final exam microbiology (jones)

prokaryotic cells

lacks a nucelar membrane (ex: bacteria, archaea)

Eukaryotic cells

has a nucleus enclosed by a membrane (ex: pants, animals, fungi, protozoa)

taxonomy

science of clarification, involving arranging related organisms into local categories

carolus linnaeus

published systems naturae in the mid 1700s which established a uniform system for naming organisms (ex: plants, animals)

Five kingdom system (1969)

Robert H Whittaker and Lynn Margulis developed the five kingdom system, giving bacteria their own kingdom

• kingdoms: animalia, plantae, fungi (yeast, molds), protista (protozoa), monera (bacteria)

carl woese

he created the three domain system which is based on data from ribosomal sequences

• domains: bacteria, archaea, eukarya

level of classification

acronym: doesn’t king Phillip come over for good soup

• domain (most general)

• kingdom

• phylum/division

• class

• order

• family

• genus

• species (most specific)

nomenclature gives scientific names to organisms: each includes two words, the genus and the species

prokaryotes (bacteria)

• lack nucleus

• DNA organized in nucleotide region in cytoplasm

• small size (0.2-10um in diameter)

• small genome

• circular chromosome

• complex cell envelope

• cell wall composed of peptidoglycan

glycocalyces

• gelatinous, sticky substance surrounding the outside of the cell

• composed of polysaccharides, polypeptides, or both

• serve an important function in attachment to surfaces and in biofilms

two types of glycocalyces

Capsule

• Thick layer composed of polysaccharide and glycoprotein
  filaments

• Firmly attached to cell surface

• Sticky layer allows bacteria to attach to surfaces

• May prevent bacteria from being recognized by host; inhibit
  phagocytosis

Slime layer

• Loosely attached to cell surface

• Water soluble

• Sticky layer allows bacteria to attach to surfaces

flagella

• Are responsible for movement

• Long structures that extend beyond cell surface

• Are not present on all bacteria

• Composed of filament, hook, and basal body (rod)

• Basal body anchors filament and hook to cell wall by a rod and a series of
  either two or four rings of integral proteins

• Energy to move the flagella is produced on the cytoplasmic membrane
  

monotrichous

a single flagellum at one end of a bacterial cell

amphitrichous

a single flagellum on each of two opposite ends of a bacterial cell

lophotrichous

several flagella present at both or one end only

peritrichous

many flagella projecting in all directions uniformly distributed over the cell

flagella movement

• Rotation propels bacterium through environment

• Rotation reversible; can be counterclockwise (runs/swims) or clockwise (tumbles)

• Bacteria move in response to stimuli (taxis)

• Chemicals/Nutrient (chemotaxis) or light (phototaxis)

endoflagella

• Spirochetes are spiral shaped bacteria that use Endoflagella to corkscrew, move, and burrow into tissues
  • Ex. Human diseases caused by spirochetes include
  • Treponema pallidum causes Syphilis (sexually transmitted disease)
  • Borrelia burgdorferi causes Lyme disease (vectored by ticks)
  • Leptospirosis interrogans causes Leptospirosis (kidney and urinary tract infections)

• Endoflagella are made up of two to over a hundred axial fibrils that extend
  from each end of the bacterium, between the cell wall and the outer
  membrane. They often overlap in the center of the cell. When the bundles of flagella rotate, they cause the spirochete to move in a twisting motion, similar to a corkscrew. This twisting motion allows the spirochete to move around.

  
  

frimbriae

• Sticky, bristle-like projections used for attachment
  • Used by bacteria to adhere to one another, to hosts, and attach to
  substances in environment
  • Shorter than flagella
  • Serve an important function in biofilms (biofilms – Topic 5)

conjugation pili

• Special type of fimbriae
  • Also known as conjugation pili or sex pili
  • Longer than other fimbriae but shorter than
  flagella
  • Bacteria typically have only one or two per cell
  • Mediate the transfer of small plasmid DNA from
  one cell to another (conjugation)

Note: only plasmid DNA, not chromosomal DNA can pass through the pili

bacteria cell walls

• Provide structure and shape and protect cell from osmotic forces
  • Assist some cells in attaching to other cells or in resisting
  antimicrobial drugs
  • Give bacterial cells characteristic shapes
  • Composed of peptidoglycan
  • Scientists describe two basic types of bacterial cell walls,
  Gram-positive and Gram-negative
  • Some antibiotics can target the cell wall (Topic 12)
  

bacterial cell walls

• Classifying Bacteria by the Gram Stain
  • Danish scientist Hans Christian Gram developed more important
  staining technique than Koch’s in 1884
  • Involves the applications of a series of dyes
  • Gram procedure used to separate into two groups
  • Some microbes are left purple, now labeled Gram-positive
  • Other microbes are left pink/red, now labeled Gram-negative