Learn: Exam 1 Chapters 1–3: Microbiology Key Concepts and Definitions

What does the three-domain system divide life into?

Bacteria, Archaea, and Eukarya

Why was rRNA used to create the three-domain system?

rRNA is found in all organisms and evolves slowly, making it useful for identifying deep evolutionary relationships.

Who proposed the three-domain system?

Carl Woese and George Fox.

Why are Archaea considered distinct from Bacteria?

rRNA comparisons showed Archaea are genetically distinct and share similarities with Eukarya.

What is a pathogen?

A microorganism capable of causing disease.

What are the criteria for a human pathogen?

A pathogen must invade tissues, produce virulence factors, establish infection, and cause disease.

What is the difference between viruses and cellular microorganisms?

Viruses are acellular and require a host cell to reproduce; cellular organisms can carry out metabolism independently.

Why are viruses studied differently?

Viruses cannot grow independently and must be studied through host interactions and replication cycles.

What is a common photosynthetic prokaryote found in aquatic environments?

Cyanobacteria.

Which organisms are prokaryotic?

Bacteria and Archaea.

What do prokaryotes lack?

A membrane-bound nucleus and membrane-bound organelles.

What region contains DNA in prokaryotes?

The nucleoid.

What is the difference between prokaryotes and eukaryotes?

Prokaryotes lack a nucleus and organelles; eukaryotes contain both.

Why can antibiotics selectively target bacteria?

Antibiotics target bacterial features like peptidoglycan cell walls and 70S ribosomes that differ from human cells.

What is binomial nomenclature?

Uses genus + species names.

What are the rules of binomial nomenclature?

Genus capitalized, species lowercase, entire name italicized.

Give an example of correct binomial nomenclature.

Saccharomyces cerevisiae.

What is a strain?

A genetic variant within a species.

What is Bergey's Manual?

A standard reference used to identify bacteria using phenotypic and genetic traits.

What is a limitation of Bergey's Manual?

It cannot always keep pace with rapidly changing molecular classifications.

What are the characteristics of fungi?

Fungi are eukaryotes that include yeasts and molds and can produce antibiotics.

Which group produces many antibiotics?

Fungi.

What is the significance of yeast fermentation?

Yeast convert sugars into alcohol and carbon dioxide, demonstrating microbial metabolism.

What did fermentation reveal?

Microorganisms perform metabolic processes useful for food production and biotechnology.

What is horizontal gene transfer?

Movement of genes between organisms outside parent-offspring inheritance.

Why does horizontal gene transfer complicate taxonomy?

It blurs evolutionary relationships.

Who argued that disease had natural causes?

Hippocrates.

What was Robert Hooke's contribution?

Coined the term 'cell' after observing cork.

What was Antonie van Leeuwenhoek's contribution?

First observed living microorganisms.

What is cell theory?

All organisms are made of cells, cells are the basic unit of life, and cells come from preexisting cells.

What was Schleiden's contribution?

All plants are made of cells.

What was Schwann's contribution?

All animals are made of cells.

What was Virchow's contribution?

All cells arise from pre-existing cells.

What evidence supports cell theory?

All living things consist of cells and cells come from existing cells.

What is spontaneous generation?

The belief that life arises from nonliving matter.

What is biogenesis?

Life comes only from existing life.

What did Needham's experiment involve?

Briefly boiled broth and observed microbial growth.

What did Spallanzani's experiment demonstrate?

Boiled broth longer and sealed flasks; no growth occurred.

What was Pasteur's swan-neck flask experiment?

Air could enter broth but microorganisms were trapped in the neck, disproving spontaneous generation.

What did Pasteur conclude?

Microbes come from pre-existing life rather than nonliving matter.

What is the endosymbiotic theory?

Mitochondria and chloroplasts originated as free-living bacteria.

What evidence supports the endosymbiotic theory?

Mitochondria and chloroplasts have circular DNA, 70S ribosomes, double membranes, and bacterial similarities.

What is the powerhouse of the cell?

Mitochondria.

What organelle is responsible for photosynthesis?

Chloroplast.

What does the Golgi apparatus do?

Packages and modifies proteins.

What is the function of the nucleolus?

Produces ribosomal components.

What is the fluid mosaic model?

Cell membranes consist of a phospholipid bilayer with embedded proteins.

What is passive diffusion?

Movement down a concentration gradient without energy.

What is active transport?

Movement against a concentration gradient requiring energy.

What is osmosis?

Movement of water across a selectively permeable membrane.

What are carrier proteins/channels?

Transport structures for large or charged molecules.

What is a vegetative cell?

An actively growing bacterial cell.

What is an endospore?

A dormant, resistant bacterial structure.

What happens during germination?

Endospores return to vegetative cells.

What are Gram-positive bacteria characterized by?

Thick peptidoglycan and stain purple.

What are Gram-negative bacteria characterized by?

Thin peptidoglycan and an outer membrane and stain pink.

Why do Gram-positive cells remain purple?

Thick peptidoglycan traps crystal violet dye.

Why do Gram-negative bacteria stain pink?

Alcohol disrupts outer membrane and removes crystal violet.

What is the purpose of the acid-fast stain?

Identifies waxy cell walls like Mycobacterium.

What is the purpose of the capsule stain?

Visualizes protective capsules.

What is the purpose of the endospore stain?

Detects bacterial spores.

What is brightfield microscopy?

Uses transmitted light and works best with stained specimens.

What is darkfield microscopy?

Uses scattered light to observe live unstained specimens.

What is phase-contrast microscopy?

Visualizes live transparent cells without stains.

What is fluorescence microscopy?

Uses fluorochromes to label specific structures.

What is confocal microscopy?

Produces 3D images of thick specimens and biofilms.

What is the function of TEM?

Shows internal structures in thin sections.

What is the function of SEM?

Shows detailed surface structures in 3D.

What is the difference between TEM and SEM?

TEM shows internal ultrastructure; SEM shows external surface features.

Why does oil immersion improve resolution?

It reduces light refraction by matching refractive indices.

How does wavelength affect resolution?

Shorter wavelengths provide higher resolution.

What determines contrast in microscopy?

Staining and how light interacts with the specimen.

What happens when fluorochromes absorb light?

They emit light at a longer wavelength.