Test 3-2 Flashcards
The metabolic differences between bacteria (prokaryotes) and eukaryotes can be utilized for
for the development of antibacterial therapies
Lag phase:
The initial period of adaptation to a new environment which is essential for the cell to accumulate metabolites necessary for maximal cell growth. There is an increase in metabolic activity so bacteria are sensitive to antimicrobials. There is little to no cell division.
Exponential (logarithmic) phase:
Bacteria multiply rapidly by binary fission, and the populations doubles at a constant rate. During this phase bacteria are most susceptible to killing by certain antibiotics.
Stationary phase:
During this time nutrients are depleted and toxic waste products/metabolites are accumulating in media resulting in a decreased growth rate. Viable cell count remains constant because bacteria have stopped dividing but are not yet dying. Bacteria are much less susceptible to killing by antimicrobials. During this phase spore forming bacteria initiate the sporulation process.
Decline phase:
More bacteria are killed than are generated resulting in a decrease in the number of live bacteria.
Obligate aerobe:
bacteria that require oxygen and metabolize by respiration (M. tuberculosis, P. aeruginosa, B. anthracis)
Obligate anaerobe:
bacteria that are inhibited or killed by oxygen and utilize fermentation exclusively for energy production (C. botulinum, Bacteroides)
Facultative anaerobe (the majority of pathogens):
bacteria that grow well under aerobic or anaerobic conditions. If oxygen is available they respire, if not they use fermentation.
Microaerophilic:
Require 5-10% oxygen for optimal growth (Campylobacter jejuni)
Superoxide Dismutase rxn
2O2- + 2H+ —> H2O2 + O2
Catalase or Peroxidase rxn
H2O2 + H2A* —> 2H2O + A
Catalase rxn if H2O2
H2O2 + H2O2 —-> 2H2O + O2
Bacteria that lack superoxide dismutase, catalase and peroxidase are very sensitive to
oxygen and likely anaerobic
aerobic bacteria express wtih enzymes?
superoxide dismutase, catalase and peroxidase
Reproduction: Binary Fission
Bacteria exist in a haploid state
Only one chromosome
A double-stranded DNA circle contained in a discrete area called a nucleoid
Binary Fission is:
An exact copy of the genome is made and,
a single cell divides into 2 (binary) daughter cells
Replication: DNA polymerization
- Replication always begins at the origin (ori)
- Bacterial DNA gyrase required for unwinding/winding DNA and are the target of quinolones
- Semiconservative replication
- each strand serves as a template therefore each resultant strand has a copy of the original genomic DNA
Requirements for growth
- Energy source
- Raw materials to build proteins, structures, and membranes
The minimum requirement for growth is
a source of carbon and nitrogen, an energy source, water and various ions
Growth in culture is determined by
pH optimum,
aerobic versus anaerobic
nutrients/composition of media
temperature
Cell density is determined by
colony counts on agar plates or by turbidity (spectrophotometry)
groups of bacteria based on metabolic properties
Autotroph: generate their own energy (eg from sunlight)
Heteroptroph: Uses organic carbon for growth
Phototroph: …
Chemoheterotrophs: Use organic compounds as both their energy source and their carbon source
most pathogenic bacteria are
chemoheterotrophs
Aerobic
- Exclusively utilizes respiration to meet its energy need
- examples: M. tuberculosis, P. aeroginosa, B. anthrasis
Anaerobe
- Exclusively utilizes fermentation to meet its energy needs
- Examples: C. botulinum, Bacteriodes
oxygen does what to anaerobes?
kills dem
Facultative anaerobes can
- respire or ferment
- (E. coli, Shigella dysenteriae, S. aureus)
Microaerophilic - grow best
best at low O2 but can grow without O2 as well (ex. C. jejuni)
Two highly reactive forms of oxygen are very toxic to cells
Hydrogen peroxide (H2O2) Superoxide anion (O2-)
