MICROBIOLOGY REVISION ALL IN ONE (SIMPLIFIED SUMMARY OF EVERY CHAPTER AND POSSIBLE QUESTIONS FROM THE CHAPTER AND ITS EXPECTED ANSWERS)

What are Bacteria? -Viruses are small as well but viruses are not independently living -Smallest, most versatile independently living cells known -Visible only with the aid of microscope -Prokaryotes; no membrane bound organelles Nature of Bacteria -In the body, out-number human cells 10:1 *Many are pathogens but do not cause disease -Human genome includes 22,000 protein-coding genes. -Human microbiome contributes ~8 million protein-coding genes -Bacteria essential for our survival Bacterial classification—Naming -Bacteria are usually named by the person who discovered it -GENUS - capitalized -SPECIES - common letter -All of the names are usually italicized in formal writing -Classified into genera and species according to binomial Linnaeus scheme -Neisseria gonorrhoeae OR Escherichia coli -Genus: Neisseria, Escherichia -Species: gonorrhoeae, coli Differences between prokaryotic and eukaryotic pathogens Eukaryote (eg. yeast) -Size: 5µm *Eukaryote microbes are much much larger then bacteria -Nuclear Structure: Nucleus, nuclear membrane -Chromosomes: Many -Haploid (Ie. Sex cells)/Diploid -Genome organization: Single gene copies; repetitive DNA -Co-linearity of gene with RNA: Introns within gene Prokaryote (bacteria) -Size: 0.5-3.0 µm -Chromosomes: One (some 1); circular or linear -Haploid (1 copy) -Genome organization: Single gene copies -Co-linearity of gene with RNA: No introns; precise sequence *Bacteria don't have the space for extra introns Differences between prokaryotic and eukaryotic pathogens (continued) Eukaryote (eg. yeast) -Regulation of gene expression: Single genes; mono cistronic -Type and level: Post-translational regulation --Transcription -Relation of transcription and translation: Separate: transcription in nucleus, translation in cytoplasm -mRNA processing: Poly A at 3' end; cap at 5' end, splicing --Translation of mRNA -First amino acid: Methionine -Ribosomes: 40S + 60S = 80S Prokaryote (bacteria) -Regulation of gene expression: Operon-polycistronic mRNA -Type and level: Mostly transcriptional --Transcription -Relation of transcription and translation: Separate: Concurrent -mRNA processing: Rare --Translation of mRNA -First amino acid: Formylated methionine -Ribosomes: 30S + 50S= 70S *This feature is what is exploited during antibiotic creation Differences between prokaryotic and eukaryotic pathogens (continued..) Eukaryote (eg. yeast) -Organelles: Present -Cytoplasmic membrane: Contains sterol -Cell wall: Absent; (seen only in in fungi) -Reproduction: Sexual, asexual -Respiration: Via mitochondria Prokaryote (bacteria) -Organelles: Absent -Cytoplasmic membrane: Does not contain sterol* -Reproduction: Binary fission -Respiration: Via cytoplasmic membrane Bacterial Classification Cell morphology Morphology=shape Shapes -Rod *BACILLUS *Do not confuse the adjective bacillus with the bacterial genus for Bacillus *Vibrio - curved rods -Coccobacillus - Small rod -Coccus (pl. cocci) -Spirochete - spiral shape - (treponema pallidum - agent of SYPHILLIS -Pleomorphic - indefinite shape (Mycoplasma) Bacterial Classification Cell arrangement -Individual -Diplo- (pairs) -Staphylo- "resembling a bunch of grapes"; clusters -Strepto- "resembling a twisted chain"; chains -Filaments Bacterial Anatomy 1. Bacterial cell wall/cell envelope 2. Structures external to the cell wall (appendages) 3. Structures enclosed by the cell wall Bacterial Anatomy 1. Cell wall/cell envelope -Major component: peptidoglycan/murein *Mureoin is a type of peptidoglycan and sometimes used interchangeably *Peptidogylcan has NAM, NAG repeating layers -Functions: *Protection from osmotic stress, environmental stress (innate immune response). Bacteria are single cells and have no control over their environment, so the cell wall helps them survive with this *Maintains cell shape, rigidity *Role in cell division -Includes an outer membrane in GRAM-NEGATIVE bacteria -Exception: Mycoplasma lacks a cell wall - therefore they have no peptidoglycan Cell wall construction—Peptidoglycan -Repeating units of NAG and NAM are joined by B-1,4 glycosidic linkage. Not only do we have single layers, but layers are attached to each other by a PENTAPEPTIDE Each of the NAMs have a PENTAPEPTIDE (5 amino acids) and they are joined to the NAMS, never to the NAGs! -A peptapeptide in one layer is joined with the pentapeptide in the other layer by the PENTA-GLYCINE BRIDGE - via the transpeptidation reaction -NAM-NAG repeating units -NAM, NAG joined by β- 1,4-glycosidic linkage *Transglycosylation -Pentapeptide attached to NAM *L-Ala, E, Lys or DAP, A, A *DAP = Diamino promolic acid - not found in proteins. Just unique to bacterial peptidoglycan *The terminal amino acid is also lost in the transpeptidation reaction -Overlying pentapeptides joined by 5G bridge *Transpeptidation DAP = diaminopimelic acid; a diamino aa unique to bacterial peptidoglycan; not found in proteins Cell wall construction: formation of peptidoglycan -Abx like BACITRACIN & the enzyme LYSOZYME target B-1,4-glycosidic linkage *By targeting the glycosidic linkage they will be breaking that linkage between the NAGs and the NAMs of a particular layer to compromise the bacterial wall *Lysozme is found in tears -Cell wall construction mechanisms are targets for antibiotics and antibiotic resistance -When cell divides, cell wall refurbished, new wall added -NAM and NAG held together by β-1,4-glycosidic linkage *Target for BACITRACIN, LYSOZYME -Binding together of peptidoglycan through peptide linkages to form mesh *Catalysed by enzymes, eg. PBP, that have transpeptidase or transglycosylase activity *PBPs are targets for beta-lactam antibiotics -PBPs = Penicillin Binding Protein - catalyze reactions such as transpeptidase and transglycosylase -They are important for the formation of the bacterial cell wall -These proteins got their names because they found that Penicillin specifically targets these enzymes Construction of cell wall Amount/thickness of peptidoglycan varies in -Gram-positive bacteria—many layers thick -Gram-negative bacteria—few layers Mycoplasma do not have a cell wall (sterols); no defined shape; not susceptible to beta-lactam drugs *Instead of peptidoglycan they have STEROLS *The Beta-lactam drugs only target the penicillin binding proteins that are important for building the bacterial cell wall (involving peptidoglycan), and MYCOPLASMA DOES NOT HAVE PEPTIDOGLYCAN! Additional cell wall components of Gram-positive bacteria TECHOIC ACIDS (wall TA) -Inserted into peptidoglycan layer; covalent linkages -Major component of their cell wall -Indicated by the extensions of the cell wall LIPOTECHOIC ACIDS (membrane TA) -Extend through peptidoglycan and link to CM glycolipids -These EXTEND through the cell wall Additional cell wall components in Gram negative bacteria -VERY THIN PEPTIDOGLYCAN LAYER -NO LIPOTECHOIC ACIDS, NO TECHOIC ACIDS -ENDOTOXIN = Lipopolysaccharides Outer membrane—asymmetrical -Inner leaflet: phospholipids, proteins, etc. -Outer leaflet: mainly LPS LPS (endotoxin) 1. How many chromosomes are harboured in the average bacterial species? 2. What is the size of bacterial ribosomes? 3. Which bacterial genus incorporates a cholesterol derivative in its membrane? 4. Which component of a cell wall is responsible for its maintaining shape? 5. Name the repeating units of this component? 6. Name the specific target of beta-lactam antibiotics 1. Average of ONE 2. 70s -This is significant because the size of bacteria is not the same size of that of eukaryotes, therefore you can have drugs that target these bacterial ribosomes without harming the patient 3. Mycoplasma 4. Peptidoglycan -Rensposible for maintaining cell wall shape, rigidity, etc 5. N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) -These repeating units form peptidoglycan. NAM and NAG are linked to together via BETA 1,4 GLYCOSIDIC BONDS. Coming off only the NAM is the PENTAPEPTIDE that connects each NAM/NAG chain. Attached to the PENTAPEPTIDE is also the 5 unit GLYCINE BRIDGE thats attaching both of the pentapeptide chains from each layer and as it does so it takes off the very last D-alanine so you'll have one less D-alanine on the second layer 6. PBPs (Penicillin Binding Proteins) -These play a major role in the formation of the cell wall -These are a family which includes some enzymes like transpeptidases, transglycosylases, etc. -They help the components of the peptidoglycan to bind to each other *Transpeptidases - transfer of peptide bonds between layers with the peptaglycine bridges connecting them So we have our NAM's and our NAG's. What might happen if the PEN