Francais dissert

BACTERIA

Goals :

Use aseptic technique and describe its importance in culturing bacteria.

Use plating strategies to produce colonies or a lawn on an agar plate.

List some of the various tools used to characterize and identify bacteria at the colony, cell, and molecular levels.

liquid medium called a broth (A liquid broth produces a mixture of cells that can reach very high cell concentrations.)

semi-solid medium made of agar, natural product derived from the structural polysaccharides in the cell walls of red algae. (On agar, each cell can produce an isolated, macroscopic colony by cell division overnight.)

colony level : colony morphology : texture (smooth, rough, wrinkled, powdery, dry) shape (punctiform, circular, rhizoid, irregular, filamentous)

cell level : Cell Shape and Arrangement (cocci, diplococci, streptococci (chains), straphylococci (clumps), baccili-steptobaccili (chains), spirilla)), also presence or absence of flagella & endospores

molecular level : Metabolic Capabilities

Photoautotrophs : use light as an energy source to produce all of their organic compounds from inorganic sources of carbon such as CO2.

Chemoheterotrophs must consume live or dead organic material to obtain organic compounds. These organisms breakdown organic compounds as a source of energy and use the carbon skeletons in organic compounds as a starting material to build other organic compounds important for life.

Photoheterotrophs (light, organic compounds) & chemoautotrophs (inorganic chemicals & carbon compounds)

thick peptidoglycan layer retain the Gram stain (crystal violet-iodine) and appear blue or purple; these are considered to be Gram positive.

thin peptidoglycan layer do not retain the Gram stain and are instead stained red, Gram negative

The zone of inhibition is the diameter of the circular clearing in the lawn of bacteria around the antibiotic disc.

 Starch Agar Test Result : positive for B. Subtilis and negative for E. coli

Norfloxacin (NOR) targets: DNA replication.

Cefotaxime (CTX) targets: Cell wall synthesis

Penicillin (P) targets: Cell wall synthesis

Streptomycin (S) targets: Protein synthesis

 PROTISTS

 Algae (Photoautotrophic Protists)

major component to phytoplankton in marine and freshwater habitats.

Green Algae ex Desmids : two semi-cells

Diatoms : chloroplasts have yellow-brown pigments that enable them to fix carbon by photosynthesis. Their cell walls, which are made of silica (not cellulose) resemble a glass house. cell wall consists of two valves that fit into each other like two lids of a Petri dish. (store glucose as oil)

Mixotrophic protists

Euglenids : capable of photoautotrophy and chemoheterotrophy. lack a cell wall but instead have a flexible pellicle, which provides certain flexibility

Heterotrophic Protists (Protozoa)

Amoeba : move with pseudopodia, food vacuole

Paramecium (ciliate): funnel-shaped gullet (mouth), large part are zooplankton, micronuclei and macronuclei

Stentor (ciliate) : moves fast

Parasits

T. gambiense causes African sleeping sickness when it enters the cerebrospinal fluid of humans. The blood parasites are transmitted from one vertebrate host to another by the tsetse fly. The organism that transmits an infectious agent is referred to as a biological vector

PLANTS

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