Microbes - Host Interactions Flashcards
What is infection / colonisation?
Acquisition of microorganisms by the host
What is commensalism?
A state of infection that results in no damage to the host
What is symbiosis / mutualism?
A state of infection where both the host and microbe benefit
What is a holobiont?
Host + microbiome
Humans = holobionts
What is a microbiome and why are they important?
All microbes that share out body space
Humans need microbiomes to perform beneficial tasks and provide protection from foreign substances and pathogens
What are commensals?
Normal mircrobes present on the skin and in the oral, respiratory, and gastrointestinal tracts, NOT INTERNAL TISSUES
These are commensals and protect the host against pathogens, provide nutrients for the host, and are acquired in the first year of life
What is the composition of the microbiome?
Huge diversity, but 5 bacterial phyla (major lineages):
- Actinobacteria
- Bacteroidetes
- Firmicutes
- Fusobacteria
- Proteobacteria
What are the characteristics of skin microbiota?
Adult skin supports many many resident and transient varieties (staphylococcus epidermis)
Environment = slightly acidic, high salt, low water content, and inhibitory substances
Bacteria reside on superficial skin (dead cells) and sweat glands and cause partial degradation of skin oil into fatty acids resulting in body odour
What are the characteristics of respiratory microbiota?
In Upper respiratory tract:
Nasal cavity = like skin, staphylococcus
Oropharnyx = like oral cavity, streptococcus
Many viruses
Not much is known about lower respiratory tract
What are the characteristics of gut microbiota?
Stomach = highly acidic, few viable bacteria
Small intestine = acid + bile juices, few viable bacteria
Large intestine = HUGE diversity (firmicutes and bacteriodetes)
Symbionts (produce biotin and vitamin K, affect drug metabolism)
In what environment within the body are you most likely to find the greatest density and diveristy of bacertia?
Neutral pH
What are the characteristics of the oral microbiota?
Mouth colonised soon after the birth with aerobes and obligate anaerobes (streptococcus)
After tooth eruption, significant increase in anaerobes
What is dysbiosis?
Disruption to the microbiota homeostasis caused by an imbalance in the microflora, changes in their functional composition and metabolic activities, or a shift in their local distribution
What is an example of dysbiosis proven by lab mice?
Obesity via germ free versus conventional mice
- Same diet, GF mice could eat more and gain less weight than conventional mice
Microbiota affected caloric absorption
What are dental conditions caused by microbiome dysbiosis?
Dental caries, periodontal disease, oral cancer
