Invasins - promote cell entry via phagocytosis, engulf bacteria to allow invasion. Can evade immune system in a host cell and feed off its nutrients
Extracellular proteases - punch holes in cells allowing entry
Type 3 secretion system - Injectosome on bacteria pierces through host cell, Effector molecules interfere with cytoskeleton, Encourage phagocytosis, Eventual cell spread, Can also code for cell lysis to release bacteria from cell
Fibrin coats surface of bacteria allowing phagocytosisevasion - phagocytes cant recognise as foreign due to coat
Coagulase coating only seen with pathogenic s.aureus
Some bacteria can change their epitope to avoid recognition by the immune system (s. aurues has protein A which affects antibody binding) - Makes the antibody bind in the wrongdirection/orientation
Benefit bacteria as they kill neutrophils + macrophages, therefore protecting bacteria from phagocytes that could kill them, Toxins that kill human cells will release iron/carbon sources - bacteria thrives
LPS - found on gram-, Chain structure with a polysaccharide O chain at the top, outer and inner core and lipid A which helps anchor it onto the cell surface
O chain at the top of LPS is toxic - Activates host complement serological specificity/host defence systems, Manipulates cytokine production to cause damage
Bypass normal antigen presentation by binding to MHC Class II. When the MHC goes to present the epitope to the T cell, it binds to non specific regions of the T cell antigen receptor. This creates an exaggerated (above antigen specific) reaction resulting in massive cytokinerelease
Usual T cell activation = 1 in 1000 cells become active and start secreting cytokines
Sag activation = 1 in 5 cells
Excess interlukin2 and tnfA production leads to tissue damage and cell lysis which helps the nutrients get out and help the bacteria grow and spread
Promoter regions are non-coding regions in DNA required for gene transcription
The 5′ untranslated region (also known as 5′ UTR, leader sequence, transcript leader, or leader RNA) is the region of a messenger RNA (mRNA) that is directly upstream from the initiation codon (helps transcribe genes)
The 5′UTR sequence has a critical role in the recruitment of ribosomes to mRNA as well as in many processes related to the mechanisms regulating translation
Non coding regions are usually promoters which helps regulate how the gene works
Promoters contain conserved sequences that are recognised by RNA polymerase
-35 is upstream from the start codon
-10 is upstream from the start codon
represent the number of base pairs upstream from each other
Then a Transcription Start Point (TSP) - either CAT or CGT start codon
Can be a variable length away from the Ribosome Binding Site (RBS) - AGGAGG
After RBS (usually 4-7 bp away) is the start codon
before start codon is promoter region
RNA polymerase holoenzyme sits at bacterial promoter sites
RNA Polymerase coreenzyme sits at promotor region and sigma factor comes in and binds the different sections of the promoter (-35, -10, etc)
Allows core enzymes to be orientated properly for the Transcription start point (TSP)
Holoenzyme = a core enzyme + sigma factor
A sigma factor is a protein needed for initiation of transcription in bacteria. It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase to gene promoters
without the appropriate sigma factor, RNA polymerase enzymes will not work.
transcriptional regulators
transcriptionrepressors
transcriptionactivators
Transcriptional Repressors
regulatory protein binds at promoter region to block transcription by blocking RNApolymerase
why repress transcription?
may need to turn off a gene (e.g. a gene which is needed for avoiding digestion when intracellular in a macrophage will not be needed when bacteria is not in a macrophage)
wasting energy
creating proteins that arent needed
may be detrimental for the cell
transcriptional repression is AKA as negative control
transcriptional activation is AKA as positive control
Transcription activators
genes may be dormant and will require activation
regulatory protein binds upstream of the DNA/gene (even before the promoter region)
will attract ribosomes to start the transcription process