Chapter 4

unicellular microorganisms

• bacteria

• archaea

• protozoa

• some fungi

• some algae

bacteria shapes

bacillus = rod

spiral

coccus = spherical or ovoid

how can bacteria group together?

in pairs, chains, or clusters

bacteria cell wall main ingrediant

peptidoglycan

methods of protozoa movement

pseudopods, flagella, and cilia

helminthes

worms (type of multicellular parasite)

virion

complete virus (protein coat, genetic material, envelope, lipids, etc.)

victims of viral infection include:

everything except archaea

capsid + what it’s made of

a virus’s protein coat that protects its genetic material; made of capsomeres

composition of a virus’s envelope

lipids and polysaccharides

5 differences between viruses and living cells:

1. have either RNA or DNA; living cells have both

2. unable to replicate on their own

3. do not divide by binary fission, mitosis, or meiosis (like cells do)

4. lack genes and enzymes necessary for energy production

5. depend on host cell for protein and nucleic acid production

capsomeres

things that compose a virus’s capsid

most common (and dangerous) viral genome types (of the four options)

• double stranded DNA virus

• single stranded RNA virus

virus genome shape

usually circular, sometimes linear

ways to classify viruses:

• type of genetic material

• shape and size of capsid

• number of capsomeres

• presence or absence of an envelope

• type of host it infects

• disease it produces

• target cells

• immunologic / antigenic properties

bacteriophages (phages) + categories

viruses that infect bacteria

• either virulent or temperate

• potential applications for treating viral diseases

virulent bacteriophage

bacteriophage that causes the lytic cycle, which destroys the bacteria host cell

temperate bacteriophage

bacteriophage that incorporates DNA into bacterial chromosome (usually) without destroying it; DNA can remain in bacterial chromosome for generations

Why do some viruses only infect certain animals or regions of the body?

viruses can only attach to and invade cells with appropriate receptors

latent virus infections + examples

virus hides from host’s immune system for a while by staying dormant; generally longterm once activated

• ex) herpes, chickenpox / shingles

antiviral agents + how they work

drugs that treat viral infections (antibiotics not effective); they interfere with virus specific enzymes and virus production by inhibiting synthesis of viral genetic material or proteins

oncoviruses / oncogenic viruses (+ three examples)

cancer causing viruses

• ex) Epstein-barr virus, human papillomaviruses, HTLV-1

HIV structure

enveloped, single stranded RNA virus

primary targets of HIV

CD4+ cells (a type of T-cell)

viroids

short fragments of single-stranded RNA, which can interfere with the metabolism of plant cells

• transmitted between plants in the same manner as viruses

prions

small infectious proteins that cause fatal neurologic diseases in animals

examples of prions

• scrapie

• mad cow disease (Bovine Spongiform Encephalopathy)

• Kuru

• Creutzfeltd-Jacob disease

mycoplasma spp

bacteria without a cell wall

characteristics of bacteria used in classification

cell morphology, staining, motility, colony morphology, atmospheric requirements, nutritional requirements, biochemical and metabolic activities, enzymes produced, pathogenicity, genetic composition

cocci structures

• single

• pairs (diplococci)

• chains (streptococci)

• clusters (staphylococci)

• packs of four (tetrads)

• packs of eight (octads)

bacilli structure

• single

• pairs (diplobacilli)

• chains (streptobacilli)

• long filaments

• branched

• extremely short (coccobacilli)

important bacilli

• Escheria (like E. Coli)

• Klebsiella

• Proteus

• Pseudomonas

• Haemophilus

• Bacillus

(spp)

important curved and spiral shaped bacteria

• Vibio

• Campylobacter

• Helicobacter

• Treponema

• Borrelia

(spp)

steps for the diagnosis of infectious disease (10)

1. patient consults clinician

2. clinician makes initial dx and orders tests

3. appropriate specimens collected for lab

4. specimen examined

5. preliminary report

6. specimen cultured and plates intubated

7. definitive report

8. clinician interprets report and prescribes tx

9. patient is monitored for success or failure

sx, dx, tx

shorthand for symptoms, treatment, diagnosis

types of staining procedures

• simple stains

• structural stains

  • capsule stains

  • spore stains

  • flagella stains

• differential stains

  • gram stain

  • acid-fast staining

fixation purposes (in the context of staining)

kills organisms, preserves morphology, and anchors smear to slife

fixation techniques (two)

• methanol fixation (standard)

• heat fixation (not standard)

  • excess eat distorts bacterial morphology

Dr. Hans Christian Gram

Danish scientist who studied lung tissue of dead pneumonia victims and invented gram staining

simple staining

just stain the bacteria and put it on a slide. Make sure you give the stain time to soak in

chemical ingredients used in gram staining

• crystal violet

  • main dye

• iodine

  • mordant (helps crystal violet stick)

  • combined with crystal violet is water insoluble and becomes yellow / brown

• alcohol or acetone

  • removes dye from gram- bacteria

• safranin

  • counterstain

  • Gram used bismarck brown

why does gram staining work?

the thick peptidoglycan layer in gram positive bacteria

• gram negative have a thin layer with an outer layer of fats and sugars (phospholipids and lipopolysaccharides)

Examples of gram staining not working well

• spirilla spp. (too thin)

  • treponema pallidum

• mycobacterium tuberculosis

  • works better with acid-fast stains