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8/14/2019 Chap 4 Diversity
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DIVERSITY OFMICROORGANISMS
Part I
Acellular and ProkaryoticMicrobes
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Acellular Infectious
Agents:VirusesVirions are complete viral particleswhich are very small and simple instructure.Size : 10 to 300nm, or can be up to1um in length(Ebola virus)1940: 1 st photographs of viruses afterthe invention of electron microscopesin 1930s
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Acellular Infectious
Agents:Viruses
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Acellular Infectious
Agents:VirusesViruses contain DNA or RNAA protein coat Some are enclosed by an envelopeSome viruses have spikesMost viruses infect only specific typesof cells in one hostHost range is determined by specifichost attachment sites and cellular
factors
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Acellular InfectiousAgents:Viruses
Five specific properties thatdistinguish viruses from living cells:
2. They possess either DNA or RNA3. They are unable to replicate on their own4. They do not divide by binary fission,
mitosis, or meiosis
5. They lack the genes and enzymesnecessary for energy production6. They depend on the ribosomes, enzymes,
and metabolites of the host cell for proteinand nucleic acid production.
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Acellular Infectious
Agents:VirusesViruses are classified by thefollowing characteristics :
2. Type of genetic material3. Shape of the capsid4. Number of capsomeres
5. Size of the capsid6. Presence or absence of an envelop7. Type of host that it infects8. Type of disease it produces9. Immunologic or antigenic properties
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Acellular Infectious
Agents:VirusesFour categories of viruses basedon the type of nucleic acid theypossess:
2. Double-stranded RNA viruses3. Single-stranded RNA viruses4. Single-stranded DNA viruses5. Double-stranded DNA viruses
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BacteriophagesViruses that infect bacteriaObligate intracellular pathogens
They may be:4. Icosahedron: almost spherical shape
with 20 facets5. Filamentous: long tubes formed into
helical structure6. Complex: icosahedral heads attached
to helical tails.
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Acellular Infectious
Agents:Viruses
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Acellular Infectious
Agents:Viruses
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Virulent bacteriophagesCause the lytic cycle , which ends in thedestruction of the bacterial cell.
The lytic cycle has 5 steps:3. Attachment (adsorption)4. Penetration
5. Biosynthesis6. Assembly7. Release
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Attachment Phage attaches by tail fibers tohost cell
Penetration Phage lysozyme opens cell wall,
tail sheath contracts to forcetail
core and DNA into cellBiosynthesis Production of phage DNA
and proteins
Maturation Assembly of phage particles
Multiplication of Bacteriophages
(Lytic Cycle)
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Temperate BacteriophagesOr lysogenic phages, do notimmediately initiate the lytic cycle,but rather, the DNA remainsintegrated into the bacterial cellchromosome, generation after
generation.
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Animal Viruses
Viruses that infect humans andanimalsSome maybe DNA viruses, whileothers may be RNA virusesMay be enveloped or may containenzymes that play a role in viralmultiplication of animal viruses.
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Animal Viruses
Double-strandedDNA,
nonenvelopedvirusesPapillomavirus (human wartvirus)Polyomavirus
Cause tumors,
some causecancer
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Animal Viruses
Orthopoxvirus (vaccinia and
smallpox viruses)Molluscipoxvirus
Smallpox, molluscumcontagiosum, cowpox
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Animal Viruses
CoronavirusUpper respiratory
infections
Hepadnavirus (Hepatitis B virus)
Use reversetranscriptase toproduce DNA frommRNA
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Animal Viruses
EnterovirusEnteroviruses
include poliovirusandcoxsackievirus
Rhinovirus
Hepatitis A virus
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Animal Viruses: Single-strandedRNA, strand, one RNA strand
FilovirusEnveloped, helical
virusesEbola andMarburg viruses
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Animal Viruses:Single-stranded RNA
Lentivirus (HIV)Oncogenic viruses
Use reversetranscriptase toproduce DNA fromviral genome
Includes all RNAtumor viruses
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Animal Viruses: Double-strandedRNA, nonenveloped
Reovirus (Respiratory
Enteric Orphan)Rotavirus
Mild respiratoryinfections and
gastroenteritisColorado tickfever
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Multiplication of Animal viruses
Attachment Viruses attaches to cellmembrane
Penetration By endocytosis or fusionUncoating By viral or host enzymesBiosynthesis Production of nucleic acid andproteins
Maturation Nucleic acid and capsidproteins assembleRelease By budding (enveloped viruses)or rupture
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Release of an enveloped virus bybudding
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Inclusion bodies
Are remnants or collections of virusesOften seen in infected cellsUsed as diagnostic tool to identifycertain viral diseasesCytoplasmic inclusion bodies: rabies,AIDS, and Guarnieri bodies of smallpoxIntranuclear inclusion bodies: herpes andpoliomyelitis
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Latent Viral InfectionsVirus remains in asymptomatic host cell forlong periods
Cold sores caused by herpes simplex virus, andshingles which occurs in person who has hadchicken pox (varicella)
Persistent Viral InfectionsDisease processes occurs over a longperiod, generally fatal
Subacute sclerosing panencephalitis (measlesvirus)Progressive encephalitis (Rubella virus)
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Cancer
Activated oncogenes transform normalcells into cancerous cells.
Transformed cells have increasedgrowth, loss of contact inhibition,tumor specific transplant and T
antigens. The genetic material of oncogenicviruses becomes integrated into the
host cell's DNA.
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Oncogenic viruses
Oncogenic DNAViruses
AdenoviridaeHerpesviridaePoxviridaePapovaviridae
Hepadnaviridae
Oncogenic RNAviruses
RetroviridaeViral RNA istranscribed to DNAwhich canintegrate into host
DNA
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Viroids
Plant VirusesPlant viruses enter through wounds or viainsects
ViroidsViroids are infectious RNA; potato spindle
tuber disease
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Some Plant viruses
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Prions
Infectious proteins that cause fatalneurologic diseases in animals.Inherited and transmissible by ingestion,transplant, & surgical instrumentsSpongiform encephalopathies: Sheepscrapie, Creutzfeldt-Jakob disease,Gerstmann-Strussler-Scheinker syndrome,
fatal familial insomnia, mad cow diseasePrP C, normal cellular prion protein, on cellsurfacePrP Sc , scrapie protein, accumulate in brain
cells forming plaques
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The Domain Bacteria
Characteristics
1. Cell Morphology2. Staining
Reactions
3. Colonymorphology4. Atmospheric
requirements5. Nutritional
6. Biochemical andmetabolicactivities
7. Specific enzymesthat the organismproduces
8. Pathogenecity9. Amino acidsequencing of proteins
10.Genetic
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1. Cell Morphology
Size: 0.2um to 10umShape:
3. Cocci round or sphericalbacteria
4. Bacilli rectangular or rod-shaped bacteria
5. Spirilla curved and spiral-shaped bacteria
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Cocci may be:2. Diplococci (in pairs)3. Streptococci (chains)4. Staphylococci (clusters)5. Tetrads (packets of four)6. Octads (packets of eight)Ex. Enterococcus, Neisseria,
Staphylococcus, Streptococcus.
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Bacilli may be:1. Single2. Diplobacilli3. Steptobacilli4. Coccobacilli
Ex. Haemophilus5. Pallisade
arrangementEx. Corynebacterium
diptheriae
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Examples of medicallyimportant bacilli are
Enterobacteria -Shigella
- Escherichia- Pseudomonas- Klebsiella
- Bacillus- Proteus- Clostridium
- Salmonella
Bacillus cereus
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Examples of curved and spiral-
shaped bacteria:2. Vibrio cholerae3. Campylobacter
4. Treponema
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Neisseria
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Cell-wall deficient (CWD) bacteria maylose their cell walls because of adverse
growth conditions.Mycoplasma has no cell wallPleomorphism is the ability to exist in avariety of shapes because of theabsence of cell wall.
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2. Staining Procedures
SmearingFixing
StainingUsed to observe cell morphologySimple stain
Differential stainGram stainAcid-fast stain
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A thin film of a solution of microbes on a slide is asmear.A smear is usually fixed to
attach the microbes to theslide and to kill the microbes.
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Stains consist of a positive andnegative ion.
In a basic dye, the chromophore isa cation.In an acidic dye, the chromophore
is an anion.Staining the background instead of the cell is called negativestaining .
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Differential Staining: GramStain
The Gram stain classifies bacteriainto gram-positive and gram-negative.Gram-positive bacteria tend tobe killed by penicillin anddetergents.Gram-negative bacteria aremore resistant to antibiotics.
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Primary stain: Color of Gram + cellsColor of Gram cells
Crystal violet Purple Purple
Mordant: Iodine Purple Purple
Decolorizing agent:Alcohol-acetone PurpleColorless
Counterstain:Safranin Purple Red
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Differential Stain: GramStaining
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Differential Stains: Acid-fastStain
Cells that retain a basicstain in the presence of acid-alcohol are calledacid-fast .Nonacid-fast cellslose the basic stainwhen rinsed with acid-
alcohol, and areusually counterstained(with a different colorbasic stain) to seethem.
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Negative staining is usefulfor capsules.Heat is required to drive astain into endospores .Flagella staining requires amordant to make the flagellawide enough to see.
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3. Motility The ability of the organism to move.Bacterial motility is associated with thepresence of flagella or axial filamentsSome exhibit motility on secreted slime onsolid agarMost spiral-shaped bacteria and one half of the bacilli are motileCocci are generally non-motileMotility can be demonstrated by stabbingorganisms into a tube or by the hanging droptechnique.
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4. Colony Morphology
Includes the size, color, overall shape,elevation, and consistency of the colony
The features of the colony serve asimportant clues in the identification of bacteriaSize of the colony is determined by theorganisms rate of growth, and it is animportant characteristic of a bacteial speciesBacterial colony is a mound or pile of
bacteria on an agar surface. It contains
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5. AtmosphericRequirements
It is useful to classify bacteria on the basisof their relationship to oxygen and carbon
dioxideBacterial isolate can be classified into one of five major groups:
1.) Obligate aerobes require anatmosphere that contains molecular oxygenin concentrations comparable to that in aroom air (20 -21 % oxygen). Ex.Mycobacteria and certain fungi
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2.) Microaerophilic aerobes require lowerconcentration (15% oxygen) than that foundin room air for multiplication. Ex. Neisseriagonorrhea, Campylobacter species
3.) Obligate anaerobes is an anaerobe thatonly grows in anaerobic environment. It willnot grow in microaerophilic environment,CO2 incubator, or in air.
4.) Aerotolerant anaerobe does not requireO2, grows better in the absence of O2, butcan survive in atmosphere containingmolecular oxygen such as air or a CO2incubator.
5.) Capnophiles microbes that grow better inincreased concentration of CO2.
l
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6. NutritionalRequirements
All bacteria need some form of elements such as C,H, O2, S, P, and N
for growthSpecial elements such as K, Ca, Mn,Mg, Co, Cu, Zn, U are needed by certain
bacteria.Some have specific vitaminrequirements.
Others need organic substances
i h i l d
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7. Biochemical andMetabolic Activities
Bacteria produce waste products andsecretions such as enzymes that enable
them to invade their host and cause disease. The pathogenic strains of many bacteria,such as staph, and strep can be tentativelyidentified by the enzymes they secrete.
Some bacteria are characterized by theproduction of certain gases such as CO2,H2S, O2, and CH4
Different types of culture media are used in
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8. Pathogenecity
Disease-producing abilities of pathogens
Many pathogens are able to causedisease because they have capsules or endotoxins , or because they
secrete exotoxins and exoenzymes that damage cells and tissues.It is tested by injecting the organism
into mice or cell cultures.
9 A i A id S i
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9. Amino Acid Sequencingof Proteins
Comparing amino-acid sequencingof certain bacterial proteins
determines the species and itsrelations to another bacteria.
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10. Genetic composition
DNA is unique to each speciesDetermining the degree or
relationship between two differentbacteria can be done by identifying orhybridizing a sequence of bases inportions of DNA or RNAMolecular diagnostic procedures aretests to identify bacteria by analyzingthe organisms DNA or RNA
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Unique Bacteria
Rickettsiasvery small parasitic bacteria that liveand reproduce within eukaryotichosts cellsCoccoid, rod-shaped, or pleomorphic
Gram-negative bacteria with abacterial-type cell wallContain both DNA and RNA
They are transmitted by arthropod
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Chl di
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Chlamydias
Most primitive of allbacteria because theylack enzymes requiredto perform manymetabolic activities,particularly productionof ATP
Transferred by directcontact between hostsC. trachomatis causes
blindness
M l
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Mycoplasmas
Smallest of the cellular microbes They assume many shapes, from
coccoid to filamentous because theylack cell walls They are gram-negative and may befree-living or parasitic and pathogenicto animals and some plants
They are resistant to treatment withpenicillin and other antibiotics
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Photosynthetic bacteria
Purple bacteria and green bacteria do not produceoxygen but they use light as source of energyCyanobacteria produce oxygen
They may create a waterbloom, a pond scumwhich resembles thick layer of bluish-green oilpaint.
They are able to convert N2 from the air toammonia in the soil.Some can produce toxins such as neurotoxins,hepatoxins, and cytotoxins.
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Especially large and especiallysmall bacteria
Largest: Thiomargarita namibensisand Epulopiscium fishelsonii
Nanobacteria have been found insoil, minerals, ocean water, humanand animal blood, human dental
calculus, arterial plaque and evenrocks of extraterrestial origin
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Especially large and especiallysmall bacteria
Thiomargarita Epulopiscium
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Domain Archaea
Discovered in 1977Archae means ancient
There is a debate whether archaeevolved first than eubacteria.Many are extremophilesOthers are methanogens
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END
OfDiversity of Acellular and
Prokaryotic microbesQuiz on August 19