problems of a microorganism trying to survive and grow in an acidic environment?
- maintain intracellular pH, in order to protect internal cell components.
- important aspect of acid resistance in G- bacteria is the ATR (adaptive acid tolerance response, where cells grown in a moderately acid pH are more resitant to being grown in neutral pH then being thrown into acid.
- surviving a pH shock which is also markedly affected by the calcium concentration in the medium.
3 mechanisms of resistance to acidity in bacteria?
1) creation of acid-sensitive mutants from acid tolerant strains, and ID of the genes involved
2) random insertion of reporter genes to create mutants with pH-dependent reporter expression
3) proteomics and ID of proteins regulated in response to acidity
when the environment gets high in HCl what happens? what do they use?
some bacteria rely on ClC chloride channels to quickly evacuate these ions without letting other small particles pass through.
XAR?
draw what into the cells?
what does this gene form?
what kind of rxns and transports?
XAR- extreme acid resistance
XAR genes draw certrain amino acids (glutamine and arginine) into the cells
XAR genes decarboxylate to form GABA or agmatine
Acid consuming-reactions
transport products outside cell
what allows the proton pump to to work moving positive charge outward?
the chloride channel enables the proton pump to function because it allows the negative chloride ion to leadk out with every positively charged proton that is getting pumped out…
Acid pH tolerance
F1F0 ATPase proton pump
6 steps
1) combination of constitutive and inducible strategies to remove protons (H+)
2) alkalinization of the external environment
3) changes in the composition of the cell membrane
4) production of general heat shock proteins and chaperones
5) expression of transciptional regulators
6) responses to changes in cell density
acid pH tolerance:
1) G+ vs G-
2) acid pH tolerance or resistance
3) acidogenic
4) aciduric
5) weak acids control what?
6) lactic acid bacteria do what?
1) G+ vital roles in health and disease, and G- primarly disease
2) acid pH tolerance and resistance is a desirable attribute for each
3) acidogenic- acid producing
4) acid resistant
5) weak acids control growth
6) lactic acid bacteria are able to survive in their own metabolism
F1F0 ATPase-
PMF facilitates?
F1F0- ATPase links production of ATP to PMF
PMF facilitate extrusion of protons from the cytoplasm
Enterococcus hirae:
- lacks what? which makes it incapable of?
- sole function of complex is the?
- ATPase activity is controlled primarly at which level?
- lacks respiratory chain, incapable of using F1F0 complex for ATP synthesis via oxidative phosphorylation
- sole function of complex is the extrusion of H+ and pH homeostasis
- ATPase activity is controlled primarily at the level of pH-dependent subunit assembly with a decrease in cytoplasmic pH and an increase in ATPase activity
Glutamate decarboxylase
- consumes what?
- three types of decarboxylases?
- reaction equation…
- consumes H+ as part of the decarboxylase event
- lysine, arginine, and glutamate decarboxylases
glutamate + H+ —> GABA + CO2
extracellular amino acid is converted to?
an extracellular product but the consumption of an intracellular proton results in an increase in intracellular pH
protection or repair of macromolecules
- what two molecules
- RecA=
- housekeeping functions?
- acid adaption=
- DNA and proteins
- RecA, mediator of homologous recombination and regulator of the SOS response. RecA protein, or recombinase, multifunctional enzyme that acts in general recombination to catalyze the ATP-dependent DNA strand exchange rxn.
- housekeeping functions of repair and restarting replication forks
- acid adaption, increase resistance to UV and H2O2
RecA-independent acid-induced DNA repair system
- purine and pyrimidine loss from?
- protonation of the… and cleavage?
- residues left at the site called?
- repair of sites is? and is inititaed by?
- purine and pyrimidine loss from DNA with intracellular acidification
- protonation of the base and cleavage of the glycosyl bond
- residues left at the site are called AP sites or abasic sites
- repair of sites is a multistep process, which is inititaed by AP endonucleases
S. mutans?
E. Coli
B. subtilis
L. lactis
SMN exonuclease
exonuclease III
excinuclease (bulky DNA lesions)
link between DNA repair and acid resistance
moderate UV exposure, proteins upregulated during acid adaption
- what protects proteins?
- DnaK chaperone is upregulated…
- DnaK increases the stability…
- DnaK is a member of the class…
- protein folding, renaturation, protect proteins, evacuation of damaged proteins
- DnaK chaperone is upregulated in response to acid shock and sustained acidification in S. mutans
- DnaK increases the stability of UvrA, DNA repair
- DnaK is a member of the class I heat shock genes
G+ are particularly sensitized to acid as a consequence of?
mutations of genes involved in cell membrane biogenesis, assembly, and maintenace
F1F0 ATPase activity lowers?
activity lowers in mutants
production of alkali
- neutralizies…
- made through what pathways…
- production of NH3 and protons in…
- Urea in saliva to…
- during ADI, arginine to….
- neutralizes acids
- urease and arginine deiminase (ADI) pathways
- production of NH3 and protons in cytoplasm to yield NH4+, raises pH
- Urea in saliva to ammonia and CO2
- ADI, arginine to ornithine, CO2, and ammonia
UREASE
- type of enzyme
- mol formula
- inactive and active where?
- constitutive or inductive?
- most common expression in presence of?
- nickel-containing oligomeric enzymes
- 2 mols of ammonia and 1 carbon dioxide
- inactive at pH 4.3
- expression increases 600 fold at pH 5.5
- constitutive or inductive
- most common expression in presence of urea or nitrogen-limiting conditions, and acidity and carb-excess
PTS and induction of urease
- repressor is…
- when sugar is adundant…
Repressor is phosphorylated in the absence of sugar (regulator protein)
When sugar is abundant, the PTS preferentially phosphorylates the sugar, leaving the repressor unphosphorylated
which microorganisms use the arginine deiminase (ADI) pathway?
virulence factor?
three main enzymes?
arginine in?
Variety of microorganisms: Mycoplasmas, halobacteria, Pseudomonas spp., Bacillus spp., lactic acid bacteria, Streptococcus spp
virulence factor: S . pyogenes
Three main enzymes: ADI, ornithine transcarbamylase and carbamate kinase
arginine in salivary peptides and proteins
sugar coat serves as a?
and thress uses?
sugar coat as a proton shelter
1-Sugar modification may protect acidophiles
2-Hydroxyl groups prevent protons from entering the cell membrane.
3-Potential for new “anti-acid” biocompatible materials.
calcium and pH tolerance
- cycling
- availing…
- nanobacteria connected to?
- calcium cycling
- availing dietary calcium
- nanobacteria and calcium as well as connected with kidney stones
