Week 10 Flashcards

Question

What is an overview of Phenazines?

Answer 1

Inhibit electron transport in pathogenic species Catalyse the formation of hydroxyl radicals in combination with ferripyochelin - damage lipids and macromolecules Contribute to oxygen shuttling in microoxic environments May contribute to iron mobilization in soil

Answer 2

Ring carbon structure with nitrogen

Answer 3

2,4-DAPG - phloroglucinol - Causes damage to oomycete membranes, e.g. Pythium spp. Toxic to plants at high concentrations. Involved in the take-all supression Pyrrolnitrin – inhibits fungal respiratory chains HCN – releases cyanide ions, metalloenzyme inhibitor

Answer 4

Produced by certain Pseudomonas spp. Hydrolyse fungal cell walls - biocontrol Secreted by type 2 secretion system

Answer 5

Digest plant material (e.g. Potatoes)

Answer 6

Degrade QS molecules Interfere with Quorum Sensing of other bugs - prevent bacteria from thinkng they are at a high enough concentration to pathogenise

Answer 7

Diverse, narrow-spectrum proteinaceous toxins Prevent other bacteria taking your niche

Answer 8

Gas Chromatography Mass Spectroscopy (GC/MS) of extracted barley root exudates shows that different varieties (Chevalier and Tipple have different exudate profiles This is done to manipulate environment as different chemicals result in different bacterial growth seen in A.thaliana with chemicals influencing species that can grow

Answer 9

Substrate of interest enriched with a heavy stable isotope (e.g. C13) that is consumed by the organisms under investigation. DNA incorporating the heavy C13 isotope is separated from naturally occurring DNA (containing C12) by isopycnic centrifugation seen which bacteria live through plant excodates eg pseudomonas live heavily off plant excodates

Answer 10

The rhizosphere (soil influenced by the root) is much richer in bacteria than the surrounding bulk soil due to root exudates eg Amino acids, organic acids adn sugars

Answer 11

Bacteria are attracted to root exudates by chemotaxis They attach and form microcolonies Biofilm forms - small communities

Answer 12

50 mL Falcon tube --> Vermiculite/Sand/Glass beads (abiotic structured environment) --> Plant rooting solution (defined, carbon-free mix of minerals, ± nitrogen) --> Plant seedling --> Bacteria under investigation

Answer 13

Examining impact of bacterial colonisation on plant growth/behaviour Total RNA/protein extraction – transcription/proteome changes during colonisation (RNAseq/qRT-PCR and mass spectroscopy) the impact bacteria have on growth

Answer 14

Luminescent/fluorescent markers. Inserted genetically Can be used to track bacterial distribution, or as biosensors for metabolite secretion from plant roots

Answer 15

16S RNA Housekeeping genes, such as DNA gyrase, recA, mutL provide more accurate assessment of within species diversity and relatedness

Answer 16

Unbiased Comprehensive Identifies pathways and gene functions in an environment Can be used to assemble unculturable genomes

Answer 17

Expensive Data processing is intensive

Answer 18

Colony picking from agar plates, Limiting dilution in liquid media in 96-well plates Microbial cell sorting (FACS)

Answer 19

Raises percentage of culturable soil bacteria from <1% to around 50%

Answer 20

Every plant and animal lives in close association with millions of micro-organisms The average human is host to 39 trillion microbes – around 1.3 bacteria for every human cell This association also holds true for insects – they span the whole range from beneficiaries, commensals to parasites Most live in the insect gut – a stable & nutrient rich environment

Answer 21

Wolbachia is a member of the Alphaproteobacteria Class – its members are Gram-negative, intracellular and include a diverse range of members such as Rhizobium a symbiont of plants and the ancestors of mitochondria. Wolbachia cant exist on its own, and survives by infecting arthropod hosts including insects, spiders and crustaceans.

Answer 22

Wolbachia is found in ∼66% of arthropod species Insects comprise ~ 85% of all animal species Wolbachia may be the most common endosymbiont in the world.

Answer 23

Wolbachia can be be horizontally transmitted between arthropods, but it also has an amazing evolutionary trick, it actually enters individual cells, growing and manipulating the cells’ components. It is then able to be transmitted vertically from parents to offspring, passing into the cytoplasm of eggs so that insects are born infected.

Answer 24

When a cell divides, it creates a structure called a spindle that helps make sure each of the new cells gets the right number of chromosomes. Wolbachia is able to latch on to the spindle, and make sure the new cells also get a healthy dose of bacteria as well.

Answer 25

By concentrating itself in the gonads and finding its way into every developing oocyte of an organism it can make sure that it infects all of its offspring – the result – this developing embryo is full of Wolbachia from the very first cell – the bacteria can now make sure that it manipulates its spread into the gonads of this organism as they develop. Concentration in the prosterior of the embryo

Answer 26

In spite of all their tricks - Wolbachia can't be transmitted via sperm – the cells are simply too small to fit enough bacteria inside for successful infection of an egg, male inheritance therefore is a ‘dead-end’ The bacterium can only be inherited from mother to offspring so an infected male would appear to have no way of helping the reproduction of Wolbachia.

Answer 27

Feminisation Parthogenesis Male killing Cytoplasmic incompatibility

Answer 28

Occurs mainly in isopods and some insects Importantly for these species genetic males develop as fully fertile females.

Answer 29

In insects, Wolbachia seems to be able to manipulate the sex determination pathway more directly. It's not clear what the bacteria do, but if the insects are given antibiotics part way through development, females will develop normally, but males that started out developing as females will end up being somewhere awkwardly between the two sexes.

Answer 30

In some isopods, the bacteria head for the organ that produces male sex hormones and destroy it, ensuring the embryo develops as a female

Answer 31

Occurs in the hymenoptera in these species of insects Males only have one set of chromosomes instead of two. Males develop from unfertilized eggs, while fertilized ones get two sets of chromosomes, and end up producing females. Wolbachia gets rid of the males entirely. Infected females produce unfertilized eggs that do one of two things: copy their chromosomes without dividing, or undergo a normal cell division that's followed by the fusion of the two nuclei that result. In either case, the animal winds up with two sets of chromosomes and goes on to develop as a normal, if infected, female.

Answer 32

In many species it can be fatal to develop as a sex that doesn’t match your chromosome type – so male killing is thought to occur in those species where feminization is not possible. Ulitmately having the same effect

Answer 33

The most common method of reproductive manipulation. Here when an infected male's sperm merge with uninfected eggs, the first cell division of the new embryo fails—the male's chromosomes never fully condense, and don't divide properly. In contrast, when they merge with infected eggs, everything works fine

Answer 34

Uninfected M x Uninfected F = Alive Uninfected offspring Uninfected M x Infected F = Alive Infected offspiring Infected M x Uninfected F = Dead children Infected M x Infected F = Alive infected offspring

Answer 35

Most such toxin–antidote systems in Bacteria studied have simple two-gene operon structures. And in Wolbachia this also appears to be the case – Genetic transformation with the cidA/cidB operon into Drosophila produced the full range of reproductive effects expected from CI

Answer 36

Co-expression of cidA/cidB produces healthy individuals – those expressing only cidB do not survive. The researchers hypothesise that only cidB is capable of entering sperm – if it fuses with a Wolbachia infected egg – then it will develop normally – if not then without cidA rescue the embryo will not survive

Answer 37

Identification of the genes/mechanisms for CI is difficult. Cannot be cultured outside of insect hosts, makes them intractable for genetic engineering Progress made with whole genome sequencing and comparative genomics with non-parasitic strains Analysis of proteins in sperm Identified the cidA cidB complex

Answer 38

Single expression of cidA or cidB on their own produce no effect Males expressing cidA/cidB were sterile Females expressing cidA/cidB were fertile Female expression of cidA in ovaries can ‘rescue’ sterile male

Answer 39

CidB causes post-fertilisation embryonic defects Paternal nuclear envelope breakdown is delayed Male pronuclear DNA replication is incomplete Nuclear division fails Late prophase, during the first division of the apposed female and male pronuclei, and accrue through mitosis

Answer 40

Poisons only have effective antidotes with females of the same strain therefore driving speciation as matings with different poison antidotes will led to embryo death

Answer 41

Aedes aegypti

Answer 42

The Aedes aegypti mosquito is the primary vector of dengue. The virus is transmitted to humans through the bites of infected female mosquitoes and vice versa. After virus incubation for 4–10 days, an infected mosquito is capable of transmitting the virus for the rest of its life. Aedes control measures – cannot use bednets Insecticides – pyrethroids – almost totally immune No competent vaccine

Answer 43

Wolbachia infection interferes with other pathogens Oral infection with Wolbachia reduces the amount of dengue virus in mosquito saliva No-one knows how this competitive exclusion occurs

Answer 44

Population supression - release Wolbachia infected mosquito males they will result in dead embryos therefore population collapse Population replacement - release males and female mosquitos that are infected and they will replace non infected natives. The Wolbachia will supress the bacteria

Answer 45

Nasonia giraulti & Nasonia vitripennis Two closely related parasitoid wasps Cannot produce fertile offspring

Answer 46

Hypolimnas bolina Found across Asia and Australasia Infected with strain wBol1 – male killer Only 1% of population is male

Answer 47

Downregulation of Masc preventing the alternative splicing of genes in Wolbachia infected males Leads to failure of dosage compensation & male death

Answer 48

2005 a suppressor gene was evolved by an as yet unknown mechanism in female blue moons on the island of Savaii (purple), which made their male offspring resistant to Wolbachia The survival of the fittest, the few resistant males mated far and wide, and because the suppressor gene was a dominant trait, resistant males proliferated

Answer 49

From being almost all-female, the population went on to become an equal mix of the sexes in less than a year Savaii Island 2001 and 2005 on Upolu, another Samoan island, showed a similar shift in the sex ratio during the intervening 4 years, but no one caught it in action because it occurred so quickly

Answer 50

Fast evolutionary responses to extreme population pressures are probably fairly routine in nature, given that Wolbachia is just one of many sex ratio distorters

Answer 51

the phenotype of four wBol1 isolates collected from Moorea following crosses to males from Southeast Asia. Compared to control crosses where the same wBol1 isolate was crossed with males from within their native population. When infected Moorean females were mated to Thai or Philippine males, creating a nuclear background that was 50% Southeast Asian/50% Moorean, the females produced significant numbers of sons: male killing did not occur Backcrossing reduced sex ratio show genetic dilution

Answer 52

The wrong mix of gut bacteria, not just starvation, could contribute to severe malnutrition

Answer 53

Severe protein malnutrition In Malawi alone there are 10s of thousands of children have this condition with 15% fatal cases Gut bacteria can affect absorption of iron zinc and vitamins

Answer 54

~10^3/g Gastric acidity kills most bacteria

Answer 55

10^4 to 10^6 Bile secretions Input from pancreas Rapid transit time of contents

Answer 56

~10^11 Slow movement of contents Constant pH and substrate availability Long term colonisation and growth of bacteria

Answer 57

Include Gram +ve, Gram -ve bacteria, archaeabacteria Also present are yeast fungi (Mycobiome) The gut also contains viruses (Virome) The Bacteriome constitutes >99% of the microbiome, hence most studies are focused on gut bacteria (100 billion per g stool)

Answer 58

Human faeces contain at least 109 virus-like particles/g The human gut virome is highly individual The great majority of the virus particles remains unidentified Viruses are important since many carry antibiotic resistant genes as well as virulence genes Viruses can modulate the microbiome composition

Answer 59

Phylum --> Examples Firmicutes --> Lactobacillus,Clostridium, Staphylococcus, Enterococcus Bacteroidetes --> Bacteroides, Prevotella Proteobacteria --> Escherichia, Pseudomonas Actinobacteria --> Bifidobacterium

Answer 60

Firmicutes and Bacteroidetes make up 90% of the human gut bacteria

Answer 61

Vaginally delivered infants microbiota is dominated by mother vaginal and faecal bacteria C-section delievered infants microbiota is dominated by skin and bacteria from hospital environment

Answer 62

Genetics Ageing Diet Stress Infection Antibiotics

Answer 63

Stimulation of host immune system Aids digestion Production of short chain fatty acids and vitamins Inhibition of pathogenic bacteria Transformation of bioactive compounds Provide fixed nitrogen to the host

Answer 64

Production of carcinogens Play a role in obesity and diabetes Involvement in inflammatory diseases

Answer 65

Microbiome provide health benefits Including vitamins and short chain fatty acids We provide microbiome a comfortable home with free food and water and constant temperature

Answer 66

Humans are superorganisms whose metabolism represents an amalgamation of microbial and human attributes

Answer 67

>50% of all humans share 75 species >90% of all humans share 57 species However at functional level there is more similarity between individuals

Answer 68

Microbiome can be altered and manipulated towards a more healthy outcome

Answer 69

Pathogen exclusion Brain development Obesity (help reduce or gain weight) Inflammatory bowel disease

Answer 70

High caloric intake Genetic predisposition Microbial metabolism

Answer 71

Obese mice have 50% fewer Bacteroidetes than lean mice and reverse for Firmicutes

Answer 72

Mice grown in germ free facility - one group was conventionalised Feed on western diet and weight measured Exposed group gained weight much quickier

Answer 73

Colonization of germ-free wild-type C mice with a caecal microbiota harvested from obese donors results in a significantly greater percentage increase in total body fat than colonization with a microbiota from lean donors

Answer 74

Physical traits like obesity and leanness can be “transmitted” to mice, by inoculating the rodents with human gut microbes 4 twin pairs Fed Low fat, high fibre diet --> mouse from obese twin agined weight compared to mice from lean staying lean But this effect was diet dependent

Answer 75

Anxiety Depression Sensitivity to pain Serotonin production Autism Parkinson’s Disease Alzheimer’s Disease

Answer 76

More than 100 years ago it was stated that ‘our gut governs our state of mind’ Our knowledge of Gut Microbiome –Brain interactions is derived from animal studies including germ free mice. ‘The microbiome may provide new class of ‘psychobiotics for treatment of anxiety, depression and other mood disorders

Answer 77

Faecal microbiota transplant can alter personality behaviour in mice The recipient mice would take up personality of the donor The daring mice would become apprehensive The timid mice would become more exploratory =>the microbial interactions with brain could induce anxiety and mood orders

Answer 78

We performed FMT from old mice to young adult mice and as control young mice to young mice FMT from aged donors led to impaired spatial learning and memory in young adult recipients

Answer 79

Remarkably, colonization of αSyn-overexpressing mice with microbiota from PD-affected patients enhances physical impairments compared to microbiota transplants from healthy human donors PD mice with healthy faeces symptoms stayed the same

Answer 80

The enteric nervous system has over 100 million neurons Your gut produces more serotonin than the brain The gut bacteria can interact with both ENS and CNS

Answer 81

Bacteriophages/ antimicrobial that target specific bacteria or groups of bacteria Diet (HMO, Resistant starch) Faecal Microbiota Transplant (Intestinal Microbiota Transfer )

Answer 82

A superbug-major cause of hospital acquired infections (community) Spores can persist in the hospital environment: hands, floor, clothing, bedding Produces toxins Possible food borne pathogen UK approx. 20,000 cases of CDI Cost to NHS £500 million

Answer 83

Mild – severe diarrhoea Abdominal pain Fever Severe case: Bowel inflamamtion (1500 deaths in UK)

Answer 84

Elderly patients who have taken broad spectrum antibiotics and Immunocompromised patients are at most risk (over 80% of CDI infection reported in people over 65 ) Clear association between disruption of normal gut bacteria by antibiotic and risk of C. difficile infection

Answer 85

Currently treatable by metronidazole or oral vancomycin but relapse can occur (20-30%) Potential risk of antibiotic resistance

Answer 86

In 4th century AD , a Chinese Physian Ge Hong prescribed a drink (yellow soup) made from human faeces to treat food poisoning

Answer 87

First performed in 1958 on 4 patients with severe diarrhoea-all recovered within 48h More than 200 sporadic case studies have been reported Recently a number of large clinical trials have proven the efficacy of FMT for treatment of CDI

Answer 88

Healthy adult aged 20-40 Risk of infectious agents (eg HIV,Hepatitis and Salmonella) Gastrointestinal comorbidity (IBS and cancers) Intake of antibiotics Travel to area with risk of diarrheal diseases

Answer 89

The patient stops taking antibiotics Patient is given enema to empty the bowls Nasojejunal (NJ) tube is inserted through the nose by a gastroenterologist On the day fresh faecal slurry is prepared at QIB Transported to hospital and delivered to the patient via NJ tube (or via colonoscopy) The FMT procedure takes only 20 minutes

Answer 90

So far we have performed FMT procedure has 92% success rate Mechanism of the exclusion process to develop knowledge improvement in FMT Analysis of the microbiome structure and function during the FMT

Answer 91

Increase in Proteobacteria numbers Case was a chronic drinker so carried on drinking making problem worse

Answer 92

Cheap (£800 compared to more than £9000 for antibiotics) High sucess rate Easy to administer Reduce risk of antibiotic resistance Safe

Answer 93

Risk of transferring unknown pathogens Public acceptance Long-term impact of the foreign microbiome still unknown

Answer 94

Frozen donor faecal material Freeze dried donor faecal Capsules Defined mix of gut bacteria instead of whole faecal microbiome

Answer 95

Obesity Type II diabetes Cancer HIV Depression IBS

Week 10 Flashcards

(119 cards)