01_Bacteria Structure Flashcards Preview

M1 Micro Bacteriology Quiz 1 > 01_Bacteria Structure > Flashcards

Flashcards in 01_Bacteria Structure Deck (43)
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Note: These are just a few cards. In info was mostly review for me.

Note: These are just a few cards. In info was mostly review for me.


When stained, what are the colors of gram positives? Gram negatives?

• Positives = violet
• Negatives = red


What are Koch’s postulates?

• find bacteria that causes disease
• grow bacteria in culture
• reproduce disease
• re-isolate bacteria from disease


What are Koch’s Molecular Postulates?

• The phenotype of the specific gene should be associated with a pathogenic strain
• Knock out should lead to reduced virulence
• Knock in should restore of virulence


What are the distinguishing characteristics (cell wall? Pathogenic? Energy source? Nucleus?) of…

• Algae: no pathogens, all photosynthetic, nucleus

• Fungi: some pathogens, non-photosynthetic; rigid cell wall; (fungi, including pathogenic fungi, will be discussed later in the course); nucleus

• Protozoa: some pathogens, no rigid cell wall; unicellular, nonphotosynthetic. Some parasites have cysts with a rigid cell wall. Ameba, Paramecium, Euglena; nucleus

• Bacteria:
o many pathogens
o most require organic compounds as energy source
o some of the non-pathogens are photosynthetic
o all (with one exception) have a rigid cell wall
o Nucleus


Explain the differences in movement of eukaryotes and prokaryotes.

• Euks: Cytoplasmic streaming (amoeboid), flagella, cilia
• Proks: flagella (with no microtubules, and does have H-Antigen)


Explain the differences in cell wall of eukaryotes and prokaryotes.

• Euks: Plants and algae have polysaccharide (glucose); fungi have chitin (acetyl glucosamine polymer) and beta1,3 glucan (glucose polymer)
• Proks: peptigoglycan polymer containing muramic acid (derivative of acetyl glucosamine); D-amino acids


What are the three shapes of bacteria?

• Coccus (round)
• Bacillus (rod)
• Spiral


Do bacteria have sterols in the cytoplasm or membrane?

• No. There is only one exception: mycoplasma.
• Euks do contain sterols.
• Proks DO NOT contain sterols


What is a diagnostic quality of Streptococci with regard to cell division? What about Staphylococci?

• Streptococci: form long chains
• Staphylococci: form clusters, like grapes


What are the layers of a gram +?

• membrane
• Thick peptidoglycan (not an antigen) with Teichoic acid (antigen) and Lipoteichoic acid (antigen)
• Note: Teichoic acid uses the sugar Ribitol


What are the layers of gram -?

• Inner membrane
• Thin peptidoglycan
• Outer membrane with Lipopolysaccharide (LPS) (endotoxin and O-antigen) and porins (passively transport
• Capsule (?)
• Note: There is the periplasmic space between the inner and the outer membrane


What is the H-antigen? What is the O-antigen?

• H = flagella
• O = LPS


What is the only bacteria without a cell wall?

• Mycoplasma (not mycobacteria!


What are the components of the cell wall in bacteria?

• N-acetyl glucosamine (NAG) linked to N-acetyl muramic acid (NAM) (this is a glycosidic bond)
• Short peptide (4 aa) linked to the lactic acid residue of the NAM
• Forms a chain linked fence
• This is called a peptidoglycan


How does penicillin affect the cell wall?

• it blocks the chain linking of the fence and the bacteria die


How does lysozyme (in tears) affect the cell wall?

• splits the glycosidic bond between NAG and NAM


What are the differences between gram – and gram +?

• see A-16 in notebook


What are the functions of the gram – outer membrane?

• B barrier to antimicrobial agents
• reacts with antibodies
• blocks entry of large molecules
o ex: lysozyme cannot degrade cell wall unless part of the outer membrane is removed
• more resistant to antibiotics and detergents than gram +


What is the function of porins in the outer membrane of gram -?

• Porins allow passive transport of small molecules and block other molecules
• Antibiotics against gram – must pass through porins in order to work on gram –


What is lipopolysaccharide (LPS)?

• found in the outer membrane of gram –
• Know: the Lipid A portion is embedded in the outer membrane, where as the oligosaccharide (the O antigen) is exposed to the environment
• There are many O antigens even within species of bacteria and are responsible for immunological specificity (different serotypes)


What is found in the periplasmic space in gram - ? How do gram + mimic this function?

• gram - : protective enzymes that degrade foreign molecules (like antibiotics)
• gram + : extrude degradative enzymes into its immediate environment


Explain the gram staining procedure.

• Stain with violet (violet enters the cytoplasm)
• Treat with iodine (the iodine binds with the violet)
• Wash with ethanol (the thick peptidoglycan of gram + traps the purple inside; for gram – the purple washes out)
• Counter stain with red (stains gram – red)


What are the exceptions?

• old gram + sometimes lose their purple-stain-retaining property
• If the cell wall of gram + were removed, it would stain as gram -
• There are “gram variable” bacteria exceptions. Some of these are medically important


What is the capsule made of? Does it stain?

• non-essential secretion of polysaccharide
• Does not stain
• Is usually found on gram -, but some gram + also have


What is the clinical significance of the capsule?

• can be pathogenic
• can be antigenic
• can be found in the urine or spinal fluid (bad)


What are flagella made of?

• flagellin


What are the two types of location for flagella?

• petrichous flagella (all over the cell)
• polar flagella (one side of cell)


Note: all motile bacterial have flagella. Not all bacteria are motile. Some motile bacteria with flagella lose their motility (age and/or conditions), but remain viable

Note: all motile bacterial have flagella. Not all bacteria are motile. Some motile bacteria with flagella lose their motility (age and/or conditions), but remain viable


What are the functions of pili and/or fimbriae? (hint: it gets raunchy) (name a second that is more modest in its function)

• Function in adherence to other cells, conjugation, and small amounts of movement
• F pili are are “male” donors that tranfer DNA to other bacteria
• The recipient now becomes an F pili
• IV pili function in “twitching motility” that can push and pull bacteria across a surface