Intro to Bacteria Flashcards
(36 cards)
Describe the following differences between Eukaryotic and Prokaryotic cells: Major groups, size, nucleus, chromosome, membrane bound organelles ribosomes, cytoplasmic membrane, cell wall, respiration, and reproduction.
Eukaryotes Prokaryotes
Major Groups: Fungi/Parasites Bacteria
Size: >5um 0.5-3um
Nucleus: classic membrane no membrane
Chromosome: >1, strands, diploid ~1, circular, haploid
MBO: Present Absent
Ribosomes: 80S (60+40) 70S (50+30)
CM: Contains sterols Anionic polymers
Cell Wall: Fungi (chitin) Peptidoglycan
Respiration: Mitochondria Cytoplasmic memb.
Reproduction: Sexual/asexual Binary fission (asexual)
What are 5 macroscopic characteristics of microbes that we can use to distinguish?
- Size
- Shape
- Fermentation of sugars
- Hemolysis
- Resistance to antibiotics
What are 4 microscopic characteristics of microbes that we can use to distinguish?
- Size
- Shape
- Arrangement
- Staining characteristics
What are 3 basic shapes of bacteria?
- Coccus (circular)
- Bacillus (rod)
- Spirillum (spiral)
Upon gram staining what color are gram negative and gram positive bacteria?
Gram negative: Pink
Gram positive: Purple
What bacteria cannot be classified by gram staining and why?
- Mycobacterium: waxy outer coat; acid fast
- Mycoplasma: no peptidoglycan
- Chlamydia: spore-like structure
- Treponema: very thin
What are 3 metabolic distinctions that can be made?
- Oxygen requirement
- Substrate utilization (lactose or non-lactose fermenter)
- Production of specific enzymes (ie catalase)
What is the most precise way of distinguishing between different microbes?
Genetic testing/Gene sequencing
Highly conserved sequences (16S rRNA) identify the genus
Highly variable sequences identify and species or subspecies
How does transcription and translation differ between eurkaryotes and prokaryotes
In prokaryotes transcription and translation may be coupled
What are the 5 functions of the prokaryotic cell membrane?
- Electron transport/ATP production
- Uptake and Secretion (ie toxins)
- Maintenance of membrane potential
- Septum formation for cell division
- Site of DNA and cell synthesis
What is the main purpose of the cell wall in prokaryotes?
- To prevent osmotic lysis of the plasma membrane
- Protect the cell from drying and desiccation
- Determine and maintain the shape of the cell
What is the structure of peptidoglycan?
Alternating and repeating disaccharide units of NAG and NAM which form a linear polymer in which the NAG is bound to a 4 amino acid oligopeptide of Ala-Glu-Lys-Ala. The polymers are then crosslinked by a pentaglycine which connects the Lys on one polymer to the Ala on another.
How does lysozyme disrupt the peptidoglycan structure?
Lysozyme cleaves the beta-1,4 glycosidic bond between NAG and NAM
How does penicillin function?
Penicillin binds to the transpeptidase which cross links the polysaccharides of the peptidoglycan wall by catalyzing the Ala-Ala cleavage during peptidoglycan crosslinking. The result is a deficient cell wall which causes swelling/osmotic lysis of the bacterium
Aside from peptidoglycan, what other components are found composing the cell wall?
Lipoteichoic acid and Teichoic acid
S. aureus is a gram positive bacteria that is particularly resistant to harsh conditions and can survive for a longer time than other bacteria. How does it achieve this at the molecular level?
There is an extra layer of cross linking that creates a more rigid cell wall
What is teichoic acid (TA) and lipoteichoic acid (LTA)? What is special about LTA?
TA is a polymer of glycerol or ribitol phosphate that is covalently attached to peptidoglycan
LTA is a polyglycerol phosphate that is covalently linked to glycolipids in the cytoplasmic membrane
LTA is antigenic with different serotypes existing and promotes adherence to mammalian cells
What 2 important components is the outer membrane of gram negative bacteria composed of?
Lipopolysaccharide (LPS) and Porin proteins
What 4 main things are found in the periplasmic space of gram negative bacteria?
- Thin layer of peptidoglycan with very little cross linking
- Hydrolytic enzymes (breakdown macromolecules)
- Binding proteins for uptake of metabolites
- Virulence factors (collagenases, proteases, hyaluronidases, and antibiotic resistance enzymes)
How does LPS function when it elicits an immune response?
As an endotoxin
How does the outer membrane of gram negative bacteria function to help the cell?
It is a barrier to…
- Lysozyme
- Antibiotics
- Harsh environments
* Only small hydrophilic molecules can pass through the porins, certain antibiotics like vancomycin cannot enter
What are the 4 components (starting with the distal end) of LPS? Give a brief description of each
- O antigen: Variable repetitive glycan polymer which antibody is directed against
- Core polysaccharide: highly conserved
- Disaccharide diphosphate
- Lipid A: Toxic portion which is recognized by TLR4
Name 5 specialized bacterial structures
- Capsule
- Biofilm
- Flagella
- Fimbriae (Pili)
- Spores (Endospores)
What is a capsule composed of and what are some of its functions?
Made of polysaccharide (peptides in bacillus)
Functions to protect the bacteria from phagocytosis as well as promote adherence to tissues, prosthetic devices, and protect against drying
