VO 2 microbiology

• In order for a cell to self-replicate, there must be a sufficient amount of energy and precursors for the synthesis of new macromolecules.
• Genetic material must be replicated so that each cell can obtain a copy after cell division.
• Gene expression (transcription and translation) must occur to form the proper amount of proteins and other macromolecules necessary to create a new cell.
• The Central Dogma of Molecular Biology states that information cannot be transferred back from protein to either protein or nucleic acid.
• DNA is stored in the form of a double helix with a sugar-phosphate backbone.
• DNA can be negatively supercoiled, and enzymes like DNA gyrase and DNA topoisomerase can introduce or remove supercoiling.
• DNA replication is catalyzed by DNA polymerase, which adds nucleotides to the growing DNA chain.
• The sigma factor allows RNA polymerase to recognize the initiation sites
• The downstream strand forms a loop to keep the components of the replisome away from each other
• The initiation and termination sites are specific nucleotide sequences on the DNA
• Reverse repeat sequences followed by a stretch of T's in transcribed DNA lead to the termination of transcription
• An mRNA has multiple possible reading frames, with the correct reading frame referred to as the "0 reading frame"
• Translation is catalyzed by the ribosome 70S, consisting of 50S and 30S subunits
• The replisome consists of two copies of DNA polymerase III, helicase, and primase
• DNA gyrase removes over-spiralization in the DNA to be replicated
• The RNA polymerase consists of five subunits with the designations β, β′, α, ω, and σ
• DNA replication occurs in a semi-discontinuous manner, with the leading strand being synthesized continuously and the lagging strand being synthesized in fragments called Okazaki fragments.
• Determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and sensitivity (with a diffusion test) for antibiotics.
• Oxygen availability and growth: Different types of growth patterns based on oxygen levels (obligate aerobe, anaerobes, facultative aerobe, microaerophiles, aerotolerant anaerobes).
• KCl is the compatible solute in extremely halophilic archaea like Halobacterium.
• Mechanisms of antimicrobial drug resistance are being studied.
• Methods to prevent microbial growth: Heat sterilization, pasteurization, ionizing radiation, filtration, chemical growth control (desinfectants, antibiotics).
• The hallmarks of cellular life include coding functions, machine functions, energy production (ADP+Pi -> ATP), and metabolism (production of precursors of macromolecules).
• Bacteriostatic agents inhibit protein synthesis and growth can resume after removal, bacteriocidal agents firmly bind to their target and kill the cell, bacteriolytic agents lyse cells (e.g. penicillin affecting cell wall synthesis).
• DEATH PHASE = the number of dying bacteria exceeds the number of growing ones
• LAG PHASE = phase before exponential growth
• pH and growth: intracellular pH is generally close to neutral, maintained by enzyme-catalyzed reactions and proton translocating efflux pump
• Osmolarity: organisms increase internal solute concentration to cope with low water activity, using compatible solutes such as sugars, alcohols, and amino acid derivatives
• STATIONARY PHASE = growth stops because of nutrient limitations and the accumulation of toxic compounds produced by the cells during growth – growing and dying bacteria are present concomitantly
• Abiotic parameters affecting growth of microorganisms: Temperature, Osmolarity, pH, Oxygen supply, Water activity (Humidity)
• Growth temperature: 'Extremophiles' - thermophiles and hyperthermophiles have heat-resistant enzymes and proteins
• LOG PHASE = each cell in a population grows and divides
• DNA ligase joins the Okazaki fragments together to complete the replication process.
• These biosyntheses are also reactions of anabolism
• In many cases, monomers must be synthesized from intermediates of catabolism or from nutrients found in nature
• Schematic representation of anabolism and catabolism, highlighting the key role of ATP and the proton motive force in coupling these processes
• Macromolecules and other cell components
• Enzymes: metabolic catalysts
• Monomers can originate as pre-formed nutrients from the environment or from catabolic pathways such as glycolysis and the citric acid cycle