Microbiology - Exam #3 Flashcards
What is regulation of gene expression?
Microorganisms are able to control HOW MUCH of each building block it makes
- On simple media, they make all amino acids
- On complex, they get all them from the media (don’t make)
What is Feedback Regulation?
Since it is a series of enzyme reactions, the cells either turn ON or OFF enzyme synthesis or enzyme ACTIVITY (FR specifically);
Turning off inhibits the beginning of the reaction to that specific products;
Conserves energy when not needed
What is Negative Transcription Regulation?
Involves the binding of a repressor to the operator to prevent transcription;
Ex = Lactose Operon
The Lactose Operon has DNA that encodes for what enzymes?
- LacZ (beta-galatosidase);
- LacY (permease);
- LacA (transacetylase)
The Lactose Operon has DNA that encodes for what regulatory protein?
Lac I (repressor protein)
How is transcription of the Lactose Operon controlled?
Regulatory protein BINDS to DNA =
- LacI = REPRESSOR;
- Operator = DNA site BOUND by LacI
What is the OFF State of the Lactose Operon?
-NO Lactose present for cell use;
-Repressor is BOUND to DNA at operator;
-VERY llittle transcription of LacZ, LacY, and LacA genes
(**Normal conditions)
What is the ON State of the Lactose Operon?
- Lactose PRESENT;
- High lactose causes accumulation of ALLOLACTOSE (inducer);
- RNA polymerase CAN interact with promoter DNA and cause HIGH levels of transcription of enzymes
What is Allolactose?
- Inducer of the lactose operon;
- Created by a side rxn of beta-galactosidase when there is a high conc. of lactose outside the cell;
- Alters the repressor so it can’t bind to the operator DNA
What is a Mutation?
- A change in the DNA sequence of a chromosome;
- Change in a NUCLEOTIDE PAIR compared to a WILD TYPE or the initial strain;
- Occurs spontaneously or by a mutagen (radiation, chemicals)
What is a Mutant?
-Organism that has a mutation
What are the causes of Induced Mutations?
- UV Light
- NItrous Acid
- Base analogs
How does UV Light cause an Induced Mutation?
- induces adjacent THYMINE molecules to link together → THYMINE DIMER;
- No DNA replication, and organism will die
How does Nitrous Acid cause an Induced Mutation?
- Converts DNA Adenine to Hypoxanthine.
- Hypoxanthine complemented by C → Give AT to GC base pair change.
- Mutation beings upon replication and H will replace in the sequence
How do Base Analogs cause induced mutations?
- Substances bearing a chemical RESEMBLANCE to nitrogenous bases;
- Can inhibit DNA replication;
- Ex: 5-Bromouracil, Acyclovir (herpes drug)
What are they types of Mutations?
- Base-pair change;
- Deletion – LOSS of DNA;
- Insertion – GAIN of DNA
- Insertion-Deletion cause Frame Shift Mutations (can come from benzopyrene or fungi toxin, Aflatoxin)
What are Point Mutations?
- Affect ONE base pair in a gene=
- Substitution or Deletion/Insertion
What is a Silent Mutation?
still codes for the same amino acid (redundant codon)
What is a Missense Mutation?
codes for a different amino acids with a different codon
What is a Nonsense Mutation?
Codes for a stop codon
What are DNA Repair Enzymes?
LOCATE and REPAIR alteration (mismatched bases) and distortions (thymine dimers) of the DNA;
- Mismatch repair;
- Damage/excision repair
What is a Mismatch Repair?
- First proof-reading by DNA polymerase as it is synthesizing → Will delete the mismatch and start over with correct coding;
- Highly efficient
What is Damage/Excision Repair?
Nucleases that cut out of damaged DNA which is repaired by DNA polymerases → Each side of the damage is cleaved, cutting out the damage, and then DNA polymerase will bind and resynthesize the correct segment
What are Transposable Genetic Elements?
- Insertion sequences;
- Transposons (jumping genes)
What are Insertion Sequences?
(Transposable)
Small segments of DNA about 1000 base pairs;
-Forms a COPY of ITSELF;
-Can move (trans-locate) elsewhere on the chromosome;
-Cause of some SPONTANEOUS mutations
What are Transposons (jumping genes)
(Transposable) -LARGER than insertion sequences and often carry drug resistant genes. Transposons move from -Plasmid to plasmid -Plasmid to chromosome -Chromosome to plasmid (Ends have INVERTED REPEAT sequences)
What is Ames Mutagen Test?
•Purpose to look for REVERTANT mutants of a Histidine requiring strain on media WITHOUT Histidine
-Back to ORIGINAL histidine form
What is Bacterial Recombination?
Involves genetic (DNA) exchange between two organisms =
- Donor cell – CONTRIBUTES chromosomal DNA or plasmid DNA
- Recipient cell – RECOMBINES with chromosome or now harbors the plasmid DNA
How can genetic information in bacteria be transferred?
-Vertically and Horizontally (laterally)
What are the 3 methods of bacterial recombination in prokaryotes?
- Transformation (DNA from environment);
- Conjugation (Active cell-cell transfer);
- Transduction (from phage infection)
What is Transformation?
- Taking up pieces of DNA from the environment and rehoming DNA into the prokaryotes chromosomes;
- Cell that can be transformed are COMPETENT;
- EX:Haemophilus, Streptococcus, Bacillus, Neisseria.
What is Competence?
-often EXPRESSED when cells are in a high cell density (late LOG phase);
There is INCREAED expression of a competence factor.
How was Natural Competence found?
- Classic transformation experiment by Griffth and Avery et al;
- Demonstrated that DNA was the transforming factor;
- They transformed a AVIRULENT Streptococcus pneumonia strain to VIRULENT with heat-killed virulent cells.
What did Griffith’s Experiment state?
- Type R (Rough) LIVE cells, AVIRULENT, took up the DNA of the S (Smooth) DEAD cells which were VIRULENT.
- RECOMBINATION of S (donor) DNA with R (recipient) chromosome converted R cells into S (virulent) cells. = TRANSFORMATION…actually DNA.
- Dead donor cells took in the DNA and transformed cell now has some of the recipient DNA
- R → S transformation through the uptake of DNA
What is Conjugation?
-Mechanism of gene TRANSFER;
oInvolves single stranded DNA TRANSFER DIRECTLY from one cell to another by a “rolling circle” mechanism of DNA replication.
-Involves a conjugative plasmid (F in E. coli) that carries the genes necessary for the DNA transfer.
What is the F plasmid (conjugation)?
- F factor or fertility factor;
- HAVE F cells are POSITIVE (male)
- Do NOT have F cells are NEGATIVE (female_
What is the Sex Pili?
- Made by F POSITIVE cells;
- External protein filaments that allows donor (F+) to form contact with recipient (F-)
How the is the F plasmid transferred?
- F+ donor (male) synthesizes sex pili;
- Pili contacts F- (female) and pulls the cells together;
- Rolling DNA replication, and F plasmid is transferred as single-stranded DNA molecule;
- DNA synthesis of F+ in BOTH donor and recipient (now also F+)
What else can be transferred by Conjugation?
- Chromosomal DNA;
- High frequency of recombination strains
Conjugation can occur between which GRAM-NEGATIVE bacteria?
- Escherichia and Shigella
- Salmonella and Serratia
- Escherichia and Salmonella
What is INTERGENIC Transfer?
Genetic transfer between various species of bacteria =
- transfer of antibiotic-resistance genes carried on plasmids.
- introduction of drug-resistant transposons between Genera
What is Transduction?
- Phage (donor) packages DNA into its phage head and then transfers this DNA by phage particle infection into a host (recipient);
- Either Generalized or Specialized transduction
What is Generalized Transduction?
- Donor strain is infected by a VIRULENT Generalized transducing phage;
- Phage expresses genes, replicates its DNA, and packages it in its head which eventually LYSES
Where do Transducing Phage Particles come from?
- Phage head packaging mechanism sometimes fill the phage heads with chromosomal DN;.
- DNA pieces from ANY PORTION of the donor chromosome can be packaged
How are generalized transducing particles transferred to the recipient?
- Recipient infected with generalized transducing particles;
- Small linear DONOR DNA enters the cytoplasm;
- DNA donor fragment recombines with recipient’s chromosomes replacing genes it contains
What are diseases of the UPPER Respiratory Tract?
- Streptococcal diseases
- Diphtheria
- Pertussis (whooping cough)
- Meningococcal meningitis
What are diseases of the LOWER Respiratory Tract?
- Tuberculosis
- Pneumonias (typical and atypical)
- Legionnares’ disease
- Q fever
- Psittacosis and Chlamydial Pneumonia
What is Pathogenicity?
- Qualitative;
- Indicates that bacterium CAN cause disease
What is Virulence?
- Quantitative;
- Measure of disease potential;
- Function of the number of bacteria with which a host must be infected multiplied by the bacteria’s virulence
What affects the number and virulence of bacteria?
the number and virulence of the bacteria to produce disease is LESSENED by the host’s resistance capacity (HEALTH)
What is the Structure of the Upper Respiratory System?
consists of the nose and throat, including the middle ear and auditory tubes
What is the Structure of the Lower Respiratory System?
consists of the larynx, trachea, bronchial tubes, and lungs
Strep. Pyogenes - Basic
- Strep throat, strep pharyngitis;
- Red pharyngeal lining, pus, pain swallowing, enlarged tonsils and lymph nodes
Corynebacteium diphtheriae - Basic
- Diphtheria;
- Mild sore throat, slight fever, swelling in neck, toxin production damages organs
Bordetella pertusis - Basic
- Pertussis (Whooping cough);
- Cold-like symptoms, mucus, coughing spasms
Neisseria meningitidis or Hemophilus influenzz - Basic
- Meningitis;
- Membrane covering brain and spinal cord (meninges) is inflamed, sever headache, sudden high fever, stiff neck;
- Children under 4
What is Pharyngitis (upper)?
Sore, inflamed throat
What is Laryngitis (upper)?
Inflammation of the larynx
What is Tonsillitis (upper)?
Inflammation of the tonsils
What is Sinusitis (upper)?
Infection of the paranasal sinus cavity
What is Epiglottis (upper)?
Inflammation of the flaplike structure of cartilage that prevents material from entering the larynx
What is Strep. pyogenes?
- Aerotolerant anaerobe;
- G-POSITICE cocci in chains;
- Found in THROAT flora and SKIN of carries
What are the Virulence factors of Strep. pyogenes?
- Beta-hemolytic;
- M protein;
- Erythogenic toxins;
- Invasion enzymes (steptokinase dissolves blood clots and Hyaluronidase allows tissue penetration)
What is Hemolytic?
“Blood-digesting” ability of streptococci;
- Alpha = PARTIAL destruction of red blood cells;
- Beta = COMPLETE destruction of red blood cells;
- Gamma = NO effect on red blood cells
Classifying Strep by Cell Wall Carbs
Group A through O streptococci;
Strep. pyogenes = Group A, beta-hemolytic
What is the M-Protein of Strep?
- Located in the cell wall and pili of strep;
- Encourages adherence to pharyngeal tissue;
- Retard phagocytosis by body’s immune cells;
- Over 100 specific types
What is the primary disease of Strep. pyogenes?
- Strep Throat from airborne droplets expelled from coughing/sneezing;
- High fever, swollen lymph nodes/tonsils, red throat;
- Can infect middle ear (Ottis media)
What is Scarlet Fever?
- Strep throat with a skin rash;
- Rash from production of ERYTHOGENIC toxin by prophage with toxin genes;
- Usually only get scarlet fever ONCE because body will make antibodies against toxin (antitoxin)
How does the prophage Erythrogenic toxin cause a rash?
- Toxin damages capillaries results in blood leaking through the walls
- Give pink-red blush on neck, chest on soft-skin areas of arms.
What are the 2 life cycles of a bacteriophage?
- Lytic (replication, making more phage);
- Lysogeny (phage DNA integrates into chromosome and become DORMANT)
What is a PROPHAGE?
Integrated viral genome
What are Lysogens or Lysogenic Cells?
Cells that have phage in the chromosome
What is INDUCTION LYSOGENIC Phage?
- A change in the environmental conditions can cause the prophage to come out of the chromosome;
- Phage will enter LYTIC cycle and make more that are released upon LYSIS (cell breaking)
What is Lysogenic Phage Conversion?
- Cells gain new properties, for example altered surface components, when they become a LYSOGEN of a phage =
- Strep will produce EXOTOXIN for scarlet fever;
- C. Diphtheria produces EXOTOXIN for diphtheria;
- C. Botulinum produces Botulinum toxin
What is Rheumatic Fever?
- Characterized by fever and inflammation of the SMALL blood vessels;
- Complication of UNTREATED Strep. pharyngitis;
- Can cause permanent scarring of heart valves (Rheumatic Heart Disease)
How does Rheumatic Heart Disease occur?
Damage arises from the reaction of the body’s antibodies (AUTOIMMUNE response) to streptococcal antigens (M protein) that cross react to similar proteins on heart muscle.
What is GLOMERULONEPHRITIS?
Complications like rheumatic fever where damage to KIDNEYS arises from BODY’S ANTIBODIES reacting with streptococcal antigens BOUND to the kidney;
-(Untreated Strep)
What is ERYSIPELAS?
-Skin infection;
-REDDISH PATCHES on skin often with HIGH FEVER;
-Involves lymph nodes, may have pus filled lesions
-Common faces of children.
(Untreated strep)
What is NECROTIZING FASCIITIS?
-Rare flesh-eating disease with extensive tissue destruction;
-Strep spreads deep within fascia (fibrous layers that hold muscles together)
-Damages from pyrogenic toxin that increases body temp;
-Toxin and bacteria make super antigen that makes immune system add to damage
(Untreated Strep)
What is Puerperal sepsis (Childbirth fever)?
UTERUS becomes infected during the birth process with Streptococcus
(Untreated strep)
What is Septicemia?
“blood poisoning” when streptococci gets into and spreads throughout the body through the BLOOD SYSTEM
(Untreated strep)
What causes DIPHTHERIA?
- Agent = Corynebacterium diphtheriae;
- G-POSITIVE , NONSPORE-forming club-shaped RODS with lysogenic corynephage that contain the genes for an EXOTOXIN production;
- Causes extreme local inflammation;
- Swelling in neck causes pseudomembrane;
- Produces toxin what damage receptor-specific organs (heart, nerve, kidney damage)
What is a Pseudomembrane that comes from Diphtheria?
- A membrane composed of fibrin and dead human and bacterial cells,
- Diphtheria from Greek word for leather because of the tough grayish membrane that forms in throat;
- Pseudomembrane may interfere with airway.
What causes Pertusis (Whooping Cough)?
- Agent: Bordetella pertussis → encapsulated Gram NEGATIVE COCOBACILLUS;
- NON-INVASIVE by destructs CILIATED Epithelium;
- Dense masses of bacteria in trachea and bronchia;
- ENDOTOXIN upon cell’s death and host’s CYTOTOXIN cause loss of ciliated cells
What are the 3 stages of Pertussis?
- Initial = CATARRHAL (common cold-like, fever, cough);
- Second = PAROXYSMAL (attempts to clear throat accumulations by cough);
- Third = Sporadic coughing for several weeks (100 day cough)
Why is it called Whooping Cough?
“Whoop” - spasmodic coughing episodes due to irritation of laryngeal surfaces stimulating strong cough reflexes.
What is Meningitis?
- Inflammation fo the meninges (layers that cover brain and spinal cord);
- Cerebrospinal fluid between the layers is typically sterile
What is Encephalitis?
-Inflammation of the BRAIN
What causes Meningococcal Meningitis?
- Agent: Neisseria meningitides – Gram NEGATIVE DIPLOCOCCUS;
- Attachment pili, endotoxin, capsule;
- Carried by human ASYMPTOMATIC carries, nose and throat flora;
- Spread by airborne droplets (Respiratory, blood to CNS)
Haemophilus influenzae b
- Aerobic, Gram-negative bacterium.;
- HAEMOPHILUS MENNGITIS
What is Haemophilus Meningitis?
- Respiratory tract disease from which the organism moves to the BLOOD and then to the MENINGES. ;
- Stiff neck, severe headache;
- Children 6 months to 2 yrs;
- Treated with Rifampin, Cefotaxime;
- Acceular vaccine combined with DTaP given to children at Tetramune
What is Tuberculosis (lower)?
Chronic LUNG disease characterized by low grade fever, weight loss and destruction of lung tissue → may spread to bone, CNS, or kidneys in late stages)
Mycobacterium tuberculosis
- ACID FAST POSITIVE, ROD-shaped bacteria with a waxy, mycolic acid, cell wall that is resistant to drying and disinfectants;
- Can survive phagocytosis inside microphages and enter deep lung tissue;
- Produce Tubercles (lumps from bodes immune system trying to limit)
How is a Tubercle formed?
- Mycobacterium tuberculosis is INHALED to the lungs.
- Bacilli enters the alveolus
- The bacilli multiply within macrophages.
- Body’s immune system dispatches other macrophages.
- Wall off infected cells – forms tubercle. (note: bacteria are NOT killed)
How is Tuberculosis Spread?
- Aerosol droplets from respiratory secretion of people with active lung infection (coughing, sneezing, speaking);
- ~22% infection rate (prolonged, frequent contact at higher risk);
- 30% primary tuberculosis;
- Organism remains infectious when dried in dust
What is ASYMPTOMATIC Laten Tuberculosis?
- 90% infection arrest and lung lesions heal;
- DORMANT bacilli can produce tuberculosis in 2 to 23% of these latent cases, but often MANY years after infection
What is ACTIVE Tuberculosis?
10% develop ACTIVE disease usually within 3 month;
If ACTIVE tubercles develop throughout the body the disease is called Miliary Tuberculosis (milium = “seed”) → consumption
Control of Tuberculosis
- Tuberculin skin test and follow up x-ray;
- Multiple antibiotics for 6-9 months due to slow growing bacteria