Symbiotic Relationships and Dysbiosis / Disease

Question 1

Define microbiome, microbiota and microhabitat

Answer 1

• Microbiome: Functional collection of different microbes in a particular environmental system
• Microbiota: Describes all the microbes in a microhabitat
• Microhabitat: Different microhabitats support different microbes

Question 2

What is symbiosis

Answer 2

• Interaction between two organisms living in close physical association

Question 3

What are resident microbiota

Answer 3

• Acquisition of normal microbiota
• Develop during birthing process, established during first months of life, mostly commensal, stable over decades
• Early gut colonisers (from parents/ siblings), have potential to exert their physiologic, metabolic, and immunologic effects for most / all our lives
• Primary clustering is by body area
• Oral, GI, skin and urogenital habitats separate

Question 4

What are transient microbiota

Answer 4

• Remain in the body for only hours to months before disappearing
• Found in same regions as resident microbiota, cannot persist in the body
• Competition from other organisms
• Elimination by the body’s defence cells, chemical or physical changes in the body

Question 5

Describe gut microbiota

Answer 5

• Individuals have mostly firmicutes, mostly bacteroidetes or a mix
• Regulates metabolism and host’s propensity for obesity
• Colonisation begins at birth, early colonisers are a source of vitamins (facultative > obligate anaeorbes)
• Examples: Bacteroidetes, firmicutes, proteobacteria

Question 6

What variables influence gut microbiota

Answer 6

• Vaginally born infants have a microbiome more similar to that of their mothers than those born via Cesarean section
• Breastfed infants have more commensal bacteria, due to oligosaccharides promoting colonisation
• Weight loss / diet
• Ageing and frailty are associated with decreased diversity
• Antibiotics and chemotherapy

Question 7

Describe skin microbiota

Answer 7

• Generally a dry, acid environment
• Readily colonised by +ve bacteria / normal flora of skin
• Proteobacteria, firmicutes and bacteroidetes are abundant
• Examples: Propionibacterium, Staphylococcus, corynebacterium, anaerococcus

Question 8

What variables can influence skin microbiota

Answer 8

• Environmental factors (weather)

- Host factors (age, personal hygeine)

Question 9

Describe oral cavity microbiota

Answer 9

• Complex, heterogeneous microbial habitat
• Tooth consists of a mineral matrix (enamel) surrounding living tissue
• Examples: Streptococcus , pasteurellaceae, prevotella, veillonella

Question 10

What variables can influence oral cavity microbiota

Answer 10

• Saliva contains antimicrobial enzymes

- High concentrations of nutrients near surfaces in mouth promote localised microbial growth

Question 11

Describe the stability of vaginal microbiota

Answer 11

• Exploration as to whether menstruation affect diversity of microbial spp.
• See a dynamic response of vaginal flora during menstruation
• Examples: Lactobacillus, prevotella, gardnerella, atopobium

Question 12

What are the 3 types of symbiotic relationships

Answer 12

• Commensalism: One organism benefits and other is unaffected (no benefit or harm), staph on skin
• Mutualism: Both organisms benefit, bacteria in colon
• Parasitism: One organism benefits at expense of the other, tuberculosis in lung

Question 13

What is dental plaque / periodontitis

Answer 13

• Cells form a biofilm, presence of strep / fermenting bacteria, produce acid, wears down enamel
• Periodontal disease is thought to contribute to several systemic conditions, including cardiovascular disease and arthritis

Question 14

What are opportunistic pathogens and their ideal conditions

Answer 14

• Normal microbiota / harmless microbes that can cause disease under certain circumstances
• Immune suppression
• Changes in abundance / diversity of normal
• Introduction of normal microbiota into unusual site in the body

Question 15

What is the function of gut microbiota

Answer 15

• Influences aspects of health / disease
• Impacts growth and development, behavioural responses, sexual activity, mating
• Chronic diseases (diabetes, obesity, CVD, HIV, malnutrition), ageing and immune regulation

Question 16

What is IBD

Answer 16

• Lower gut microbiome diversity
• Chronic inflammation of the gut and disruption of homeostasis (dysbiosis)
• Antibiotic use increases risk
• Once developed it may be transmissible between family members

Question 17

What influence do antibiotics have on gut microbiota

Answer 17

• Decrease all microbes in human gut (target and non-target)
• Use in first months of life increase risk of IBD / dysbiosis related disorders
• Clostridium difficile (spore former, generally antibiotic resistant) infections are associated with antibiotic use

Question 18

What is the purpose of a faecal transplant

Answer 18

• Transfer of microflora from healthy to infected patient
• Attempt to reverse dysbiosis
• Used in obesity, microbiota from lean donors reduce adiposity gain

Question 19

What occurs from pregnancy to childhood to adulthood in the gut

Answer 19

Pregnancy:
- Increased IgG
- Sterile GI tract
- C-section (staph) vs vaginal delivery (lactobacillus)
Childhood:
- Decreased TLRs, enable stable bacterial communities to establish in GI tract
- Solid food / diet change sees increased diversity, Bacteroidetes and carbohydrate utilisation
- Differentiate commensal / pathogenic bacteria
Adulthood
- Stable
- Microbial dysbiosis sees development of allergies (IL-4), obesity (TNF-a), Crohn’s disease (IL-1b)

Question 20

What influence does obesity have on gut microbiota

Answer 20

• Obese humans have more Firmicutes than non-obese humans
• Nature and transferability of gut microbiota is dependent on diet as well genetics
• Metabolites produced from the bacteria are thought to impact on weight gain