Lecture 1.2: Microbiota Flashcards
What is the Microbiota?
Community of microorganisms living in a specific environment
What is the ‘Normal Flora’?
Microorganisms regularly found at an anatomical site in healthy humans & not causing infection or disease
What is the Microbiome?
The term “microbiome” refers to the collective genomes of the microorganisms in a given environment, meaning the collection of all their genetic material (DNA and RNA)
What are the 4 dominant phyla in the human gut?
• Firmicutes
• Bacteroidetes
• Actinobacteria
• Proteobacteria
Acquisition of Microbiota: Vertical Transmission
Acquisition of microbes directly from an organism’s parents
Exposure to mothers vaginal and gut bacteria are part of the main seeding event for founding microbiome
GBS bacteria can travel up from vagina to amniotic fluid, in birth canal through lung aspiration
Exposed to GBS from contact with mothers faecal matter during birth process
Acquisition of Microbiota: Horizontal Transmission
Acquisition of microbes from sources other than an organism’s direct parents
Such as the environment or from non-parental conspecifics
What is Group B Streptococcus? Where is it found?
• Gram positive, beta haemolytic bacteria
• Common coloniser of human gastrointestinal and genitourinary tracts
• Recognised as causing disease in humans in the 1930s
Problems related to Group B Streptococcus
Causes serious disease in young infants, pregnant women and older adults
Emerged as most common cause of sepsis and meningitis in infants <3 months in the 1970s
Obstetric Risk Factors for Early-Onset GBS Disease
• Preterm delivery
• Prolonged rupture of membranes
• Infection of the placental tissues or amniotic fluid/fever during labour
• GBS in the mother’s urine during pregnancy (marker for heavy colonisation)
• Previous infant with GBS disease
• Low maternal levels of anti-GBS antibodies
Demographic Risk Factors for Early-Onset GBS Disease
• African American
• Young Maternal Age
Horizontal Transmission: Diet Effects
Diet is one of the major factors involved in shaping the gut microbiota composition
What is the gut microbiome of humans comprised of?
• Diverse group of trillions of microorganisms including
• Symbiotic organisms
• Opportunistic pathogens
• Commensal organisms
What does microbiota plays a major role in?
• Digesting food
• Absorbing and synthesizing some nutrients and releases their metabolites
• Deliver a variety of growth-promoting and growth-inhibiting factors that
influence human health either directly or indirectly
What are Biofilms?
• Microbial community enclosed by an extracellular materials such as mineral
crystals, blood & other substances
• Form on tissue, medical devices & surfaces
• Biofilms environment for genetic exchange
Problems with Biofilms
• >80% of microbial infections are related to biofilms -National Institute of
Health
• Bacteria within Biofilms have increased resistance to antimicrobial drugs
What is Dysbiosis?
Disturbance to microbiota homeostasis due to an imbalance in the flora itself, changes in their functional composition and metabolic activities, or changes in their local distribution
Effects of Dysbiosis (3)
1) Loss of beneficial organisms
2) Excessive growth of potentially harmful
organisms
3) Loss of overall microbial diversity
Effects of Microbiota on Adiposity
Gut microbiota increases energy production from food, provides low-grade inflammation, and impacts fatty acid tissue composition
These mechanisms may link the gut microbiota with obesity
What is included in Symbiotic Intervention? (4)
• Probiotics
• Prebiotics
• Synbiotics
• Faecal Matter/Bacteriotherapy
What are Probiotics?
They are live microorganisms that are intended to have health benefits when consumed or applied to the body
What are Prebiotics
They are non-digestible food components that selectively stimulate the growth or activity of desirable microorganisms
What are Synbiotics?
They are products that combine probiotics and prebiotics
What is Faecal Transplantation (FMT)/Bacteriotherapy?
It is the transfer of stool from a healthy donor into the gastrointestinal tract for the purpose of treating recurrent
Probiotics: Pros vs Cons
PROS:
• Oral Application
• Restoration of good bacteria and gut barrier
CONS:
• Oral dose that reached gut is variable
• Potential loss of adaptation of culture-derived
probiotics in the gut
FMT: Pros vs Cons
PROS:
• Safe Application
• Simple Procedure
CONS:
• Variable Imapact
• Not effective in IBD (Inflammatory Bowl Disease)
• Quality of donor stool is important
Effect of Symbiotic Intervention
Changing the environment microbial status can either promote disease or confer protection
Effects of Antibiotics on Microbiota (2)
Antibiotics can alter the population structure of the microbiome
While the overall structure of such microbiomes is recovered after some time, the genomic structure is not fully equivalent
