Question | Answer |
Microbiology | The study of microorganisms (microbes):
- Viruses
- Bacteria
- Parasites
- Fungi
- Others |
Prokaryotes vs Eukaryotes | PROKARYOTES DO NOT HAVE:
- membrane bound nucleus
- membrane bound organelles
- DNA that is organized into chromosomes. |
Prokaryotes Classification | - All living cells are either prokaryotes or eukayotes
- All bacteria are prokaryotic cells
- Divided into (5) classes
- Prokaryons in Kingdom Monera
- Many classes
- Earth's most abundant form
- 0.5-2UM in size |
Prokaryotic Cell Structures | - Cytoplasm
- Ribosomes
- Nucleoid (chromosome)
- Inclusion Bodies
- Some prokaryotes secrete a capsule & have plasmids. |
Prokaryotic Cytoplasm | - Semi-fluid substance that fills inner cellular space
- Primarily water with carbohydrates, lipids, and various enzymes. |
Prokaryotic Ribosomes | - Consists of RNA and protein
- Used in protein synthesis |
Prokaryotic Nucleoid | - Chromosomes
- No real nucleus |
Prokaryote Inclusion Bodies | Stores molecules essential to cell function. |
Capsule | A protective structure that serves as a defense mechanism in some prokaryotes consisting of:
- Tightly bound wall with complex polysaccharide molecules that form a gel-like covering that surrounds the bacterial cell. |
Plasmids | Some prokayrotes contain a self-replicating extrachromosomal DNA that carry 1 or more pieces of genetic information, not required to sustain life. |
Prokaryote Cell Structure | Cell Wall:
- Shape & stability
- Contain peptidoglycan, large polymer resembling a "chain link fence"
- Antibiotics target cell wall (i.e penicillin)
"Eukaryotes do not have cell wall" |
Prokaryote Cell Membrane (aka plasma membrane) | - Regulates transport of material in and out of the cell
- Made of phospholipids
- Long-chain fatty acids and proteins
- Selectively permeable |
Peptiglycan | Large polymer which makes up a prokaryote cell membrane with an immense, covalently-linked molecule linked in multi-layers resembling a "chain-link" fence |
Flagellum (singular); Flagella (plural) | Filamentous organelles of locomotion found on half all known bacteria |
Motile | Various degrees of movement |
Pili (singular: pilus) | Tiny, tube-like projections from the cell's surface associated with adherence |
Prokaryotic Bacterial Cells: (Shape & Arrangement) | - characterized by shape & size
- before culture information is available, location and appearance characteristics were used |
Cocci (singular: coccus) | Spherical bacterial cells |
Bacilli (singular: bacillus) | Rod-shaped bacterial cell resembling a hot dog |
Vibrios | Comma shaped bacterial cell |
Coccobacillus | Bacterial cell shaped between cocci & bacilli |
Spirillia | Bacterial cell which appears loosely-coiled or wavy |
Spirochetes | Bacterial cell which appear tightly coiled, corkscrew-shaped rods. |
Gram Stain | Method used to group bacteria into 2 different catagories:
- Gram positive bacteria (purple)
- Gram negative bacteria (pink) |
Gram-Positive Bacteria | - Thick layer of peptidoglycan (thick cell wall)
- Teichoic acid causes retention of crystal violet (blue) dye |
Gram-Negative Bacteria | - Thin layer of peptidoglycan (thin cell wall)
- High lipoprotein content which releases crystal violet dye when rinsed with alcohol
- The safranin (pink) counterstain is retained |
Gram Stain Method | 1-Sample smeared on slide & fixed with heat
2-Slide stained with crystal violet (purple)@ 1-2 mins.
3-Gram's iodine used to "fix" the crystal violet (help retain stain)
4-Acetone used to decolorize slide
5-Stain slide w/safranin (pink) |
Diplococci | - Cocci in pairs
- Ex.: Gonorrhea |
Streptococci | - Cocci in chains
- Ex.: Aureus, Boils |
Staphylococci | - Cocci in grape like pairs
- Ex.: Staphylo (irregular clusters) |
Culture Media - Identifing Specific Bacteria | - Can be liquid or semi-solid
- 3 Different Types:
< Enriched Media
< Selective Media
< Differential Media |
Tetrad | - Group of four
- Micrococcus
- Rarely pathogenic |
Enriched Media | encourages the growth of most bacteria (Sheep's blood "Agar plate") |
Selective Media | Encourages the growth of some bacteria which inhibiting others ("MacConkey" Agar) |
Differential Media | Groups bacteria based on the fermentation of carbohydrates ("MacConkey" Agar) |
MacConkey Agar | Used in both Selective and Differential Media |
Aerobes | - Require atmospheric oxygen
- Ex.: Staphylococcus, Streptococcus, E. coli |
Anaerobes | - Require no oxygen
- Ex.: Colstridium species, Gangrene
- Used to put candle in the container until it burns out |
Microaerophilis | - Require reduced oxygen & increased CO2
- Ex.: Campylobacter |
Binary Fission | - Term used to describe cell division
- Aka "Transverse Fission"
- Do not have a cell cycle replicating their DNA
- Continuosly dividing & |
Lag Phase | - Gear up phase
- Organisms not greatly increasing in #, but metabolically active
< Growing, synthesizing enzymes, & producing lrg. amounts of ATP |
Log Phase | - Once bacteria have adapted to nutrient-rich environment, growth is exponential (Logarithmic)
- Generation time: genetically determined period of log. growth
- Varies by species (min to hr)
- Ex.: generation = 20 min
< 1000 org/ml - initial
< |
Stationary Phase | - When the # of new cells produced is the same as the # of cells dying |
Decline (Death) Phase | - # of cells dying is greater than the # of new cells arising from division |
Symbiosis | - "Living together" in relation to bacteria
- 3 Different types:
< Mutualism
< Parasitism
< Commensalism |
Mutualism | - Both the host & the microorganism benefit
< E. coli, a bacterium that lives in the large intestines |
Parasitism | - One organism benefits, the other is harmed
< Tapeworm, Malaria |
Commensalism | - One organism benefits, the other is neutral
< skin bacteria, normal flora
< majority of microbes |
Normal Flora | - Organisms that live on or in the body but do not usually cause disease (commensals)
< skin, conjunctiva, mouth, nose, throat, urinary tract, reproductive, & GI tracts.
- Nutrients from oils & sweat facilitate colonization up to a dozen staph specie |
Normal Flora in Infants | Infant have:
- not acquired normal flora
- less organic acid available to minimize growth
- ideal environment to grow pathogens
- Pathogens include: Grp B strep & Candida (yeast) |
Resident Microflora | Organisms found on/in specific areas of the body |
Transient Microflora | Organisms that "come and go" and exist in the same areas occupied by resident flora |
Pathogenicity | Organism which benefits from its host and often lead to infection |
Virulence | Term used to describe the intensity of bacterial & other microbial infections |
Pathogenic Mechanisms of Bacteria | 3 Types:
- Adherence
- Colonization
- Formation of a capsule |
Adherence | Bacteria use pili to cling to surface of host cells, multiply & form colonies |
Colonization | Once in place within host tissue, bacterial replication forms colonies and may overcome host defenses.
< colonization in small #s of non-invasive organisms is normal in all animals |
Formation of a Capsule | Capsule contributes to organism's virulence due to thick, polysaccharides structure - helps to resist host defense processes |
Invasiveness | Ability of organisms to penetrate host tissue, usually by special enzyme |
Enzymes contributing to Invasiveness | 3 Different Types:
- Hyaluronidase
- Coagulase
- Streptokinase and Staphylokinase |
Hyaluronidase | Attacks hyaluronic acid, the ground substance of connective tissue |
Coagulase | Breaks down collagen, the framework of muscles |
Streptokinase & Staphylokinase | Digest fibrin & prevent the clotting of blood
< "flesh-eating bacteria" ex. of organism that produces streptokinase |
Exotoxins | Secreted primarily by Gram-positive organisms
< Gram (+) = botulism, gas gangrene, tetanus, staphylococcal food poisoning
< Gram (-) = E. coli O157:H7 Shiga toxin |
Endotoxins | - Release from Gram (-) bacteria when they die
- Non-specific gastrointestinal symptoms such as diarrhea, cramping, & generalized malaise
< Ex.: cholera, salmonella |
Endospores | - Dormant form
- Form when conditions are unfavorable for growth
- Survive under harsh conditions
< excessive heat or cold
- Revert to active under favorable conditions
- Clostridia species that cause tetanus, botulism, & gas gangrene form endosp |
Exchange of Genetic Material | Bacteria can exchange genetic material 3 different ways:
< Transformation
< Transduction
< Conjugation |
Transformation | - DNA is acquired directly from the environment which was released from another cell through lysis etc.
- Fragments are then "spliced" into the host cell's DNA |
Transduction | - An asexual genetic process
- Viruses (Bacteriophages or phages) transfer genes between mating bacteria |
Conjugation | - Requires contact between 2 bacteria
- utilizes a plasmid
- transfers a greater amount of DNA than transformation or transduction
- DNA is to be transferred from a donor cell to a recipient cell |
F-Pilus | - Sex pilus
- transfers DNA from one cell to another in conjugation |
Plasmid | Extra-chromosomal DNA in the cytoplasm of some bacteria but not required by the bacterium |
Resistance Transfer Factors | Bacteria which develop a drug resistance through plasmids |
Genetic Recombination | By 3 different processes, transfers DNA leading to new strains of bacterium including antibiotic resistant strains |
Antimicrobial Agents | Substances used to specifically treat infectious microbial diseases |
Antibiotics | Antimicrobial agent containing substances derived from other organisms |
Spectrum of Activity | Antimicrobial classifications:
< Broad Spectrum
< Narrow Spectrum |
Broad Spectrum | Antimicrobials which are effective against a wide range of microorganisms including both gram (+) & gram (-) bacteria |
Narrow Spectrum | Antibiotics are effective against a limited # of microorganism or single taxonomic group |
Bacteriocidal Drug | Kills the organism |
Bacteriostatic Drug | Inhibit the organism growth & allows immune defenses to act against the invader |
Resistance Factors (Causes of) | Occurs through:
- overuse of antibiotics
- plasmids
- genetic transfer mechanisms
- development of neutralizing enzymes
- alteration of pathways used by antibiotics
- altering cell membrane permeability |
Agar Disc Diffusion (Kirby Bauer Method) | - Uses paper discs impregnated with specific concentration of the antimicrobial to be tested
- Result reported as either:
< Sensitive: stays away from seed; inhibiting
< Intermediate
< Resistant: grows up to seed |
Upper Respiratory Tract Infections | Pharyngitis
- infections of upper tract:
< pharynx
< ears
< eyes
< sinuses
< upper bronchioles
- e.g. Strep throat caused by Streptococcus pyogenes |
Lower Respirator Tract Infections | - Pneumonias
- Casulated organisms that cause pneumonias include:
< haemophilus influenza
< Klebsiella pheumoniae
< Streptococcus pneumoniae |
Gastrointestinal Bacterial Infections | - Gastrointestinal
- Contaminated food or water
< Salmonella (raw eggs)
< Shigella
< Staphylococcus aureus
< E. coli O157:H7 (raw hamburger, contaminated fecal material) |
Nervous System Infections | - Meningitis
< haemophilus influenzae (children)
< Neisseria meningitidis
< Vaccines available for both |
Toxin-Induced Infections | - Botulism (Colstridium botulinum)
- Tetanus (Colstridium tetani)
- Toxic Shock Syndrome (Staphylococcus aureus) |
Intracellular Bacteria | 2 Different Classes:
- Chlamydia
- Rickettsias
- To a lesser extent: Mycoplasmas |
Chlamydia Trachomatis | - intracellular organisms
- require eukaryotic cell to replicate
- causes variety of human infections including:
< Trachoma (eye infection)
< Sexually-transmitted disease causeing pelvic inflammatory dise.
< Conjunctivitis in newborns |
Richettsias | - Obligate intracellular parasite
- Transmitted by a vector (ex. ticks & lice)
- Rocky Mountain Spotted Fever (RMSF)
- To human transmitted through the bite of the vector
- Rocky Mountian spotted fever, Lyme Disease |
Mycoplasma Pneumoniae | Primary atypical pneumonia "walking pneumonia" |
Mycoplasmas | - Tiniest free-living organisms
- Do not have a cell wall
- Mycoplasma pneumoniae (walking pneumonia)
< causes primary atypical pneumonia |
Viruses | - Obligate Intracellular Parasite
- Replicates w/n host cell
- virus provides RNA or DNA to replicate
- Host cell provides energy & resource
- Contain RNA or DNA (not both)
< RNA viruses contain code for reverse transcriptase, enzyme which makes D |
Viral Structure | - Nucleic Acid (RNA or DNA)
- Capsid: protective coat enveloping nucleic acid
- Envelope
< present in some viruses
< May have glycoprotein spikes
* determine specificity
* hide virus from immune system |
Nucleic Acid | Either a single or double strand of DNA or RNA, differing among viral groups |
Capsids | - Enclosed within a protective coat
- Determines the shape of the virus
- Composed of individual protein subunits (capsomeres)
- Can be helical, polyhedral (multi-sided) or bullet-shaped |
Capsomeres | Individual protein subunits found in a capsid |
Nucleocapsid | Combined capsid/nucleic acid arrangement |
Viral Envelope | - External to the capsid
- Acquired from combo of proteins, lipids & carbohydrates found in host cell |
Spikes | A projection, usually glycoprotein molecules, that attach to specific sites on host cell wall |
Viral Replication | Five Steps:
- Adsorbtion
- Penetration
- Synthesis
- Maturation
- Release |
Adsorption (Viral Replication - Step 1) | Attachment of virus to host cell
< specificity to certain cells |
Penetration (Viral Replication - Step 2) | Virus enters host cell (endocytosis or fusion) and "uncoats" (takes off envelope and capsid) |
Synthesis (Viral Replication - Step 3) | Utilizes host nucleus to make new genetic material |
Maturation (Viral Replication - Step 4) | Virus is packaged into new complete virons |
Release (Viral Replication - Step 5) | Departure of new virons from host cell
< host cell may rupture OR
< host cell remains intact & releases the virus |
Uncoating | Process of a virus loosing the envelope & capsid |
Viral Pathogenicity | Two Main Catagories:
- Acute Infections
- Latent/Persistent Infections |
Acute Infections | - Disease cycle is relatively short
- Host cell ruptures; virus spreads to neighboring cells
< Common cold (rhinovirus), influenza, some hepatitis viruses |
Latent/Persistent Infections | - Virus becomes relatively inactive by reemerges
- Provirus remains in host cells
- Replicates new virions when triggered by some external event (stress, fever, etc)
< Herpes Virus, Epstein-Barr Virus, Human Immunodeficiency Virus (HIV); T-Helper Ce |
Immune System Viruses | Epstein-Barr Virus (infectious mononucleosis) & Human Immunodeficiency Virus (HIV) |
Oncogenic Viruses | - Possess oncongenes (cancer causing genes) that cause uncontrolled & abnormal division of host cells by altering cell cycle "checkpoints"
< Hepatitis B, Hepatitis C
< Human Papilloma Virus (cause of cerical cancer) |
Oncogenes | Uncontrolled and abnormal division of host cells |
Interferon | Antiviral therapy which inhibits viral activity |
Prions | - Infectious proteins w/o genetic material
- Come in contact w/normal proteins and transform them into infectious
- Affects cells of the brain
- Creutzfeldt-Jakob disease ("mad cow") |
Infectious Particle | Infectious protein which affects the cells of the brain |
Transmissible Spongiform Encephalopathies | - "Spongiform" = cytopathic effect on brain tissue
- "Infection" = produces microscopic holes in brain resembling a sponge |
Prion Characteristics | - Generally resistant to inactivation by heating to 90*
- Resistant to radiation treatments
- Not susceptible to enzymes that inactivate RNA & DNA
- Susceptible to protein denaturing agents |
Fungi | - Important for decomposition & recycling
- Divided into 2 different groups:
< Yeasts = unicellular
< Molds = multicellular
- Ex.: Candida Albicans (yeast infection) & Tinea Corporis (ringworm, mold) |
Spores | Small deposits from the enviroment |
Molds | - Multicellular fungi
- One or more spores grows into filamentous, thread-like mass called "mycelium"
- Ex.: Athlete's foot, jock itch & ringworm |
Yeasts | - Unicellular fungi
- important in beer, bread, and alcohol production
- most common yeast infection: Candida albicans (infections: mouth & pharynx = thrush); vaginitis |
Protozoa | - Parasites except Helminths (worms)
- found in the Kingdom Protista
- single-celled organism
2 Different Stages:
- Motile trophozoite
> infective stage
- Cyst stage
> dormant state |
Parasitic Organisms (Protozoa & Helminths) | - Live at expense of host
- Transmitted to humans by vectors
> Biological = mosquito transmitting malaria
> Mechanical = transmission of parasite eggs to food by flies & other insects |
Helminths | - Known as "worms"
- multicellular
- found in Kingdom Animalia
- 4 Different Groups:
> Flukes
> Tapeworms
> Roundworms
> Tissue Parasites |
Trophozoite Stage | Stage of the protozoa which is the motile, invasive form of the organism |
Cyst Stage | Stage of the protozoa which allows the organism to survive in a dormant state in the external enviroment |
Common Pathogenic Protozoans | - Giardia Lamblia:
> ingesting cysts from animal contaminated water
> intense gastrointestinal (GI) distress & diarrhea
- Cryptosporidium:
> self-limiting GI symptoms
> if infected, can become carrier
> recently associated w/recreati |
Anopheles | Mosquito which serves as the definitive host in Malaria |
Helminths (Parasitic Worms) | - Hosts are definitive or intermediate
> Definitive: harbor parasite when it reproduces
> Intermediate: harbor parasite during a developmental stage in the parasite's life cycle
> Accidental: not part of the normal cycle; "dead end" hosts |
Tapeworms | - Segmented worms that contain a head (scolex) and many segments call "proglottids"
- Hermaphrodites
- Infective stage is larvae found in cattle & swine
- Most prevalent in
> Beef & Pork (taenia)
> Fish (Dibothrocephalus)
- Several cm to meter |
Roundworms (intestinal) | - Live in lumen of intestinal tract
- Infection occurs by ingestion of egg or penetration of the skin by larvae
> Pinworms (Enterobius)
> Ascarids (Giant intestinal worms)
> Hookworms |