Unit 2 Lecture 4
Microorganisms vs. Microbes: Definitions and Distinctions
Microorganism: A broader term referring to all living things that are microscopic. It encompasses all microscopic organisms, both beneficial and harmful.
Microbe: A subset of microorganisms, specifically referring to those that cause disease or infection. While often used interchangeably in layman's terms, technically, a microbe is disease-causing.
Similarities:
Both refer to microscopic organisms, tiny life forms too small to be seen with the naked eye.
Both terms generally include bacteria and viruses (though viruses are considered non-living, they act like living entities in many contexts).
Differences:
Scope: Microorganisms ($\text{broad term}$) vs. Microbe ($\text{limited range}$). Microorganisms can be anything, while microbes are more specific.
Connotation: Microorganisms ($\text{neutral term}$) vs. Microbe ($\text{disease-causing}$). The term 'microbe' inherently carries a connotation of pathogenicity.
Usage: Microorganisms are more commonly used in a scientific context (e.g., discussing the 'microbiome' which includes beneficial and harmful entities). Microbe is used more in everyday life.
Specificity: When discussing pathogenic organisms, the term 'microbe' is used (e.g., pathogenic microbes). When referring to the entire community of organisms, beneficial or otherwise, 'microorganisms' is preferred (e.g., our microbiome).
The Human Microbiome: Definition and Influencing Factors
Definition: The microbiome is the collective community of all microorganisms (bacteria, viruses, fungi, etc.) that live in and on us. It significantly contributes to who we are.
Factors Influencing the Microbiome: Our microbiome is shaped by a complex interplay of various factors:
Genetics: Inherited predispositions from parents.
Environment: The surroundings and external factors we are exposed to.
Diet: The food we consume directly impacts the composition and function of our gut microbiome.
Lifestyle: Habits and daily routines.
Hormones: Endogenous chemical messengers within the body.
Industry: Includes the types of foods available, medicines taken (e.g., antibiotics), and sanitation practices.
Microbes in Specific Body Systems
Nose
Mucus Production: The nose produces mucus not only to trap incoming particles but also contains antimicrobial chemicals.
Antimicrobial Mechanisms: Substances within mucus actively break down bacterial walls and trap viruses, fungi, and other particles, preventing them from entering the body.
Tears
Exposure: Eyes are highly exposed to foreign materials due to their lack of a shield.
Lysozyme: Tears contain a chemical called lysozyme.
Lysmeans to break. Lysozyme is an enzyme thatlyses(breaks down) the walls of bacteria, providing an immediate defense against pathogens entering the eyes.
Large Intestine
Absorption: Primarily responsible for absorbing bicarbonate buffer and water, the large intestine also absorbs certain complex carbohydrates.
Vitamin Production: A significant amount of vitamins are absorbed from the large intestine; these are produced by beneficial gut bacteria.
Symbiotic Relationship: We provide gut bacteria with a warm home and food, and in return, they produce essential vitamins that we absorb.
Reproductive System
pH Criticality: Maintaining the correct pH is crucial for reproduction and to kill harmful microbes.
Acidity in Women: The female reproductive tract is typically acidic for a vital reason.
Sperm Capacitation: The covering on the head of sperm is thick and must be dissolved to allow genetic material to reach the egg. Sufficient acidity in the female body is necessary to dissolve this covering; without it, reproduction would be hindered.
Skin
Immune System Fortification: The skin serves as a primary barrier and fortifies the immune system.
Scent Production (Pheromones): The skin releases chemicals (pheromones) that determine our individual scent.
Subconscious Attraction: Humans subconsciously choose individuals they are attracted to or dislike based on their scent. This has a genetic basis.
Disease Detection: Historically, and still subconsciously, scent helped detect disease. When an individual is sick, their scent changes (e.g., a female lion choosing a healthy mate based on scent).
Menstrual Cycle Synchronization: Scent plays a role in synchronizing menstrual cycles among women living in close proximity (e.g., dorms, families), by affecting hormone release.
Eyelash Mites: Commensal eyelash mites live on us; their populations are kept in check by secretions from our skin. Imbalances can lead to eye infections.
The Microbiome as an Essential Organ
Indispensable Organ: The microbiome should be considered another vital organ of the human body, one that we cannot live without.
Comparison to Other Organs:
Some organs we can live without (e.g., gallbladder, appendix, stomach with surgical adaptations).
Some organs are essential for survival (e.g., pancreas).
Similarly, a balanced microbiome is essential for our survival and well-being.
Balance: Without a balanced microbiome, our body systems would be out of balance, significantly impacting our ability to survive and thrive.
Microbial Diversity, Health, and Disease
Microbial Cloud: Humans are covered by thousands of different kinds of microbes, with millions of microbial genes in our human microbiome.
Health and Illness Differences: The variation in microbial diversity between individuals is now thought to be responsible for some differences in health and illness.
Specific Health Implications:
Type 1 Diabetes: Current thinking suggests that one trigger for Type 1 diabetes (an autoimmune condition) may be related to an improper immune response, potentially involving a miscommunication within the microbiome rather than effectively fighting a pathogen.
Ileal Transplants: In intestinal transplant procedures, surgeons now opt to leave some of the donor's microbial community in the ileum, as it may benefit the recipient.
Birth Colonization: Babies delivered vaginally are colonized by their mother's microbes, which play a crucial role in establishing their initial microbiome.
Cesarean Section (C-section) Risks: C-sections may be associated with risk factors due to 'missed colonization,' as the baby does not pass through the birth canal to acquire maternal microbes. While C-sections can be medically necessary, optional C-sections are discouraged by some experts due to this missed early microbial seeding.
Germaphobia and Cleanliness: Excessive cleanliness and widespread use of antibiotics (e.g., on kitchen counters) might negatively impact the microbial community and potentially contribute to health issues.
Autoimmune Diseases: A significant area of research links autoimmune diseases to microbiome imbalances.
Mechanism: It is hypothesized that a miscommunication or dysregulation within the microbiome could trigger the body to attack its own cells.
Examples: Crohn's disease (body attacks the lining of the small and large intestine, causing sores and inflammation), rheumatoid arthritis, lupus, Graves' disease (thyroid-related autoimmune condition). These diseases often involve chronic inflammation and attacks on the body's own tissues.
Analogy: Moving to a foreign country with different flora and fauna, causing initial discomfort until the body adapts to the new microbial environment, illustrates how changes in microbial exposure can impact health.
Probiotics and Prebiotics
Probiotics: Involve adding more beneficial bacteria or microbes directly to the gut (e.g., through supplements or fermented foods).
Prebiotics: Involve adding nutrients that specifically feed and support the existing beneficial microorganisms already present in the body.
Note on historical context: Over the last 100 years, our understanding of microbes and their profound impact on human health has evolved significantly, moving from a view of microbes primarily as pathogens to recognizing their essential role in immunity and overall well-being. This shift has led to new perspectives on health conditions like autoimmune diseases and the importance of maintaining microbial balance. The idea of the human microbiome as another organ is a relatively recent but critically important concept in biology and medicine.