptors can be used in respiration instead of oxygen

70
Q

What is the relationship with nitrogen for the environment?

A

Both NH3 and NO3- are available for uptake by plants
NO3- leached from soil results in groundwater pollution
Generates N2O (greenhouse gas & depletes ozone)

71
Q

What is the relationship with nitrogen fixation?

A

The only process by which atmospheric N2 is incorporated into biological matter
Biological vs anthropogenic nitrogen fixation
Free living (cyanobacteria, Azotobacter in strand 1 cell specialised for N fixation) vs symbiotic organisms (rhizobium root nodules of legumes)

72
Q

What is an overview of organic nitrogen fixation?

A

Nitrogenase (nif): catalyses conversion of N2 into NH3
N2 + 3 H2 –> 2 NH3 –> amino acids –> proteins
Extremely energy-costly process – triple bond of N2 is hard to break
Tightly regulated

73
Q

What is an overview of the haber-bosch process?

A

Haber-Bosch process - How N fertilisers are made
Requires intense temperatures 300-500°C and pressures, 150-250 bars
~50% of the world’s human population today would not exist without the Haber-Bosch process

74
Q

What is an overview of mineralisation (ammonification)?

A

Conversion of organic N into NH3, making it available for plants and microbes
Wide variety of microorganisms can carry out this process

75
Q

What is an overview of nitrification?

A

Links fixed and mineralised forms of organic nitrogen to denitrification
Very important process for fertiliser loss

76
Q

What was the traditional thought for nitrification process?

A

Traditionally thought of as a two-step process
- this is not the case any more
Can still be two steps depends on bacteria
Ammonia oxidisers - NH3 –> NO2-
Nitrate oxidisers - NO2- –> NO3-

77
Q

What is an overview of nitrification?

A

NH3 + O2 → NO2− + 3H+ + 2e− e.g. Nitrosomonas
NO2− + H2O → NO3− + 2H+ + 2e− e.g. Nitrobacter

78
Q

What is the consequences of nitrifications?

A

Can lead to nitrate leaching into aquatic environments
Causes eutrophication / environmental pollution
Both hydroxylamine and NO are intermediates in ammonia oxidation
Nitrification produces NO and N2O which are climate active gases

79
Q

What do Aerobic chemolithoautotrophic microorganisms which use for energetic processes?

A

NH3 and NO2- as e- donors,
O2 as an e- acceptor
CO2 as carbon source

80
Q

What is an overview of Ammonia oxidising bacteria?

A

First discovered by Percy and Grace Frankland (1890) and isolated by Sergei Winogradsky (1891)
Low cell densities and growth rates
Typical soil AOB (Nitrosospira and Nitrosomonas) belong to β-proteobacteria, typical marine AOB (Nitrosococcus) to γ-proteobacteria

81
Q

What was the belief about nitrification?

A

For >100 years, it was thought that only specific groups of bacteria can perform autotrophic ammonia oxidation.

82
Q

What changed the traditional belief about nitrification?

A

In 1992, two research groups report the unexpected discovery of novel archaea in marine environments
In the next decade, numerous reports on the “non thermophilic Crenarchaeota” in soil ecosystems
For 13 years, nothing was known about the function of these archaea

83
Q

What is an overview of ammonia oxidising archaea?

A

Soil fosmid 54d9 contained 16S and 23S ribosomal subunits. This enabled identification of the fosmid as an archaeon
amoA and amoB encode for subunits of the ammonia monooxygenase, a key enzyme in the global nitrogen cycle
Some ammonia oxidisers can also use urea and cyanate as substrates

84
Q

Where do ammonia oxidising archeae exist indepently from ammonia oxidising bacteria?

A

AOA can nitrify in conditions where AOB struggle (acidic soils, open ocean), have lower growths rate but can live in lower pH environments

85
Q

What is an overview of comammox?

A

“Comammox” stands for complete ammonia oxidation into nitrate
Existence of comammox was predicted in 2006, but the microorganisms were not discovered until 2015
Nitrospira sp. nitrite oxidiser which acquired ammonia oxidation genes by horizontal gene transfer
Anammox is especially significant for N turnover in ocean and is the largest single source of dinitrogen gas on Earth

86
Q

What do chemolithoautotrophic bacteria use nitrogen for?

A

Chemolithoautotrophic bacteria use NH4+ as an electron donor and NO2- as the electron acceptor
Recently discovered reaction carried out entirely by members of the Planctomyces phylum of the Bacteria

87
Q

What allows for anammox to occur?

A

Anammox uses unique (“ladderane”) membrane lipids that form an intracellular “anammoxosome” organelle
Site of membrane-bound enzymes that combine nitrite and ammonia to N2 gas. Hydrazine (N2H4; rocket fuel) is an intermediate
Electron flow in this process generates ATP

88
Q

What is a human application of anammox?

A

Slow growing bacterium in culture
Low-cost method for N removal in wastewater treatment
90% of operational costs savings and CO2emission cuts compared to conventional nitrification/denitrification
At least three genera of bacteria:Brocadia,Kuenenia, Scalindua
Process is patented

89
Q

What is the reaction for anammox?

A

NH4++ NO2-→ N2+ 2H2O

90
Q

What is an overview of denitrification?

A

Phylogenetically very diverse, carried out by all 3 domains of life, Eukarya, Bacteria and Archaea
Anaerobic respiration, only occurs in the absence of O2
Denitrification is a major process leading to the loss of nitrogen from system as dinitrogen
Denitrification completes the N cycle by returning N2to the atmosphere (as does anammox).

91
Q

What bacteria can perform denitrification?

A

The process is performed primarily by heterotrophic bacteria (such asParacoccus denitrificansand various pseudomonads), although autotrophic denitrifiers have also been identified (e.g. Thiobacillusdenitrificans).

92
Q

What are real world applications of denitrification?

A

Detrimental process for agriculture removes nitrogen from the field
Beneficial process - wastewater treatment removes nitrogen from the system prevents eutrophication of receiving waters

93
Q

What is an overview of the denitrification process?

A

In the absence of oxygen, N-oxides serve as e- acceptors for organic carbon oxidation
Both NO and N2O are climate active gases and intermediates in the denitrification pathway
2NO3-+ 10e-+ 12H+→ N2+ 6H2O
nirS or nirK (never found in the same organism) encode nitrite reductase and are a key marker gene for population studies

94
Q

What is a problem with the production of NO and N2O?

A

Production of NO and N2O from soil is a result of several different processes
In denitrification, NO and N2O are directly produced during stepwise reduction of nitrate to N2 but intracellular retention of NO and N2O (gases) is not 100% efficient
In nitrification, N2O is formed during chemical decomposition of two intermediary metabolites (NH2OH and NO2-

95
Q

What are the negative impacts of N2O?

A

N2O is a powerful greenhouse gas in the lower atmosphere. NO reacts in lower atmosphere and produce nitrogen dioxide (NO2; pollutant) and ozone (a greenhouse gas)
~300 times greater global warming potential than CO2

96
Q

What is the future of the nitrogen cycle?

A

Sustainable intensification of food production an important area of biogeochemical research involves identifying human practices that will result in decreased emissions of potent greenhouse gases

97
Q

What are ways for improving soil N efficiency?

A

Slow release fertilisers
Commercial nitrification inhibitors (e.g. DCD, nitrapyrin)
Demand-driven fertilisation

98
Q

What is the overview of the uses of sulphur?

A

Natural occurring element (Atomic number of 16)
Is ~1% of the dry weight of organisms
Exists as sulfide (S2-) and sulfate (S042-) minerals
Used as fertiliser (Plants = high demand) and in manufacturing of e.g. insecticides and fungicides etc

99
Q

Why is sulphur important for living organisms?

A

Metabolism – as a fuel (electron donor) and respiratory electron acceptor
Proteins - amino acids cysteine and methionine
Disulfide bonds – g`ives proteins stability and structure
Cofactors in enzymes, e.g. FeS in Aconitase (TCA cycle)
Antioxidant molecules e.g. glutathione and thioredoxin
Some sulfate incorporated into polysaccharides

100
Q

What are sulphur microbial sulphur process?

A

Assimilation- use sulfate to form organic compounds (energy dependent) [animals depend on preformed S-compounds]
Dissimilatory sulfur metabolism – bacteria and archaea use sulfur in energy yielding reactions (Ox or An)
Use as electron acceptors or donors in e.g. sulfate reduction & oxidation, respectively
The generation of signalling molecules
The generation of anti-stress molecules

101
Q

How abundant is sulphur in marine envrionments?

A

Sulfate is abundant in marine environments (~ 10^6 times more abundant other S)

102
Q

How is sulfate converted to methione?

A

Sulfate –> Sulfide –> Cysteine –> Cystathionine –> Homocysteine –> Methionine
sulfate reduced to sulfide in most microbes and production of methionine (requires energy)

103
Q

What organisms can transform sulphur?

A

Phytoplankton –> Haptophytes
Seaweeds –> Green and red macroalgae
Angiosperms –> Spartina spp
Coral –> Acropora (symbiotic relationship, dinoflagellates)
Heterotrophic bacteria –> Labrenzia spp

104
Q

What is an overview of methionine?

A

Universal amino acid
Energy required to make from sulfate via sulfide and cysteine etc.

105
Q

How is Dimethylsulfoniopropionate (DMSP) produced?

A

Energy requiring DMSP synthesis pathway converting methionine to DMSP

106
Q

What is an overview of DMSP?

A

Stable and soluble zwitterion
Produced at very high [mM] e.g ½ M
> 8 billion tonnes made per year

107
Q

What organisms can produce DMSP?

A

Some marine Eukaryotes
Marine bacteria (Alphaproteobactaria)

108
Q

Whyis DMSP produced?

A

Osmoprotectant - balancing the osmotic difference between the cell’s surroundings and the cytosol similar to terrestrial betaine
Cryoprotectant - play a protective role by maintaining enzyme activity in high and low temperatures
Grazing deterrent - DMSP and its catabolises are proposed to deter predators due to their bad taste/toxicity
Oxidative stress protectant - DMSP and its catabolites scavenge oxygen free radicals generated by oxidative stress
A storage molecule for Sulfur and Carbon

109
Q

What is an overview of the establishment of DMSP production?

A

None of these roles have been definitively established - just theorised - osmoprotectant based off of not being produced in non-salty water

110
Q

Why are the genes behind DMSP production still a mystery?

A
  1. Marine biology was generally lacking in molecular biological approaches compared to terrestrial systems
  2. The marine eukaryotes that make DMSP lack genetic manipulation tools
111
Q

How does DMSP impact carbon production?

A

DMSP accounts for 3-10% of global marine primary carbon production

112
Q

What is an overview of DMSP catabolism?

A

DMSP - a the major nutrient for heterotrophic bacteria (C&S)
supplies 3-10% of the carbon & 30-100% of the sulfur requirements of marine heterotrophic bacteria

113
Q

What is an overview of the main catabolism of methanethiol?

A

DEMETHYLATION (dmd genes) break DMSP to MeSH
~70%
Done by SAR11 bacteria

114
Q

What is an overview of SAR11 bacteria?

A

SAR11 clade or Pelagibacteraceae are Alphaproteobacteria
most abundant and ubiquitous clade of heterotrophic marine bacteria (1/3 of cells in the photic zone)

115
Q

What is an overview of the first SAR11 bacteria cultured?

A

Candidatus Pelagibacter ubique was the first cultured SAR11
P. ubique genomes are very small (1.3 Mbp) and encode the smallest number of genes for a free living organism has pathways for all 20 amino acids and most cofactors

116
Q

What is unique about sulphur reduction in P.ubique?

A

P. ubique genomes lack assimilatory sulfate reduction genes
P. ubique requires reduced sulfur, e.g. methionine or DMSP for growth
Uses dmd (demethylation genes) converts DMSP to MeSH as a source for biological sulphur

117
Q

What is an overview of DMSPlysis?

A

DMSP LYSIS (ddd genes)
~30%
350 million tons of Dimethylsulfide (DMS) produced

118
Q

What is the formula for the lysis of DMSP?

A

DMSP –> DMS + Acrylate or 3-hydroxypropionate

119
Q

What are examples of DMSPlysis genes?

A

Huge biodiveristy includes, dddK, dddP and alma1 (only in eukaryotic phytoplankton)

120
Q

What is the relationship between SAR11 and DMSP lysis?

A

SAR11 also produce DMS from DMSP
SAR11 contain a DMSP lyase termed DddK
SAR11 use DMSP lysis for Carbon assimilation - acrylate

121
Q

What organisms can lyse DMSP?

A

Many marine bacteria, including some that also make DMSP, e.g. Labrenzia, alpha Roseobacters and gamma Halomonas
Many phytoplankton and macroalgae e.g. Emiliania huxleyi & Ulva
Some fungi e.g. Fusarium lateritium

122
Q

What is an overview of Roseobacters?

A

Marine a-proteobacteria.
10–25% bacteria in marine surface waters, sediments and sea ice (abundant)
Easily cultured (SAR11 difficult)
Many genomes available
Model organisms for studying marine biogeochemical cycles

123
Q

What is an overview of Ruegeria pomeroyi DSS-3?

A

Model roseobacter
Isolated from DMSP enrichments of coastal Georgia Seawater by Marie Ann Moran
Genome sequenced in 20043.
Genetically tractable

124
Q

What is an overview of DMSP of Rugeria pomeroyi?

A

Like R. pom many roseobacters both lyse and demethylate DMSP
Being genetically tractable many of the ddd (dddP, dddQ and DDW) and dmd genes were isolated in roesobacters
Thus genetic tools are available.

125
Q

What is the outcome of DMS?

A

~90 % of the DMS produced is re-catabolised by marine bacteria as a carbon source
Gammaproteobacteria of the Methylophaga genus are largely responsible for this

126
Q

How much DMS is released into atmosphere?

A

~35 million tonnes DMS released into atmosphere per annum

127
Q

What is an overview of atmospheric DMS?

A

DMS is the major form of biogenic Sulfur transferred from marine environments into the atmosphere.
Was thought to be H2S but disproved by Sir Lovelock
DMS oxidation products act as Cloud Condensation Nuclei (CCN) and have a climate cooling effect

128
Q

How is DMS returned back into the ocean?

A

Sulfur is transferred back to the ocean or land as dissolved sulfuric acid completing the cycle

129
Q

What is the claw hypothesis?

A

The authors of Charlson et al., 1987 proposed DMSP dependent DMS production as a negative feedback mechanism by which the phytoplankton regulate their environment in “CLAW”.
Too warm climate –> Make more DMSP –> More DMSP cleavege –> DMP cloud forming (vice versa)
Semi disproved

130
Q

What is an overview of DMS smell?

A

It is said to have the characteristic smell of the seaside
Indeed many organisms are very sensitive to it
For this reason it is used a signalling molecule

131
Q

What organisms as a chemoattractant?

A

Shearwaters, African penguins, Copepods, Harbour seals
Eat alga that produce DMSP or the fish that eat the alga

Sem 2: Microbiology (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions