Microbiology Vocabulary: Cell Structure, Growth, and Laboratory Techniques

Microbiology

Study of organisms too small to be seen with the naked eye.

Prokaryote

Simple cell lacking a nucleus; includes bacteria & archaea.

Eukaryote

Complex cell with a nucleus and organelles.

Virus

Acellular particle with nucleic acid and protein coat; requires a host.

Abiogenesis (Spontaneous Generation)

Life from non-living matter.

Biogenesis

Life comes from pre-existing life.

Fermentation

Microbial conversion of sugars into alcohol, gases, or acids.

Germ Theory of Disease

Microorganisms cause specific diseases.

Antonie van Leeuwenhoek

First to accurately describe microbes.

Louis Pasteur

Disproved spontaneous generation with swan-neck flask.

Culture Medium

Nutrient solution that supports microbial growth.

Agar

Gel-like polysaccharide used to solidify media.

Defined (Synthetic) Medium

Exact chemical composition is known.

Complex Medium

Contains unknown nutrient mixtures (e.g., yeast extract).

Selective Media

Promotes growth of certain microbes, inhibits others.

Differential Media

Distinguishes microbes based on biochemical traits.

Enriched Media

Contains growth factors for fastidious organisms.

Microscopy

Techniques (brightfield, darkfield, etc.) to visualize microbes.

Aseptic Technique

Prevents contamination in laboratory work.

Colony-Forming Unit (CFU)

A visible colony that arose from one viable cell.

Cell Theory

All life is made of cells; cells come from pre-existing cells.

Cytoplasm

Gel-like fluid containing nutrients and organelles.

Nucleoid

Region in prokaryotes where DNA is concentrated.

Plasmid

Small, circular DNA molecule outside the chromosome.

Ribosome (70S)

Protein synthesis machinery in prokaryotes.

Inclusions

Storage granules inside prokaryotes.

Cell Wall

Provides structure; made of peptidoglycan in bacteria.

Gram-Positive Bacteria

Thick peptidoglycan layer, teichoic acids.

Gram-Negative Bacteria

Thin peptidoglycan layer, outer membrane.

Flagella

Tail-like appendage for motility.

Pili/Fimbriae

Structures for attachment (fimbriae) or DNA transfer (pili).

Glycocalyx

Protective outer coating; includes slime layers & capsules.

Endospore

Dormant, resistant bacterial structure for survival.

Binary Fission

Asexual reproduction in prokaryotes.

Generation (Doubling) Time

Time required for population to double.

Exponential Growth

Population doubles each generation (2I).

Growth Curve

Four phases: Lag, Log, Stationary, Death.

Lag Phase

Cells adapt, no immediate growth.

Log (Exponential) Phase

Rapid cell division, high metabolic activity.

Stationary Phase

Nutrients deplete; cell growth = cell death.

Death Phase

More cells die than divide.

Biofilm

Community of microbes embedded in a protective matrix.

Quorum Sensing

Cell-to-cell signaling that coordinates activity.

Viable Plate Count

Dilution and colony counting method.

Turbidity

Cloudiness used to estimate cell density.

Spectrophotometer

Measures light absorbance to estimate growth.

Coulter Counter

Automated method for counting cells.

Obligate Aerobe

Requires oxygen for growth.

Facultative Anaerobe

Grows with or without oxygen.

Obligate Anaerobe

Cannot grow in oxygen.

Halophile

Salt-loving microbe.

Psychrophile / Thermophile

Cold-loving / Heat-loving microbes.