Lecture 3 - Respiratory Metabolism Flashcards
3 relationships between bacteria and its environment
- depends on metabolic capabilities of species
- grows if has appropriate metabolic machinery
- may affect its environment to suit its needs(oral cavity, bacteria build up in day, use sugars in diet - use up oxygen (anearobic) then ferment sugars to lactic and acetic acid, tooth decay)
do bacteria have more metabolic capabilities than higher euk?
euk must wait for mutation whereas bacteria can literally take genes from other bacteria nearby by horizontal gene transfer or by phage.
what are the 3 main functions of respiration?
generation of atp
generation of proton motive force
disposal of reducing equivalents (NADH) (using up hydrogens)
where does respiration happen in bacteria?
in the membrane around the cell
what is oxidative stress?
incomplete turnover of oxygen. oxygen when reduced to water sometimes produces intermediates.
superoxide (will react with organic molecules) then to peroxide then to hydroxyl then to water. intermediates toxic.
how do enteric bacteria deal with oxidative stress?
have sensory system for superovide SoxRS (sensore + transcriptional activator) and for peroxide (OxyR, sensor and activator in one protein) to upregulate superoxide dismutase and peroxidases to break down.
What host cell deliberately produces oxidative stress and how?
macrophages by producing superoxide which has an odd number of electrons so the extra wants to join onto things like metalloproteins, causing damage.
which bacteria produces oxidative stress, with what enzyme and why?
Streptococcus
pyruvate oxidase
kill off competition
examples and Key features of enteric bacteria
e coli, salmonella, klebsiella, shigella, citrobacter
large core of genes they all contain however have slight differences such as hosts and symptoms
all adapted for life in mammalian gut
potential to be toxic
most live in the colon
What are the features of the colon in terms of bacterial respiration??
oxygen used up so very anaerobic
lots of carbon left
dominated by strict anaerobes using fermentative metabolism
What enzyme does the host immune cell use to create the oxidative burst?
NADPH oxidase
What enzyme does the host immune cell use to create the nitrosative burst?
inducible NO synthase
Who writes the Shigella paper in this lecture?
Benoit Marteyn
What is the type 3 secretion system and what does shigella particularly do?
mechanism bacteria use to transfer proteins from one cytoplasm to host cytoplasm
shigella secretes Ipa proteins to mediate cell invasion
How did Marteyn’s results demonstrate Koch’s postulates?
showed that without FNR (anaerobic regulator) there was less virulence in microvilli of mice than wild type
What does FNR do?
transcriptional regulator that activates gene expression in absence of oxygen for anaerobic respiration of shigella.
How did Marteyn show how the FNR is involved in regulating T3SS function?
showed using western blots that in wildtype shigella they could increase t3ss and ipa using Congo Red (CR).
then showed that in absence of oxygen there was no increased ipa using CR
in FNR mutant you do get an increase in IPA using CR in absence of oxygen as FNR is no longer regulating.
What also happens to shigella in anaerobic conditions?
longer and more variable T3SS needles
Describe the processes and genes involved in T3SS needle production
spa32 controls needle length
spa33 blocks ipa secretion
both respressed anaerobically, but not in FNR mutant.
shows they are controlled by oxygen
FNR directly interacts with spa promoters.
how did marteyn explain the switch?
Using microelectrodes proved that oxygen contamination is present above epithilial cells which is sufficient to re-repress ipa secretion.
Also used luciferase to show oxygen content as needs oxygen to glow
Explain Shigella’s overall virulence strategy
under anaerobic conditions doesnt need to release factros but wants to be primed, so creates t3ss but doesnt release virulence
detects oxygen so fnr is absent, switch to virulence factors release.
good way to save virulence factors for times when needed
Who wrote the Salmonella paper and what is it called?
SEBASTIAN E WINTER - GUT INFLAMMATION PROVIDES A RESPIRATORY ELECTRON ACCEPTOR FOR SALMONELLA
How does Salmonella use gut inflamation to increase its prominence?
reactive oxygen species generated during inflammation react with endogenous sulphur compounds (thiosulphate) to form new respiratory electron acceptor tetrathionate which gives salmonella an advantage as it has the genes required to use it.
What part do anaerobic bacteria and intestinal mucosa have in salmonella infection?
bacteria reduce sulphate to hydrogen sulphide and mucosa oxidises it to thiosulfate then tetrathionate by further oxidation
How much more does salmonella colonise as wildtype rather than a mutant for tetrathionate?
30x more
what did sebastian e winter show involving e coli?
E coli uses nitrate reductases to take advantage of inflamed gut.
Where in the body does Pseudomonas colonise and in what particular type of person?
The Lung, people with cystic fibrosis
What makes Pseudomonas interesting?
Much bigger genome so found in environmental reservoirs like soil, plants, rivers
What are the features of biofilms and explain them.
Intrinsically resistant to antibiotics - structure stops antibiotics get in
oxygen depleted - structure stops o getting in
What does Pseudomonas use denitrification for?
nitric oxide required for biofilm formation, those unable to reduce nitrate have reduced biofilm formation and virulence.
How does tuberculosis survive inside cells?
Dormancy
How does tuberculosis become dormant?
Using nitrate reduction and uses nitrite to shut down cell
express genes against nit and oxi stress.
