01_Bacteria Structure Flashcards
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 Fungi Protozoa Bacteria
- 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
What are pili made of?
- pilins
* Adhesins (on tip) (typically a lectin, which is a protein that binds to carbs)
Explain examples of clinical significance of pili.
• adherence to epithelial cells
o in urinary tract, bacteria are richly piliated and bind to the urethra
o Gonococci (gonorrhoea)
• formation of microcolony
• bacterial evolution via conjugation and horizontal transfer
What other bacterial structures are used for adherence (other than pili)?
• glycocalyx in gram + (this is a polysaccharide)
o bind to heart valves, catheters, and teeth
What are spores? Are they common? Under what conditions do they form?
- During nutrient deprivation, one spore can form from one bacteria, which contains the essential components of the bacteria, and can be “re-constituted” when environmental conditions return.
- Trivia: spores can last at least 250 million years
What are spores resistant to? What compounds in spores confer resistance? What can kill spores?
- Resistant to drying, heat, and chemical agents (detergents).
- Dipicolinic acid (calcium chelator)
- High heat and pressure. They can survive boiling.
Spores are rare. What are examples of spore-forming bacteria?
• Large Gram +
o Bacillus and clostridia (gangrene)
o Bacillus Anthracis (anthrax) (can germinate in the lungs)
Aside from passive diffusion, what are the three transport mechanisms for bacteria membranes?
• Facilitated diffusion
o Followed by rapid metabolism of compound. Intracellular concentration is kept low
• Phosphoenolpyruvate: Sugar Phosphotransferase system
o Involves chemical transformation during transport
o PEP + sugar ==> sugar-P + pyruvate
o Sugar-P is trapped in cell and metabolized
• Active transport (in or out)
o Intracellular concentration > extracellular (often)
o Example antibiotic pumps
What are some common secreted factors?
- Exotoxins
- Proteases
- Amylases and other polysaccharide-specific degradation enzymes
- Lipases
What are examples of exotoxins?
• Exotoxin A, pertussis toxin, Anthrax, Hemolysins, and others
What are examples of proteases?
• elastase
What are examples of polysaccharide degradation enzymes?
- rhamnogalacturonate lyase
* alginate lyase
What are examples of lipases?
• phospholipase C
Explain chemotaxis
- sugars, proteins, and other compounds can function as attractants (positive chemotaxis) or repellants (negative chemotaxis0
- Bacteria have “tasters” that control flagella
- Flagella counter clockwise ==> move straight
- Flagella clockwise ==> change direction
