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118 Cards in this Set
- Front
- Back
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Classes of Microorganisms
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Algae
Fungi (some pathogens) Protozoa (some pathogens) Bacteria (many pathogens) |
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Distinguishing characteristics of:
ALGAE |
no pathogens
all photosynthetic |
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Distinguishing characteristics of:
FUNGI |
some pathogens
nonphotosynthetics rigid cell wall |
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Distinguishing characteristics of:
PROTOZOA |
some pathogens
NO rigid cell wall (some may have cysts w/ rigid cell walls) UNICELLULAR NONphotosynthetic |
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Distinguishing characteristics of:
BACTERIA |
many pathogens
mostly require organic compounds as energy source, but some of the non-pathogens are photosynthetic all (but one!) have a rigid cell wall |
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what makes antibiotic effects on bacteria and fungi different?
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RIGID CELL WALLS in bacteria and fungi are different
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Higher Microorganisms (Eukarya domain)
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Fungi
Protozoa Algae (have "true" nucleus) |
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Lower Microorganisms (Bacterial domain)
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Bacteria
(procaryotic cells) |
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Eucaryotic vs. Procaryotic:
CHROMOSOME(S) |
EUCARYOTIC: each cell contains # of difft linear chromosomes contained WITHIN the NUCLEAR MEMBRANE (mitosis occurs)
PROCARYOTIC: generally 1 circular chromosome/ cell (NO NUCLEAR MEMBRANE, NO MITOSIS) |
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Eucaryotic vs. Procaryotic:
MITOCHONDRIA and other MEMBRANE BOUND STRUCTURES |
EUCARYOTIC:
-mitochondrian contains oxidative enzymes, carries out ox/phos -also contain membrane-bound structures such as vacuoles, peroxisomes, etc... PROCARYOTIC CELLS: no mitochondria (though mito likely evolved from them) oxidative enzymes (and ox/phos) are associated with cytoplasmic membrane of cell |
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Eucaryotic vs. Procaryotic:
Mechanism of cellular movement |
EUCARYOTIC:
-cytoplasmic streaming (amoeboid mvtm) or -contraction of flagella or cilia (membrane continuous w/ cell membrane enclosing longitudinal fibers) PROCARYOTIC: -no cyto streaming (cyto too dense, due to high ribosome content) -flagella (no longitudinal fibers and no membrane coat) |
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Eucaryotic vs. Procaryotic:
FLAGELLA |
EUCARYOTIC:
- surrounded by membrane continuous with cell membrane -encloses system of regularly arranged longitudinal fibrils PROCARYOTIC: --fibrous protein composed of repeating subunits -no longitudinal fibers -no membrane coat |
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Eucaryotic vs. Procaryotic:
CELL WALL |
EUCARYOTIC:
higher plants & green algae: composed of polysaccharide cellulose in most fungi: composed of chitin (polymer of acetyl glucosamine) PROCARYOTIC CELL: composed of peptidoglycan polymer |
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Peptidoglycan Polymer of bacterial cell wall is composed of:
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muramic acid (derivative of acetyl glucosamine)
D-amino acids and other unusual amino acids (unique compopnents, not found in Eucaryotic cells) |
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penicillin preferentially targets bacteria by:
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interferring with formation of peptidoglycan (main component of bacterial cell wall)
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Most bacteria of medical intereset have dimensions ~
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~ 1 micrometer
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what gives the bacterial cell a characteristic size and shape?
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strength and rigidity of its cell wall
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spherical bacteria are called what?
a) general diameter b) small variations seen in some organisms |
COCCUS
(general diameter of 0.8 to 1.0 micrometers) ELONGATED COCCI (pneumococcus and gonococcus) PERFECT SPHERE (staphylococcus) |
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bacillus
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rod shaped bacteria
may be long and slender, short and thick, may appear square or rounded and tapered |
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coccus
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spherical shaped bacteria
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coccobaccili
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bacteria that are somwhere between rounded rod and elongated sphere shape
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example of a characteristically pleomorphic bacillus
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Corynebacterium diphtheriae
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The virbrios (e.g. the cholera vibrio) are what shape?
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curved rods
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The spirochetes are bacteria with what shape?
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spiral
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why are spirochetes classified differently?
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they do not have a rigid wall
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Treponema pallidum
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causative agent of syphilis
(a spirochete) |
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Berrelia burgdorferi
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cause of Lyme Disease
(a spirochete) |
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shape of mammalian cells will change depending on:
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ionic strength of surrounding medium
(will swell/burst in distilled water, whereas bacterial cells remain stable) |
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most bacteria multiply by what mechanism?
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binary fission
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binary fission occurs by the formation of what?
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occurs by the formation and subsequent joining of a central transverse wall
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filaments
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many-celled aggregates
result if daughter cells do not separate after completion of the transverse wall in binary fission common among the cocci |
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why are filaments common among the cocci?
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the aggregates are stable
(therefore useful for identification) |
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what is a streptococci?
and how does it form? |
a chain of cocci
formed by successive divisions of cocci along the same axis |
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regular, successive divisions at right angles result in what shape aggregations?
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tetrads or flat plates (NO MEDICALLY IMPORTANT BACTERIA DO THIS)
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3 successive divisions at right angles to one another will result in what type of uncommon arrangement?
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cuboidal
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If successive divisions of cocci can occur in any direction, what type of aggregates result?
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irregular clusters (as found in the Staphylococci)
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cell division in rod shaped bacteria
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always takes place at right angles to the long axis
only chains can result (common among some aerobic Bacilli) |
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unique characteristic of Corynebacterium (genus of rod shaped bacteria)
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rods stick together at the ends, but may slip under eachother without separating... leads to STACKS of rods or to groupings resembling chinese alphabet
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composition of cytoplasmic membrane
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phospholipid bilayer
similar composition to mammalian cell 20-30% lipid (mainly phospholipid) 60% protein rarely contains sterols semi-permeable (freely to water, slowly to glycerol, impermeable to larger) |
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protoplasts can be made by:
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digesting all or most of the bacterial cell wall with specific enzymes
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what happens to rod-shaped bacterium converted to a protoplast?
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assumes spherical shape (cell wall dissolved)
will burst if put in hypotonic media |
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functions of bacterial cytoplasmic membrane
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contains oxidative enzymes (cytocrhomes, quinones, ATPase) and resembles inner mito membrane in structure and function
also contains enzymes which fxn in external cell wall synthesis ability to pump nutrients (selective transport system for sugars, aa's, metals. 3 mechanisms of (including active) transport mechanisms for secreting toxins and enzymes into EC medium |
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periplasmic space
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between the outer membrane and the cytoplasmic membrane
contains enzymes (esp for degrading EX substances of high molecular weight) |
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bacteria equivalent of Nucleus
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nucleoid:
NO nuclear membrane no organization of DNA into visible chromosomes |
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bacterial ribosome
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similar structure and fxn to those in mammalian cells
smaller (70S) than most mammalian ribosomes (80S) |
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Cytoplasmic granules of bacteria
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bodies found in the cytoplasm of some bacteria under certain conditions
storage bodies formed under growth conditions when excess food is available allow storage of nutrients w/o increasing osmolarity of cytoplasm |
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types of cytoplasmic granules in bacteria
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-high molecular weight lipid
-glycogen accumulates in other bacteria -metachromatic granules (mostly polymerized phosphate, stains deeply w/ basic dyes) |
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characteristics of bacterial cell wall
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relatively large structure (20-35% of cell weight)
present in all bacteria (EXCEPT: MYCOPLASMA) contains unique polymer called peptidoglycan |
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peptidoglycan
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aka mucopeptide
unique polymer of N-acetyl glucosamine, linked to muramic acid by a glycosidic bond. (tetrapeptide of unique (often D) amino acids) |
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what is peptidoglycan cross-linking?
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bonding between amino acid side chains that gives rigidity and strength to cell wall
(via peptide bridge between terminal carboxyl of a tetrapeptide to a neighboring amino or carboxyl group on another tetrapeptide chain) |
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how does penicillin target bacteria?
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blocks cross-linking of peptidoglycans essential to integrity of cell wall
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lysozyme
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enzyme found in tears and other body fluids
antibiotic property, because it splits glycosidic bond between NAG and NAM in bacterial cell well peptidoglycans |
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Gram positive bacterial walls are composed mostly of:
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a thick layer of peptidoglycan and
mosly different carbohydrate polymers (e.g. a polymer of ribitol (a sugar alcohol) phosphate (a techoic acid) in staphylococcus or other sugars in streptococcus) |
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technoich acids linked to the peptidoglycan are important why?
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they are important antigens, appear to impart immunological specificity
Ab response of the host seems mainly direceted against these polymers, rather than against the peptidoglycan |
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what distinguishes gram negative bacteria?
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thinner peptidoglycan layer
presence of an OUTER MEMBRANE (outer surface of which contains lipoposaccharide (LPS)) |
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LPS
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lipoposaccharide (an endotoxin)
found in outer surface of OM of gram negative bacteria |
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periplasmic space
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space between the OM and inner cytoplasmic membrane of gran negative bacteria
contains some binding proteins and digestive or hydrolytic enzymes |
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functions of OUTER MEMBRANE of gram negative bacteria
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-reacts with Abs
-blocks entry of large molecules into periplasmic space -barrier to antibicrobial agents and detergents -makes gram neg bacteria generally more resistant than gram positives |
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PORINS (of OM)
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matrix proteins in outer membrane of gram neg bacteria
allow passage only of smaller molecules (> MW 600-700) i.e. antibiotics may gain entrance to periplasmic space via PORINS |
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LPS
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located in outer layer of OM
endotoxin (bound to bacterial cell and causes shock and fever in gram negative sepsis) composed of POLYSACCHARIDE (responsible for antigenic specificity) and LIPID A (confers the toxicity) |
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LIPID A
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composed of glucosamine linked to FAs and pyrophosphate
embeddeed at the base of the OM toxic part of LPS (along with a POLYSACCHARIDE, that confers antigenic specificity) |
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"O" specific region
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repeating oligosaccharide units of outer layer of outer membrane of gram negative bacteria
SUGARS IMPART IMMUNOLOGICAL SPECIFICITY TO CELL since they pretominate at the very surface of the cell |
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"O" antigens
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polysaccharides in "O" specific region of OM that confer immunological specificity
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"O" in "O" specific region and "O" antigens is from
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"ohne," since it was first regognized in strains WITHOUT (ohne) characteristic colony morphology
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examples of periplasmic enzymes
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amylases (degrade starch)
penicillinase may be located in this space |
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endotoxin is only found in what type of bacteria
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gran negatives
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gram stain procedure
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1. Stain cell (fixed to slide) with crystal violet (a basic dye)
2. treat with iodine (forms water insoluble complex with dye, inside of the bacterium) 3. DECOLORIZE by brief treatment w/ 70% ethanol (only gram negatives decolorize, if done briefly/correctly) 4. COUNTERSTAIN the decolorized (gram negative) cells with a red stain |
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some gram positive organisms lose their gram positive property with...
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increasing age (always use fresh cultures!)
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gram variable
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encountered in a few important species of bacteria
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likely mechanism for gram staining properties
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high mucopeptide content probably retains dye in gram positive cell cell
also, cell walls of gram positives become largely impermeable to low MW compounds when in 70% alcohol (trapping dye-iodine complex in the cytoplasm) whereas dye-I2 complex rapidly leads out through the wall of gram negatives w/ only thin mucopeptide layer |
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what happens to a gram positive cell if the cell wall is removed and it is stained?
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it reacts as a gram negative in staining procedure
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capsule
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non-essential secretion on cell surface, usually polysaccharide composition (different from cell wall)
doesn't stain in the gram stain when present, plays important role in disease production Ab target |
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Pneumococcus mutants which have lots ability to produce capsule are...
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able to grow in culture media, but have lost all pathogenicity (capsule plays key role in resisting phagocytosis)
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many bacteria do not have capsules (T or F)
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TRUE
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presence of capsular material in urine or spinal fluid
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an important diagnostic test, indicates infection caused by encapsulated bacteria (e.g. Haemophilus influenzae, Streptococcus pneumoniae)
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bacterial Flagella
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organs of locomotion (10-20nm thick)
thinner than the cell itself (8-12 micrometers long) longer than cell itself |
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chemical composition of bacterial flagella
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multiple flagellin (fibrous protein) subunits, wound hilically around a hollow core or arranged in longitudinal rows
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petrichous flagella
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many flagella over whole cell
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polar flagella
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originate from one end of cell only
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all motile bacteria contain
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flagella
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motile bacteria may become non-motile when?
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in later stages of growth
in energy-poor conditions cells may still remain viable |
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flagella move bacteria by
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propelling cell much like a propellar, rigid flagella spin around their long axis
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pilli
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aka fimbrae
filamentous, surface appendages, sorter than flagella |
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function of pilli
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not generally involved in motility
means of adherence to other cells (bacterial or animal) |
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F pili
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found only on "male" strains of bacteria, necessary for bacterial conjugations which results in the transfer of DNA from one cell to another
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sex pili are responsible for
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bacterial attachment during conjucation
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type IV pili can..
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extend and retract, thereby push or pull bacteria across a surface
TWITCHING MOTILITY |
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TWITCHING MOTILITY
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pili-mediated bacterial movement
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moleclar structure of pilli
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hollow tubes, assembled by polymerization of presynthesized protein molecules
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pili and virulence
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appear to be important virulence factors, prevent bacterial from being washed out in bulk flow
(e.g. GONOCOOCI produce pili which bind to specific receptors of cervical epithelial cells) |
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adherence components of bacterial cells
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pili/fimbriae
glycocalyx (carb polymers on surface of cell wall of gram positive bacteria) adhesins (proteins localized to OM of gram negatives or cell wall of gram positivses) |
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biofilm
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= the surface attached to bacteria
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spores are only found in:
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a few species of bacteria
LARGE GRAM POSITIVE RODS in the genera BACILLUS and CLOSTRIDIA |
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sporulation occurs
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AFTER THE RAPID (logarithmic) PHASE of growth is finished
triggered by NUTRIENT DEPRIVATION |
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each spore-forming bacterium forms how many spores?
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1 per life cycle
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where is spore produced?
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within the bacterial cell = endospore
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what is unique about spore composition
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contain chemicals found only in spore and not made by actively growing bacteria (eg dipicolinic acid)
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spores are in what type of state?
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dormant
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spores are resistant to ...
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drying
heat (can survive boiling) chemicals staining |
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possible explanations for extreme resistance of spores:
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low water content within spre may explain heat resistance
keratin-like proteinaceous outer coat not present in actively growing bacterium (may explain resistance to disinfectance) |
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germination of a spore
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occurs under appropriate conditions (in response to a specific trigger, ie presence of certain nutrient)
give rise to one bacterial cell accompanied by loss of heat resistance, a swelling, and uptake of water spore coat ruptures and a vegetative cell grows out |
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vegatative form
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reproductive, or non-spore form
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spores are rarely seen in what type of cultures?
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very young cultures
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some clostridia (such as tetanus) readily form spores in what type of cultures?
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OLDER cultures
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some clostridia (such as gangrene) rarely form what?
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spores, whereas tetanus clostridia does readily form spores (even in OLDER cultures)
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Bacillius antrhacis
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spores are likely required for survival in environment, but also used as bioterror agent
stable for years powder-like and germinate in arm, wet, nutrient rich environment of lung (causing inhalation anthrax) |
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position and size of spore in the rod-shaped cell is characteristic for what?
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different species of bacteria
useful in ID of difft species |
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what can enter cytoplasmic membrane by passive diffusion?
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water
lipid-soluble molecules |
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Facilitated diffusion
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a) no energy required
b) single mebrane associated protein, facilitates rapid equilibration of nutrient ax membrane c) entry followed by rapid metabolism (to maintain favorable gradient for further influx) |
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Phosphoenol pyruvate: SUGAR PHOSPHOTRANSFERASE SYSTEM
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a) involved chemical transformation during transport
b) overall rxn: phosphoenolpyruvate + sugar ---> sugar phosphate + pyruvate e) energetically favorable, permitting uptake and conversion to a phosphorylated intermediate in a single step. sugar-Pi is trapped in cell can can be immediately metabolized |
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ACTIVE TRANPORT
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requires:
- metabolic energy (either as ATP or oxidative energy) and - a specific membrane protein (against concentration gradient) substrate molecule is not chemically altered |
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positive chemotaxis factors
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"attractants"
various sugars and amino acids serve as attractants |
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negative chemotaxis factors
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repellants
phenols and acids serve as repellants |
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"tasters"
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sensory chemoreceptors possessed by bacteria, in membrane
control a phosphocascade, which in turn controls the direction of flagellar rotation |
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when direction of flagellar rotation is counter-clockwise..
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bacteria travel in a straight line
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when direction of flagellar rotation is clockwise...
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organism will tumble in place
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when moving up a gradient of "attractant"
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straight line movements last longer than tumbles
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when moving away from an attractant or toward a repellent
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tumbling occurs more frequentyl until the net movement is properly redirected
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