Microbiology exam 1 - chapters 1-6

What is the main difference between prokaryotes and eukaryotes?

Prokaryotes do not have a nucleus or membrane-bound organelles. Eukaryotes have a nucleus and membrane-bound organelles.

What organisms are prokaryotic?

Bacteria and Archaea.

What organisms are eukaryotic?

Fungi, animals, plants, and protists.

What characteristics are used to classify microbes?

Cell structure, cell type, genetics/DNA, metabolism, physical characteristics, and evolutionary relationships.

What is a major structural difference between bacteria and fungi?

Bacteria are prokaryotic and have peptidoglycan cell walls. Fungi are eukaryotic and generally have chitin cell walls.

What makes viruses different from bacteria and fungi?

Viruses are acellular (not made of cells) and cannot reproduce independently. They must use a host cell to replicate.

What are pathogens?

Microorganisms or infectious agents that can cause disease.

What is spontaneous generation?

The old belief that living organisms could arise from nonliving matter.

What is biogenesis?

The idea that living organisms come from other living organisms.

What did Francesco Redi's experiment show?

Maggots came from flies, not from the meat itself. His experiment supported biogenesis.

What did Louis Pasteur's swan-neck flask experiment show?

Microorganisms came from existing microorganisms/contamination, not spontaneous generation. It supported biogenesis.

What did Robert Hooke discover?

He observed cork under a microscope and coined the term “cell.”

🧠 Hooke = Cell

What did Anton van Leeuwenhoek discover?

He was one of the first to observe and describe microorganisms, including bacteria and protozoa.

🧠 Leeuwenhoek = Microbes

What did Ignaz Semmelweis discover?

Handwashing by physicians dramatically reduced infections and deaths in childbirth.

🧠 Semmelweis = Handwashing

What did Joseph Lister contribute to microbiology?

He introduced antiseptic techniques in surgery to reduce infections.

🧠 Lister = Antiseptic surgery

What is Robert Koch famous for?

Establishing methods for linking specific microorganisms to specific diseases and developing Koch’s postulates.

🧠 Koch = Disease-causing microbes

What did Edward Jenner contribute?

He developed the first successful smallpox vaccine, helping establish vaccination.

🧠 Jenner = Vaccine

What did Alexander Fleming discover?

Penicillin, the first widely recognized antibiotic.

🧠 Fleming = Penicillin

What did Avery, MacLeod, and McCarty discover?

They provided strong evidence that DNA is the genetic material.

🧠 Avery = DNA

What did Rosalind Franklin and Raymond Gosling contribute?

Their X-ray diffraction work provided important evidence about the structure of DNA

What did Watson and Crick discover?

They proposed the double-helix structure of DNA, using available experimental evidence, including Franklin and Gosling's work.

🧠 Watson & Crick = DNA double helix

What did Paul Berg contribute?

🧠 Berg = Recombinant DNA

How is darkfield microscopy an improvement over brightfield microscopy?

It makes the specimen appear bright against a dark background, providing better contrast for small, thin, or live organisms.

How is phase-contrast microscopy an improvement over brightfield/darkfield?

It allows you to see living, unstained cells with improved contrast and detail.

What are benefits of fluorescence microscopy?

It can identify specific cells or structures using fluorescent dyes, provides high contrast, and can show the location of specific molecules.

What is an advantage of confocal microscopy?

It produces sharp images by eliminating out-of-focus light and can create detailed 3D images of specimens

What is the difference between light microscopy and electron microscopy?

Light microscopes use visible light, while electron microscopes use beams of electrons. Electron microscopes provide much higher resolution and magnification.

What is the purpose of dyes and stains?

To increase contrast, making cells and their structures easier to see under a microscope.

What is negative staining?

The background is stained, while the cells remain unstained. It can show the size and shape of cells without significantly distorting them.

What is a differential stain?

A staining technique that uses multiple stains/reagents to distinguish between different types of cells or structures.

What is the Gram stain?

A differential stain used to distinguish bacteria based mainly on differences in their cell wall structure.

What color are Gram-positive bacteria?

Purple because they retain the crystal violet–iodine complex due to their thick peptidoglycan layer.

What color are Gram-negative bacteria?

Pink/red because they do not retain the crystal violet–iodine complex after decolorization and take up the counterstain.

What major structure determines Gram-positive vs. Gram-negative staining?

The bacterial cell envelope, especially the thickness of the peptidoglycan layer.

What is the acid-fast stain used for?

Identifying bacteria with waxy, lipid-rich cell walls, especially Mycobacterium.

What component makes acid-fast bacteria resistant to decolorization?

Mycolic acid in their cell wall.

🧠 Acid-fast = Mycolic acid

What color are acid-fast bacteria after staining?

Typically red/pink, while non-acid-fast cells take the counterstain and appear a different color.

What is the endospore stain used to identify?

Endospores produced by certain bacteria, especially Bacillus and Clostridium.

Why are endospores difficult to stain?

They have a tough, resistant structure that does not easily take up ordinary stains.

What color are endospores typically seen after an endospore stain?

Endospores are typically green, while the vegetative cells are typically red/pink.

What are the three basic shapes of bacterial cells?

1. Cocci = spherical

2. Bacilli =rod-shaped

3. Spirilla/spirochetes

What are cocci?

Round/spherical bacteria

What are bacilli?

Rod shapes bacteria

What are spirilla?

Spiral shaped bacteria with a rigid spiral shape

What are spirochetes?

Thin,flexible, corkscrew shaped bacteria

What are common bacterial arrangements?

Diplo= pairs

Strepto= chains

Staphlo= clusters

What is glycoalyx?

Sticky layer outside of cell wall that helps bacteria attach to surfaces and avoid phagocytosis. It can form a capsule or slime layer.

What is bacterial capsule?

Organized glycocalyx that is firmly attached to the cell, can help bacteria avoid immune defenses and adhere to surfaces.

What is flagella?

Long,whip like structures used for bacterial movement.

What are fimbriae?

Short, numerous hair like structures used primarily used for attachment to surfaces or host cells

What are Pili?

Hair like structures involved in attachment and for certain Pili DNA transfer between bacteria.

What is the bacteria cell wall?

A rigid layer that provides shape and structural support and helps prevent the cell from bursting due to osmotic pressure.

What is peptidoglycan?

Mesh like polymer made of sugars and amino acids that form major structural component of bacteria cell walls.

Which type of bacteria has a thick peptidoglycan layer?

Gram positive bacteria

What are teichoic acids ?

Molecules found in gram positive cell walls that the lip cell wall structure and ion movement and contribute to interactions with the environment.

What is lipopolysaccharide (LPS)

Major component of outer membrane of gram negative bacteria

What part of LPS can cause strong inflammatory responses?

Lipid A also called endotoxin

What is the plasma membrane?

Selectively permeable membrane that controls what enters and leaves the cell and contains proteins involved in transport and energy production.

What is the nucleoid?

Región where the bacterium main chromosomal DNA is located. Not surrounded by a membrane

What are plasmids?

Small, usually circular pieces of extra chromosomal DNA that carry useful genes, such as antibiotic resistance genes.

What are bacterial ribosomes?

Structures that make proteins by translating mRNA

What type of ribosomes do bacteria have?

70S ribosomes

What is the major structural difference between gram positive and gram negative bacteria?

Gram positive have a thick peptidoglycan wall and no outer membrane.

Gram negative have a thin peptidoglycan layer plus a outer membrane.

What is the gram positive cell wall like?

Thick peptidoglycan with teichoic acids: no outer membrane.

What is gram negative cell wall like?

Thin peptidoglycan locates between the inner plasma membrane and an outer membrane containing LPS

What color are gram positive bacteria after gram staining?

Purple

What color are gram negative after gram staining?

Pink/red

Why do gram positive bacteria remain purple during gram staining?

Their thick peptidoglycan layer traps the crystal violet iodine complex

Why so gram negative bacteria become pink/red?

Their thin peptidoglycan doesn’t retain the crystal violet complex after decolorization, so they take up the counter stain.

Which bacteria have an outer membrane ?

Gram negative bacteria

Which bacteria contain teichoic acids?

Gram positive

Which bacteria contains LPS

Gram negative

What makes an acid fast cell wall unique ?

High amount of mycolic acid, waxy lipid that makes wall resistant to many stains and helps bacteria resist drying and some chemicals.

What does acid fast mean?

Bacteria retain a primary stain even after treatment with an acid alcohol decolorizer.

Give an example of an acid fast bacterium?

Mycobacterium tuberculosis TB

What substance is especially important in the acid fast cell wall?

Mycolic acid

What is passive transport

Movement of substances across the membrane without using cellular energy (ATP)

What is simple diffusion?

Movement of molecules from high concentration to low

What is facilitated diffusion ?

Movement from high concentration to low through a membrane transport protein

What is osmosis?

Movement of water across a selectively permeable membrane toward the side with the higher solute concentration

What is active transport?

Movement of substances against their concentration gradient using energy (ATP) and transport proteins.

Which transport processes require ATP?

Active transport require cellular energy. Simple diffusion, facilliates diffusion, and osmosis do not directly require ATP.

What is the key different between simple and facilitated diffusion?

Simple diffusion passes directly through the membrane, facilitated require a membrane protein .

What are direction does diffusion occur ?

High concentration to low

What direction does active transport occur?

Low concentration to high

What bacterial structures / processes can antibiotics target?

Cell wall synthesis, protein synthesis, DNA/RNA synthesis, metabolic pathways and cell membrane function.

Why is peptidoglycan an important antibiotic target?

Humans don’t have peptidoglycan, so drugs targeting bacterial cell wall synthesis can selectively damage bacteria.

What bacteria structure is targeted by antibiotics that inhibit protein synthesis?

Ribosomes

What cellular processes can antibiotics target besides the cell wall?

Protein synthesis, DNA replication, RNA synthesis, metabolism, and membrane function.

What is endospore?

Highly resistant, dormant structure produced by some bacteria to survive harsh environmental conditions.

Are endorsporez a way for bacteria to reproduce ?

No, one bacterial cell forms one endospore , it is a survival mechanism not reproduction.

What conditions can endospore survive?

Extreme heat, drying, chemicals, radiation, lack of nutrients better than normal bacterial cells.

What happens when conditions become favorable again?

The endospore can germinate and return to an active bacterial cell

What are bacteria secretion systems used for?

Used to move proteins or other molecules out of the bacterial cell wall.

Why are secretions systems important for bacteria?

Help bacteria interact with their environment, obtain nutrients , attract to host and cause disease .

What is the broad purpose of secretion systems in pathogenic bacteria?

Deliver molecules that alter or manipulate host cells helping bacteria survive or cause disease.

What is endosymbiotic theory?

Theory that some eukaryotic organelles especially mitochondria and chloroplasts originate as free living bacteria

What evidence supports the endosymbiotic theory?

Mitochondria and chloroplasts have their own DNA

DNA is circular

Have 70s ribosomes

Binary fission

Double membranes

What is unique about fungal cell walls compared with bacteria cell walls?

Fungal cell walls contain chitin while bacterial cell walls contain peptidoglycan

What are major structural differences between fungal and bacterial cells?

Fungi are eukaryotes they have

• nucleus

• Membrane bound organelles

• Complex internal structure

• Different ribosomos

Bacteria are prokaryotes they

• do not have a nucleus or membrane bound organelles