MICRO FINAL REVIEW 2026

Microorganisms

Microscopic organisms not visible to the naked eye

Shared cell structures

Cell membrane, cytoplasm, ribosomes, DNA

Eukaryotic cells

Have nucleus, organelles, larger, 80S ribosomes

Prokaryotic cells

No nucleus, smaller, 70S ribosomes

Louis Pasteur

Disproved spontaneous generation; showed microbes cause disease

Antonie van Leeuwenhoek

First to observe microbes (“animalcules”)

-named them beasties

Robert Koch

Linked microbes to disease (Koch’s postulates)

Scientific naming

Genus capitalized + species lowercase, italicized

• Homo sapiens

Five I’s

Inoculation, Incubation, Isolation, Inspection, Identification

Selective media

Inhibits some microbes

Differential media

Distinguishes microbes (color change)

Complex media

Unknown exact composition

Defined media

Exact chemical composition known

Pure culture

One species

Mixed culture

Multiple known species

Contaminated culture

Unwanted microbes present

Magnification

Ocular × objective lens

Ribosomes

Protein synthesis

Plasmids

Extra DNA, often antibiotic resistance

Endospores

Survival structures

Peptidoglycan sugars

NAM and NAG

Bacterial shapes

Cocci, bacilli, spirilla

Bacterial arrangements

Diplo (pairs), strepto (chains), staph (clusters)

Endospore producers

Bacillus and Clostridium

Hyphae

Thread-like fungal cells

Mycelium

Mass of hyphae

Saprobe

Feeds on dead matter

Parasite (fungi)

Feeds on living host

Protozoa movement

Flagella, cilia, pseudopodia

Trophozoite

Active stage

Cyst

Dormant stage

Virus structure

DNA or RNA + capsid ± envelope

Capsid

Protein coat made of capsomeres

Envelope

Host-derived membrane layer (not all viruses have it)

Lytic cycle stages

Attachment, entry, synthesis, assembly, release

Animal virus entry

Direct penetration, membrane fusion, endocytosis

Micronutrients

Needed in small amounts

Macronutrients

Needed in large amounts

Obligate aerobe

Requires oxygen

Obligate anaerobe

Oxygen is toxic

Main elements

CHONPS

Carbon Hydrogen Oxygen Nitrogen Phosphorus Sulfur

Diffusion

Movement from high to low concentration

Osmosis

Diffusion of water

[low] → [high]

Active transport

Requires energy to move substances

Psychrophile

Cold-loving

Mesophile

Moderate temperature (human pathogens)

Thermophile

Heat-loving

Hyperthermophile

Extremely hot environments

Halophile

Requires salt

Facultative halophile

Tolerates salt

Mutualism

Both benefit

Commensalism

One benefits, other unaffected

Parasitism

One benefits, host harmed

Lag phase

No growth, adjustment

Log phase

Rapid growth

-exponential stage

Stationary phase

Growth = death

-toxic waste accumulation

-nutrients are used up

-depletion of nutrients

-increases density of cells

Death phase

Cells die rapidly

-cells die faster than they can be produced

Metabolism

All chemical reactions

Catabolism

Breaks down molecules

Anabolism

Builds molecules

Enzymes

Biological catalysts

Substrate-level phosphorylation

Direct ATP production

Oxidative phosphorylation

ATP via ETC

• involved redox reactions

• uses the reduction of oxygen to generate high-energy phosphate bonds (ATP)

Cellular respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Total ATP

~30–32 ATP

Glycolysis total ATP

2 ATP

ETC ATP

~28–32 ATP

Nucleic acids

Made of nucleotides

Nucleotide parts

Phosphate, sugar, base

DNA

Double-stranded, thymine

RNA

Single-stranded, uracil

Base pairing

A-T, G-C

Anti-parallel

Strands run opposite directions

• 5’ → 3’ going up

• 3’ → 5’ going down

Transcription

DNA → RNA

Translation

RNA → protein

Start codon

AUG

Anticodon

UAC

Ribosome sites

A, P, E

Antimicrobials target

Cell wall, membrane, proteins, DNA

Resident microbiota

Permanent microbes

Transient microbiota

Temporary microbes

Most common portal of entry

Respiratory tract

Sign

Observable

Symptom

Felt by patient

Disease stages

Incubation, prodromal, illness, decline, convalescence

Transmission modes

Contact

• direct contact

• indirect contact (spread via a fomite)

• droplets (pathogens spread via sneeze, cough)

Vehicle

• airborne (travels >1 meter like A/C units, wind)

• waterborne (fecal/oral transmission: Cholera)

• foodborne (inadequately processed, packaged, refrigerated, and undercooked foods also feces contamination)

• body fluids (anything blood, urine, saliva)

Vectors

• animal that transit diseases among hosts

• biological vectors -transmit pathogens and serve as host for some stage in life

  • harbor pathogens that reproduce within them and are then transmitted

• mechanical vectors - passively transmit pathogen on body to new host

  • carry pathogens on their body

Fomite

Contaminated object

• inanimate object; doorknob, toys, utensils

HAI

Healthcare-associated infection

• transmission of pathogens between staff and patients and among patients

• handwashing is most effective way to reduce them

• immunocompromised patients

• presence of microorganisms in hospitals

First line defense

Skin

• epidermis, dermis,

  • has phagocytic cells to remove microbes

Mucous membrane

• lines all body cavities that open to the environment

• lysozyme is the chemical that defends against pathogens

• Cillia, tears, saliva, urine, vaginal secretion, blood flow, etc.

• AMP’s (antimicrobial peptides)

Chemical barriers

• dermcidins (from sweat glands, broad spectrum)

• perspiration (salt prevents growth and saltiness keeps most microbes at bay)

• sebum (nat oil production)

  • lowers pH

  • prevents skin from breaking and tearing

Second line defense

Phagocytes, inflammation, fever

• operates when pathogen penetrates the skin or mucous membrane

• made of cells, antimicroboial chemicals and process

Lysozyme

Enzyme in tears that breaks cell walls and help prevent infection

Phagocytosis steps

Chemotaxis

• microbe releases secretion, sensed by the phagocyte, then moves toward the microbe

Adhesion

• phagocyte attaches via surface proteins

  • Opsonization - increasing the # of binding sites

Ingestion

• engulfed microbe

Maturation

• phagosome (a vesicle or bubble of microbes)

Killing

• phagolyzosome (digestive enzymes merge with phagosomes)

Elimination

• enzymes destroy the microbe → release of residual debri

Eosinophils

Target parasitic helminths

TLRs (toll-like receptors)

Detect pathogen-associated molecular patterns (PAMPs) “danger signals”

Complement pathways

Classical , alternative, lectin

Complement result

MAC formation → cell lysis

Adaptive immunity cells

B cells, T cells

T cell types

Helper, cytotoxic, regulatory

Antibodies

Bind and neutralize pathogens

Antibody types

IgM, IgG, IgA, IgE, IgD