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What is microbiology?
Microbiology is the study of living organisms of microscopic size.
Which of the following are examples of microorganisms? (Select all that apply)
Fungi can be photosynthetic.
False
Protozoa are ________ cells that usually occur singly.
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Match these microbiologists with their contributions:
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What is the most practical and dependable agent for sterilization?
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Boiling water is commonly used in the laboratory as a method of sterilization.
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What is the controlled heat treatment called for milk, cream, and certain alcoholic beverages?
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Vertical transmission of genetic information from parents to offspring is known as ________ transmission.
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Match the following terms with their descriptions:
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What is the field of biology that studies the composition and structure of biomolecules such as nucleic acids and proteins?
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Which of the following are morphological characteristics used to describe microorganisms?
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The development of the electron microscope in the 1930s enabled the visualization of viruses.
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The Glycocalyx is made up of polysaccharides, polypeptides, and is responsible for __________.
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Match the following shapes with their corresponding microorganism terminology:
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What are spores?
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Which genera produce Endospores?
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Endospores are resistant to staining and radiation.
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In binary fission, a cell duplicates its components and divides into two cells. The daughter cells become independent where a (partition) grows between them and they separate.
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Match the following temperature adaptations with the corresponding organisms:
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Study Notes
General Veterinary Microbiology
- Course Description: DVM-1204, 3(2-1) credits, taught by Dr. Syeda Fakhra Waheed
- Textbooks:
- Microbiology: An Introduction (11th Edition) by Tortora, G.J., B.R. Funke, and C.L. Case
- Clinical Veterinary Microbiology (Practical Manual) by Quinn, P.J., M.E. Carter, B.K. Markie, and G.R. Carter
- A Laboratory Manual for the Isolation and Identification of Avian Pathogens
Learning Outcomes
- Describe general characteristics of bacteria, fungi, and viruses
- Elaborate physico-chemical requirements for microbial growth
- Describe preliminary identification of microorganisms
Microbiology
- Study of living organisms of microscopic size
- Includes bacteria, fungi, algae, protozoa, helminths, and viruses
- Can be defined based on size, techniques, structure, distribution, and physiology
Microorganisms
- Bacteria:
- Distinguished by size and prokaryotic cell structure
- Most are unicellular and quite small
- Can be spherical, rod-shaped, helical, comma-shaped, or square
- Some are motile, while others are not
- Can obtain energy by processing organic compounds or light energy through photosynthesis
- Can cause a vast spectrum of diseases
- Fungi:
- Eukaryotic, non-photosynthetic, and either microscopic or macroscopic
- Include mushrooms, yeasts, and molds
- Ecologically important for decomposing dead organisms
- Some are pathogenic to animals and humans
- Protozoa:
- Small, prokaryotic cells that usually occur singly
- Originally thought to be ancient bacteria, but are distantly related to bacteria and eukaryotes
- Examples: Amoeba, Giardia, Trichomonas
- Algae:
- Eukaryotic organisms that carry out plant-like photosynthesis
- Have a nucleus and membrane-bound organelles, including chloroplasts
- Some are unicellular and microscopic, while others are multicellular and macroscopic
- Helminths:
- Worms that belong to the animal kingdom
- Most are macroscopic
- Include Platyhelminthes (flatworms) and Nemathelminthes (roundworms)
- Viruses:
- Not cells, but particles of nucleic acid (RNA or DNA) packaged in a protein coat
- In incapable of reproducing themselves and require a host cell
- Can infect animals, plants, and other microorganisms
- Extremely small, requiring an electron microscope to be seen
History of Microbiology
- Father of Microbiology: Antony Van Leeuwenhoek
- Observed bacteria using a homemade single-lens microscope
- Louis Pasteur:
- Developed vaccines against diseases like cholera, anthrax, and rabies
- Disapproved the theory of spontaneous generation of organisms and diseases
- Postulated the germ theory of disease
- Introduced the concept of liquid media and sterilization techniques
- Edward Jenner:
- Developed the first vaccine (smallpox vaccine)
- Used cowpox virus
- Joseph Lister:
- Father of antiseptic surgery
- Introduced the use of disinfectants to reduce infections
- Advocated for the use of carbolic acid
- Robert Koch:
- Father of Bacteriology
- Discovered bacteria such as anthrax bacilli, tubercle bacilli, and cholera bacilli
- Developed staining techniques and solid media for isolation
- Established the germ theory of disease
- Awarded the Nobel Prize in 1905
Branches of Microbiology
- Basic Microbiology:
- Bacteriology
- Virology
- Mycology
- Immunology
- Phycology
- Nematology
- Protozoology
- Applied Microbiology:
- Medical Microbiology
- Aquatic Microbiology
- Environmental Microbiology
- Food Microbiology
- Agricultural Microbiology
- Industrial Microbiology
- Molecular Biology
Microbes and Life Today
- Microorganisms still cause a vast spectrum of human illnesses and sufferings
- Advances in medical microbiology have made it possible to identify and control many pathogens
- Development of vaccines, antibiotics, and antiseptics has decreased mortality rates
Characteristics of Microorganisms
- Morphological characteristics:
- Size, shape, arrangement, and structure
- Chemical composition:
- Composed of bio-molecules such as nucleic acids, proteins, carbohydrates, and lipids
- Cultural characteristics:
- Growth requirements and responses to environmental factors
- Metabolic characteristics:
- Energy sources and metabolic pathways
- Antigenic characteristics:
- Surface antigens and immune responses
- Genetic characteristics:
- DNA structure and genetic code
- Pathogenicity:
- Ability to cause disease
- Ecological characteristics:
- Interactions with the environment and other organisms### Cellular Structure and Function
- Cytoplasm: an aqueous fluid containing nuclear material, ribosomes, nutrients, enzymes, and other molecules
- Synthesis, cell maintenance, and metabolism occur in the cytoplasm
- Storage granules may be present under certain environmental conditions
- Ribosomes: composed of ribonucleoproteins, up to 25 nm in size
- Consist of two subunits: 50S and 30S
- Sedimentation rate (Svedberg unit) is dependent on both size and shape of the particle
- Ribosomal RNA is complexed with many different proteins and accounts for about 80% of the cell's RNA
- Nuclear material: composed of a single haploid circular chromosome containing double-stranded DNA
- Small amounts of protein and RNA are also associated with the nuclear material
- Genes in the bacterial chromosome code for all vital functions of the cell
- Bacterial genomes vary in size depending on the species
Endospores and Exospores
- Endospores: thick-walled, highly refractile bodies produced by Bacillus, Clostridium, and few other genera
- Extremely resistant to desiccation, staining, disinfectants, radiation, and heat
- Resistance due to low water content (20%) and large amounts of dipicolinic acid (10-15% of spore dry weight)
- Exospores: spores external to the vegetative cell
- Produced by budding and desiccation
- Desiccation and heat resistant
- Do not contain dipicolinic acid
Growth and Cell Division
- Microbial growth: defined as the increase in the number of cells
- Occurs by cell division, usually by binary fission
- DNA synthesis is continuous and replicates the single bacterial chromosome shortly before cell division
- Phases of bacterial growth:
- Time Lag Phase: cells do not increase in number, but are metabolically active
- Log Phase: population growth occurs at an exponential or logarithmic rate
- Stationary Phase: cell growth and death are balanced
- Decline Phase: cell death occurs due to a loss of limiting nutrients or a build-up of toxins
Factors Affecting Bacterial Growth
- Physical factors:
- pH: measures hydrogen ion (H+) concentration
- Temperature: optimum temperature is the temperature at which an organism grows best
- Oxygen requirement: organisms differ in their requirements for molecular oxygen (O2)
- Osmotic pressure: concentration of dissolved substances can impact cell growth and survival
- Nutritional factors:
- Source of carbon: autotrophs (produce complex organic compounds from simple substances) and heterotrophs (use organic carbon for growth)
- Water requirement: essential for cellular function, serves as a universal solvent
- Oxygen: provided in various forms, including water, molecular oxygen, and component items of various nutrients
- Sulfur: needed for synthesis of amino acids, obtained from organic and inorganic sources
- Phosphorus: essential component of nucleotides, nucleic acids, phospholipids, and teichoic acids
- Trace elements: required in small quantities, often used as enzyme cofactors
Physical Agents
- Temperature:
- Moist heat: effective method of killing microorganisms, coagulates proteins
- Dry heat: destroys microorganisms by oxidizing their chemical constituents
- Autoclaving: uses steam under pressure to sterilize equipment and materials
- Fractional sterilization (Tyndallization): used for materials that cannot be heated above 100°C
- Pasteurization: controlled heat treatment to kill microorganisms of certain types
- Low temperature: slows down metabolism, can be used for preservation of cultures
Genetics
- Genetics: study of the inheritance and variability of characteristics
- Microbial genetics: study of the transmission of genetic information from parents to offspring
- Transformation: process of DNA uptake by bacteria from the surrounding environment
- Competent cells: capable of taking up DNA
- Bacterial competence: achieved through chemicals and electrical pulses
- Genotype: genetic structure of the cell
- Phenotype: expression of the genotype in observable properties
- Genome: genetic information in a cell
- Chromosomes: structures containing DNA that carry hereditary information
- Nucleotides: building blocks of nucleic acids, composed of a nitrogenous base, a five-carbon sugar, and at least one phosphate group
- Mutation: change in the nucleotide sequence of a gene/DNA### Types of Mutations
- Mutations can occur in the purine-pyrimidine base sequence of a gene, resulting in a substituted base pair
- These mutations can lead to the insertion of an incorrect amino acid in a protein
Point Mutations
- A point mutation occurs when a single base is substituted in a gene
- Types of point mutations:
Missense Mutation
- Results in an amino acid substitution in the synthesized protein
- Example: Sickle cell disease is caused by a single base change in the gene for globin
- This change results in a change in the shape of hemoglobin molecules under low oxygen conditions
- Impedes the movement of RBC in small capillaries
Nonsense Mutation
- Creates a gap (nonsense) codon in the mRNA molecule
- Prevents the synthesis of a complete functional protein, resulting in a fragment only
- Altered gene triplet produces a chain-terminating codon in mRNA, resulting in premature termination of protein formation during translation
Frameshift Mutations
- Occur when one or more nucleotides are inserted or deleted in a gene
- Results in a shift of the reading frame
- Can occur spontaneously due to mistakes during DNA replication
- Almost always results in a long stretch of altered amino acids and the production of an inactive protein from the mutated gene
- Examples: Progressive neurological disorders caused by extra bases inserted into a particular gene
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Description
This quiz covers the fundamentals of veterinary microbiology, including topics from Tortora's Microbiology: An Introduction and Clinical Veterinary Microbiology by Quinn et al.
