Study Guide for mid-trimester test:
Koch’s postulates
Four criteria that were established by Robert Koch to identify the causative agent of a particular disease, these include: the microorganism or other pathogen must be present in all cases of the disease and absent from healthy animals [tool: microscopy staining] the pathogen can be isolated from the diseased host and grown in pure culture [tool: laboratory culture] the pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal [tool: experimental animals] the pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen [ laboratory reisolation and culture]
Calculations based on SA/V ratio and Resolution (d)
Proton motive force
In most cases the proton motive force is generated by an electron transport chain which acts as a proton pump, using the energy of electrons from an electron carrier (Gibbs free energy of redox reactions) to pump protons (hydrogen ions) out across the membrane, separating the charge across the membrane. Bacterial flagella are powered by proton motive force (chemiosmotic potential) established on the bacterial membrane, rather than ATP hydrolysis which powers eucaryotic flagella.
Types of Active Transport
ABC Transport: the ABC system consists of three components: a substrate-binding protein, a membrane-integrated transporter, and an ATP-hydrolyzing protein.
Grams staining
On the basis of their reaction to the Gram stain, bacteria can be divided into two major groups: gram-positive and gram-negative. After Gram staining, gram-positive bacteria appear purple-violet and gram-negative bacteria appear pink. The color difference in the Gram stain arises because of differences in the cell wall structure of gram-positive and gram-negative cells. After staining with a basic dye, typically crystal violet, treatment with ethanol decolorizes gram-negative but not gram-positive cells. Following counterstaining with a different-colored stain, typically safranin, the two cell types can be distinguished microscopically by their different colors
Flagella – types and location on bacteria
A flagellum consists of several components and moves by rotation, much like a propeller of a boat motor. The base of the flagellum is structurally different from the filament. There is a wider region at the base of the filament called the hook. The hook consists of a single type of protein and connects the filament to the motor portion in the base.
The motor is anchored in the cytoplasmic membrane and cell wall. The motor consists of a central rod that passes through a series of rings. In gram-negative bacteria, an outer ring, called the L ring, is anchored in the lipopolysaccharide layer. A second ring, called the P ring, is anchored in the peptidoglycan layer of the cell wall. A third set of rings, called the MS and C rings, are located within the cytoplasmic membrane and the cytoplasm,
Many prokaryotes are motile by swimming, and this function is due to a structure called the flagellum (plural, flagella). The flagellum functions by rotation to push or pull the cell through a liquid medium.
Flagella Movement
The flagellum is a tiny rotary motor. How does this motor work? Rotary motors contain two main components: the rotor and the stator. In the flagellar motor, the rotor consists of the central rod and the L, P, C, and MS rings. Collectively, these structures make up the basal body. The stator consists of the Mot proteins that surround the basal body and function to generate a spin.
Rotation of the flagellum is imparted by the basal body. The energy required for rotation of the flagellum comes from the proton motive force. Proton movement across the cytoplasmic membrane through the Mot complex drives rotation of the flagellum. About 1000 protons are translocated per rotation of the flagellum. In this model called the proton turbine model, protons flowing through channels
