Microbiology Quiz 3 PowerPoint s 4 5 7 LECTURE 4 5 Heterocyst oxygenic and nitrogen fixers Streptomyces anaerobic cell which excludes O2 so that cyanobacteria can be both o Prokaryote o Gram positive o Form a network of filamentous cells called mycelium o If life gets bad they differentiate morphologically to allow them to disperse and form desiccation resistant spores because they are sessile LECTURE 5 Normal growth conditions o Sea level o 20 40oC o pH 7 o 0 9 salt o Ample nutrients Anything outside of these is considered extreme Temperature o The temperature matches its environment No temperature control o Affects membrane fluidity DNA and RNA stability enzyme structure and o Each organism has an optimum temperature as well as minimum and activity maximum temperatures 70 o Enzyme activity and temperature The higher a temperature the higher the rate At high temps enzyme denature At low temps fluidity and enzymatic activity are compromised live in the temperature range we re used to We re considered normal can live in very cold temperatures o Mesophiles o Psychrophiles 70 o Thermophiles Have ether links instead of ester links live in high temperatures and pressures o Hyperthermophiles enzymes stabilized by low glycine content and N end folded and bound inside enzymes where inaccessible Oxygen can only grow in O2 only grow at low O2 levels killed by traces of O2 grow with or without O2 o Strict aerobes o Microaerophiles o Strict anaerobes o Facultative anaerobes o Aerotolerant anaerobes metabolism o Culturing anaerobes in the lab grow in the presence of O2 but use anaerobic 1 Ordinary broth add special reducing agents thioglycolate or enzyme systems oxyrase 2 Anaerobe jar 3 Anaerobe chamber O2 is removed and N2 and CO2 are taken out o Catalase Superoxide dismutase make hydrogen peroxide Peroxidase takes peroxide and converts it into water and oxygen takes superoxide radical and adds hydrogen to All 3 for aerobes degrades peroxide to water and NAD Microbial Growth o Sterilization No such thing as almost sterile or somewhat sterile killing of all microorganisms present o Disinfection sanitation Removal of pathogens to reach safe levels Disinfectants Antiseptics Example alcohol rub before given a shot for living tissues for inanimate objects and surfaces brief heat treatment to reduce organisms that cause food o Decimal reduction time D value treatment time needed to kill 90 of i e time needed to reduce population Bacillus Clostridium resistant to heat drying UV organic o Pasteurization spoilage population Resistant Microbes o Endospores solvents etc o P rotozoan cysts and oocysts Giardia Cryptosporidium excreted in feces can grow in presence of and even in many chemical waxy mycolic acid walls in diarrheal disease o Mycobacterium o Pseudomonas disinfectants Often nosocomial o Prions Denatured using autoclaving More resistant than the ones that have membranes because the lacking envelope poliovirus papilloma virus etc protein misfolding diseases o Naked viruses membranes can be damaged Physical Methods of Control o Autoclaving produce sterility o Liquid filtration o Air filtration pores high pressure permits high temperature without evaporation to heat sensitive fluid drugs filtered through 0 2 m pores removes nearly all of the microbes in the air through 0 2 m Chemical Methods of Control o Main targets DNA cytoplasmic membranes and proteins o Bacteriostatic o Bacteriocide o Water alcohol solutions halt bacterial growth kill bacteria 70 80 is more effective because proteins are more soluble when water is present All 3 damage macromolecule o Iodine solutions o Hydrogen peroxide o Ozone gas o Ethylene oxide gas EtO o Antibiotics LECTURE 6 Genome DNA Very little non coding DNA Variety in shape in size o Linear circular or both at much lower concentrations than antiseptics disinfectants molecules made by microbes that kill or inhibit other microbes an organism s complete genetic information usually in the form of How DNA fits in the cell o Supercoiling Most DNA is negatively supercoiled Topoisomerase Type II Topoisomerase cuts one strand to relax unwind supercoils control DNA supercoiling Type I Topoisomerase Uses ATP Example DNA gyrase Quinolone antibiotics inhibit bacterial type II topoisomerase cuts both strands to introduce supercoils Some archaea positively supercoiled Reverse DNA gyrase positively supercoils archaea DNA o Looped domains Rules to Remember Held by anchoring proteins HU HN S o 1 By convention DNA sequences are written 5 to 3 unless labeled o 2 New DNA and RNA is synthesized 5 to 3 AKA addition of nucleotides to the 3 end of the growing polymer otherwise chain o 3 New DNA synthesis requires a primer Replication o Replication is bidirectional origin of replication replication terminus oriC ter Bind Tus proteins Tus ter counter helicase that stops DNA polymerase the interlocked rings that form after replication is o Linked catenane complete Topoisomerase IV reattaches them in order to separate the two and XerC XerD enzymes cuts both rings and two DNA Polymerase III molecules DNA primase and o Replisome helicase o DNA polymerase III 1 Synthesis grows by adding phosphodiester bonds 2 Process 3 Proofreading o Initiation Balance of SeqA and DnaA ATP determines initiation Right after cell division DnaA ATP is low SeqA avidly binds the hemimethylated DNA where 1 strand is methylated New DNA is slowly methylated and SeqA comes off DnaA ATP rises with growth until there is enough to bind the 9 mer repeats again 1 DnaA ATP proteins bind to oriC 2 Helicase loaders open helicase rings and place them around the ssDNA 3 Helicase loaders leave 4 Helicase recruit DNA primase 5 Clamp loader brings 2 DNA polymerase III and a sliding clamp 6 Clamp loader loads sliding clamp onto leading strand 7 Helicase unwinds DNA 8 Gyrase relieves tension 9 DNA polymerase III binds the sliding clamp 10 Leading strand and then lagging strand synthesis start o Elongation 1 Leading strand DNA polymerase III replicates the leading strand and SSBs protect the ssDNA Single strand DNA binding proteins stranded regions of DNA to protect them from nucleases SSBs coat exposed single 2 DNA helicase unwinds the lagging strand Helicase Gyrase pulls apart two strands causing positive supercoil torsion relives tension caused by helicase by introducing negative supercoils 3 Lagging strand DNA polymerase III synthesizes the lagging strand 4 A new RNA primer is synthesized on the lagging strand after DNA helicase has