Microbiology Unit One Test

1. Normal Flora

2. What does Microbiology study?

3. What are the domains of life based on?

4. What does scientific naming use?

5. Microbes can be…

1. Normal flora = mostly non-pathogenic & often beneficial microbes living in/on the body.

2. Microbiology studies bacteria, viruses, fungi, protozoa, algae, helminths.

3. Domains of life classification based on ribosomes, nucleic acids, cell type, not habitat.

Classification-> domain, kingdom, phylum, class, order, family, genus, species (in order of most general to most specific) “Dear King Philip Came Over For Good Soup”

4. Scientific naming uses Genus (capitalized) + species (lowercase), both italicized
   Example: Proteus vulgaris

Microbes can be prokaryotic (cells smaller than eukaryotic cells that lack a nucleus and organelles), eukaryotic (nucleus, membrane-bound organelles, mitotic cell division), or non-living (viruses/prions)

Fungi, protozoa, algae, and helminths are all eukaryotic.

Give the cell type and key features of the following microbes…

Bacteria, archaea, fungi, Protozoa, virus/prions

1. Bacteria- prokaryotic; Unicellular, no true nucleus, ubiquitous

Cell wall made of peptidoglycan, and all have a cytoplasmic membrane, cytoplasm, ribosomes, and 1 or a few chromosome(s) ←all are microorganisms

2. Archaea- prokaryotic; Unicellular, no true nucleus

Unusual cell walls that lack peptidoglycan, extremophiles (live in harsh habitats) ←all are microorganisms

3. Fungi- eukaryotic; Micro- and Macroscopic heterotropic (rely on organic compounds for their carbon and energy needs) organisms that can be uni- or multicellular.

Cell walls made of chitin and includes yeast, molds, and mushrooms

4. Protozoa- eukaryotic; Unicellular, heterotropic

No cell wall (flexibility) and can move through fluids via pseudopods, flagella, or cilia

5. Viruses/Prions- nonliving; Acellular non-living particles that are the smallest microbe

Viruses have a protein shell (capsid) surrounding a nucleic acid core

Prions have no nucleic acid, only protein

1. What are the 5 I’s to Culture Microorganisms

2. Inoculum

3. Agar

4. General Purpose Media

5. Enriched Media

6. Anaerobes

7. Selective Media

8. Differential Media

9. Chemically defined Media

1. Inoculation→ Incubation→ Isolation→ Inspection→ Identification

2. The sample introduced into media (to culture it) ← process of inoculation

3. Solid surface for bacteria to grow; not food!

4. Grow a broad spectrum of microorganisms (nutrient agar, broth)

5. Nutrient media supplemented with blood, serum, or some growth factor to promote the multiplication of fastidious (need specific conditions) microorganisms

6. Grow best on reducing media (growth media that absorbs oxygen so it is reduced)

7. Allows some microbes to grow while inhibiting others. Speeds up isolation.

8. Allows multiple organisms to grow but shows visible differences between microbes (variations in colony size or color, production of bubbles)

Note- a medium can be selective and differential

9. Has exact chemical composition listed. If it doesn't then it is a complex media.

State the purpose of the different types of stain below…

1. Simple stain

2. Differential stain

3. Negative stain

4. Special stain

Gram stain outcome meaning

What microscope do we use to see viruses and why?

1. A type of positive stain that only requires a single dye. It is an uncomplicated procedure that causes all cells to appear the same color (regardless of type) and reveals shape, size, and arrangement.

Example- crystal violet

2. A type of positive stain that uses 2 differently colored dyes (the primary dye and the counterstain). It is more complex and is used to distinguish cell types or parts.

Example- acid-fast stain (identifies Mycobacterium tuberculosis), gram stain, and endospore stain

3. Does not stick to the specimen but settles some distance from its outer boundary, forming a silhouette. The smear is not heat-fixed so the distortion and shrinkage of cells is reduced. It is also used to accentuate a capsule.

Nigrosin and India ink are used (negatively charged cells repel the negatively charged dye and remain unstained)

4. Used to emphasize cell parts that are not revealed by conventional staining methods.

Example- capsular staining (observe microbial capsule), flagellar staining (reveal flagella used for locomotion)

Gram stain= crystal violet→ Gram’s iodine→ alcohol rinse (decolorizer)→ contrasting counterstain (safranin)

Gram+= purple, thick peptidoglycan cell wall

Gram-= pink, thin peptidoglycan cell wall+ outer membrane with LPS (Lipopolysaccharide)

Viruses requires electron microscope (too small for light microscopes)

State the function of the bacterial structure

1. fimbriae

2. sex pili

3. flagella

4. s-layer

5. endospore

6. capsule

7. plasmids

What do all bacteria have?

Cell wall material

1. fimbriae- Fine, hair-like bristles extending from the cell surface that help in adhesion to other cells and surfaces.

2. sex pili- An appendage used for drawing another bacterium close in order to transfer DNA to it

3. flagella- Specialized appendage attached to the cell by a basal body that holds a long, rotating filament. The movement pushes the cell forward and provides motility.

4. s-layer- Single layers of thousands of copies of a single protein linked together used for protection and/or attachment. Only produced when bacteria are in a hostile environment.

5. endospore- Dormant body formed within some bacteria that allows for their survival in adverse conditions.

6. capsule- The gel-like covering or slime made chiefly of polysaccharides. This layer is protective and can be associated with virulence (greater disease-causing abilities).

   • Glycocalyx is called this when its bound more tightly to the cell than a slime layer and thicker and denser.

   • Protect the bacteria against host white blood cells called phagocytes.

7. plasmids- Double-stranded DNA circle containing extra genes that replicate independently and be passed from 1 cell to another.

   • Confer protective traits like antibiotic resistance or pathogenicity

All bacteria have: cytoplasmic membrane, cytoplasm, ribosomes, cytoskeleton, and one or a few chromosomes

Bacteria= peptidoglycan

Fungi= chitin

Plants/algae=cellulose

Shapes and arrangements…

1. strep-

2. staph-

3. cocci-

4. bacilli-

5. spirilla/spirochete-

Streptococci means..

Staphylobacilli means…

1. Bacteria arranged in long, continuous chains

2. Bacteria arranged in irregular, grape-like clusters.

3. Round, spherical (can be oval,bean-shaped, or pointed variants)

   • Have the greatest variation in arrangement: can be in singles, pairs (diplococci), tetrads, irregular clusters, or chains.

   Typically have a circumference of 1 µ width of 1 µmm

4. Rod-shaped (can be blocky, round ended, threadlike, drumstick shaped)

   • Less varied in shape: only divide in 1 plane- single cells, pair (diplobacilli), or chains (streptobacilli)

   Typically have a length of 2 µm with a width of 1 µm

5. Slightly curled or spiral-shaped (corkscrew-shaped)

chains of spheres

clusters of rods

Archaea

Bacteria

Eukaryotes

• Archaea → no peptidoglycan, unusual cell walls, extreme environments.

^unique sequence in rRNA

• Eukaryotes → membrane-bound organelles, may cause disease.

• Prokaryotes → no nucleus, circular DNA, binary fission.

Fungi, Protozoa, Helminths:

1. Fungal spores

2. Bacterial endospores

3. Protozoa

4. Helminths

1. Fungal spores = reproductive (produced by reproductive or fertile hyphae- asexual spores by mitotic division and sexual spores by fusing 2 parental nuclei and then meiosis) ← dispersed by environment (water, air, living things)

2. Bacterial endospores = survival

3. Protozoa have cyst (dormant ← resting stage when conditions are unfavorable) & trophozoite (active ← motile feeding) stages

4. Helminths include: flatworms (thin, often segmented body plan), flukes, roundworms (cylindrical, unsegmented body) (NOT trophozoites- they go through life stages involving eggs, larvae, and adults)

1. Viruses are..

2. Animal virus life cycle

3. Retroviruses

4. Oncoviruses

1. Nonliving, require host.

2. adsorption (invade specific host)→ penetration and uncoating (virus is engulfed and enzymes break down capsid freeing nucleic acid)→synthesis (replication and protein production)→assembly (mature virus particles are made using parts manufactured during synthesis)→ release from host cell

3. Retroviruses use reverse transcriptase (RNA → DNA → host genome).

• Oncoviruses can trigger cancer. Cells affected by these viruses are “transformed.” The virus either carries genes that cause cancer or produces proteins that induce a loss of growth regulation leading to cancer.

• Tropism = tissue-specific infection (e.g., lungs vs liver).

^Virus ability to selectively infect (determined by compatibility between viral surface proteins and host cell receptors)

Viral exit mechanisms and virus type that uses it

• Budding→ takes host membrane (a virus whos nucleocapsid is enclosed by a membrane derived in part from the host cell)

^ enveloped viruses (ex-HIV)

• Lysis→ bursts cell (host cell dies)

^Non-enveloped (naked) viruses and complex viruses (that reach maturation in cell nucleus or cytoplasm) (ex-bacteriophage)

1. Exocytosis→Vesicle (packaged with viral proteins) fusion to membrane (to release viral particles into extracellular space)

^enveloped viruses (ex-Flaviviruses) ←not naked viruses b/c they lack lipid membrane to fuse with host membrane

Lytic vs. Lysogenic cycle

Lytic: immediate replication → cell bursts (infected host cell lyses to release mature virions)

• In a phage life cycle: adsorption→ penetration (no uncoating-genetic material injected directly in cell)→replication of virus genetic material & duplication of phage components ->assembly of new virions->maturation->lysis

Lysogenic: viral DNA integrates in host → can activate later
(lysogenic conversion may make bacteria more harmful)

• Viral DNA is duplicated along with the regular genome and can provide adaptive genes for the host 

• Phages undergo adsorption and penetration into the bacterial host but not replication or release immediately (enter prophage state)

• Induction is a process where a prophage in a lysogenic cell will be activated and move directly into viral replication and the lytic cycle.

Lytic vs lysogenic infection preference & why?

Lytic infection. This is because the lysogenic cycle that brings on a lysogenic infection introduces a dangerous phenomenon known as lysogenic conversion, which can cause bacteria to produce enzymes or toxins that do not exist in a standard lytic infection.

Since the viral genetic material is incorporated into the host’s, the daughter cells also inherit toxin-producing genes, creating a large population of these deadly pathogens.

If the prophage becomes active and enters the lytic cycle, the host cell bursts and releases a wave of toxins, which often causes more severe, life-threatening bacterial diseases than those caused by the lytic cycle (a lytic infection).

How biofilms form and why they increase virulence.

Biofilms form when free-floating microorganisms like bacteria attach to an organic surface coating using cell surface structures like flagella or fimbriae.

The cells will stick to the coating, and as they divide form a dense mat bound together by sticky extracellular deposits (glycocalyx- a coating of repeating polysaccharide or glycoprotein units that helps a cell adhere to its environment and protects it).

Additional microbes are attracted to developing film and create a mature community with complex function. 

They transform free-floating cells to protected communities that are shielded from our immune system (phagocytes, immune cells) and antibiotics (which struggle to penetrate the matrix).

Cells now have adhanced adhesion and can detach from the colony → firmly attach and colonize new surfaces (host tissue, medical devices) → cause persistent and treatment-resistant infections.

Why bacteriophages matter in medicine.

Bacteriophages (a virus that specifically infects bacteria- “bacteria eating”) often make the bacteria they infect more pathogenic for humans.

During a phenomenon called lysogenic conversion a bacterium carrying a temperate phage can produce toxins or enzymes, transforming harmless bacteria into disease-causing pathogens.

^Thus, they matter in medicine because they are a direct cause of toxicity in several human diseases. 

They can also destroy bacteria such as those that are resistant to antibiotics without affecting normal flora due to their high specificity to their bacterial hosts. Thus, providing a treatment option for bacterial infections.

How lysogenic conversion increases pathogenicity

Lysogenic conversion increases pathogenicity because it allows a bacterium to gain new genetic traits due to the presence of genetic material from an infecting phage.

For instance, phage genes in the bacterial chromosome occasionally cause the production of toxins or enzymes that the bacterium would not otherwise have. This phenomenon can render harmless bacteria virulent, as seen with the diphtheria toxin, which is a bacteriophage product that makes C. diphtheria harmful.