Introduction to Medical Microbiology
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Questions and Answers

What term is used to describe a disease that is consistently present in a specific region?

  • Epidemic
  • Pandemic
  • Hyperendemic
  • Endemic (correct)

    • Which type of microorganisms is classified as prokaryotes?

  • Bacteria (correct)
  • Eukarya
  • Fungi
  • Viruses

    • What is dysbiosis characterized by?

  • A balanced microbiome
  • An increase in beneficial microbes
  • Complete absence of microbes
  • An imbalance in microbiota (correct)

    • Which of the following is NOT one of the four main types of microorganisms in Medical Microbiology?

    <p>Viruses</p> Signup and view all the answers

    Which nutrient do microorganisms primarily provide to the host?

    <p>Metabolic functions</p> Signup and view all the answers

    What is the largest known group of microbial organisms on Earth?

    <p>Bacteria</p> Signup and view all the answers

    What is the primary role of the human microbiome in relation to immune responses?

    <p>It stimulates innate and regulatory immunity.</p> Signup and view all the answers

    Which of the following diseases is attributed to bacteria?

    <p>Syphilis</p> Signup and view all the answers

    Who is known as the Father of Microbiology for his early observations of microorganisms?

    <p>Anton Van Leeuwenhoek</p> Signup and view all the answers

    Which scientist is credited with the development of the concept of vaccination?

    <p>Edward Jenner</p> Signup and view all the answers

    What is the defining characteristic of a virus that categorizes it as an enveloped virus?

    <p>Presence of a lipid membrane</p> Signup and view all the answers

    What was Robert Koch's significant contribution to microbiology?

    <p>Establishment of the germ theory</p> Signup and view all the answers

    Which process was pioneered by Louis Pasteur that is crucial for food safety?

    <p>Pasteurization</p> Signup and view all the answers

    Which of the following is NOT a basis for classifying viruses?

    <p>Type of nucleus in host organism</p> Signup and view all the answers

    What is the complex of nucleic acid and protein in a virus called?

    <p>Nucleocapsid</p> Signup and view all the answers

    What major advancement in microbiology occurred between 1931 and 1938?

    <p>Development of the electron microscope</p> Signup and view all the answers

    Which substance was first discovered by Alexander Fleming and is known for its antibacterial properties?

    <p>Penicillin</p> Signup and view all the answers

    In the three-domain taxonomic system, which of the following is NOT a domain?

    <p>Fungi</p> Signup and view all the answers

    What percentage of similar rRNA is shared among organisms within a species?

    <p>97%</p> Signup and view all the answers

    What is one significant role of microbes in the ecosystem?

    <p>Photosynthesis and oxygen production</p> Signup and view all the answers

    What is the primary concern of taxonomy?

    <p>Classification and nomenclature</p> Signup and view all the answers

    What did Ignaz Semmelweis implement in the medical field to reduce maternal mortality rates?

    <p>Mandatory hand washing and instrument disinfection</p> Signup and view all the answers

    How are the domains of life organized below the domain level?

    <p>By phyla, classes, orders, families, genera, and species</p> Signup and view all the answers

    What unique reproductive characteristic defines a species in sexually reproducing organisms?

    <p>Reproductive compatibility</p> Signup and view all the answers

    What is the shape of bacteria classified as Coccus?

    <p>Round shape</p> Signup and view all the answers

    Which component is primarily responsible for the structural integrity of Gram-negative bacteria?

    <p>Lipopolysaccharides</p> Signup and view all the answers

    What distinguishes Gram-positive from Gram-negative bacteria regarding their cell wall composition?

    <p>Thicker peptidoglycan layer in Gram-positive</p> Signup and view all the answers

    What role do pili play in the pathogenicity of bacteria?

    <p>They help in the attachment to host cells.</p> Signup and view all the answers

    Which of the following structures is NOT considered an extracellular component of bacteria?

    <p>Ribosome</p> Signup and view all the answers

    What type of bacteria is characterized by a thin peptidoglycan layer and an outer membrane?

    <p>Gram-negative bacteria</p> Signup and view all the answers

    What is the function of flagella in bacteria?

    <p>Enable movement towards chemicals</p> Signup and view all the answers

    Which of the following statements about bacterial metabolism is true?

    <p>Bacterial metabolism can vary widely among species.</p> Signup and view all the answers

    What are teichoic acids primarily involved in within Gram-positive bacteria?

    <p>Uptake of Mg2+</p> Signup and view all the answers

    What role does a capsule play in bacterial virulence?

    <p>It protects against the host immune system</p> Signup and view all the answers

    Which of the following correctly defines metabolism in bacteria?

    <p>The sum of biochemical reactions for energy generation and material synthesis</p> Signup and view all the answers

    What are the two main components of bacterial metabolism?

    <p>Biosynthesis and degradation</p> Signup and view all the answers

    What distinguishes Gram-negative bacteria in terms of nutrient uptake?

    <p>They can uptake larger molecules after digestion in the periplasmic space</p> Signup and view all the answers

    Which respiratory mechanism is utilized by bacteria when oxygen is not present?

    <p>Anaerobic respiration</p> Signup and view all the answers

    What determines the nutritional classification of bacteria?

    <p>Source of energy and carbon</p> Signup and view all the answers

    What is likely a function of teichuronic acids in some Gram-negative bacteria?

    <p>Similar polymer function to teichoic acids</p> Signup and view all the answers

    What is the primary distinguishing characteristic of a strain within a species?

    <p>Contains unique distinguishing features</p> Signup and view all the answers

    Which of the following correctly describes the structure of a scientific name?

    <p>Genus name capitalized, species name lowercased and italicized</p> Signup and view all the answers

    What resource provides identification schemes for bacteria and archaea based on phenotypic and biochemical characteristics?

    <p>Bergey's Manual of Determinative Bacteriology</p> Signup and view all the answers

    In naming fungi, which of the following sources is specifically mentioned?

    <p>Mycobank</p> Signup and view all the answers

    Which of the following statements is true regarding the classification of bacteria?

    <p>Bacteria are unicellular and lack a nucleus.</p> Signup and view all the answers

    Which type of bacterial morphology is characterized by an elongated, rod shape?

    <p>Bacilli</p> Signup and view all the answers

    What is the key component of the bacterial cell wall primarily responsible for its structural integrity?

    <p>Peptidoglycan</p> Signup and view all the answers

    Which structure enhances the pathogenicity of bacteria by aiding in attachment and evasion of the immune system?

    <p>Pili</p> Signup and view all the answers

    Which statement is true regarding Gram-positive bacteria in comparison to Gram-negative bacteria?

    <p>They contain a thicker peptidoglycan layer.</p> Signup and view all the answers

    What role does lipopolysaccharide (LPS) play in Gram-negative bacteria?

    <p>It provides structural integrity.</p> Signup and view all the answers

    Which feature distinguishes spirochetes from other bacterial shapes?

    <p>They have a spiral structure.</p> Signup and view all the answers

    What is the primary function of flagella in bacteria?

    <p>Movement and chemotaxis</p> Signup and view all the answers

    Which statement accurately describes the cellular structures found in bacteria?

    <p>Bacteria can have both intracellular and extracellular structures.</p> Signup and view all the answers

    What distinguishes protozoa from helminths in terms of reproduction in humans?

    <p>Protozoa can multiply in humans while helminths cannot.</p> Signup and view all the answers

    Which statement correctly describes the nature of viruses?

    <p>Viruses are obligate intracellular parasites that require living cells for replication.</p> Signup and view all the answers

    What is the primary living environment for fungi?

    <p>Worldwide, including soil, plants, trees, and human skin.</p> Signup and view all the answers

    Which characteristic defines ectoparasites?

    <p>They attach to the skin of the host and may remain for extended periods.</p> Signup and view all the answers

    What is a common feature of mild fungal skin diseases?

    <p>They often resemble a rash and are quite prevalent.</p> Signup and view all the answers

    What is one hypothesis regarding the origin of modern viruses?

    <p>Viruses originated from pieces of nucleic acid that became active.</p> Signup and view all the answers

    Why are helminths visible to the naked eye, unlike protozoa?

    <p>Helminths are larger multicellular organisms.</p> Signup and view all the answers

    What is a key factor in the pathogenicity of microorganisms like protozoa?

    <p>Their capability to multiply within the host.</p> Signup and view all the answers

    What type of viruses is characterized by the presence of a lipid envelope?

    <p>Enveloped viruses</p> Signup and view all the answers

    Which of the following factors does NOT influence virus classification?

    <p>Presence of antibiotic resistance</p> Signup and view all the answers

    In taxonomy, which classification level comes directly after phylum?

    <p>Class</p> Signup and view all the answers

    What is the basic unit of taxonomy that represents a specific type of organism?

    <p>Species</p> Signup and view all the answers

    What percentage of similar rRNA do organisms within a species typically share?

    <p>97%</p> Signup and view all the answers

    Which classification system was developed by Dr. Carl Woese in 1990?

    <p>Three-domain system</p> Signup and view all the answers

    Which characteristic is NOT a criterion for classifying microbial species?

    <p>Size and shape</p> Signup and view all the answers

    Which of the following components combines with nucleic acids to form the virus nucleocapsid?

    <p>Capsomers</p> Signup and view all the answers

    What best describes an epidemic?

    <p>An unexpected increase in the number of disease cases in a specific region.</p> Signup and view all the answers

    Which statement accurately represents the role of the human microbiome?

    <p>It assists in metabolic functions and stimulates immune responses.</p> Signup and view all the answers

    What characterizes a dysbiosis in the human microbiome?

    <p>An imbalance leading to potential chronic inflammation.</p> Signup and view all the answers

    Which category of microorganisms includes prokaryotes?

    <p>Bacteria</p> Signup and view all the answers

    What is a primary characteristic of fungi?

    <p>They are the second most common category after insects.</p> Signup and view all the answers

    What is the significance of 16S rRNA sequencing in microbiology?

    <p>It helps classify microorganisms into domains and further taxonomic levels.</p> Signup and view all the answers

    What is the implication of a core microbiome shared among humans?

    <p>95% of the microbiome at specific sites is shared across individuals.</p> Signup and view all the answers

    What is true regarding the characteristics of bacteria?

    <p>They generally possess a circular molecule of DNA.</p> Signup and view all the answers

    Study Notes

    Introduction to Medical Microbiology

    • The study of microorganisms, particularly those that cause diseases in humans and animals.
    • Microbes are essential for life on Earth, playing crucial roles in nutrient cycling, food production, and medicine.
    • Microorganisms are responsible for many diseases in humans and animals.
    • Links between microorganisms and disease were established through germ theory.

    History of Microbiology

    • 1590: Hans and Zacharias Jansen, Hans Lippershey invented the microscope, revolutionizing the study of microorganisms.
    • 1665: Robert Hooke discovered cells using the microscope.
    • 1677: Anton van Leeuwenhoek, known as the "Father of Microbiology," observed microorganisms like bacteria, protozoa, and blood cells.
    • 1796: Edward Jenner coined the term "vaccine" and developed the first vaccination against smallpox.
    • 1846: Ignaz Semmelweis implemented hand washing and chlorine disinfection of instruments in hospitals, significantly reducing maternal mortality.
    • 1864: Louis Pasteur developed pasteurization, a method of heating liquids to kill harmful microorganisms.
    • 1867: Sir Joseph Lister applied Pasteur's principles to surgery, introducing the use of phenol (carbolic acid) for sterilizing instruments and cleaning wounds.
    • 1876: Robert Koch established the four postulates to identify the causative agent of an infectious disease. He also studied Bacillus anthracis and its role in anthrax.
    • 1892: Dimitri Ivanoski laid the foundation of virology by studying tobacco mosaic disease.
    • 1910: Paul Ehrlich, known as the "Father of Antimicrobial Therapy," introduced the concept of chemotherapy and developed Salvarsan, an arsenic derivative for treating syphilis.
    • 1928: Alexander Fleming discovered penicillin, the first antibiotic, produced by the Penicillium notatum fungus.
    • 1931-1938: Max Knoll and Ernst Ruska developed the electron microscope, allowing for greater magnification and detail in visualizing microorganisms.

    Importance of Microbiology

    • Microbes appeared around 3.5 billion years ago and contribute significantly to Earth's oxygen production through photosynthesis.
    • Microorganisms play a vital role in decomposition and nutrient recycling.
    • Microbes are used in industries like food production and medicine for synthesizing pharmaceuticals and vaccines.
    • They are also used in bioremediation for cleaning contaminated water.

    Epidemics, Pandemics, and Endemics

    • Epidemics: Characterized by a sudden increase in disease cases within a specific region.
    • Pandemics: Occur when a disease spreads globally. (Example: COVID-19)
    • Endemics: Diseases that are consistently present in a particular region. (Example: Malaria)

    Healthy Microbiome

    • The human fetus lives in a sterile environment, but infants are exposed to bacteria, archaea, fungi, and viruses from their mother and the environment.
    • Microbes establish communities on the body's surfaces, including the skin, nose, mouth, intestines, and genitourinary tract.
    • These microbial communities are collectively known as the microbiome or normal flora.
    • The most personal microbiome is found in the intestines and mouth.
    • The host provides a place to colonize, nutrients, and immune protection, while microbes provide essential metabolic functions and stimulate the immune system.
    • An imbalance in the microbiota, known as dysbiosis, can lead to chronic inflammation and potentially cancer.

    The Microbial World: Woese's Three Domains

    • Carl Woese introduced a three-domain system of classification based on 16S rRNA sequences:
      • Archaea: A domain of single-celled organisms that are prokaryotic, meaning they lack a nucleus. They are often found in extreme environments.
      • Bacteria: A domain of single-celled organisms that are prokaryotic. They are diverse and found in various environments.
      • Eukarya: A domain of single-celled and multicellular organisms that have a nucleus. They include fungi, protists, plants, and animals.

    The Four Main Types of Microorganisms in Medical Microbiology

    • Bacteria:
      • Prokaryotic organisms with a single chromosome, often circular, and sometimes with additional DNA in plasmids.
      • Typically less than 2 micrometers in diameter.
      • Responsible for numerous human and animal infections (such as syphilis, pharyngitis, endocarditis, and anthrax).
    • Fungi:
      • Eukaryotic organisms that include yeasts, molds, and mushrooms.
      • Known for their ability to decompose organic matter, and some are utilized in food production and medicine.
      • Can cause various infections, particularly in those with weakened immune systems.
    • Archaea:
      • Prokaryotic organisms often found in extreme environments such as hot springs, acidic environments, and saline lakes.
      • While some archaea are human pathogens, most are not.
    • Eukarya:
      • Eukaryotic organisms with a nucleus, and include fungi, protists, plants, and animals.
      • Some protists can cause diseases in humans, but the vast majority are not pathogens.

    Virus

    • Not alive
    • DNA or RnA, not both
    • Enveloped (prot+lipidic coat) or not
    • Structure: nucleocapsid (nucleic acid + capsid)
    • Enclosed in a membrane: enveloped virus
    • No envelope: naked virus

    Taxonomy

    • Taxonomy organizes, classifies, and names living organisms.
    • The three-domain system (Archaea, Bacteria, and Eukarya) is commonly used in modern biological taxonomy.
    • Classification within each domain:
      • Phylum
      • Class
      • Order
      • Family
      • Genus
      • Species

    Species

    • The fundamental unit of taxonomy representing a specific type of organism.
    • Traditionally defined by reproductive compatibility, which is not always applicable to microbes.
    • Categorized based on morphology, structure, and metabolism.

    Bacterial Morphology

    • Coccus: Round shaped

    • Bacilli: Elongated, rod shaped

    • Other shapes:

      • Vibrio: Comma shaped.
      • Spirillum: Spiral shaped, not common pathogens in humans.
      • Spirochetes: Spiral shaped, cause diseases like syphilis (Treponema pallidum).

    • Bacteria vary in size from 0.1 to 50 micrometers.

    Bacterial Structure

    • Intracellular Structures:
      • Bacterial chromosome: The single molecule of DNA that contains the bacterial genetic information.
      • Plasmids: Extrachromosomal DNA molecules that can provide bacteria with additional genes.
      • Ribosomes: Ribonucleoprotein complexes responsible for protein synthesis.
      • Cell membrane: A selectively permeable membrane that surrounds the cytoplasm.
    • Extracellular Structures:
      • Flagella: Long, helical filaments made of flagellin that aid in bacterial movement (chemotaxis).
      • Pili (Fimbriae): Short, rigid hair-like appendages that help bacteria attach to surfaces, evade phagocytosis, and avoid immune recognition.
      • Cell Wall: A rigid outer layer that provides structural support and protection.
      • Capsule: A layer of polysaccharides external to the cell wall that can protect bacteria from host defenses.

    Gram Pattern

    • Christian Gram developed a staining method to differentiate bacteria based on their cell wall properties.

    Gram-Positive and Gram-Negative Structure

    • Gram-positive bacteria: Have a thick peptidoglycan layer, external to the cell membrane.
    • Gram-negative bacteria: Have a thin peptidoglycan layer overlaid by an outer membrane containing lipopolysaccharide (LPS) and lipoprotein.
    • Periplasm: The space between the inner and outer membranes of Gram-negative bacteria.
    • Teichoic Acids: Polymers found in the cell walls of Gram-positive bacteria that likely play a role in Mg2+ uptake.
    • Teichuronic Acids: Similar polymers found in the capsules or LPS of some Gram-negative bacteria.

    Lipopolysaccharide (LPS)

    • Commonly known as endotoxin.
    • Essential for the structural integrity and viability of Gram-negative bacteria.
    • Induces a strong immune response in the host, and is involved in surface adhesion.

    Capsule

    • A layer of polysaccharides external to the cell wall that can increase bacterial virulence by protecting them from the host immune system.

    Bacterial Nutrition and Metabolism

    • Nutrition: Process of acquiring nutrients from the environment for cellular activities.
    • Bacteria take up small molecules such as amino acids, oligosaccharides, and peptides across the cell wall.
    • The cell membrane uses facilitated diffusion or active transport to move nutrients into the cytoplasm.
    • Gram-negative bacteria can also take up larger molecules after preliminary digestion in the periplasmic space.
    • Metabolism: The sum of biochemical reactions required to generate energy and use that energy for cell growth and biosynthesis.
      • Anabolism (Biosynthesis): Building complex molecules from simple ones, requiring energy (ATP).
      • Catabolism (Degradation): Breaking down complex molecules into simpler ones, releasing energy (ATP).
    • Metabolic Diversity:
      • Classification into nutritional groups based on:
        • Source of energy
        • Source of carbon
    • Metabolic Mechanisms:
      • Aerobic Respiration: Uses oxygen to generate ATP.
      • Anaerobic Respiration: Uses other electron acceptors (like nitrate) to generate ATP.
      • Fermentation: Obtains energy from the breakdown of organic molecules without using oxygen.

    Epidemics, Pandemics, Endemics

    • Epidemics: Surge in disease cases within a specific region.
    • Pandemics: Widespread outbreak, affecting a large geographical area (e.g., COVID-19).
    • Endemics: Diseases consistently present in a particular region (e.g., Malaria).

    Microbiome

    • Human fetus lives in a sterile environment.
    • Infants are exposed to bacteria, archaea, fungi, and viruses from their mothers and environment.
    • Microbiota (normal flora) forms on surfaces like skin, nose, and intestines.
    • Humans share a core microbiome (95%) at specific sites.
    • The most personal microbiome is found in the intestines and mouth.
    • Microorganisms influence all aspects of human life, considered "the last organ."
    • Hosts provide a place for colonization, nutrients, and protection from unwanted species.
    • Microbes:
      • Provide necessary metabolic functions.
      • Stimulate immune responses.
      • Prevent colonization by harmful pathogens.
    • Dysbiosis (imbalance in microbiota) leads to chronic inflammation and potential cancer.

    Microbial World

    • Woese's three domains: includes Archaea, Bacteria, and Eukarya.
    • Microbiological classification:
      • Kingdom
      • Phylum
      • Class
      • Order
      • Family
      • Genus
      • Species
    • Four main types of microorganisms in medical microbiology:
      • Bacteria
      • Fungi
      • Archaea
      • Eukarya

    Bacteria

    • Prokaryotes (lacking a nucleus).
    • DNA is usually a single, circular molecule (bacterial chromosome).
    • May have extra-chromosomal DNA (plasmids).
    • Smaller than eukaryotic cells, typically less than 2 micrometers in diameter.
    • Responsible for numerous human and animal infections (e.g., syphilis, pharyngitis, endocarditis).

    Fungi

    • Eukaryotes.
    • Approximately 1.5 million species, but only about 300 cause human diseases.
    • Found in soil, plants, and on various surfaces, including human skin.
    • Mild fungal skin diseases are common.
    • Lung infections can be similar to illnesses like the flu or tuberculosis.

    Parasites

    • Organisms that live on or in a host and obtain nourishment from it.
    • Three main classes:
      • Protozoa: Microscopic, single-celled organisms that can multiply in humans, leading to serious infections.
      • Helminths: Large, multicellular organisms visible to the naked eye in their adult stage. They cannot multiply in humans.
      • Ectoparasites: Ticks, fleas, lice, and mites that attach or burrow into the skin.

    Viruses

    • Genetic elements that can replicate only inside living cells.
    • Submicroscopic, composed of a single nucleic acid (DNA or RNA) surrounded by a protein coat (capsid).
    • Obligate intracellular parasites.
    • Viruses exist in an extracellular state as virions, which are metabolically inert.
    • Origin is unclear, with two hypotheses:
      • Fugitive pieces of nucleic acid from larger organisms.
      • Former external organisms that evolved a parasitic lifestyle.
    • DNA or RNA viruses, but not both.
    • Enveloped viruses: Contain a lipidic coat in addition to the protein coat.
    • Naked viruses: Lack a lipidic coat.

    Taxonomic Classification

    • System for organizing, classifying, and naming living organisms.
    • Focuses on classification and nomenclature.
    • Modern system uses the three-domain system (Archaea, Bacteria, Eukarya).

    Domain: Bacteria

    • Further classified into phyla, classes, orders, families, genera, and species.

    Species

    • The basic unit of taxonomy, representing a specific type of organism.
    • For sexually reproducing organisms, reproductive compatibility defines a species.
    • Organisms within a genus share 93% similar rRNA.
    • Organisms within a species share 97% similar rRNA.
    • This definition doesn't apply to most microbial species (including bacteria) due to their asexual reproduction.

    Species in Non-Sexually Dividing Organisms

    • Population of cells with similar characteristics.
      • Clone: Genetically identical cells derived from a single cell.
      • Strain: Subgroup within a species with distinguishing characteristics.

    Binomial System of Nomenclature

    • Scientific or systematic name:
      • Genus name + species name
      • Italicized or underlined
      • Genus name is capitalized and can be abbreviated.
      • Species name is never abbreviated.
      • Genus name can be used alone, but species name cannot.

    Examples

    Scientific Binomial Genus Name Species Name
    Klebsiella pneumoniae Honors Edwin Klebs The disease
    Francisella tularensis Honors Edward Francis Tulare (California)
    Streptococcus pyogenes Chains of cells (strepto-) Forms pus (pyo-)
    Trypanosoma cruzi Corkscrew-like (trypano-) soma (-body) Honors Oswaldo Cruz

    Naming Bacteria

    • Bergey's Manual of Determinative Bacteriology (phenotypic/biochemical): Provides identification schemes for bacteria and archaea.
    • Bergey's Manual of Systematic Bacteriology (genetic): Provides phylogenetic information on bacteria and archaea.
    • Approved Lists of Bacterial Names: Lists known prokaryotes.

    Naming Fungi, Parasites, and Viruses

    • Fungi:
      • Mycobank
      • Index Fungorum
    • Parasites:
      • CDC (Centers for Disease Control and Prevention)
    • Viruses:
      • International Committee on Taxonomy of Viruses (ICTV)

    Bacterial Classification

    • Single-celled microbes with simpler cell structure than other organisms.
    • Classification based on:
      • Morphology
      • Structure
      • Metabolism

    Bacterial Morphology

    • Coccus: Round shape
    • Bacillus: Elongated, rod shape
    • Other shapes:
      • Vibrio
      • Spirillum
      • Spirochetes (e.g., Treponema pallidum - Syphilis)

    Summary

    • Bacterial shape (morphology).
    • Size ranges from 0.1 to 50 micrometers.

    Bacterial Structure

    • Intracellular structures:
      • Bacterial chromosome
      • Plasmids (not always present)
      • Ribosomes (70S): Two subunits, 30S and 50S
      • Cell membrane (lacks cholesterol)
    • Extracellular structures:
      • Flagella
      • Pili (Fimbriae)
      • Cell wall
      • Capsule (not always present)

    Flagella

    • Long helical filaments extending from the cell surface, composed primarily of flagellin.
    • Involved in chemotaxis (movement toward or away from stimuli).

    Pili (Fimbriae)

    • Short, rigid, and numerous.
    • Involved in:
      • Attachment to other bacteria or host cells.
      • Evasion of phagocytosis and immune recognition.

    Cell Wall

    • Main structural component is peptidoglycan (murein).
    • Composed of hexose sugars and amino acids.

    Gram Pattern

    • Gram staining method differentiates bacteria into two major groups: Gram-positive and Gram-negative.

    Gram-Positive and Gram-Negative Structure

    • Gram-positive: Thick layer of peptidoglycan (20-80 nm). May contain other macromolecules.
    • Gram-negative: Thin layer of peptidoglycan (5-10 nm), overlaid by an outer membrane containing lipopolysaccharides and lipoprotein.
    • Periplasm: Space between the inner and outer membranes in Gram-negative bacteria. Smaller periplasmic space in Gram-positive bacteria.

    Lipopolysaccharide (LPS)

    • Conserved structure in all Gram-negative bacteria.
    • Essential for structural integrity and bacterial viability.
    • Also known as endotoxin, triggering a strong immune response in the host.

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