Microbiology exam 2

• Selective toxicity refers to antibiotics causing more harm to bacteria than to human cells, crucial in antimicrobial agent development
• Antibiotics are ineffective against viruses but may be prescribed in viral infections to prevent or treat secondary bacterial infections that can arise
• Many antibiotics are derived from compounds produced by microorganisms like bacteria and fungi, particularly Streptomyces
• In environments with limited resources like soil, bacteria produce antimicrobial compounds to eliminate competition, harnessed to develop antibiotics
• The widespread use of antibiotics has led to an evolutionary drive for bacteria to develop resistance, posing a significant challenge in modern medicine
• The high cost of developing new antibiotics and the potential for rapid emergence of resistance make it less economically attractive for pharmaceutical companies to invest in antibiotic research
• Bacteriophages, viruses that target bacterial cells, are researched as an alternative to traditional antibiotics
• Antibiotics target various bacterial structures and processes like cell wall synthesis, protein synthesis, and nucleic acid synthesis to inhibit bacterial growth or kill bacteria
• Antibiotics that inhibit cell wall synthesis prevent bacteria from replicating effectively, aiding the immune system in dealing with the infection
• Certain antibiotics can cause permanent changes to color vision, making colors appear less vibrant
• Aminoglycosides cause errors in protein synthesis by changing the shape of the bacterial ribosome, affecting protein functionality
• Chlorophenicol has limited use due to side effects, being typically used in the United States only in eye ointments and drops
• Certain antibiotics prevent the formation of peptide bonds, crucial for linking amino acids together to form proteins
• Some antibiotics target the ribosome's ability to move along mRNA, essential for protein synthesis, a process known as translocation
• Specific antibiotics target tRNA molecules, depriving the ribosome of necessary amino acids for protein synthesis
• Antibiotics like zivox prevent the assembly of ribosome subunits, necessary for the initiation of protein synthesis
• Tetracycline prevents the formation of hydrogen bonds between mRNA codon and tRNA anticodon, affecting accurate translation
• Some antibiotics disrupt bacterial cell membranes, leading to the death of the bacterium
• Polymyxins create holes in bacterial membranes, causing cell death, and are considered last-resort antibiotics
• PZA targets mycobacteria by disrupting the proton motive force across the cell membrane, essential for ATP production
• Chlorophenicol is an antibiotic with limited use due to side effects, typically used in the United States only in eye ointments and drops, while countries like India and China may use it internally
• Certain antibiotics prevent the formation of peptide bonds, crucial for linking amino acids together to form proteins, by removing a hydrogen atom from one amino acid and a hydroxide from another
• Some antibiotics target the ribosome's ability to move along mRNA, a process known as translocation, essential for protein synthesis, by blocking the movement of the ribosome, halting protein synthesis
• Certain antibiotics target specific tRNA molecules, depriving the ribosome of necessary amino acids for protein synthesis, affecting protein synthesis by inhibiting the function of tRNA that carries isoleucine
• Tetracycline prevents the formation of hydrogen bonds between mRNA codon and tRNA anticodon, essential for accurate translation, by blocking the hydrogen bonds that would normally hold the tRNA in place on the mRNA
• Some antibiotics function by disrupting the bacterial cell membrane, leading to the death of the bacterium, by forming dimers that create channels in the bacterial membrane, allowing unregulated ion movement
• Polymyxins, including polymyxin B and E (colistin), create holes in bacterial membranes, leading to cell death, and are considered last-resort antibiotics with low resistance rates
• PZA targets mycobacteria by disrupting the proton motive force across the cell membrane, essential for ATP production, theorized to inhibit the buildup of protons needed for ATP synthesis
• Enzymes are biological catalysts that speed up chemical reactions in the body, with the lock and key model describing how a specific substrate fits into the enzyme's active site to form a product
• Competitive inhibition is a form of enzyme inhibition where a substance resembling the enzyme's substrate competes for the active site, reducing the rate of the reaction, and can be overcome by increasing the concentration of the substrate
• Sulfonamides inhibit bacterial growth by acting as competitive inhibitors for an enzyme involved in folate synthesis, essential for nucleotide production and DNA, RNA, and protein synthesis, by mimicking the structure of PABA
• Trimethoprim inhibits bacterial dihydrofolate reductase, an enzyme involved in converting dihydrofolic acid to tetrahydrofolic acid, a step in the folate synthesis pathway, by inhibiting its conversion to tetrahydrofolic acid
• Fluoroquinolones target bacterial DNA gyrase, inhibiting DNA synthesis by preventing the relaxation of supercoiled DNA necessary for replication fork progression, with Ciprofloxacin (Cipro) being a well-known example
• Rifampin inhibits bacterial RNA polymerase, blocking transcription and protein synthesis by preventing the synthesis of essential bacterial proteins, often used to treat tuberculosis and other bacterial infections
• Sterilization eliminates all microorganisms capable of reproduction, while sanitization reduces the number of microorganisms to a safe level, with methods like autoclaving and chemical sterilants used for sterilization
• Aseptic technique involves procedures to prevent contamination by microorganisms, critical in medical settings to prevent infection, including practices like hand washing, using gloves, and sterilizing equipment
• An autoclave is a device used to sterilize equipment and supplies by subjecting them to high-pressure saturated steam, commonly used in medical settings to ensure instruments are free of viable microorganisms
• Pasteurization heats liquids to kill harmful bacteria and reduce microorganisms, increasing shelf life, typically around 60 degrees Celsius, denaturing proteins and reducing microbial load
• Filtration passes fluids or air through a membrane to remove microorganisms, used for sterilizing heat-sensitive items and concentrating bacteria from samples, with pore size determining effectiveness
• Ionizing radiation, like gamma radiation, creates ions and free radicals that damage DNA and proteins, used for sterilizing medical instruments, while non-ionizing radiation, such as UV light, causes damage to DNA by forming thymine dimers, used for disinfection