Prokaryotes Basics Flashcards
Types of microorganisms
Bacteria
Archaea
Microeukaryotes
Viruses
What features do bacteria have
-plasmids
-70s ribosomes
-one rna polymerase
-Cell wall muramic acid
-ester bonds in the cell membrane that act as lipid linkage
-sensitivity to chloramphenicol,streptomycin,kanamycin
Examples of eukaryotes
Microeukaryotes
Protists
Parasites
Fungi
Features that archaea have
-plasmids
-70 s ribosomes
-Several rna polymerases
-ester bonds in the cell membrane that act as lipid linkage
Features in an eukarya
-membrane enclosed nucleus
-80 s ribosomes
-3 rna polymerases
-ester bonds in the cell membrane that act as lipid linkage
Prokaryote cell division
-process called binary division
-3 stages:cell elongation,septum formation,completion of septum formation,formation of walls and cell separation
What is DNA
DNA is a double helix containing unique distribution of TA and GC nucleotide pairs for every gene.
Heredity
Transmission of properties from a mother cell to daughter cells during cell divisions
Role of dna replication
Makes possible existence of heredity
Semi conservative replication
Every dna strand serves as a template for the synthesis of the complementary strand
Process of gene expression
-DNA gets replicated by dna polymerase
-dna gets transcribed to rna by rna polymerase
-rna gets translated into a protein by tRNA and ribosomes
-the protein then gets folded ans modified to have a biological activity
4 main classes of compounds
proteins
- structural components of the cell, enzymes and regulators; encoded by genes; synthesised in ribosomes;
Nuclei acids
-Genetic material
Lipids
Components of cellular membranes,cell wall and storage granules
Polysaccharides
-components of cell wall and capsule
Metabolism
Uptake of nutrients from the environment,their transformation within the cell and elimination of wastes into the environment.It is an open system
Reproduction
1)Chemicals from the environment are turned into new cells under the direction of pre-existing cells
2)It is a process based on
-replication of dna
-equal distribution of replicated dna into two cells after division of the initial cell
3)it’s a core way of colonisation of a host by pathogenic microbes causing diseases
Differentiation
Formation of a new cell structure such as a spore,usually as a part of a cellular life cycle
Communication
-Cells communicate or interact primarily by means of chemicals that are released or taken up
-one of the consequences is quorum sensing mechanism.It allows a population to sense critical amount of cells and stop divisions
Quorum sensing mechanism
Process of cell-cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly
Movement
Living organisms are capable of self-propulsion(ability to move using their own power)
However motility is not compulsory property of all microbes
Evolution
Cells contain genes and evolve to display new biological properties
What does closed system mean
Limited amount of nutrients
5 phases of microbial growth in a closed system
Lag phase
Log phase
Stationary phase
Death phase
Long term stationary phase
Lag phase
Metabolic activity but no growth/adaptation period
Log phase
Cells doubling through binary fission
Exponential phase
Stationary phase
Growth ceases but cells remain metabolically active
Death phase
-Waste builds up and nutrient rich media is depleted
-living cells stop metabolic functions and begin to process of death
Long-term stationary phase
Birth and death rate are balances
Dna in prokaryotic cells
-bacterial chromosome as main molecule of dna;considered to encode for essential genes
-located in cell cytoplasm
-bacterial plasmids as smaller molecules of dna: considered to encode for accessory genes
Pathogenic traits/ virulence factors
-contributed or directly cause damage in host eg
• pili formation
• biofilm production
• spore formation
• toxin production
• capsule production
Stages in infection
Adhesion
Colonisation
Invasion
Evasion
Adhesion
Adhesive molecules expressed on bacteria surface bind to host surface receptors
Colonisation
-Bacteria on the surface doesn’t cause disease yet
-virulence factors such as biofilm(A biofilm is an assemblage of surface-associated microbial cells that is enclosed in an extracellular polymeric substance matrix)
Invasion
Dissemination of a pathogen through local tissues or the body
Pathogens may produce enzymes/toxins that act as virulence factors
Invasion
Dissemination of a pathogen through local tissues or the body
Pathogens may produce enzymes/toxins that act as virulence factors
Evasion
-pathogens can bypass of evade the immunogenicity response of hostscells and continue its growth and transmission into the new host
Tag dna polymerase
-found in all cells
-synthesis complementary dna strand to dna template
-extremphile(heat stable)
Function of dna polymerase
In the cell:
Replication of the genome through by binding to single strand (template) and incorporation of nucleotides on synthesising strand using Okazaki fragment to bind initially
- Nobel prize won in 1956
In Polymerase Chain Reaction:
Binds to denatured template strain with guide of primer to bind to initially and extend from.
- PCR was Nobel prize won in 1993
Other properties of dna polymerases
• Processivity – affinity for DNA template = speed
• fidelity - synthesis accuracy and proof reading ability (not all have)
• substrate nucleotide selectivity –
T4 DNA ligase -gene engineering
-dna ligases are essential for dna replication,repair and recombination
-The bacteriophage T4 infects E. coli.
-The T4 DNA ligase seals the nicks between Okazaki fragments during replication of the phage genome.
-The T4 DNA ligase is ATP- dependant and catalyses the formation of new phosphodiester linkages in DNA.
-Has ability to perform “blunt”-end ligation – not a nick but two ends of DNA molecule together but also “sticky” ends with overhangs
-Used in cloning for insertion of cloned section (e.g. PCR product or restriction product) into the vector (plasmid).
