Ch 4 – Microbiology Test Questions – Flashcards
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tetrad |
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group of 4 cocci |
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sarcinae |
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group of 8 cocci |
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staphylococci |
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grapelike |
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types of bacilli |
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-diplobacilli -streptobacilli -coccobacilli |
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types of spiral |
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-vibrio -spirillum -spirochete |
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vibrio |
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curved rods |
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spirillum |
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helical shape (use flagella) |
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spirochete |
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helical and flexible (axial filaments) |
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3 other shapes |
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-star -rectangle -triangle |
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star |
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stella |
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rectangular |
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haloarcula |
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triangular |
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angulomicrobium |
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external structures to the cell wall |
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-glycocalyx -flagella -pili/fimbriae |
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glycocalyx |
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-general term to describe substances that surround the cell -viscous, sticky, gelatinous polymer of polysaccharides/polypeptides or both -capsule (organized tight) -slime layer(loose) |
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functions of glycocalyx |
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-act as a barrier to toxic hydrophobic molecules (detergents) -can enable adherence to other bacteria or host tissue (biofilms) -major virulence factor due to its weak antigenic and antiphagocytic properties |
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flagella and types |
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-composed of helically coiled proteins (flagellin) -peritrichous -monotrichous and polar -lophotrichous and polar -amphitrichous |
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peritrichous |
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distributed over entire cell |
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monotrichous and polar |
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single flagellum at one pole |
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lophotrichous and polar |
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many flagella at one pole |
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amphitrichous |
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flagella at both poles |
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flagella movement |
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-driven by rotary engine composed of proteins located at flagellum's anchor point on the inner cell membrane (basal body) -powered by proton motive force |
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pili/fimbriae |
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-thin protein tubes originating from plasma membrane -found in all gram negative bacteria |
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pili |
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-shaft composed of pilin -involved in motility -bring bacteria together and allow transfer of DNA (conjugation) |
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fimbriae |
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-can occur at poles or over entire surface -promote attachment to other bacteria and host -virulence factor -ex. E. coli colonization -N. gonorihoeae urinary infection |
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the cell wall and functions |
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-contains semi rigid, tight knit, molecular complex of peptidoglycan(NAG,NAM,peptides) -protects inside of cell from detrimental changes in the outside environment -prevents cell from rupturing in hypotonic conditions -maintains shape -provides ligands(binds to receptors) for adherence -essential structure for cell viability |
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NAM and NAM |
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-linked in rows of 10-65 sugars -attached to peptide chain of 4 amino acids (direct and cross linked) |
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The gram stain |
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-named after Hans Christian Gram (1884) -one of the most important techniques in microbio -based on ability of bacteria cell wall to retain primary crystal violet dy during solvent treatment |
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Gram stain steps |
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-apply crystal violet -apply iodine (mordant) -decolorize with alcohol -apply safranin (counterstain) |
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Gram + stain mechanism |
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-high peptidoglycan -low lipid -pores shrink from alcohol -CVI complex retained |
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Gram - stain mechanism |
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-low peptidoglycan -high lipid -dissolution of lipid membrane from alcohol -CVI complex washes out -cell takes up counterstain |
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Gram + cell wall characteristics |
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-thick peptidoglycan (20-80nm) -contains teichoic acids (wall and lipo) -contains alcohol group (glycerol,ribitol) and phosphate group -may be involved in regulating flow of cations -important surface antigens involved in adherence |
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Gram - cell wall characteristics |
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-thin peptidoglycan (7-8nm) -no teichoic acids -possesses outer membrane -lipoprotein bind peptidoglycan to outer membrane |
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outer membrane |
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-LPS -lipoproteins -phospholipids -porins |
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LPS |
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-lipid A -core polysaccharide -O antigen |
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lipid A |
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-basic component -endotoxin activity |
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core polysaccharide |
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-branched 9-12 sugars -structural |
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O antigen |
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-50-100 repeating saccharide units -allows serotype distinction |
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mycoplasma |
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-have no cell wall -plasma membrane contains sterols |
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Archea |
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-may lack cell wall or are composed of polysaccharides and proteins -pseudomurein instead of peptidoglycan |
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plasma membrane |
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-thin semi permeable membrane composed of phospholipid bilayer -polar ends form innermost and outermost -peripheral proteins found at innner or outer surface -integral proteins span membrane or are channels with a pore (transmembrane proteins) |
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functions of plasma membrane |
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-selective semi permeable membrane that determines what goes on in and out of organism -breakdown of nutrients -production of energy (ATP) |
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cytoplasm |
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-gel like substance -80% water -contains proteins, carbs, lipids, inorganic ions. low MW compounds |
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major structures of cytoplasm |
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-nucleoid -plasmids -ribosomes -inclusions |
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nucleoid |
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-long single molecule of double stranded helical supercoiled DNA |
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plasmids |
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-small molecules of double stranded helical non chromosomal DNA -code for proteins not coded by nucleoid (antibiotic resistance, exotoxins) |
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ribosomes |
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-composed of rRNA and protein -composed of two subunits with densities of 30S and 50S -two subunits combine during protein synthesis to make 70S |
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inclusions |
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-reserve deposits -may be starch glycogen, lipids, sulfur, phosphate -bacteria live in competitive environment where nutrients are in short supply so they store up whenever possible -gas vacuoles are hollow cylinders that maintain buoyancy |
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endospores |
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-resistant structures formed by Gram + bacteria under adverse conditions -most resistant life from known -able to survive 100 degrees C for long periods -reisistant to UV light, drying up, and harmful chemicals -some disease organisms like anthrax and botulism form spores that reside in soil -size shape and location are genetic characteristics |
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formation of endospores |
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-spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm -Plasma membrane starts to surround DNA, cytoplasm, and membrane isolated in step 1 -spore septum surrounds isolated portion forming an forespore -peptidoglycan layer forms between membranes -spore coat forms -endospore is freed from cell |
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NAG |
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N-acetylglucosamine |
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NAM |
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N-acetylmuramic acid |
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