Medical Microbiology Lecture 1

Study Notes

Microbial flora is dynamic, reflecting ongoing changes in nutrition, hormonal levels, and health conditions.
The human microbiome comprises a unique set of microorganisms for each individual, with the gut microbiome being the most significant.
The Human Microbiome Project: a 5-year study analyzing microbial populations in healthy adults via samples from various body sites (nose, mouth, skin, gut, vagina).

Microbe identification leveraged sequencing of the 16S ribosomal RNA gene, a genetic marker unique to each species, composed of RNA and proteins.
The 18S gene is used for identifying eukaryotes.
Operational Taxonomic Unit (OTU) classifies closely related microbial groups.

Core microbiome: consists of species present in 95% or more of individuals at specific body sites, with high taxonomic diversity yet consistent functional properties.
Functional redundancy: multiple species can fill similar ecological roles, ensuring ecosystem resilience.
The microbiome offers metabolic functions, enhances innate immunity, and protects against harmful pathogens.

Normal flora consists of core and secondary microbiota formed through symbiosis and interspecies competition.
Composition is affected by hygiene, diet, water source, medication (notably antibiotics), and environmental toxins.

Nutrition significantly influences the interplay between humans and their microbiome.
Gut bacteria metabolize complex carbohydrates into short-chain fatty acids, which are crucial for cellular energy and inhibiting harmful bacteria.
Specific bacteria (Bacteroidetes and Firmicutes) efficiently break down complex and host-derived carbohydrates.
Increased ratios of these bacteria may enhance metabolic efficiency and impact health outcomes, including malnutrition and obesity.

Emerging research suggests that a community of organisms, rather than just individual species, contributes to disease, affecting conditions such as inflammatory bowel disease, obesity, type 2 diabetes, and celiac disease.
The concept of infectious diseases is being redefined by the understanding of microbiome interactions.

Dysbiosis indicates a disruption in normal microbial communities, leading to disease by either depleting beneficial organisms or promoting harmful ones.
Recognizing dysbiosis can lead to advanced diagnostics and innovative therapies, exemplified by Clostridium difficile infections resulting from normal flora depletion due to antibiotics.
The consequences of microbiome alterations contribute to various diseases, emphasizing the importance of maintaining microbial balance for health.