Module 1 Flashcards
(17 cards)
Characteristics of microorganisms
- too small to be seen without microscope
- less than 0.1mm
- usually unicellular
- also called “germs” “microbes” “bugs”
Groups of microorganisms (in order of decreasing size)
- Protozoa
- fungi
- Bacteria
- Viruses
Protozoa
- unicellular, able to move by flagella or ameboid motion
- live in water and soil
- Giardia infections aka “beaver fever” results in diarrhea and moves by flagella
- Amoeba causes diarrhea and moves by extension of pseudopods and do not have flagella
Fungi
- non-photosynthetic plants
- primitive plants
- divided into two groups:
Yeasts= unicellular
-reproduce by budding
-Candida is a type of disease that may cause oral thrush, vaginal discharge, skin infections, pneumonia, or death
Molds= multicellular
-microbes that causes ringworm and athletes foot
Bacteria
- unicellular; no organized nucleus cell wall
- Ubiquitous: meaning they are just about everywhere there is moisture and nutrients
- Strept throat caused by bacteria Streptococcus
- causative agent of strept throat, staph infections, salmonella infections
Viruses
- even smaller than bacteria
- a bit of DNA or RNA surrounded by a protein coat and sometimes a lipid coat
- grow only in other living cells
- influenza virus, mumps, measles, rubella
Size of microorganisms
- measured in micrometers
- 1 micrometer= 1/1000 of a millimetre
- All microorganisms are smaller than 0.1 mm which equals 100 micrometers
Protozoa= 15-20 micrometers Fungi= 5-10 micrometers Bacteria= 0.3-5 micrometers Viruses= 0.02-0.2 micrometers
Shapes of bacteria
Round= cocci (coccus)
Rectangular= rods/bacilli (bacillus)
Spiral/curved= spiralla (spirillum)
Gram reaction of bacteria
Gram stain
Appear dark blue (gram positive)
Appear red (gram negative)
-determined by cell wall structure
Using the gram reaction bacteria can be divide into 6 groups: A. Gram positive cocci B. Gram negative cocci C. Gram positive rods D. Gram negative rods E. Gram positive spiralla F. Gram negative spiralla
Why the gram reaction is important
- first step in identifying bacteria (look at shale and gram reaction)
- determines effectiveness of antibiotics
- determines effectiveness of disinfectants
Bacterial Endospores
- Only a few bacteria (gram positive rods such as tetanus, gangrene, botulism, anthrax) can form these under adverse conditions (too dry, too cold, lack of nutrients)
- Spores vegetate (start growing) when growth conditions become good–> refer to summary sheet diagram
- Spores resist drying, heat, and disinfectants (hard to kill)
- heat: may take 121 degrees to kill
- disinfectants: high level and long exposure time
- cold: can resist very cold temps
- also resistant to UV light, acids, alkalis
Bacterial Growth
- Reproduce by binary fission–> refer to diagram in booklet 1.2
Time for this to occur (for population to double)= generation time= 15-30 minutes for rapidly growing bacteria (under ideal conditions)
Generation time is related to the rate at which bacteria cause disease.
- In lab, grown bacteria on culture media
- Colony= visible mass of bacteria that forms on surface of solid culture media
- usually takes 18-24 hrs to form from 1 original cell
- each colony is a clone; all descendants of a single bacterial cell
Bacterial growth curve
& growth curve relating to infection
Four phases–> refer to summary sheet diagram
- Lag- adapting to new environment
- Log- max. Reproduction.
- Stationary- not change in #
- Death- spores may form
Viral characteristics
- metabolically inert: can multiply only in living host cells
- contain DNA or RNA, not both
- have protein coat that surrounds nucleic acid +/- lipid envelope
Lipid viruses are generally easier to destroy than those with only a protein coat (exception Hepatitis B- lipid virus survives 7 days on surfaces)
Multiplication of animal viruses
- Attachment to complementary site on host cell membrane
- Penetration
- Viral nucleic acid–> nucleus: takes command of host cell and directs synthesis of new viral components
- Synthesis of viral components:
- nucleic acid: in nucleus
- protein coat: in cytoplasm
- Assembly of viral components
- Release from host cell
Effects of viruses on host cell
- Usually host cell dies:
- lysis; cell fills with virus particles
- diversion of metabolic pathways
- destroyed by hosts own lymphocytes (ex. Hep B virus) - Host cell may be transformed into tumor cell (oncogenic virus, ex. Hep B)
Control of viruses
- Antibiotics have NO effect
- Antiviral drugs: Acyclovir, ZDV, etc.
- More and more antivirals being developed. Problem is that have to develop drugs which will destroy viruses without destroying host cells.
