Human Microbiome and Microbial Ecosystems PDF

11/11/2024 Human Microbiome and Microbial Ecosystems Mouth Microbiome The mouth is a highly diverse ecosystem with different habitats: ○ Anaerobic zones: Found between teeth and gums. ○ Aerobic zones: Found on teeth surfaces. Microbial activities: ○ Bacteria for...

11/11/2024 Human Microbiome and Microbial Ecosystems Mouth Microbiome The mouth is a highly diverse ecosystem with different habitats: ○ Anaerobic zones: Found between teeth and gums. ○ Aerobic zones: Found on teeth surfaces. Microbial activities: ○ Bacteria form biofilms, which are collections of microorganisms attached to surfaces. ○ Biofilms occur mainly in anaerobic environments and are difficult to disrupt completely. ○ Bacteria metabolize food residues and natural sugars, producing energy and waste gases (e.g., stinky, reduced gases). ○ Anaerobic metabolism dominates in areas like gum pockets, where oxygen is scarce. Oral hygiene (brushing, flossing) reduces but cannot eliminate these microbial communities. Microbes in biofilms stick to each other or to surfaces. Can form on both hard (pipes, catheters) and soft surfaces (body tissues). Biofilm Functions and Capabilities: Gene Sharing: ○ Biofilms enable horizontal gene transfer (Between organisms that are not directly related) Resistance: ○ Biofilms make bacteria more resistant to antibiotics through gene sharing. Hospital-Acquired Biofilm Infections: Example: A patient with a urinary catheter (silicone tube) in the bladder. ○ Normally, the bladder has few or no microbes. ○ If a microbe (e.g., Proteus vulgaris or Pseudomonas) attaches to the catheter, it can: Form a biofilm. Thrive in urine, which is rich in water, sugar, nitrogen, and nutrients. Spread antibiotic resistance genes, worsening infections which can make the patient severely ill. Gut Microbiome The gastrointestinal tract is home to trillions of microbes. Key regions: ○ Stomach: Low pH environment (acidic); certain bacteria like Helicobacter pylori thrive here and are gram negative. ○ Intestines: More neutral pH, supportive of diverse microbial growth. Probiotics and Prebiotics: ( just for fun) ○ Probiotics: Live bacteria (e.g., Lactobacillus, Bifidobacterium) consumed to support gut health and feminine health. ○ Prebiotics: Nutrients like fiber that feed beneficial gut bacteria. Specific Microbial Species 1. Helicobacter pylori: ○ Gram-negative bacterium that lives in the stomach. ○ Historically linked to gastric ulcers but part of normal flora for many individuals. ○ Regulates digestive hormones controlling hunger/satiety. ○ Overuse of antibiotics has reduced its existence, potentially contributing to obesity trends. 2. Bacteroides: ○ Gram-negative bacteria, dominant in the gut (as shown in the figure). ○ Important for immune regulation, metabolism of alot sugars and anti-inflammatory functions. 3. Clostridium difficile (C. diff): ○ A firmicutes, gram-positive, spore-forming anaerobe present in normal gut flora. ○ Can cause severe infections that can kill people when gut biodiversity is disrupted (e.g., after antibiotic use). ○ C diff is associated with in many cases, not always, hospital acquired infections and is very difficult to treat with antibiotics ○ Treatment: Fecal microbiota transplants (restoring microbiome diversity). “They take feces of healthy individuals who have a biodiverse abundant community and inject it up into the sick person with c.diff to retire the bacteria community.” 4. Firmicutes: ○ Gram-positive bacteria, including Lactobacillus and Clostridium species. ○ Play a role in digestion and metabolic health. Microbiome and Obesity Monozygotic Twin Study: ○ Took gut microbiomes from lean and obese twins were transplanted into germ-free mice. ○ Mice receiving microbiomes from obese twins gained significant weight. ○ Mice receiving lean microbiomes stayed lean (gained no weight), ○ Even when co-housed, they (started eating each other’s feces and getting eat other microbes) and the obese one didn't gain as much as weight as when it was by itself and the lean lost some weight ○ Key Conclusion: Lean-associated microbes can dominate and override obese microbes and reduce weight gain effects from obesity-associated microbes. Pathogenicity & Virulence: Refers to the ability of microbes to cause disease. Microbes with genes that produce toxins or other harmful substances can cause disease and lead to pathology. We can classify pathogen in terms of their pathogenicity and virulence based on their LD50 Measured using LD50 (Lethal Dose 50%): ○ The amount of a microbe required to kill 50% of the test population.  Highly virulent organisms (e.g., Agent 1) require low doses to cause severe illness. Less virulent organisms (e.g., Agent 2) require higher doses to cause illness. Disease Transmission Vocabulary 1. Horizontal Transmission: ○ Direct spread between individuals (e.g., sneezing, touching contaminated surfaces). 2. Fomites: ○ Non-living objects (e.g., doorknobs, dirty utensils, desk, hospital bed) that transmit microbes. 3. Vectors: ○ Living organisms (e.g., mosquitoes, ticks causing Lyme Disease ) that carry pathogens. Example: Mosquitoes transmitting West Nile virus. 4. Zoonotic Diseases: ○ Diseases transmitted from animals to humans. ○ Example: Lyme disease (carried by ticks). 5. Reservoir: Is when the mosquito bit the bird and got the disease from it 11/18/2024 Pathogenesis: How Bacteria Cause Disease Pathogenic Mechanisms 1. Exotoxins (discrete proteins): ○ Definition: Toxic proteins secreted by bacteria that target specific physiological functions such as the liver and intestines ○ Key Features: Can be generated by a gram-positive and gram-negative bacteria. Often encoded on plasmids or pathogenicity islands (mobile genetic elements). Highly Antigenic: Trigger strong immune responses, making them suitable for vaccine development. Highly Toxic Can be denatured and turned into toxoids (e.g., tetanus vaccine). Can be targeted by vaccines Can cause fevers sometimes ○ Examples:  Clostridium tetani: Tetanus toxin targets the nervous system, causing muscle spasms. Vibrio cholerae: Cholera toxin targets the intestines, leading to dehydration from severe diarrhea. Clostridium botulinum: Botulism toxin causes paralysis by blocking nerve function. ○ Vaccination: Effective for exotoxin-mediated diseases because denatured proteins (toxoids) retain immunogenicity. 2. Endotoxins (systemic): ○ Key Features: Can be generated by a gram-negative bacteria (e.g., Neisseria meningitidis). Found in LPS. Lipid A portion of LPS is the toxic component and makes us sick, Released upon bacterial cell lysis. Poorly antigenic (something foreign), so immune response is weak. Systemic effects: Fever, shock, and widespread inflammation usually results in an overreaction by the immune system Toxoids cannot be made Produces fever most of the time Genes found on the cell anatomy’s chromosome ○ Challenges: Antibiotics can worsen symptoms by causing bacterial lysis and endotoxin release. ○ Examples: Neisseria meningitidis: Causes meningitis, spreading through the bloodstream and affecting coagulation./ (leg pic) Salmonella typhi: Causes typhoid fever with systemic effects. Key Bacterial Diseases Cholera (Vibrio cholerae): Bacterial Disease Type: Gram-negative, exotoxin-producing. Transmission: Fecal-oral pathogens, often linked to poor sanitation. Pathogenesis: ○ AB exotoxin alters osmotic balance in intestinal cells. B unit docks then releases toxin into cytoplasm allowing the A subunit to move in ○ Ions like sodium and potassium are pumped out, followed by water → severe diarrhea.  Epidemiology: ○ Often associated with natural disasters and poor sanitation infrastructure. Symptoms: Severe watery diarrhea, dehydration, and potential death. Prevention: Vaccines, clean water, and sanitation. Meningitis (Neisseria meningitidis): Bacterial Disease Type: Gram-negative, Cocci, endotoxin-producing. Transmission: Airborne or direct contact. Pathogenesis: ○ Lipid A triggers systemic immune responses. ○ Dissemination through the bloodstream causes systemic microbleeds and coagulation issues. Symptoms: Fever, headache, stiff neck, rash (microbleeds), and systemic inflammation. Treatment Challenges: ○ Antibiotic-induced lysis releases more endotoxins, complicating treatment. Tuberculosis (TB) (Mycobacterium tuberculosis): Bacterial Type: low GC, Gram-positive, acid-fast bacteria. Has mycolic acid Not Endotoxin or Exotoxin Transmission: Airborne, Primarily in the lungs Pathogenesis: ○ Slow-growing bacteria remain dormant in the lungs. ○ Form granulomas (tubercles) as the immune system walls off the bacteria and causes Ghon’s Complex.. ○ Can remain latent for years before becoming active. Symptoms: ○ Latent TB: No symptoms. ○ Active TB: Chronic cough, weight loss, fever, night sweats, and fatigue. Challenges: ○ Slow growth makes antibiotic treatment lengthy (4-6 months minimum). ○ Multidrug-resistant TB (MDR-TB) is a significant global concern. ○ Spreads easily by coughing Public Health: ○ Strong correlation with HIV-infected populations because it ruins the immune system and the Latent TB goes into activation. ○ High prevalence in low-income areas with limited healthcare access. Introduction to Viruses Key Viral Diseases 1. Flu (Influenza): ○ Negative-sense, single-stranded RNA virus. ○ Requires RNA-dependent RNA polymerase to replicate. ○ Symptoms: Fever, body aches, cough, fatigue. ○ Vaccine: Developed annually due to rapid viral evolution. 2. Coronavirus (e.g., SARS-CoV-2): ○ Positive-sense, single-stranded RNA virus. ○ Uses host ribosomes directly for protein synthesis. ○ Causes COVID-19, with symptoms ranging from mild respiratory issues to severe systemic effects. 3. HIV (Human Immunodeficiency Virus): ○ Retrovirus: Converts RNA to DNA using reverse transcriptase. ○ Integrates into the host genome, targeting immune cells (CD4 T cells). ○ Leads to AIDS, characterized by severe immunodeficiency. ○ Positive-sense, single-stranded RNA virus. Retroviruses: Use reverse transcriptase to convert RNA into DNA, integrating into the host genome. Example: HIV. Tips for Memorization Pathogenesis Vocabulary: ○ Antigenic: Triggers immune response. ○ Toxoid: Modified toxin used in vaccines. ○ Lipid A: Toxic component of endotoxins. Disease-Specific Details: ○ Cholera: Targeted exotoxin (intestines). ○ Meningitis: Systemic endotoxin (bloodstream). ○ Tuberculosis: Latent, lung infection; acid-fast staining. 11/21/2024 Viruses and Infections (Both Positive Sense And Negative Sense RNA have to do with RdRp) RNA-Dependent RNA Polymerase (RdRp): ○ Enzymes critical for RNA virus replication.  ○ Negative-sense RNA viruses must package RdRp to convert -RNA to +RNA upon infection. ○ Positive-sense RNA viruses encode RdRp after infection using the host's ribosomes. Positive Sense RNA (+): ○ Acts directly as mRNA for translation into proteins by ribosomes. ○ Immediately ready for genome replication and protein synthesis. Negative Sense RNA (-): ○ Complementary strand of +RNA. ○ Requires RdRp for conversion to +RNA to enable translation. Influenza Virus (Flu) 1. Genome Composition: ○ Segmented ssRNA (Negative Sense): - 8 separate RNA segments (genomic "shuffling" allows rapid evolution and reassortment). ○ Requires RdRp to transcribe -RNA into +RNA for protein synthesis. 2. Structural Features: ○ Hemagglutinin (H): Spike protein on flu to help dock onto the host. ○ Neuraminidase (N): Spike protein for enzymatic release of new virions. ○ Ion Channels: Facilitate RNA release into the cytoplasm. ○ Nucleocapsid Proteins: Protect and stabilize RNA segments because the -ve sense is highly unstable. 3. Replication Cycle: 1. Virus Entry The virus binds to host cell receptors via hemagglutinin (H) and enters through endocytosis. A pH drop in the endosome triggers fusion with the viral envelope, releasing the 8 RNA genome segments into the cytoplasm. 2. RNA Transport to the Nucleus Each of the 8 RNA segments, wrapped in nucleoproteins and RdRp, is transported into the nucleus. 3. Genome Replication in the Nucleus Negative-sense RNA (-RNA) is the viral genome. Inside the nucleus: 1. RdRp transcribes -RNA into positive-sense RNA (+RNA): Some +RNA serves as mRNA for protein production. Some +RNA acts as a template to make new -RNA genomes. 2. The new -RNA genomes will later be packaged into new viruses.  The +ve sense will be converted back to -ve Note: RDRP acts on -ve & +ve sense 4. Protein Production in the Cytoplasm The +RNA (mRNA) leaves the nucleus and goes to the cytoplasm. Host ribosomes translate the mRNA into viral proteins, including: ○ Capsid proteins: Form the shell around the genome. ○ Nucleoproteins: Stabilize RNA segments. ○ Hemagglutinin (H) and Neuraminidase (N): Viral spike proteins that help entry and exit of the flu. H and N proteins are processed in the endoplasmic reticulum (ER) and transported to the cell membrane via Golgi apparatus 5. Assembly of New Viruses The 8 replicated RNA segments are exported from the nucleus into the cytoplasm, where capsid proteins and nucleoproteins assemble around them. The virus uses the host cell membrane, embedded with H and N proteins, to form its envelope. 6. Virus Exit The virus buds off from the host cell membrane, with neuraminidase (N) aiding its release. The new virus particles are now ready to infect other cells. 4. Genomic Segmentation: ○ Each of the 8 RNA segments codes for essential components: Hemagglutinin, Neuraminidase, RdRp subunits, matrix proteins, and nuclear export proteins. ○ Segmentation allows reassortment when multiple strains infect a host (e.g., avian + human flu mixing in pigs). SARS-CoV-2 (COVID-19) Type: Positive-sense single-stranded RNA virus (+RNA). Zoonotic: Jumps from animals (e.g., bats, civets, pangolins) to humans. COVID-19 Replication Cycle 1. Entry: ○ Virus binds to host receptors and enters the cell. ○ Releases its RNA genome into the cytoplasm. 2. Protein Production: ○ Host ribosomes translate the +RNA to make proteins, including: RNA-dependent RNA polymerase (RdRp): Needed for copying the genome. Structural proteins (e.g., spike, nucleocapsid).  3. Genome Replication: ○ RdRp makes a negative-sense RNA (-RNA) copy. ○ -RNA is used to create new +RNA genomes. 4. Virus Assembly: ○ Proteins and +RNA are assembled into new virus particles. ○ Virus exits the cell via exocytosis. Immune Response Triggers a cytokine storm (overactive immune system), causing: ○ Fever, aches, inflammation, and severe symptoms. Severe cases lead to organ damage and death. Comparison to Flu COVID-19: ○ Single-stranded +RNA genome. ○ Makes RdRp after infection. Flu: ○ Segmented -RNA genome. ○ Brings RdRp with it. 11/25/2024 HIV (Retrovirus) HIV Basics Type: Retrovirus, single-stranded RNA genome (positive-sense). Unique Feature: Uses reverse transcriptase to convert its RNA genome into DNA. Target Cells: T-helper cells (CD4 lymphocytes), critical for acquired (specific) immunity. HIV Structure 1. Capsid: Contains viral RNA and enzymes like reverse transcriptase and proteases. 2. Envelope: Derived from host cell membrane. 3. Spikes (Surface Glycoproteins): ○ Essential for binding to host cell receptors. ○ Dock specifically onto CD4 receptors on T-helper cells. ○ T Cells: help acquire immunity and when these t-cells decline, it becomes AIDS disease. Life Cycle of HIV 1. Attachment and Entry: ○ Spikes on HIV bind to CD4 receptors on T-helper cells. (T-lymphocytes) ○ The virus fuses with the host cell membrane, releasing the capsid into the cytoplasm.  2. Reverse Transcription: ○ Reverse transcriptase converts the viral RNA into double-stranded DNA. ○ The process is error-prone, leading to frequent mutations. 3. Integration: ○ Viral DNA integrates into the host genome as a provirus. ○ Provirus remains dormant, hidden from the immune system, for years. 4. Activation: ○ Host RNA polymerase transcribes viral DNA into RNA: Acts as the genome for new viruses. Serves as mRNA for protein production. 5. Translation and Assembly: ○ The viral RNA is sent out of the nucleus into the cytoplasm. ○ Ribosomes in the cytoplasm use this RNA to make viral proteins. ○ Some proteins, like the spikes, are processed in the ER and Golgi apparatus because they need to be exported to the cell's surface. 6. Release: ○ Virions bud off from the host cell, taking a portion of the host membrane as their envelope. ○ Newly formed HIV particles can immediately infect other T-helper cells. Disease Mechanisms Destruction of T-helper Cells: ○ Leads to reduced immune communication. ○ Patients lose the ability to mount effective immune responses against infections. Progression to AIDS: ○ Advanced stage marked by critically low T-helper cell counts. ○ Patients are highly susceptible to opportunistic infections (e.g., tuberculosis, pneumonia) and cancers. Epidemiology Transmission: ○ Bloodborne, sexually transmitted, vertical transmission (mother to child). ○ Early epidemics saw transmission through blood transfusions and needle sharing. Global Patterns: ○ High HIV prevalence in sub-Saharan Africa and Russia (regions with poor healthcare systems.) ○ Strong correlation with tuberculosis prevalence in co-infected populations. Timeline of Infection 1. Acute Phase: ○ Flu-like symptoms within weeks of exposure. ○ High viral load and detectable antigen levels.  2. Latency: ○ Viral load decreases; antibodies rise and remain detectable. ○ Virus remains dormant as a provirus, often undetectable in the bloodstream. 3. Activation: ○ Environmental or immune stress triggers viral replication. ○ T-cell count declines sharply, antigen count goes up and symptoms of AIDS appear. Part 2: Microbial Interactions in the Environment Symbiotic Relationships 1. Lichens: ○ Definition: Symbiosis between a fungus (heterotroph) and algae or cyanobacteria (autotroph). ○ Roles: Algae: Photosynthesize, providing organic carbon (sugars). Fungi: Extract minerals from substrates and offer structural protection. ○ Environmental Impact: Break down rocks and contribute to soil formation. Visible as green or orange crusts on trees, rocks, and tombstones. 2. Ruminants and Gut Microbes: ○ Ruminants: Herbivores with multi-chambered stomachs (e.g., cows, deer, goats). ○ Microbial Roles: Bacteria, archaea, and protozoa digest cellulose anaerobically. Byproducts include fatty acids, which the host uses for energy. Bacteria: They digest cellulose Archaea: These specialize in methanogenesis (producing methane gas). ○ Human Relevance: Enables efficient conversion of plant biomass into high-protein meat and milk. Supports agricultural industries. 3. Hydrothermal Vents: ○ Location: Deep-sea volcanic regions (e.g., Mid-Atlantic Ridge). ○ Chemolithoautotrophs: Use hydrogen sulfide (H₂S) as an energy source. Fix CO₂ into organic carbon, supporting diverse ecosystems. ○ Symbiosis: Tube worms house chemosynthetic bacteria as endosymbionts.Taking CO2 into an organic compound (chemolithoautotrophs). And these microbes live in worms. Worms benefit from bacterial metabolism by feeding on it, creating a unique food web. ○ Significance: Demonstrates microbial adaptability in extreme environments. Note: There’s a lot of oxygen down in the sea but not alot of organisms live there. Part 3: Nitrogen Fixation – Rhizobia Overview Organism: Gram-negative proteobacteria. Host Plants: Legumes (e.g., soybeans, peanuts, peas, alfalfa). Process: ○ Rhizobia is a proteobacteria and is highly aerobic due to its enzymatic activity which convert atmospheric nitrogen (N₂) into ammonia (NH₃) organic nitrogen, which is incorporated into amino acids. Symbiotic Mechanism 1. Root Nodules: ○ Plants form nodules to house rhizobia colonies. ○ Nodules protect bacteria and facilitate nitrogen fixation. 2. Mutual Benefits: ○ Plants: Receive organic nitrogen for protein synthesis. ○ Bacteria: Obtain sugars from the plant for energy. Use oxygen-bound leghemoglobin to respire. 3. Ecological Impact: ○ Enhances soil fertility and reduces the need for synthetic fertilizers. ○ Supports protein-rich crops, benefiting both human and animal diets. 4. Modern Relevance: ○ The Haber-Bosch process mimics bacterial nitrogen fixation, enabling large-scale fertilizer production. ○ Revolutionized agriculture, supporting the global food supply. 12/02/2024 Rhizobia and Nitrogen Fixation Metabolic Process: Nitrogenase Enzyme: ○ Rhizobia are bacteria and break strong triple bonds of N₂ gas. ○ Converts atmospheric nitrogen into organic nitrogen using energy from plants. ○ Requires significant energy and oxygen to function. Energy Source: Plant supplies organic carbon (sugars) through photosynthesis. Ecological Importance: Rhizobia-legume relationship enriches soil with nitrogen, reducing synthetic fertilizer use.  Supports growth of protein-rich crops. Mycorrhizae and Plant-Fungi Interactions Organism: Fungi (eukaryotic microbes). Live in direct association with plant roots Classification: Eukaryotes; genetically closer to humans than bacteria. Symbiotic Relationship: 1. Plant Benefit: ○ Mycorrhizae is a plant fungi which extends root surface area, improving nutrient and water absorption. ○ Capture nitrogen, phosphorus, and water from the soil. 2. Fungi Benefit (Heterotroph): ○ Receive sugars (organic carbon) from plant photosynthesis. Comparison of Mycorrhizae to Rhizobia: Similarities: ○ Both form mutualistic relationships with plants. ○ Both exchange nutrients for organic carbon. Differences: ○ Rhizobia are bacteria (prokaryotes); mycorrhizae are fungi (eukaryotes). ○ Rhizobia fix nitrogen; mycorrhizae primarily transport nutrients. ○ Rhizobia makes a metabolic conversion for nitrogen while mycorrhizae makes enzymes Eutrophication Definition: Excessive nutrient input (e.g., nitrogen, phosphorus) causes overgrowth of microorganisms. Causes: ○ Fertilizer runoff from agriculture. ○ Nutrient pollution from urban or industrial sources. Examples: ○ Algal blooms in the Great Lakes and Jersey Shore and affects the potable water. ○ Water contamination in Michigan. Consequences: ○ Oxygen depletion (hypoxia). Makes shellfish highly toxic ○ Toxin production, affecting water safety and ecosystems. Carbon Cycle 1. Phytoplankton (Photosynthetic Microbes) in Oceans:  ○ Photosynthetic microbes fix CO₂ into organic carbon. ○ Form the base of the marine food web (e.g., feed zooplankton, fish). 2. Biological Carbon Pump: ○ Phytoplankton capture carbon and store it in biomass. ○ When they die, some carbon sinks to ocean floors, storing it long-term. 3. Respiration and Methane Production: ○ Aerobic Respiration: Microbes convert organic carbon back to CO₂. ○ Anaerobic Environments: Methanogens (Archaea) produce methane (CH₄) instead of CO₂. 4. Primary Reservoir of Carbon ○ In the crust/soil below the ocean in the form of fossil fuels Nitrogen Cycle 1. Nitrogen Fixation: ○ Process: N₂ gas → Organic nitrogen (e.g., amino acids). ○ Key Organisms: Rhizobia, other prokaryotes. 2. Nitrification: ○ Process: Ammonium (NH₄⁺) → Nitrite (NO₂⁻) → Nitrate (NO₃⁻). ○ Key Organisms: Chemolithotrophic bacteria. 3. Denitrification: ○ Process: Nitrate (NO₃⁻) → N₂ gas (back to atmosphere). ○ Key Organisms: Anaerobic bacteria. 4. Primary Reservoir ○ In the atmosphere in the form of N2 gas (*important for making amino acids*) 5. Microbe Utilization ○ Microbes utilize nitrate throughout redox states, energetic in most states ○ Nitrate can be a terminal electron acceptor when oxygen is not available. Synthetic Fertilizer Impact: Increased agricultural production through artificial nitrogen fixation. Excess fertilizer runoff disrupts nitrogen cycle, causing eutrophication. Archaea - Produce Methane which itself is responsible for a main source of greenhouse gasses. ○ Methane Can also come from livestock such as sheep and cows ○ Archaea is famous for making methane ( anaerobic) 2. Rice Paddies: ○ Flooded fields create anaerobic environments. ○ Methanogens break down organic matter on roots, producing methane.  ○ Due to the flooding and being in an anaerobic environment the byproduct methane is not able to be consumed by microorganisms 3. Livestock (Cows, Sheep): ○ Anaerobic gut microbes (methanogens) release methane as a byproduct. 4. Climate Impact: ○ Methane is a potent greenhouse gas, more impactful than CO₂ https://www.youtube.com/watch?v=GQUCCkHNjN8 https://www.youtube.com/watch?v=N88Dzu5k8Pc https://www.youtube.com/watch?v=N0Gv96uDctM https://www.youtube.com/watch?v=siDmvDCjlo4 (rlly good) https://www.youtube.com/watch?v=7IXqQOagnUY (rlly good) Questions on EXAM 3: 1- Facts based on what cholistridium (firmicutes) do? 2- Rhizobia: -helps fix N2 into organic N2, its proteobacteria (hard facts) 3- Flu Covid Same Both ssRNA, Horizontal Both ssRNA, Horizontal airborne transmission, PH airborne transmission, PH change, Cytokine storm, change, Cytokine storm, zoonotic disease? zoonotic disease? Different Cell entry diff Cell entry diff  RNA (-) sense RNA (+) sense RNA dep Rna Make RNA dep Rna polymerase polymerase prepacked 4- Endotoxin and exotoxin: generated by bacterial pathogens not a virus Separated by Gram + or - 5- Autotrophs C fixation Co2 CH2O Heterotrophs 6- Anaerobes (archaea) makes methane. Gut of a cow also produces methane and other gases like sulfide