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Lecture 4

week 4 microbio.docx

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BIOL 2900
Malini Persaud

- Periplasmic space (metabolism or digestion happens outside the cell for the gram positive cell and you have to secrete molecules for digestion so exotoxins. Toxins - chemicals produced by the pathogen - harm tissues or trigger host immune responses that cause damage  Exotoxins: ex. E.coli  Endotoxins: can be found in both gram (+) and (-). LPS can trigger abnormal activity. Molecules found in live bacteria inside the bacterial cell while exotonixs are released but found outside the cell and ALIVE Exotoxins - Proteins: secreted by live pathogen. For ex: Diphteria - Abnormal signals to cells - Destroys cellular and extracellular structures. For ex. MRSA and VRE - For ex. S.aureus (resistant to antibiotics). This bacteria causes damages to soft tissues. For ex. S. aureus causes abcess, cellulities, invase infection such as lung infection with influenza A, necrotizing fascitis. - :Many pathogens are developing reistance to multiple drugs, some to nearly all. Hospitals have become hotbeds for highly resistant pthogens like MRSA, increasing the risk that hospitalization kills instead of cures. These are end of the road pathogens that are resistant to last line antimicrobials. Endotoxinss -LPS (certain activity with gram negative ones released from dead bacteria which is a problem). - LPS= lipopolysaccharide structure, has O side chain, core polysaccharide, Lipid A (which has outer leafleft out of the outer membrane) O157 is a Ecoli has O-side chain, it’s a marker. - O side chain varies depending on bacterium - Core polysaccharide: relatively constant composition - Lipid A: composed of glycolipids, associated with toxic activity in Gram negative bacterium. - LPS function: may play a role in infection by any Gram negative bacterium, released from dead cells when cell wall disintegrates, causing inflammation. - LPS causes inflammation, part of the immune system, activates macrophages and neutrophils. It also produces pyrogens molecules that increases temperature and it can trigger fever. - Vasodilatation: to allow neutrophils and other type of WBC to move circulation to infected cells. LPS as an exotoxin - For acute inflammation it can release of too much LPS. It can be induced by antimicrobial drugs that kill bacteria - Systemic infection (sepsis). - activates blood coagulation - Acute whole-body inflammation: drop of BP, shock - Multi-organ failure (even with the use of steroids and stuff, its hard to deal with this problem) -The cytoplasm: DNA - prokaryotic chromosome:  Typically one large circular molecule of DNA  With no nuclear membrane - May have plasmids. - main roles of bacterial DNA  Contain the genetic material  Transcription  Replication Ribosomes - protein synthesis - some differences between eukaryotes  The ribosome’s of prokaryotes (70S) are smaller than cytoplasmic ribosome’s of eukaryotes (80S)  But 70S ribosome’s can be found in eukaryotes’ mitochondria. - Endospores: are formed by a few groups of Gram positive bacteria as intracellular structures, but utilmately they are released as free spores. Organisms that make spores are both gram (+). - Formed by vegetative cells in response to environmetal signals that indicate a limiting factor for vegetative growth, in response to environmental signal that indicate a vegetative state. Factors such that oxygen, nutrients OR lack of those things for different bacteria  Eg. Exhaustion of an esstenial nutrient. - Endospores exhibit no signs of life. Although, they retain viability indefinitely. Very small amount of water in spores - endospores are highly resistant to environmental stresses such as high temperature, irrdation, strong acids, disinfectants, etc. - Endospores germinate and become vegetative cells when they environmental stress is relived. Endospore-formation s a mechanism of survival rather than a mechanism of reproduction. Endospores tay alive in most aggasive state. - anthox (article on this) OR bacterial spore formation. Genetic Changes in Bacteria Mutations in bacteria - mutations arise in bacterial populations  Spontaneous  Induced o Cancer treatment: cancer drugs cause mutations but bacterial cells in the body of the patient is affected as well. o Radiation: kills mutating cancer cells o Some chemotherapy agents - Rare mutations are expressed as a phenotype. In general, not all mutations are expressed as phenotype but in bacteria most of the genomes are expressed as proteins. - However, bacteria are haploid  Rapid growth rate  Selective advantage enriches for mutants Exchange of genetic information in Bacteria (antibiotic resistance
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