Symbiotic Relationships and Dysbiosis / Disease Flashcards
Define microbiome, microbiota and microhabitat
- 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
What is symbiosis
- Interaction between two organisms living in close physical association
What are resident microbiota
- 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
What are transient microbiota
- 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
Describe gut microbiota
- 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
What variables influence gut microbiota
- 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
Describe skin microbiota
- 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
What variables can influence skin microbiota
- Environmental factors (weather)
- Host factors (age, personal hygeine)
Describe oral cavity microbiota
- Complex, heterogeneous microbial habitat
- Tooth consists of a mineral matrix (enamel) surrounding living tissue
- Examples: Streptococcus , pasteurellaceae, prevotella, veillonella
What variables can influence oral cavity microbiota
- Saliva contains antimicrobial enzymes
- High concentrations of nutrients near surfaces in mouth promote localised microbial growth
Describe the stability of vaginal microbiota
- Exploration as to whether menstruation affect diversity of microbial spp.
- See a dynamic response of vaginal flora during menstruation
- Examples: Lactobacillus, prevotella, gardnerella, atopobium
What are the 3 types of symbiotic relationships
- 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
What is dental plaque / periodontitis
- 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
What are opportunistic pathogens and their ideal conditions
- 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
What is the function of gut microbiota
- 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
What is IBD
- 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
What influence do antibiotics have on gut microbiota
- 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
What is the purpose of a faecal transplant
- Transfer of microflora from healthy to infected patient
- Attempt to reverse dysbiosis
- Used in obesity, microbiota from lean donors reduce adiposity gain
What occurs from pregnancy to childhood to adulthood in the gut
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)
What influence does obesity have on gut microbiota
- 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
