Microbes internalize nutrients either using energy or not using energy. Active transport, bulk transport (endocytosis) require energy. Osmosis, diffusion, facilitated diffusion requires no energy. Diffusion moves molecules from high concentration to low concentration across cell membrane, facilitated diffusion moves molecules from high concentration to low but with the help of cell membrane proteins, osmosis is water molecules moving from less concentrated solutes to more across a semi-permeable membrane, active transport moves molecules from low concentration to high against concentration gradient, and bulk transport is mass transport of large substances moved into cell by engulfment. Hypertonic has high solute in solution than in cell so water moves out of the cell, isotonic has equal amounts of solute in cells and solution so water moves in and out of cell together, Hypotonic has lower solute in solution than cell so water moves into the cell. Some microbes live happily in hypotonic because microbes with cell walls can do this without bursting. Psychrophiles grow at or near 0deg c, mesophiles, mesophiles contain most microbes pathogenic to humans (10-50deg c), thermophiles grow at temperatures above 45 deg c. Obligate aerobes require 02 to live, facultative anaerobes will use 02 but can grow in the absence, obligate anaerobes are killed by 02. Generation time or doubling time is the time requirement for one binary fission cycle. Each new cycle doubles the population. If environment remains the same, the doubling effect can continue at a constant rate. The length of the generation time is a measure of the growth rate of an organism. Lag phase is a flat period when population is not growing because they are adapting to new environment, lagging. Log phase is a dramatic growth curve increase and phase continues as long as cells have adequate nutrients and environment is favorable. Stationary phase is when cells stop growing and no nutrients are around and environment is no longer favorable, population enters survival mode. Death phase is when the limiting factors increase, and cells begin to die so growth curve dramatically decreases. Catabolic reactions degrade macromolecules into smaller molecules, a process that yields energy. An example is hydrolysis when polymers turn to monomers. Anabolic reactions assemble smaller molecules into larger molecules for the cell using energy. An example is dehydration synthesis when monomers are made into polymers. Enzymes act as catalyst which speed up reactions by either adding heat which increases the velocity of molecules, adding reactants which increases chance reactants will collide in solution, or by adding a catalyst which cells use enzymes as catalyst to speed up reactions. Simple enzymes are composed of proteins only. Conjugated enzymes have a nonprotein part (cofactor) in addition to the protein part (apoenzyme) and this altogether is called a holoenzyme. Exoenzyme is created inside the cell but transported extracellularly to breakdown food or harmful chemicals outside the cell. Endoenzymes are created and function inside the cell. Exoenzymes are necessary for some microbes because they help with extracellular digestion in a saprobe with a cell wall. Constitutive enzymes are present in constant amounts inside the cell and the addition of more substrates does not cause the number of constitutive enzymes to increase or decrease. Regulated enzymes concentration in a cell increases or decreased in response to substrate levels. Might be coded for by an operon. Sterilization is the destruction of all microbial life from inanimate surfaces (dry heat, fixation) Antisepsis destroys most microbes from animate surfaces but not bacterial endospores (skin wounds) Bactericidal is an agent that destroys/kills bacteria (cide=to kill) Bacteriostatic is an agent that inhibits bacterial growth (stasis=to stop). Microbial death is harder to detect because there are no conspicuous signs that would show us; loss of movement cannot be used to indicate death. Four categories of cellular targets are cell wall, cell membrane, DNA & RNA synthetic synthesis, and protein. Cell wall is affected by blocking the synthesis of cell wall or destroys the cell wall. Surfactants destroy cell membrane by using loss of selective permeability (loss of control of what can get in, what can get out of the cell). Results in: loss of vital molecules from cell, entry of potentially damaging chemical into the cell. They physically bind to the phospholipid layer and penetrate the internal hydrophobic region of membranes. This opens up leaky spots that allow damaging chemicals to seep into the cell and important ions to leak out. UV radiation inhibits ribosomes (targeting protein synthesis) or binds to or damages DNA, inhibiting replication/ transcription (targeting nucleic acid synthesis/ protein synthesis, respectively) Ultraviolet (UV) radiation causes formation of improper bonds between thymine (T) bases or cytosine (C) bases of nucleotides located next to one another on the same strand. Protein denaturation is the disruption of proteins, rendering them nonfunctional, breaks the bonds that maintain the secondary and tertiary structure. When the protein in an enzyme is denatured, it disrupts the function of the enzyme by: Completely unfolding it or folding it incorrectly into a different shape. Moist heat operates at lower temperatures and shorter exposure times to achieve the same microbe-killing effect as dry heat. Moist heat methods operate at lower temperatures and shorter exposure times to kill microbes and their mode of action is coagulation (coming together) and denaturing proteins. (60C –135C) Dry heat methods operate at high temperatures and their mode of action is when at high temps the microbes are turned to ashes. (60C to 1000C) Moist heat is more efficient (faster) than dry heat at killing microbes at the same temperature because proteins are denatured by moist heat but not dry heat, and that denaturation is the unfolding of proteins, and that the unfolding is the result of the breaking of secondary and/or tertiary protein structure level bonds). Boiling water is disinfection that can kill vegetative cells of bacteria, viruses, and fungi if boiled for 10 min and kills most non-endospore-forming pathogens if boiled for 30 min. Pasteurization is the disinfection of liquids for consumption which is heat applied to liquids to kill potential pathogens and agents of spoilage while retaining liquid’s flavor and value. Steam under pressure is sterilization which applies both a high temperature (121oC) and pressure (1atm) to chamber. Water included in chamber, causing steam to contact all surfaces. Desiccation and exposure to cold temperatures are not reliable methods for getting rid of microbes because cold temperatures are bacteriostatic so they don’t kill only inhibit growth and desiccation (dry out) often preserve proteins and many microbes can withstand desiccation, endospores can remain viable after years in dormancy. Osmotic pressure as a control method example is adding salt/sugar to food creates hypertonic environment for cells. Bacteria cannot multiply. Meats being cured with salt, high sugar concentration in jellies/jams. The leading cause of death used to be influenza, pneumonia, and tuberculosis and then the discovery of antibiotics in 1928 led to changing the leading cause to heart disease and cancer which can’t be cured by antibiotics. Selectively toxicity is killing pathogenic microbes without damaging host tissues or beneficial microbes. Conjugation: one bacterium transfers DNA to another bacterium to which its connected to; Transformation: bacterial cell takes up DNA from its environment or DNA from dead bacterium; Transduction: DNA is accidentally moved from one bacterium to another by a virus; Cloning: Bacteria with plasmids live which means all will have antibiotic resistance gene. Selective pressure of an antibiotic can lead to evolution of an antibiotic resistant population because the bacteria with no plasmids die which leaves only those with a plasmid and those with plasmids carry the antibiotic resistance gene making it one big population of antibiotic resistance bacteria. MIC is smallest concentration of antibiotic drug that inhibits growth of bacteria and it is useful because it helps determine the lowest amount of antibiotic that can be used to inhibit bacteria growth. Antibiotic resistance is a problem because it makes antibiotics become ineffective which means more deaths if we can’t find ways to treat. Antibiotics come from naturally derived sources like soil or synthetically derived chemically, originally from fungi. Antibiotics only inhibit the growth or kill on the body of bacteria not viruses, fungus, or protozoa. Viral infections can’t be treated by antibiotics. Mode of action is the way an antimicrobial agent chooses to kill or target a bacterium. Antibiotics attack bacterial that are the same or similar in structure or functional feature. Broad Spectrum antibiotic: Effective against large number of bacterial species Narrow spectrum antibiotic: Effective against a small number of bacterial species Antibiotics with similar structure typically attack similar microbial targets and microbes are also resistant to similar structured antibiotics. Penicillin’s, cephalosporins, carbapenems all contain beta-lactam rings and the use of betalactamase inhibitors like clavulanic acid. Beta lactamases are enzymes that provide resistance to beta lactam antibiotics like penicillin. Antibiotic membrane impermeability: bacterial cell walls with certain characteristics are impermeable to some structural classes of antibiotics. Antibiotic efflux: some bacteria pumps structural classes of antibiotics out the cell (efflux). Antibiotic degradation: some bacteria are able to destroy beta-lactam rings, there is a low concentration of this both intra-and extracellularly over time, suggesting that this one gets degraded. Target alteration/mutation: antibiotics attack targets but if target is mutated then it won’t be recognized by the antibiotic, it is going inside the cell and staying there, but is still unable to harm the bug. A bacterium can be resistant to low concentrations of antibiotic but not to higher concentrations. It depends on the number and type of antibiotic resistance genes that it has. New antibiotics can be engineered by chemically altering the structure of naturally occurring antibiotics to generate new variations with increased permeability and/or toxicity to bacterial targets. Humans can reduce the prevalence of antibiotic resistance by not overprescribing antibiotics, increase hospital level regulation, complete full course of antibiotic treatment, not use antibiotics in animal farming, and decrease global transport. Do not use an antibiotic to treat an infection if the patient’s microbiome includes strains that are already resistant to to the antibiotic. Doing so can promote transfer of resistance genes to the pathogen. This requires difficult task of screening patient’s microbiome before antibiotic treatment. Microbiome: organism, which may exist in its single-celled form or a colony of cells. Human cells: 21,000 protein-coding genes vs. Microbes living inside us: 8,000,000 protein-coding genes. Microbes live in areas we thought were sterile (e.g., lungs). Vast quantities of viruses are found in healthy humans and may be part of our normal biota. All healthy people harbor potentially dangerous pathogens in low numbers, our normal biota prevent pathogenic microbes from multiplying and causing harm. The gut microbiome influences many aspects of human health. Presence of a healthy microbiome can prevent pathogens from taking over (but still allow pathogens to remain present in small numbers) Additionally, infection only proceeds when enough pathogenic microbes (an “infectious dose”) is present. Pathogens can enter through the conjunctiva, respiratory tract, gastrointestinal tract, skin, urogenital tract, and during pregnancy/birth. Pathogens cause damage to host cells by secreting enzymes and/or toxins directly damaging them (direct), causing the host’s immune defenses to overreact, resulting in host cell damage (indirect), and altering the host’s genome or transcription processes (epigenetic changes that temporarily or permanently disrupt normal host cell function) (direct). Reservoir is the primary habitat in the natural world from which a pathogen originates, Source is whatever thing/place a new host acquires the pathogen from, vector is a live animal that transmits an infectious agent from one host to another, and carrier is an individual who inconspicuously shelters a pathogen and can spread it to others without knowing. Asymptomatic carriers are infected but show no symptoms at all–Incubating carriers are Infected but show no symptoms during the incubation period–Convalescent carriers are Recuperating patients no longer showing symptoms but continuing to shed viable microbes able to infect new hosts for short period–Chronic carriers are Recovered patients who continue to shed viable microbes able to infect new hosts long after the disease period (for years, sometimes life)–Passive carriers move microbes from one host to another without being infected themselves (e.g. Health care workers handling materials with infectious microbes on them from one patients, then passing on these microbes via touch). Communicable infections occur when an infected host transmits the pathogen to another host and establishes infection there. Non-communicable infections do not arise from transmission from one host to another but are acquired through some other circumstance (An immunocompromised person is invaded by own microbiota. person infected by microbe that not living in host, lives in a non-living environment. An infectious disease is endemic to an area/population if is regularly found in that particular geographic area or among that particular human population. An infectious disease is sporadic if occasional cases are reported at irregular intervals at random locales. Epidemic is when prevalence of an endemic or sporadic disease increases beyond what is expected for that area/population. Pandemic is when an epidemic spread across continents. Examples: Covid19.
