Lecture 1: Basic Microbiology & Bacterial Taxonomy Flashcards
1) Define Microbiology 2) History of Microbiology (not included) 3) Different types of microbes 4) Differentiate bacteria based on gram stain, morphology, and metabolic characteristics
What is the definition of Microbiology?
the study of organisms called microorganisms (microbes) that are too small to be perceived clearly by the unaided human eye
Microbes include:
some metazoan animals, protozoa, many algae, and fungi, bacteria, and viruses
Why are microbes probably the most significant life form sharing the planet with humans?
because they are ubiquitous in nature, capable of utilizing any available food source, including humans whose defenses may be compromised
Infection
the invasion of the body by a harmful microbe resulting in a disease
Disease
a disorder with a specific cause and recognizable signs and symptoms
Pathogen
any microbe that has the capacity to cause disease
Koch’s Postulates
1) pathogen found in diseased organisms, but not healthy
2) able to isolate pathogen from diseased host and grow on culture
3) pathogen from pure culture must cause disease in inoculated healthy animal
4) able to isolate pathogen from inoculated animal
Exceptions to Koch’s Postulates
- some microbes have unique culture requirements or do not grow on cultured media (ie Treponema pallidum, Mycobacterium leprae, rickettssial and viral pathogens)
- some pathogens do not show distinct symptoms *some diseases involve several pathogens
3 Major microbe categories
Viruses
Prokaryotes (bacteria, mycoplasmas, rikettsiae, and chlamydiae)
Eukaryotes (fungi, protozoans, and multicellular parasites)
Prions
noncellular infectious proteins, also inherited form
Characteristics of Prions
- long incubation time
- characteristic spongiform changes associated with neuronal loss and failure to induce inflammatory response
- prion proteins modify the folding of normal human cellular proteins (cellular proteins or PrP^c) into additional prions (PrP^sc)
Human Prion Diseases
Creutzfeldt-Jakob disease (CJD)
Variant Creutzfeldt-Jakob disease (vCJD)
Kuru
Animal Prion Diseases
Mad Cow Disease (bovine spongiform encephalopathy)
Chronic Wasting Disease (CWD)
Scrapie
Viruses
- classification - size - cellular or noncellular? - structure - examples
VIRUSES ARE OBLIGATE INTRACELLULAR PARASITES
*smallest and simplest of all microbes (except for prions and viroids)
*NONCELLULAR
*DNA or RNA (not both) enclosed by a protein coat
*may or may not have a lipoprotein envelope
EX: HIV, SARS, Viral Hepatitis (A,B,C,D,E) H1N1
Viral attachment
attachment proteins on capsid or envelope determine specificity of infection
Viral reproduction
dependent on host cell
Prokaryotes
- Def - Nucleic Acid - Organisms
- Unicellular organisms with no clearly defined nuclear membrane
- Nucleic acid not complexed with histones, no chromosomes
- Bacteria, mycoplasmas, chlamydiae, rickettsiae
Eukaryotes
- Def - Nuclear material (arrangement) - size
- uni- and multicellular organisms with well defined nuclear membranes and organelles
- nuclear material (nucleic acid plus histones) is arranged in chromosomes
- usually larger than prokaryotic cells
Fungi
- Prok. or Euk.? - Cell wall composition - Major Sterol in membranes - 4 Types
Eukaryotes
*Cell walls containing chitin, glucans, and mannans
*Membranes with ergosterol as major sterol
Include:
-Yeasts (Unicellular)
-Filamentous molds (Mycelia)
-Dimorphic fungi (can grow like yeast or mold)
-Saprophytes (utilize organic matter for energy e.g. mushrooms)
Parasite
- Def - Animal parasite characteristics
- an organism that lives in or on another organism (host) and causes damage to the host
- animal parasites are euk. organisms with no cell walls, single celled to large organisms, multicellular worms
Classification of bacteria is based on what?
1) Morphological differences
2) Biochemical/metabolic differences
3) Immunololgic characteristics
4) Genetic characteristics
2 common stains for identification of bacteria
Gram stain
Acid fast stain
Questions to ask when identifying bacteria
1) Gram + or Gram -
2) Morphology (rod, coccus, spiral, pleomorphic)
3) Cells occur singly or in chains
4) Size of cells
Gram Stain components
1) Crystal Violet -primary stain
2) Iodine -mordant
3) Alcohol -decolorizer
4) Safranin -counter stain
Cell Wall
- functions - components
semirigid cell wall outside the cell membrane
- maintains shape
- prevents cell from bursting
- porous
- Peptidoglycan -molecules of N-acetyl glucosamine alternate with N-acetyl muramic acid
Gram (+) Amino Acids
Gram (-) Amino Acids
G(+): L-Alanine, D-Glutamic Acid, L-LYSINE, D-Alanine
G(-): L-Alanine, D-Glutamic Acid, L-DIAMINOPIMELLIC ACID, D-Alanine
Teichoic Acid
- G(+) or G(-) - Def - 2 Classes - Functions
Gram (+) only
-polyol phosphate polymers with either ribitol or glycerol linked by phosphodiester bonds
Classes: (1) Lipotechoic acids
(2) Wall techoic acid
Functions:
(a) binds and regulates movement of cations in and out of the cell
(b) provides wall’s antigenic specificity
(c) may also assume a role in cell growth, preventing extensive wall breakdown and possible cell lysis
Outer Membrane
- G(+) or G(-)
- function
- contents
Primarily in Gram (-)
-bilayer membrane
-controls transport of certain proteins from the environment
Contents:
-surface antigens and receptors present
-Lipopolysaccharide (LPS) -consists of:
a) O-antigen polysaccharides (antigenic)
O for outer
b) water soluble core polysaccharide
c) Lipid A
Lipid A
responsible for toxic properties
Gram (-) Endotoxin
Gram (+) vs. Gram (-)
-Envelope
Gram (+) -2 Layers 1) Peptidoglycan (open, netlike) 2) Cytoplasmic membrane (hydrophobic) Gram (-) -3 Layers 1) Outer membrane (hydrophobic) 2) Peptidoglycan (open, netlike) 3) Inner membrane (hydrophobic)
Gram (+) vs. Gram (-)
-Unique features
Gram (+)
-Teichoic Acids -helps in the attachment to human cells (along with pili and specific virulence factors)
Gram (-)
- Outer membrane and endotoxin - Pili - Specific Virulence Factors
Gram (+) vs. Gram (-)
-Antigens & Proteins
Gram (+)
- Surface antigens- Teichoic acids - Surface specific proteins * M-protein (Streptococcus (fimbria)) * Tuberculin (M. tuberculosis) * A-protein (S. aureous)
Gram (-)
- O antigens (polysaccharide of LPS) - Outer membrane proteins - Fimbria and pili
Gram (+) vs. Gram (-)
-Capsules and Flagella
Gram (+)
- Capsular material (except S. pyogenes hyaluronic acid capsule)
- Flagella
Gram (-)
- Capsular material
- Flagella
Gram (+) vs. Gram (-)
-Peptidoglycan
Gram (+)
-thick layer, highly cross linked by pentaglycine bridges
Gram (-)
-thin layer, not highly cross linked
Gram (+) vs. Gram (-)
-Susceptibility to lysozyme and beta lactam drugs
Gram (+)
-more susceptible
Gram (-)
-less susceptible
Gram (+) vs. Gram (-)
-Major trigger of inflammation
Gram (+)
-peptidoglycan-teichoic acids
Gram (-)
-endotoxins
4 major shapes of bacteria
1) Cocci: spherical
2) Bacilli: rods (short bacilli are cocco-bacilli)
3) Spiral forms: comma, S, or spiral shaped
4) Pleomorphic: lacking a distinct shape (like jello)
Gram (+) Bacteria
6 classic: 2 cocci, and 4 bacilli
- Streptococcus
- Staphylococcus
- Bacillus (spores)
- Clostridium (spores)
- Corynebacterium
- Listeria
Gram (-) Bacteria
Cocci - Neisseria
Spiral - Spirochetes
-rest are G(-) rods or pleomorphic
Acid Fast Stain
1) Corbol Fuschin with heat
2) Alcohol
3) Methylene blue
*acid fast =red, non acid fast =blue
Mycobacterium ->acid fast
Nocardia ->partially acid fast
All bacteria except Legionella micadadei ->non-acid fast
Non Gram Staining Bacteria
Mycoplasma -permanently lack peptidoglycan
*Diagnosis -largely clinical. 65% patients produce cryoagglutinins (agglutinate RBC’s in cold) -suggestive, not specific
Ureaplasma -does not have a cell wall
Poorly Gram staining or poorly visible bacteria
- Mycobacteria -waxy cell wall, does not take stain
- Rickettsiae and Chlamydiae -stain color not visible (too small to be visualized)
- Spirochetes -Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease) detected by dark field microscopy
Obligate Aerobes
-require Oxygen for growth at atmospheric oxygen levels (21%)
-no fermentive pathways
-generally produce superoxide dismutase
(eg Pseudomonoas, M.tuberculosis, Bacillus)
Microaerophiles
-require oxygen for growth, but concentration of oxygen must be below atmospheric level (<21%)
(eg Campylobacter, Helicobacter)
Facultative Aerobes
-organisms will use oxygen if it is present but can grow by anaerobic respiration or fermentation in the absence of oxygen
(eg most human pathogens, Streptococci, Enterobacteria)
-Aka Facultative anaerobes
Aerotolerant Anaerobes
-organisms can grow in the presence of oxygen by they cannot use it
(eg Streptococcus spp.)
Obligate Anaerobes
-organism cannot grow in presence of oxygen
-utilize fermentive pathways
(eg Actinomyces, Bacteriodes, Clostridium)
(^ABC of anaerobiosis)
