Microbiome and Metagenomics Notes

Quantitative Traits (QT)

QT refers to quantitative traits like height, eye color, and hair color.

Genetic Engineering

The possibility of genetic engineering to design babies is discussed. Although actively disallowed, it may be happening covertly.

Bacteria and Scar Color

The mechanism behind bacteria making scars black is explored.

Bacteria

• Crucial for health, particularly in the gut and soil.

• Humans heavily depend on them.

• Imbalance leads to health issues.

• Form communities in various environments like lakes, cold environments, and petroleum.

Metagenomics and 16S RNA Sequencing

• Metagenomics often involves 16S RNA sequencing.

• Studied due to the limitations of culture methods like those used by Robert Cook.

• Sequencing is essential to understand the complete scope of microorganisms.

Human Microbiome

• The human stomach contains more bacterial cells than human cells.

• This community is vital for health.

Importance of Microbes

• Microbes' role as probiotics is highlighted.

• Influence psychological states, potentially leading to depression if imbalanced.

• Linked to conditions like Alzheimer's and aging, emphasizing their importance in various health aspects.

• Cesarean sections can alter the bacterial composition, leading to lasting differences.

PCR and Enzymes

• PCR utilizes enzymes resistant to high temperatures ($95$ degrees Celsius) for extended periods.

• These enzymes facilitate polymerization at $72$ degrees Celsius.

Germ-Free Mice

• Germ-free mice studies show that the absence of microbes leads to slower growth, shorter stature, and impaired immune system development.

• These studies emphasize the necessity of microbes for proper development and health.

Microbiome and Diet

• A scientist from India notes vegetarians may consume eggs or other animal products.

• Vegans avoid all animal-derived products.

• Switching to a vegan diet rapidly alters the bacterial community.

Adaptation of Bacteria

• Specific strains of cyclobacillus are unique to certain regions, showcasing high adaptability.

• High haploid genome mutation rates mean individuals carry unique bacteria.

• Antibiotic use can deplete these bacteria.

Metagenomics Questions

Metagenomics aims to answer three key questions:

1. Taxonomical profiling: Identifying the types of bacteria present.

2. Functional profiling: Understanding the roles and activities of the microbial community.

3. Analyzing metabolic processes, such as how they process food and produce essential vitamins.

Vitamins and Microbial Activity

• Vitamins from natural sources are better absorbed than multivitamins.

• Multivitamins often go to waste if the microbial community is not conducive to their absorption.

Statistical Analysis and Pipelines

• Statistical analysis methods are utilized.

• Cloning bacteria in E. coli, sequencing, or direct analysis are pipeline steps.

• Protocols vary.

Skin Microbiome and Aging

• Research on the skin microbiome of mice studies its effects on aging.

Metagenomic Sequencing Steps

1. Extract DNA.

2. Amplify universal genes from genomic DNA.

3. Sequence.

4. Assemble sequences as needed.

5. Predict genes.

6. Annotate functions.

7. Conduct phylogenetic analysis using 16S rRNA.

8. Analyze remaining sequences to understand functions and identify organisms.

Challenges in Metagenomics

• Assigning functions to unassembled sequences is challenging due to diversity.

• Quantifying the number of organisms.

• Finding genes in metagenomic data.

• E. coli substrates can differ by up to $30$% in long-term studies, highlighting variability even within species.

Functional Profiling

• Involves identifying taxonomic classes and types associated with functions.

• Understanding abundant taxa.

• Diversity analysis includes alpha and gamma diversity.

Issues Caused by Microbial Imbalance

• Obesity.

• Nonalcoholic fatty liver disease: Gut bacteria convert glucose into ethanol, affecting the liver.

Role of Gut Bacteria

• They aid digestion, vitamin absorption, and metabolism.

• Enzymes facilitate resource extraction from food.

• Important for psychological well-being and mood via the gut-brain barrier.

• Lack of beneficial bacteria can cause stress and vitamin deficiencies like B12.

Hypothesis on Modern Human Suffering

Modern humans suffer due to imbalances in micro bacteria.

System Biology Approach

• Global approach considering health and environmental responsibilities.

• Involves profiling bacteria taxonomically, functionally, and genetically.

Future Directions

• Isolating and culturing specific bacteria is a new direction.

Technical Aspects of Metagenomics

• Screens the environment to find highly conserved regions, like those in 16S rRNA.

• Conserved structures are crucial for protein function.

• Analysis targets variable sites to differentiate bacteria.

Importance of 16S DNA Data

Classifying bacteria based on metagenomic sequences is essential.

Diversity in 16S RNA

A study of $14$ skin sites from $10$ people could reveal approximately $5,000$ variety sites within the 16S RNA.

Viruses in Microbiome

• Viruses lack ribosomal RNA, posing unique identification challenges.

• Bacterial phages are specific to bacteria.

• A diverse viral community, including those infecting bacteria, exists within the body.

Viral Analysis

• Random sampling and microscopy help identify viruses.

• Many viral sequences remain unknown.

• Studying viral load variations is important.

Plant-Based Viruses

• PCR can identify plant-based viruses in fecal samples.

Random Community Genomics

• Identifies bacteria in various environments, including mosquitoes.

Metagenomics Processing

• Involves taxonomic assignment.

Conclusion

Many aspects of our microbial communities remain unknown, especially concerning viruses.