Taxonomy, Structure, Physiology Flashcards
What can bacteria be classified as medically?
Medically speaking, bacteria can be classified as:
– Frank Pathogens
• Capable of causing disease in any host; always considered a pathogen when isolated
– Opportunistic Pathogens
• Capable of causing disease given the opportunity; often a
commensal and part of the normal host flora, but is capable of causing disease in normally sterile tissues (most pathogens fall into this group)
– Non-pathogens
• However, even weak or non-pathogenic bacteria can cause
disease in hosts with weakened immune systems
What is a frank pathogen?
Capable of causing disease in any host; always considered a pathogen when isolated
What is an opportunistic pathogen?
Capable of causing disease given the opportunity; often a
commensal and part of the normal host flora, but is capable of causing disease in normally sterile tissues (most pathogens fall into this group)
What is a non pathogen?
However, even weak or non-pathogenic bacteria can cause
disease in hosts with weakened immune systems
What is the formula for virulence and resistance?
D= N*V/R
Disease
Number of organisms
Virulence of the organism
Resistance
What is the purpose of artificial classification schemes?
Bacterial classification schemes are artificial in order to:
- speed up the identification process
- identify bacteria using a limited # of characteristics
What is involved in bacterial nomenclature?
Bacterial nomenclature involves use of
- binomial system to assign a genus and species
- specific conventions for naming
- Example: Salmonella cholerasuis
What is bacterial identification normally based on?
- morphological, biochemical and serological “traits”
- other: nucleic acid profile (DNA/RNA)
What are the cell arrangements/ division planes?
- Diplococci
- Streptococci
- Tetrad
- Sarcinae
- Staphylococcus
What are the parts of a procaryotic cell?
What are the parts/ steps to bacterial spores?
What are gram negative and positive bacteria? What is their characteristic differences?
- The terms gram-positive and gram-negative refer to the color of the bacteria after Gram staining.
- Gram-positive bacteria have a thick peptidoglycan cell wall and appear blue/violet.
- Gram-negative bacteria have a thin peptidoglycan wall, but have a –lipid-rich outer membrane, and appear red after Gram staining.
How do you make a gram stain?
- Make a THIN smear from a pure culture on a slide and heat-fix.
- Cover smear with crystal violet; let stand for 30 sec.-1 min. Rinse.
- Cover smear with Gram’s iodine (mordant); let stand for same amount of time. Rinse.
- Hold slide at an angle and rinse with alcohol or alcohol-acetone until blue runs off. Rinse.
- Cover smear with safranin for 30 sec.-1 min. Rinse, blot dry, and examine under oil immersion at 100X.
What are Lipopolysaccharides?
Lipopolysaccharide (LPS) – LPS is also known as endotoxin, and is the predominant lipid in the outer leaflet of the outer membrane of the Gram-negative cell. LPS acts as the prototypical endotoxin because it binds theCD14/TLR4/MD2 receptor complex, which promotes the secretion of pro-inflammatory cytokines in many cell types, but especially in macrophages.
What is flagella?
Flagella - filamentous appendages ( 2-20 um) composed of
flagellin monomers; allow for motility; “H” antigens can be
detected with specific antibodies.
Flagella and pili may be glycosylated proteins.
What is a glycocalyx?
Glycocalyx – capsule or slime layer that is composed of
carbohydrates or glycoproteins; not necessary for growth, but
inhibits phagocytosis and antibiotic uptake; antigenic when on
cell and “K” antigens can be detected with specific antibodies.
What is pili?
Pili - filamentous appendages (0.5-2.0 um) composed of pilin
monomers; allow for adhesion (fimbriae) and specialized sex pili
allow for transfer of DNA between a donor and a recipient; highly
antigenic and antibodies can be used for sero-diagnosis.
