WEEK 2 (part I): BACTERIAL CELL STRUCTURE, CLASSIFICATION, AND MORPHOLOGY Flashcards
▪ Unicellular organisms
▪ Lack a nuclear membrane and nucleus
▪ Classified as prokaryotes
Bacteria
▪ Eukaryotic
▪ Exist as unicellular or multicellular
▪ Categorized by their locomotive structures
Parasites
▪ Eukaryotic
▪ Exist as unicellular (yeast) or multicellular (mycelial forms)
Fungi
▪ DNA or RNA core surrounded by a protein coat
▪ Acellular
▪ Obligate intracellular parasites
Viruses
Is the academic discipline of defining groups of organisms on the basis of shared common characteristics and giving names to those groups.
Taxonomy
three interrelated categories of Taxonomy
Classification, Nomenclature and Identification
Method to categorize organisms into groups such as genus or specie.
Classification
➢ Genetic makeup of the organism
➢ E.g. base sequencing of DNA or RNA
Genotype
➢ Readily observable physical and functional
features expressed by the organisms genotype
➢ E.g. Macroscopic and microscopic characteristics
Phenotype
Binomial system. Every organism is assigned a genus and a species name.
Nomenclature
It is always written with the capital
letter while species designation is never
capitalized. Both are printed in italics or
underlined when written in script.
Genus
Neisseria gonorrhoea
Gonococcus
Streptococcus pneumoniae
Pneumococcus
Mycobacterium tuberculosis
Tubercle bacilli
Salmonella typhosa
Typhoid bacilli
Klebsiella pneumoniae
Friedlander’s bacillus
▪ The process by which the microorganisms key features are delineated so that it can be assigned a genus and a species name.
➢ Genotyping
➢ Phenotyping
Identification
nucleus: membrane bound
chromosomal DNA: in the nucleus
organelles: present
cell wall: polysaccharides
pili and fimbriae: absent
Eukaryote
nucleus: no nuclear membrane
chromosomal DNA: in the nucleoid
organelles: absent
cell wall: peptidoglycan
pili and fimbriae: present
Prokaryote
single circular chromosome attached to a
mesosome
nuclear Area (nucleoid)
➢ small circular, dsDNA molecule
➢ antibiotic resistance
plasmid
➢ site of protein synthesis
➢ consists of RNA and protein
ribosomes
represents reserves of polyphosphates used in the
synthesis of ATP.
metachromatic granules
consist of glycogen and starch granules
polysaccharide granules
highly refractile resting cells that are highly
durable and dehydrated with thick walls
Spores/Endospores
A phospholipid bilayer with embedded
proteins that envelop the cytoplasm
Plasma Membrane (Cell membrane)
➢ Maintains the shape of the cell and protects cell from osmotic pressure
➢ Repeating disaccharide attached by polypeptides.
Cell Wall (Peptidoglycan or murein layer)
➢ Between cell membrane and cell wall.
➢ Consist of gel like matrix containing nutrient binding nutrients
➢ Contains enzymes for degrading and
detoxifying macromolecules
Periplasm Space
➢ Cells initial barrier (certain antibiotics and
evasion of phagocytes)
➢ Composed of Lipopolysaccharides (LPS),
lipoproteins and phospholipids.
➢ Contains Porins
Outer Membrane
Water-filled structures that control
the passage of nutrients and solutes
Porins
I. Lipid A (endotoxin)
II. Core polysaccharide
III. O-specific polysaccharide
components of LPS (Lipopolysaccharides)
gram (+) contain waxy layer of glycolipids and fatty acids (mycolic acid). e.g. Mycobacterium and Nocardia
Acid-Fast Cell Wall
peptidoglycan layer: thick (multilayered)
teichoic acids: present in many
periplasmic space: absent
outer membrane: absent
LPS content: lipid and lipoprotein: virtually none
lipid & lipoprotein: low
gram positive
peptidoglycan layer: thin (single layered)
teichoic acids: absent
periplasmic space: present
outer membrane: present
LPS content: lipid and lipoprotein: high
lipid & lipoprotein: high (due to outer membrane)
gram negative
➢ Prevents phagocytosis
➢ Attachment to various surfaces in its natural environment
➢ B. anthracis
➢ S. pneumoniae
➢ K. pneumoniae
➢ General substances that surround cells
➢ Gelatinous polymer of polysaccharide,
polypeptide, or both.
Glycocalyx (Slime Layer and Capsule)
substance is organized and firmly attached to cell wall.
Capsule
unorganized and loosely attached to the cell wall.
Slime Layer
➢ Exterior protein filaments that rotate and
cause bacteria to be motile
Flagella
without flagella
Athrichous
a single polar flagellum
Monotrichous
two or more flagella at one pole of the cell.
Lophotrichous
single/tuft of flagella at each end of the cell.
Amphitrichous
flagella distributed over the entire cell.
Peritrichous
Hairlike appendages that are shorter, straighter
and thinner than flagella
Fimbriae and Pili
also called common pili, can occur at the poles or can be evenly distributed from few to several
hundred.
Fimbriae (sing. fimbria)
FUNCTION: for adherence of cells to one another
and to environmental surfaces
Fimbriae
also called sex (conjugation) pili, are hollow protein tubes , longer than fimbria and number is 1 or 2 per cell.
Pili (pilus)
FUNCTION: join bacterial cell in preparation of DNA transfer from one cell to another.
Pili (pilus)
➢ Bundles of fibrils anchored at one end of
spirochete and spiral around the cell.
➢ The rotation of filaments propels the
spirochete in a spiral motion.
Axial Filaments (endoflagella)
occurs in pairs
- Cocci (Spherical or Ellipsoidal)
Diplococci
cells arranged on chains
- Cocci (Spherical or Ellipsoidal)
Streptococci
irregular clusters “bunch of grapes”
- Cocci (Spherical or Ellipsoidal)
Staphylococci
four cells arranged in same plane
- Cocci (Spherical or Ellipsoidal)
Tetrads
cuboidal arrangement of 8 or more cells
- Cocci (Spherical or Ellipsoidal)
Sarcinae
occurs in pairs
- Bacilli (Cylindrical or Rod Shape)
Diplobacilli
occurs in chains
- Bacilli (Cylindrical or Rod Shape)
Streptobacilli
tendency to group side by side
- Bacilli (Cylindrical or Rod Shape)
Palisade
slightly longer than they are wide.
- Bacilli (Cylindrical or Rod Shape)
Coccobacilli
Cylindrical or Rod shape
Bacilli
Spherical or Ellipsoidal
Cocci
Spiral Shaped
Spirochetes
comma shaped
Vibrio
Loosely coiled
Spirillum
Tightly coiled
Treponema
Stain bacteria that have high lipid and wax content in their cell walls
Acid-Fast Stains
Binds to the nucleic acid of the cell and fluorescence as a bright orange under UV
light
Acridine Orange
For observation of metachromatic granules of C. diphtheriae.
Methylene Blue