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Questions and Answers
Which factor primarily influences the effectiveness of nutrient transport in bacterial cells?
Which factor primarily influences the effectiveness of nutrient transport in bacterial cells?
What is a significant consequence of the horizontal gene transfer mechanisms in bacteria and Archaea?
What is a significant consequence of the horizontal gene transfer mechanisms in bacteria and Archaea?
What distinguishes a microbial strain from a species?
What distinguishes a microbial strain from a species?
Which aspect of Koch's postulates is often cited as a limitation?
Which aspect of Koch's postulates is often cited as a limitation?
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Which of the following is a role of molecular chaperones in microbial cells?
Which of the following is a role of molecular chaperones in microbial cells?
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What type of microorganism did Robert Hooke first document?
What type of microorganism did Robert Hooke first document?
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What is the primary function of gas vacuoles in bacteria?
What is the primary function of gas vacuoles in bacteria?
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Which of the following correctly describes the last universal common ancestor (LUCA)?
Which of the following correctly describes the last universal common ancestor (LUCA)?
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Which pathway is primarily responsible for CO2 fixation in many prokaryotes?
Which pathway is primarily responsible for CO2 fixation in many prokaryotes?
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What is the main role of nitrogenase in prokaryotes?
What is the main role of nitrogenase in prokaryotes?
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Which process involves the reduction of nitrate to ammonia in bacteria?
Which process involves the reduction of nitrate to ammonia in bacteria?
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Which statement is true about catabolic and anabolic pathways?
Which statement is true about catabolic and anabolic pathways?
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Which of the following is not a product of fermentation?
Which of the following is not a product of fermentation?
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What role do many chemolithotrophic bacteria play in energy production?
What role do many chemolithotrophic bacteria play in energy production?
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Why is reverse electron flow important for some autotrophs?
Why is reverse electron flow important for some autotrophs?
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Which of the following statements about gluconeogenesis is correct?
Which of the following statements about gluconeogenesis is correct?
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Which statement about macromolecule transport is correct?
Which statement about macromolecule transport is correct?
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What is one of the key functions of molecular chaperones?
What is one of the key functions of molecular chaperones?
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Which mechanism is NOT involved in horizontal gene transfer?
Which mechanism is NOT involved in horizontal gene transfer?
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What aspect of the genetic code ensures that codons are read without overlapping?
What aspect of the genetic code ensures that codons are read without overlapping?
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Which of the following best describes the role of the SOS response in bacteria?
Which of the following best describes the role of the SOS response in bacteria?
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What characterizes the polyribosome during protein synthesis?
What characterizes the polyribosome during protein synthesis?
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How do sulfonamides exert their selective toxicity against bacteria?
How do sulfonamides exert their selective toxicity against bacteria?
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Which type of RNA is primarily used as a template for protein synthesis during translation?
Which type of RNA is primarily used as a template for protein synthesis during translation?
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Which level of protein structure describes the 3D folding and spatial arrangement of polypeptides?
Which level of protein structure describes the 3D folding and spatial arrangement of polypeptides?
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In which way do mutations affect the phenotype of an organism?
In which way do mutations affect the phenotype of an organism?
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Study Notes
Evolution of Microorganisms
- Members of the microbial world are relatively simple in their structure, lacking highly differentiated cells and distinct tissues.
- Acellular infectious agents include viruses, viroids, and prions.
- Viruses consist of protein and nucleic acid, while viroids contain RNA. Prions are composed of protein.
- The last universal common ancestor (LUCA) determines the relatedness of archaea and eukarya, but not the time of divergence.
- Archaea and eukarya evolved independently of bacteria, diverging from a common ancestry.
- Bacteria and archaea increase their genetic pool through horizontal gene transfer.
- Bacteria and archaea reproduce asexually, and species are collections of strains. Strains originate from a pure microbial culture.
Discovery of Microorganisms
- Robert Hooke published drawings of the fungus Mucor in his book Micrographia in 1665.
- Antony van Leeuwenhoek was the first to accurately observe microorganisms.
Koch's Postulates
- Koch's postulates are a set of criteria to establish a link between a microorganism and a specific disease.
- The first criterion states that the microorganism must be present in every case of the disease but absent from healthy organisms.
- The second postulate involves isolating and growing the suspected microorganism in a pure culture.
- The third postulate requires that the same disease must result when the isolated microorganism is inoculated into a healthy host.
- The fourth postulate dictates isolating the same microorganism again from the diseased host.
Bacterial Cell Structure
- Bacterial arrangement is determined by the plane of division.
- The larger the surface area to volume ratio, the more easily nutrients move in the cell.
- Smaller cells have a higher surface area to volume ratio, facilitating nutrient transport.
Bacterial Cell Organization
- FtsZ, MreB, and CreS are bacterial cytoskeleton molecules with homologues in eukaryotic cells.
- FtsZ is a tubulin homologue in many bacteria, while MreB is actin homologue in many rods. CreS maintains cell shape in bacteria.
- Bacteria contain various inclusions, including gas vacuoles and magnetosomes.
- The plasma membrane is essential to all living organisms. It functions as a selectively permeable barrier, interacts with external chemicals and nutrients, and supports metabolic processes.
Bacterial Lipids
- Lipid saturation reflects environmental conditions.
- Bacterial membranes lack sterols but contain hopanoids.
- Eukaryotic membranes contain sterols.
- Nutrients enter prokaryotic cells via passive diffusion, facilitated diffusion, active transport, and group translocation.
Bacterial Cell Walls
- Cell wall functions include maintaining cell shape and protecting against environmental stresses.
- Peptidoglycans, also known as murein, are present in two types: gram-positive and gram-negative.
- Mycobacteria have mycolic acid in their cell walls and are resistant to acid-fast staining.
External Components of Bacterial Cells
- Capsules, made of polysaccharides, offer protection against phagocytosis, desiccation, and viruses.
- Slime layers aid in attachment and protection.
- Motility, including flagella, allows bacteria to move and swarm.
- Various flagellation patterns include monotrichous, lophotrichous, amphitrichous, and peritrichous.
- Different mechanisms of Bacterial motility include flagellar swarming, spirochete motility, twitching motility, and gliding motility.
- Bacterial endospores are complex, dormant structures.
Archaeal Cell Envelopes
- Archaeal cell envelopes contain S layers, capsules/slime layers, and pseudomurein.
Pathogenic Fungi
- Mycoses are fungal infections classified into superficial, cutaneous, subcutaneous, systemic, or opportunistic.
- Cryptococcosis, caused by Cryptococcus neoformans, is a systemic mycosis associated with dried pigeon droppings.
- Nosocomial candidiasis is associated with bloodstream infections.
- Malaria is caused by four Plasmodium species.
Viral Infections
- Virus size ranges from 10-400nm,. including DNA viruses, RNA virus and virusoids.
- Viral structures include nucleic acid (DNA or RNA), a protein coat (capsid), and sometimes, envelopes with spikes or peplomers, which correlates to fever.
Bacterial and Archaeal Viral Infections
- Viral infections are similar in prokaryotes and eukaryotes.
- Viral multiplications have 5 steps include attachment, entry and uncoating of genome, synthesis, assembly, and release.
- Viral infection types include virulent phage, temperate phage, lysogenic conversion
- Specific types of influenza viruses include type A and B, with subtypes determined by hemagglutinin and neuraminidase.
- Prions cause degenerative diseases in humans and animals.
Microbial Growth- Reproductive Strategies
- Eukaryotic microbes can reproduce asexually or sexually (haploid or diploid).
- Prokaryotes reproduce asexually. Reproduction strategies include binary fission, budding, and filamentous growth.
- Examples of this include ParA/ParB proteins in C. crescentus.
Microbial Growth-Measurement
- The growth rate constant, k, and generation time, g, are calculated based on population numbers at different times.
- The number of generations (n) can be determined using log-based equations.
Microbial Growth-Environmental Factors
- Extremophiles thrive in extreme environments with differing osmotic concentrations.
- Extremophiles adjust osmotic concentrations by reducing osmotic concentration through mechanosensitive channels or contractile vacuoles, or by increasing internal solute concentrations using compatible solutes.
- Extremophiles are resistant to differing salinity levels depending on their adaptations.
- Extremophiles exhibit tolerance to varying pH levels, temperature and oxygen concentrations.
Microbial Growth-Biofilms
- Most microbes attach to surfaces rather than floating freely (planktonic).
- Extracellular polymeric substance (EPS) is a critical component of biofilms.
Microbial Growth-Metabolic Strategies
- Organisms classified as chemoorganotrophs utilize organic compounds, including glucose, as both energy and carbon sources.
- Lithotrophs obtain energy from inorganic chemicals and use inorganic compounds as electron sources.
- Phototrophs use light as an energy source, and may be further classified by carbon and electron sources.
Central Metabolic Pathways
- Three core pathways - glycolysis, the Entner-Doudoroff pathway, and the pentose phosphate pathway - convert glucose to glyceraldehyde-3-phosphate (G3P).
- The citric acid cycle (Krebs cycle) utilizes G3P and yields ATP, NADH, and FADH2.
Microbial Growth-Electron Transport Chain
- NADH and FADH2 release energy through electron transport chain (ETC), a series of electron carriers.
- ETCs in prokaryotes and eukaryotes have similar functions but also differ.
- ETC's in prokaryotes can be branched, shorter, or have a lower P/O ratio.
- Common fermentation pathways are named after the major acid or alcohol produced.
Microbial Growth-Metabolic Strategies - Assimilatory Nitrate Reduction
- Assimilatory nitrate reduction is used by bacteria to reduce nitrate to ammonia in the cytoplasm.
- Nitrate reductase catalyses nitrate to nitrite reductions.
- Nitrite reductase catalyses Nitrite to ammonia reductions.
Microbial Interactions
- Microorganisms live in complex communities called consortia, which can involve both intermittent and permanent relationships.
- These communities have a positive, negative, or neutral impact.
- Microorganisms can influence each other through cooperation, commensalism, predation, parasitism, and competition.
- Microbial relationships can affect the host's behavior through the gut-brain axis.
Immune System- Innate Immunity
- The innate immune system is the first line of defense against microbes.
- It lacks memory and is nonspecific.
- It includes physical barriers (skin, mucous membranes), phagocytes, and inflammation.
Immune System- Adaptive (Specific) Immunity
- The adaptive immune system recognizes specific pathogens and has memory for future encounters.
- Two types of adaptive immunity include humoral and cellular immunity.
- Humoral immunity involves antibodies and B cells.
- Cellular immunity involves T cells, particularly cytotoxic T cells (Tc cells).
- Immunity types are characterized through antibody-mediated immunity from B cells and cell-mediated immunity from T cells. Each of these has additional subdivisions.
Host-Pathogen Interactions
- Pathogenicity is the ability of a pathogen to cause disease.
- Signs and symptoms describe the observable and subjective feelings of the infected host.
- Virulence factors, such as exoenzymes and toxins, are components of pathogens that aid in infection.
- Examples of virulence factors include hyaluronidase, coagulase, fibrinolysin, streptokinase, lipase, and collagenase.
Host-Pathogen Interactions - Exotoxins
- Exotoxins are secreted proteins, usually heat-labile.
- They are produced by bacteria, often Gram-positive.
- Exotoxins function as virulence factors capable of harming host cells. Specific types with differing functions are noted.
Host-Pathogen Interactions - Endotoxins
- Endotoxins are components of the bacterial outer membrane, typically heat-stable.
- Endotoxins function similarly to exotoxins as virulence factors for host damage
- The notable endotoxin is lipopolysaccharide (LPS).
Additional Bacterial Virulence Factors
- The bacterial secretion systems, including T3SS injectisomes are used by many Gram-negative pathogens to deliver effector proteins into host cells
- Endotoxins, heat stable components of the outer bacterial membrane are potent inflammatory mediators.
- These factors contribute to pathogenicity and disease development by altering host cell structures, functions, and processes.
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