Microbiology Lecture: Introduction, Bacterial Structure, and Growth

Comprehensive vocabulary flashcards covering microbial classification, cell structures, staining techniques, growth phases, and environmental requirements based on lecture notes.

Domain

The highest level in biological classification; the three domains are Bacteria, Archaea, and Eukarya.

Eukaryotic cell

A cell type characterized by a membrane-bound nucleus.

Prion

An acellular infectious agent made entirely of protein with no nucleic acid.

Prokaryote

A single-celled organism consisting of a prokaryotic cell, which has no nucleus.

Viroid

An acellular infectious agent consisting only of RNA with no protein coat.

Virus

An acellular infectious agent consisting of nucleic acid surrounded by a protein coat.

Germ theory

The theory stating that microorganisms are the cause of many infectious diseases.

Robert Koch

The scientist who developed postulates to link specific microbes to specific diseases.

Louis Pasteur

The scientist who used swan-neck flasks to disprove the theory of spontaneous generation.

Coccus

A bacterial shape described as spherical or like a "cocopuff."

Bacillus

A rod-shaped bacterium.

Strepto-

A prefix indicating that bacteria are arranged in chain formations.

Staphylo-

A prefix indicating that bacteria are arranged in grape-like clusters.

Peptidoglycan

A cell wall component forming glycan chains linked by tetrapeptide chains; it is thick in Gram-positive cells and thin in Gram-negative cells.

Gram-positive

Bacteria that stain purple because their thick peptidoglycan layer (300-500 layers) retains crystal violet-iodine complexes.

Gram-negative

Bacteria that appear red or colorless after decolorization; they have a thin peptidoglycan layer and a unique outer membrane containing Lipopolysaccharide (LPS).

Lipopolysaccharide (LPS)

A molecule in the outer membrane of Gram-negative bacteria; it contains Lipid A, which acts as a toxin and alerts the immune system.

Gram's iodine

A mordant used in staining that forms complexes with crystal violet to decrease its solubility inside cells.

Capsule

A distinct, gelatinous layer outside the cell wall that may allow bacteria to avoid the immune system; visible in a capsule stain where the background is stained dark.

Endospore

A unique dormant cell resistant to heat, desiccation, chemicals, UV, and boiling water; produced by Bacillus and Clostridium.

Sporulation

An 8-hour process triggered by nutrient depletion (specifically carbon) that results in the formation of an endospore.

Flagella

Appendages used for motility; peritrichous refers to being all over the surface, while polar refers to being at one end.

Nucleoid

The gel-like region in a prokaryotic cell that contains the chromosome.

Plasmid

Small, circular, supercoiled DNA pieces; a bacterial cell that loses its plasmid will usually survive.

70S

The size of prokaryotic ribosomes, composed of $30S$ and $50S$ subunits; they are targeted by antibiotics like Erythromycin and Tetracyclines.

80S

The size of eukaryotic ribosomes, which are not impacted by antibiotics targeting 70S ribosomes.

Immersion oil

An oil used with a $100X$ objective lens to displace air, prevent light refraction, and increase resolution.

Binary fission

The process by which prokaryotic cells divide into two identical copies.

Generation time

The time it takes for a population of cells to double; this is measured during the exponential (log) phase.

Biofilms

Polysaccharide-encased communities of bacteria (e.g., dental plaque, scum in sinks) that protect the microbes and make them hundreds of times more resistant.

Quorum sensing

A mechanism by which bacteria sense cell density and change gene expression to regulate virulence, biofilm formation, and antibiotic production.

Lag phase

The growth phase where cells are waking up and synthesizing macromolecules but no increase in cell number occurs.

Stationary phase

The growth phase where the number of viable cells remains constant because the rate of cell division equals the rate of cell death.

Obligate aerobe

An organism that requires $O_2$ for respiration and cannot grow without it.

Obligate anaerobe

An organism that cannot grow in the presence of $O_2$ and does not produce superoxide dismutase or catalase.

Superoxide dismutase

An enzyme that inactivates superoxide by converting it into $O_2$ and $H_2O_2$.

Catalase

An enzyme that converts $H_2O_2$ into $O_2$ and $H_2O$, used by most aerobic organisms to deal with toxic oxygen.

Halophiles

Microbes that require high salt concentrations for growth; marine bacteria require approximately $3\%$, and extreme halophiles (like those in Utah) require even higher.

Critical items

Medical instruments like needles, scalps, and venous catheters that come into contact with body tissues and must be sterile.

Autoclaving

A sterilization method involving both temperature and pressure; the pressure increases the temperature of the steam to effectively kill microbes.