Microbiology 1 - Exam 2 Flashcards

Question

Define resolution, resolving power, condenser, iris diaphragm, and field diaphragm.

Answer 1

Resolution: the extent to which detail in the magnified object is maintained. Resolving power: it is the closest distance between objects that when magnified still allows the two objects to be distinguished from each other. Condenser: focuses light on specimen. Iris Diaphragm: adjust the amount of light emitted from the condenser. Field Diaphragm: adjust the amount of light being emitted from the bulb.

Answer 2

Dark Field: darkfield condenser, enhances contrast in unstained samples, bright objects appear in a dark background. Phase Contrast: for unstained, live organisms. Contrasts refracted light from organism from light refracted by surrounding environment. Fluorescent: built-in UV light source, organism stained with fluorophore, UV strikes fluorophore causing excitation and then emission of long wavelengths which results in specimen glowing in a dark background. Mercury-vapor or laser light source. Dichroic mirror (to separate excitation and emission light in the same light path). Electron Microscope: enabled visualization of viruses, no live organisms can be observed, source of light is electron beam, magnets replace lenses. Ø Transmission Electron microscope: enables study of internal structures of cells, 1000X more resolving power than light microscope. Ø Scanning Electron microscope: enables study of outer surfaces of objects.

Answer 3

Acridine Orange: crosses cell membranes and binds nucleic acid (DNA/RNA) Auramine-Rhodamine: used in acid-fast staining of mycobacteria, binds mycolic acid in cell wall Calcofluor: binds chitin and cellulose, used for staining fungi

Answer 4

Start codon: AUG Stop codons: UGA, UAG, UAA

Answer 5

Lac Operon: genes are expressed only when lactose is present. LacI = repressor protein (in the absence of lactose, repressor protein binds to the operator sequence (lacO) close to the promoter and prevents the binding of RNA polymerase.). When lactose is present, it binds to the repressor and changes its conformation so that it can no longer bind to the operator sequence. RNA polymerase can then bind to the promoter and transcribe the lacZ, lacY, and lacA genes. Genetic Recombination: DNA alteration by exchanging the DNA segment. The donor cell > the recipient cell > homologous recombination.

Answer 6

PYR test: pyroglutamyl-naphthylamide. Detects for the enzyme pyrrolidonyl arylamide (pyrrolidonase), which hydrolyzes PYR into L-pyrrolidone and beta-naphthylamine. Beta-naphthylamine combines with the PYR reagent and a red color is produced. Ornithine Decarboxylase: used to see if organism can use this amino acid as sole energy source.

Answer 7

Lancefield Classification: Ø Group A – S. pyogenes (pyogenic = pus forming) Ø Group B – s. agalactiae Ø Group C & G – S. dysgalactiae

Answer 8

Hippurate Hydrolysis test: determines if the isolate produces the enzyme Hippurate hydrolase (hippuricase). Benzoic acid and glycine are produced if Hippurate hydrolysis is present. Glycine is detected by adding ninhydrin reagent. Deep bluish purple color within 5 minutes is positive result. Bile-esculin hydrolysis test: esculin can by hydrolyzed to esculetin, which forms dark brown complex with ferric citrate. Blackening of the media is positive test. CAMP factor: diffusible extracellular protein that acts synergistically with staphylococcal hemolysin to cause enhanced lysis of RBCs. An arrowhead-shaped zone of enhanced hemolysis in the area into which both the hemolysin and the CAMP factor have diffused represents a positive test result. Bile Solubility test: bile will enhance an autocatalytic enzyme produced by S. pneumoniae, causing colony to flatten. Flat colony is positive test result. In tube reaction, the microbe is added to bile reagent and the mixture becomes turbid. A decrease in turbidity is considered positive reaction. Quellung test: antiserum visually enhances the capsule, making it appear larger, especially when the preparation is examined by phase contrast microscopy. Pneumoslide test: latex agglutination test where latex beads are coated (sensitized) with anti-pneumococcal antibodies. If agglutination occurs when isolate is suspected of being S. pneumoniae is mixed with a drop of the reagent, the organism has been identified as S. pneumoniae. LAP test: detects the presence of the enzyme leucine aminopeptidase (LAP). In the presence of LAP, leucine-alpha-naphthylamide is hydrolyzed to leucine and free alpha-naphthylamine. Adding para-dimethylaminocinnamaldehyde (DMACA) reagent produces a red color. ALL streptococcus and enterococcus are LAP positive.

Answer 9

LIA: Dextrose (glucose) carbohydrate. Dextrose fermenting organisms will produce yellow butt and purple slant and sometimes gas. Lysine is there to show a decarboxylation reaction, which causes alkaline situation, resulting in a purple butt. Yellow is seen only if lysine decarboxylation negative. Also tests for H2S. Lysine deamination has red slant. LAP: leucine aminopeptidase test measure how much of that enzyme is present in an organism. MUG: effective and rapid method for detection and verification of E. coli in vehicles. It is a fluorogenic assay used to detect beta-glucuronidase by using t-methylumbelliferyl-beta-D-glucuronide (MUG). ONPG: used to detect late lactose fermenters by using a similar reagent to lactose that ferments faster. Distinguishes late lactose fermenters from non-lactose fermenters. PAD: Phenylalanine deaminase test (PAD). Proteus, Morganella, and Providencia are only organisms that produce phenylpyruvic acid from phenylalanine. Intense green color indicates positive result.

Answer 10

H Antigen: flagella antigen O Antigen: surface antigen polysaccharide of gram negative bacteria. K Antigen: capsule antigen

Answer 11

M Protein: enables S. pyogenes to adhere to surfaces. Antiphagocytic. Beta-Hemolysins: streptolysin O (inactivated by O2) & S (stable in presence of O2). Spe (streptococcal pyrogenic exotoxin): causes toxic shock-like syndrome, erythrogenic toxin that causes scarlet fever, pyrogenic = fever inducing. Hyaluronidase: invasion and spread Exoenzymes: streptokinase, DNase Diseases: pharyngitis, impetigo, scarlet fever, toxic shock syndrome, Rheumatic fever, glomerulonephritis.

Answer 12

Protein A: component in cell wall that binds to the Fc region of IgG molecules, preventing opsonization from occurring. Exfoliatins: causes serious skin condition known as staphylococcal scalded skin syndrome. Ø Panton-Valentine toxin: destroys leukocytes Ø Toxic shock syndrome 1 toxin: cause of TSS. Ø Enterotoxin: causes staphylococcal food poisoning (very common). Exoenzymes: · Protease, lipase, and hyaluronidase destroy tissues. · Hemolysins destroy RBCs. · Coagulase causes clot formation. · Staphylokinase: dissolves clots.

Answer 13

Indole: + MR: + VP: - Citrate: - TSI: A/AG Urease: - Lactose: F Decarboxylase: L+ MUG: + ONPG: N/A