Basic Bacteriology I and II

Cocci in clusters

E.g., Staphylococcus aureus

Cocci in chains

E.g., Streptococcus pyogenes

Cocci in pairs with pointed ends

E.g., Streptococcus pneumoniae

Cocci in pairs with kidney shape

E.g., Neisseria gonorrhoeae

Shape of Bacteria Cells

Three basic groups: cocci, bacilli, and spirochete.

Size of Oscillatoria

Approximate diameter is 7,000 nm.

Size of E. coli

Approximate length is 1,300 x 4,000 nm.

Size of Rickettsia

Approximate diameter is 475 nm.

Size of Poxvirus

Approximate diameter is 230 x 320 nm.

Size of Influenza virus

Approximate diameter is 85 nm.

Size of T2 E. coli bacteriophage

Approximate length is 65 x 95 nm.

Size of Tobacco mosaic virus

Approximate length is 15 x 300 nm.

Size of Poliomyelitis virus

Approximate diameter is 27 nm.

Bacteria are measured in

micrometers (μm) typically between 1-10 μm.

Cell wall

Structure external to the cell membrane, provides shape and protection.

Pilus

Structure involved in attachment and DNA transfer.

Cytoplasm

Gel-like substance inside the cell containing proteins, carbohydrates, and nucleic acids.

70s ribosomes

Sites of protein synthesis in prokaryotic cells.

Plasma membrane

Selective barrier that regulates what enters and exits the cell.

Nucleoid

Contains the bacterial chromosome, a single long, circular strand of DNA.

Inclusion bodies

Sites for nutrient storage within the bacterial cell.

Capsule

A well-organized glycocalyx that protects bacteria from phagocytosis.

Flagella

Appendages that provide motility to bacteria.

Fimbriae

Hair-like structures used primarily for attachment.

Glycocalyx

Sugar coat surrounding bacteria; can be organized (capsule) or unorganized (slime layer).

Flagella characteristics

Types include peritrichous, polar, lophotrichous, amphitrichous.

Basal body of flagella

Anchor structure in the cell wall and plasma membrane.

Hook of flagella

Curved structure that connects the basal body to the filament.

Filament of flagella

Long, whip-like structure composed of flagellin, enabling movement.

Treponema pallidum

Causes syphilis; a type of spirochete.

Borrelia burgdorferi

Causes Lyme disease; another type of spirochete.

Fimbriae function

Attachment and colonization rather than motility.

Pili

Longer than fimbriae, involved in motility and DNA transfer.

Gram stain primary stain

Crystal violet is the first step in Gram staining.

Mordant in Gram stain

Gram's iodine serves as a mordant.

Decolorizing agent in Gram stain

Alcohol or acetone is used for rapid decolorization.

Counterstain in Gram stain

Safranin or basic fuchsin is used after decolorization.

Gram-positive bacteria

Have a thick peptidoglycan cell wall that stains purple.

Gram-negative bacteria

Have a thin peptidoglycan layer, stain pink, and possess an outer membrane.

Function of cell wall

Maintains cell shape and prevents lysis under osmotic pressure.

Peptidoglycan composition