Prokaryotic Cells
Classification and Structure
Genetic and Growth
Prokaryotic Domains
Aerobes and anaerobes
Prokaryotic cell structure
Archaea
Bacteria
Cell wall
Flagella
Other organelles
D - Simple organism, include all bacteria
No membrane bound organelles
single circular molecule of DNA located in a region of the cell called nucleoid region
Cause infections and important to understand the structure of the bacteria to treat the infection
All life can be categorized into three domains - arcahea, bacteria and eukarya
D: single cell organism similar in structure to bacteria
D: contain genes and metabolic pathway that makes it more similar to eukaryotes
Historically known as extremophiles - does not exist in extreme condition - recent research has shifted that perspective
Use alternative source of energy
some are photosynthetic, others are chemosynthetic and can generate energy from inorganic compounds such as sulfur and nitroged based components such as ammonia
Hypothesized they have the same origin as eurokarytes, they both start with translation with methionine, contain RNA polymerases and associate DNA with histones
Archaea contains a single circular choromosome, divide by by binary fission or budding, and overall share a similar structure to bacteria
Resistant to many antibiotics
contain cell membrane and cytoplasm, some have flagella or fimbriae (similar to cilia)
bacteria and eurokaryates have similar structure - so it is difficult to develop medicine that targets only one
there are enough biochemical difference that antibacterial vaccines can be developed to target bacteria
antibiotic aim for the bacterial ribosome which is significantly smmaler than the eukaryotic ribosome
More bacteria than animals and plants combined
Mutualistic symbiotics - co-exist with cells and good for us
Pathogens or parasites - provide no advantage and are harmful - ex. Chlamydia trachomatis - sexually transmited infection or clostirdium tentani - cause tetanus
Classification of bacteria by shape
Spirilli - spiral shaped bacteria - ex. treponema pallidum
Bacilli - rod-shaped bacteria - ex. escherichia coli
Cocci - spherical bacteria - ex. streptococcus pyogenes
Aerobes -
require oxygen for metabolism
Anaerobes
Obligate
Aerotolerant
Facultative
cannot survice in an environment that does not have any oxygen
using oxygen when present but switching when it is not present
unable to use oxygen but do not die when oxygen is present
Does not use oxygen - use fermentation or other forms of cellular metabolism
Cell wall is the outer barrier to the cell, cell membrane (plasma membrane) is the next layer and composed of phospholipids - together they are called envelope
F: provide structure
F: control the movement of solutes in and out of the baterium
Two types of cell wall
Gram positive
Gram negative
D.Thin walls, contain peptodoglycan bu in very low doses
Detection method - stain using crystal violet stain and counter stain with safranin
if the envolope absorbs the crystal violet stain - gram positive
if it does not absorb the stain - then pink-red - gram neg
adjacent to cell membranne and separated by periplasmic space
they also have outer membrane - contains phospholipids and lipopolysacccarides (this trigers an immure response in human beings)
The inflammatory response to lipopolysaccharides is much stronger thant the response to lipoteichoic acid
D: thick layer of peptidoglycan (polymeric substance made from amino acids and sugars)
F: cell wall provides structure and may aid a pathogen by providing protection from a host organism's immune system
Cell wall also contains lipteichoic acid - the human immane system might be activated by exposure to this
D: whiplike structures used for propulsion
F: to move toward food or away from toxins or immune cells
Chemotaxis - ability of the cell to detec chemical stiumli and move toward or away from them
Structure
Filament
hollow, helical structure composed of flagellin
basal body
complex structure that anchors the flagellum to the cytoplasmic membrane, motor of flagellum, rotates upto 300Hz
Hook
contains the filament and the basal body - as basal body rotate, it exerts torque on the filament, which creates spin and propel bacterium forward
overall structure similar in gram positive and negative - some different physical structure and chem composition
Some of the DNA in prokaryotic cel is carried on plasmids - can make it more resistant to antibiotics
do not have mitochondria - ATP production is done in the cell membrane
have a mild version of cytoskeleton
Contain ribosomes but they are different size from the eukaryotes - pro ribo- 30S to 50S subunits, vs. euk ribo - 40S to 60S subunits
Genetic recombination
Transformation
Conjugation
Transduction
Transposons
Foreign genetic material integrates to host genomes - they come from bacteria after lysing
The mating for bacteria - the donor male with pilus transfers genetic material to recipient femalel. The female becomes a male. The conjugation bridge is formed using the pilus.
When a vector (virus that is carrying genetic material) is used to transfer gene from one bacterium to other one
Genetic elements capable of inserting and removing themselves from the genome
Growth phases
Lag phase - adapting to environment
Exponential/log -growing
Stationary - growth slows down
Death - the environment cannot support