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Intracellular Stuctures of Prokaryotes (Ribosomes (Two subunit (small…
Intracellular Stuctures of Prokaryotes
Plasma Membrane
Destruction of the plasma membrane
Disinfectants
alcohols and quaternary ammonium compunds
Plasmolysis : cell shrink
lysis : cell burst
cause leakage of intacellular contents
Uptake of nutrients
Getting Through the Barrier
Micronutrients
often supplied in water or in media components
ubiquitous in nature
required in trace amounts
serve as enzymes and cofactors
Mn,,Zn,Co,Mo,Ni,Cu
Some unique substances may be required
Macroelements
-K,Ca,Mg and Fe
-required in relatively large amounts
-C,O,N,H,S,P
Functions
Synthesizes cell wall components
Assists in DNA replication
Carries on respiration
captures energy as ATP
Selectively permeable barrier
Fluid Mosaic
Lipid Bilayer with floating proteins
amphipathic lipids
polar ends
non-polar tails
membrane proteins
The movement of materials across membranes
Passive process
Facillitated Diffusion
Osmosis
Simple diffusion
Active process
Active transport
Group Translocation
Structure
Phospholipid bilayer with proteins embedded in and attached to the inner(intacellular) and outer(extracellular) surface
Cytoplasm
substances of the cell inside the plasma membrane
Thick , aqueous,semitransparent and elastic
also contains proteins(enzymes), carbohydrates, lipids, inorganic ions and many low molecular weight compounds
The major stuctures in the prokaryotic cytoplasm are DNA, ribosomes and inclusions
About 80% water
Plasmid
Contain features that enhance survivability
example : gene for drug resistance
Transferable from one bacterial to another
Do not contain genetic material essential for growth(limited)
Small circular, double stranded DNA
Extrachromosomal genetics elements
not connected to bacterial chromosomes
replicate independently of chromosomal DNA
Intracytoplasmic Membranes
Plasma membrane infoldings
-observed in many photosynthetic bacteria
-observed in many bacteria with high respiratory activity
Anammoxosome in Planctomycetes
organelle
-site of anaerobic ammonia oxidation
The Nucleur Area
Bacterial chromosome do not include histones and are not surrounded by nuclear envelope
Bacterial chromosome, bacteria often contain small circular , double-stranded DNA molecules called plasmid
Single long circular molecule of double-stranded DNA (bacterial chromosome)
Ribosomes
Each subunit consists of protein and RNA called ribosomal RNA or rRNA
can be inhibits by certain antibiotics
Two subunit
small subunit-30S
large subunit-50S
cells that have high rates of protein synthesis, have a large number of ribosomes
70S ribososmes (S-Svedberg unit)
several antibiotics work by inhibiting protein synthesis on procaryotic ribosoms
Streptomysin and gentamicin attach to the 30S subunit
Erythromycin and chloromphenicol attach to the 50S subunit
Function : as the sites of protein synthesis
Inclusions
Can serve as a basis of identification
Types of inclusions
g. Gas vesicles
collectively called
Appeared bright, refractile areas with an irregular outline in the phase microscope
membrane bounded
consists of thin membrane surrounding a hollow space
found in photosynthetic group
cynobacteria
proteobacteria
green sulfur bacteria
heterotropic bacteria
archea
-methanogen
-halophiles
function : provide buoyancy for aquatic procaryotes- to receive sufficient amounts of Oxygen , lights and nutrients
hallow cylinders covered by protein
e. Carboxysomes
used for CO2 fixation during photosynthesis
Nitrifying bacteria, cynobacteria, and thiobacilli- i=used CO2 as sole source of carbon
Contain the enzyme ribulose 1,5-diphosphate carboxylase
a. Metachromatic granules
-collectively known as volutin
-Corynebacterium diphtheriae
-Stain red with certain blue dyes such as methylene blue
-also found in algae, fungi, protozoa
-large inclusion
b. Polysaccharide granules
consist of glycogen and startch
differentiated by using iodine
-reddish brown indicates glycogen granules
-blue indicates starch granules
f. Magnetosomes
For downward movement until reaching suitable attachment site
Function : to protect the cell against hydrogen peroxide accumulation
Iron oxide (Fe3O4) that act like magnets
Aquaspirillum magnetotacticum (gram -ve bacteria)
c. Lipid Inclusions
-storage material -polymer polt-B-hydroxybutyric acid
-revealed by Sudan dyes (fat-soluble)
-Mycobacterium, Bacillus, Azotobacter, Spirillum
d. Sulfur granules
Thiobacillus
- sulfur bacteria
-Derive energy by oxidising sulfur and sulfur-containining compounds
-serve as an energy reserve
reserve deposits
Endospores
resting structures formed by some bacteria for survival during adverse environmental conditions
germination results in leaving the dormant stage and once again becoming a typical , multyplying cell(vegetable cell)
Characteristics
cannot be destroyed easily, even by harsh chemicals
are formed internal to the bacterial cell membrane
highly resistant differentiated bacterial cell
Enable the organism to endure extreme environmental conditions
Endospore formation leads to a highly dehydrated structure thick walls and additional layers
contain essential macromolecules and a variety of substances absent from vegetative cells
Endospore structure
spores are very impermeable to dye. however, they can be stained with special dye, Malachite green
small acid-soluble proteins
Protect DNA from UV radiation, desiccation, and dry heat
serve as a carbon and energy source during germination
Endospore (so called because the spore is formed within the cell)
can remain dormant indefinitely but germinate quickly when the appropriate trigger is applied
Endospores and Infectious Disease
involved in the tranmission of some diseases to humans.Infections transmitted to human by endospores include :
Bacillus anthracis
Clostridium perfringens
Clostridium tetani
Clostridium botulinum