Microbiology- Exam2

Bacterial and Archaeal DNA Packaging

Nuclear material is free in the cytoplasm, not enclosed in a true nucleus.

Bacterial and Archaeal Internal Structures

They lack membrane-bound organelles.

Average Bacterial Size

Approximately 1 micrometer (μm).

Three General Bacterial Shapes

Coccus (sphere), rod/bacillus, and curved (vibrio, spirillum, spirochete).

Pleomorphism

Variations in size and shape among cells of a single species due to environmental or structural factors.

Biofilms

Microbial communities attached to moist surfaces, enclosed in an extracellular matrix.

Flagella and Axial Filaments Function

Provide cellular motility.

Fimbriae, Pili, and Nanowires Function

Provide attachment points or channels.

Monotrichous Flagellar Arrangement

A single flagellum attached at one end of the cell.

Peritrichous Flagellar Arrangement

Flagella dispersed randomly over the entire surface of the cell.

Chemotaxis

Movement of a cell in response to chemical signals.

Bacterial Run

Counterclockwise movement of flagella causing the cell to swim in a smooth, linear direction.

Bacterial Tumble

Flagellum reverses direction, causing the cell to stop and change course.

Axial Filaments (Periplasmic Flagella)

Internal flagella enclosed between the cell wall and cytoplasmic membrane in spirochetes, imparting a twisting motion.

Fimbriae

Short, bristle-like fibers providing adhesion to surfaces and other cells.

Pili

Long, rigid tubular structures found in gram-negative bacteria, required for conjugation.

Conjugation

The partial transfer of DNA from one bacterial cell to another via pili.

Slime Layer

A loosely formed, unorganized glycocalyx that protects cells from water and nutrient loss.

Capsule

A tightly bound, dense glycocalyx that protects bacteria from phagocytosis and desiccation.

S-Layer

A single protective protein or glycoprotein layer produced by bacteria and archaea in hostile environments.

Peptidoglycan

A unique polymer of NAG, NAM, and amino acids providing strong structural support in bacterial cell walls.

Gram-Positive Cell Wall

A thick, homogenous sheath of peptidoglycan containing teichoic and lipoteichoic acids.

Gram-Negative Cell Wall

A single, thin sheet of peptidoglycan providing greater flexibility and susceptibility to lysis.

Mycolic Acid

A very-long-chain fatty acid found in Mycobacterium and Nocardia cell walls that confers chemical resistance.

Mycoplasmas

Bacteria that naturally lack a cell wall and have membranes stabilized by sterols.

Cytoplasmic Membrane Permeability

A selectively permeable barrier regulating the transport of nutrients and wastes.

Lipopolysaccharide (LPS)

An outer membrane molecule in gram-negative bacteria containing O-antigen and endotoxin Lipid A.

Porin Proteins

Outer membrane proteins that completely span the membrane and restrict molecule penetration.

Bacterial Nucleoid

A non-membrane-bound region containing the single, circular bacterial chromosome.

Plasmids

Extrachromosomal, small circular double-stranded DNA molecules that confer protective traits.

Bacterial Ribosomes

70S complex structures composed of RNA and protein responsible for protein synthesis.

Inclusion Bodies

Storage granules or globules of organic/inorganic material stockpiled for future use.

Cytoskeletal Filaments (FtsZ and MreB)

Protein polymers that aid in cell division, maintaining shape, and positioning DNA.

Bacterial Endospores

Complex, dormant structures formed by some bacteria to withstand hostile environmental conditions.

Sporulation

An elaborate 6-8 hour genetic program of spore formation induced by nutrient depletion.

Endospore Germination

The return of a dormant endospore to vegetative growth when favorable conditions arise.

Methanogens

Archaea that convert carbon dioxide and hydrogen into methane gas.

Archaeal Cell Walls

Chemically distinct cell walls that lack true peptidoglycan.

Archaella

Archaeal appendages similar to bacterial pili, involved in adhesion, biofilm formation, and motility.

Gracilicutes

Taxonomic division for bacteria with thin-skinned, gram-negative cell walls.

Firmicutes

Taxonomic division for bacteria with thick, strong, gram-positive cell walls.

Tenericutes

Taxonomic division for bacteria that lack a cell wall.

Mendosicutes

Taxonomic division designating archaea.

Phototaxis

Movement of a cell toward light.

Lipoproteins

Molecules that anchor the outer membrane to the peptidoglycan in gram-negative bacteria.

Medical Microbiology

Deals with microbes that cause diseases in humans and animals.

Antonie van Leeuwenhoek

Made a crude microscope in the 1600s and drew microorganisms he called 'animalcules'.

Louis Pasteur

Disproved spontaneous generation and invented pasteurization.

Robert Koch

Established a series of proofs that verified the germ theory of disease.

Levels of Classification

From most general to most specific: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Public Health Microbiology and Epidemiology

Monitors and controls the spread of diseases in communities via agencies like the USPHS, CDC, and WHO.

Immunology

Studies protective substances and cells produced in response to infection, including vaccination and allergy.

Bioremediation

The introduction of microbes into the environment to restore stability or clean up toxic pollutants.

John Tyndall

Found that microbes in the dust and air have high heat resistance.

Ferdinand Cohn

Discovered and described bacterial endospores.

Industrial Microbiology

Safeguards food and water and uses microbes to create amino acids, beer, and drugs.

Agricultural Microbiology

Studies the relationships between microbes and domesticated plants and animals.

Environmental Microbiology

Studies the effect of microbes on diverse habitats such as aquatic, soil, and geomicrobiology.

Recombinant DNA Technology

Techniques allowing the transfer of genetic material from one organism to another to alter DNA.

Phylogeny

The taxonomic scheme representing the natural relatedness between groups of living things based on evolution.

Helminths

Multicellular animals whose mature form is visible to the naked eye, studied alongside microbiology.

The Five I's of Microbiology

Five basic techniques: Inoculation, Incubation, Isolation, Inspection, and Identification.

Inoculation

The introduction of microbes into or upon media for culture.

Sterile

Free of all life forms including spores and viruses, required for sampling and inoculation.

Incubation Temperatures

Usual temperatures used in the lab range from 20°C to 45°C.

Chemically Defined (Synthetic) Media

Media with exact chemical compositions and molecular contents defined by an exact formula.

Complex Media

Media containing at least one component, such as animal extracts or yeast, that is not chemically definable.

General-Purpose Media

Complex media containing a mixture of ingredients that support a wide variety of microbial life.

Enriched Media

Contains complex organic substances or special growth factors that fastidious bacteria require for growth.

Selective Media

Contains one or more agents that inhibit the growth of certain microbes and encourage a select microbe to grow.

Differential Media

Allows multiple microorganisms to grow, but displays visible differences between colonies like size, color, or gas formation.

Pure Culture

A culture containing only a single known species or type of microorganism.

Subculture

A second-level culture grown from a well-isolated colony.

Mixed Culture

A culture holding two or more identified, easily differentiated species of microorganisms.

Contaminated Culture

A culture that was once pure or mixed that now contains unwanted microbes of uncertain identity.

Biochemical Tests in Microbiology

Determine fundamental chemical characteristics such as nutrient requirements, enzyme presence, and energy mechanisms.

Transport Media

Media designed to maintain and preserve specimens.

Assay Media

Media used to test the effectiveness of antimicrobial drugs and disinfectants.

Enumeration Media

Media used to count the numbers of organisms in industrial and environmental samples.

Axenic Culture

A culture that is free of other living things except the one being studied.

Fastidious Organism

An organism that has complex or particular nutritional requirements.

Growth Factors

Specific vitamins or amino acids required by fastidious bacteria for growth.

Genotypic Testing

Analytical tool that detects microbes based on their DNA.

Immunologic Testing

Analytical tool testing a microbial isolate against known antibodies.

Refractive Index

A measure of how greatly a substance slows the velocity of light.

Phase-Contrast Microscope

A specialized type of bright-field microscope that provides built-in contrast.

Fluorescence Microscope

A light microscope that uses ultraviolet radiation as its illuminating source.

Confocal Microscope

A light microscope that uses a laser beam as its illuminating source.

Heat Fixation

A method routinely used with bacteria and archaea to kill and attach specimens to a slide while preserving overall morphology.

Basic Dyes

Dyes possessing positively charged groups that bind to negatively charged molecules such as nucleic acids and cell surfaces.

Acidic Dyes

Dyes possessing negatively charged groups that bind to positively charged cell structures.

Dark-Field Microscope

A microscope that produces a bright image against a dark background, ideal for viewing living, unstained specimens.

Super-Resolution Light Microscope

An advanced light microscope that uses two lasers to overcome the traditional diffraction limit of light.

Chemical Fixation

A fixation method used with larger, more delicate organisms to protect fine cellular substructures and morphology.

Numerical Aperture

A measure of a lens's ability to capture light, where a higher aperture results in greater resolution.

Acid-Fast Stain

A differential stain particularly useful for detecting members of the genus Mycobacterium due to high lipid content in their cell walls.

Virus Size Range

Viruses range from 20 to 800 nm in dimensions.

Focal Length

The distance between the center of a lens and the focal point; a shorter focal length provides more magnification.

Bright-Field Microscope

A light microscope that produces a dark image against a brighter background.

Parfocal Microscopes

Microscopes that remain in focus when objective lenses are changed.