Introduction to Bacteria Flashcards
What type of bacteria is shown from this differential staining?
Gram (+)
What type of bacteria is shown from this differential staining?
Gram (-)
Describe the differences between gram (+/-) bacteria that make them stain different colors.
The structure of their cell walls.
Gram (+) bacteria have a thick, uniform peptidoglycan cell wall.
Gram (-) have a thin peptidoglycan cell wall, plus an outer membrane consisting of lipopolysaccharide (LPS).
Describe the 4 key characteristics of prokaryotes (bacteria).
- Unicellular
- Lack a membrane-bound nucleus
- Lack membrane-bound organelles
- Smaller & less complex than eukaryotes
What is the process of binary fission?
2 daughter cells resulting from a single cell replicating its own DNA
Describe acid-fast bacteria.
Bacteria with thick, outer lipid-rich layers comprised of mycolic acids, which render “acid-fast” bacteria that are resistant to becoming decolorized (with acid-alcohol) once stained red. Can survive inside cells and are targets for other antibiotics.
What is the importance of differential staining of bacteria?
Antimicrobial therapy = the most effective when it is narrow-spectrum targeted. The type of bacteria determines the drug type (i.e., how the cell wall can be degraded)
What shape of bacteria is shown?
Coccus
What shape of bacteria is shown?
Rod (or Bacillus)
What shape of bacteria is shown?
Sprillum/Spirochete
What shape of bacteria is shown?
Mycobacteria
What shape/arrangement of bacteria is shown?
Corynebacteria (palisades arrangement)
“Coryne” = rod-like shaped
Palisades = fenced arrangement
What shape of bacteria is shown?
Coccobaccilli
What arrangement of bacteria is shown?
Streptococci (cocci in chains)
What arrangement of bacteria is shown?
Staphylococci (large cocci in irregular clusters)
What arrangement of bacteria is shown?
Spore-forming rods
What arrangement of bacteria is shown?
Streptomycetes (mold-like, filamentous)
-mycete = mushroom, fungus
What are the features of the “capsule” that encloses some bacteria?
Amorphous, gelatinous material enclosing around the cell wall; has pili attached to it; comprised of carbohydrates; antigenically diverse; anti-phagocytic!
Can you see capsules in a gram stain?
No
What is the importance of determining if a bacterium is enclosed in a capsule or not?
Determines type of antimicrobial needed (i.e., for cell-wall penetration/degradation)
Describe the gram stain protocol.
- Heat-fix
- Stain with crystal violet
- Stain with iodine treatment
- Stain with de-colorizer
- Counter-stain with safranin
- Will be either purple or pink
What is the purpose of pili?
Adherence
What is the purpose of flagella?
Motility
What is the importance of bacterial spores?
Dormant form of bacteria that are resistant to harsh conditions (extreme temperatures/pH; antibiotic exposure; lack of nutrition)
What forms a single colony on an agar plate?
A single bacterium that has undergone clonal expansion
If the # of colonies increases, then the # of bacteria ___.
increases
What are the two states bacteria can exist in?
Planktonic (free) or sessile (attached)
What forms a biofilm, and what state of bacterium is it?
Biofilm: sessile
Formed when a bacterial population becomes adherent to each other and/or a surface, and then becomes enclosed within a biopolymer matrix = “goop”
What is quorum sensing?
A communication mechanism used by bacteria within a biofilm that allows them to function as one/an “organism”
How do biofilms aid in the pathogenesis (development) of bacterial infections? (3)
- Aid in colonization
- Aid in avoiding phagocytosis
- Aid in avoiding antibiotics
Which type of bacteria requires O2 for growth (respiratory catabolism)?
(Strict or obligate) aerobes
Which type of bacteria is killed by O2 (fermentative pathways)?
(Strict or obligate) anaerobes
Which type of bacteria can grow either aerobically or anaerobically?
Facultative Anaerobes
Which type of bacteria require reduced O2?
Microaerophiles
What type of infection can you rule out anaerobic bacteria from your differential dx?
Surface-skin infection
What is the importance of knowing the atmospheric requirements of bacteria?
Influences your dx approach, which influences your tx plan
Where do anaerobic bacteria live in the body?
Epithelial surfaces of: G.I. tract lumen, gums, vagina
Describe the bacterial genome.
Haploid; circular chromosome with dsDNA
What is the significance of the plasmid molecule in bacteria?
carries genes for antibiotic resistance
What are 3 ways bacteria can undergo genetic variation?
- Mutation (change in nucleotide seq)
- Recombination (exchange of DNA b/w two separate bacteria; transduction, conjugation, transformation)
- Transposition (transposons “jumping genes”/integrons move locations within the genome, or integrate into plasmid –> jump to other bacteria)
