Chapter 1: Bacterial Metabolism Flashcards
What 3 enzymes break down toxic oxygen products?
1) Catalase
2) Peroxidase
3) Superoxide dismutase
What toxic products can be formed by reactive oxygen? (3)
1) hydrogen peroxide H2O2
2) superoxide radicals O2-
3) hydroxyl radical OH.
Catalase - function?
breaks down hydrogen peroxide to water and oxygen:
H2O2 –> H2O + O2
What enzyme breaks down hydrogen peroxide to water and oxygen?
H2O2 –> H2O + O2
Catalase
Peroxidase - function?
breaks down hydrogen peroxide to water
What enzyme breaks down hydrogen peroxide to water?
Peroxidase
Superoxide dismutase - function?
Breaks down superoxide radical to hydrogen peroxide and oxygen:
O2- + O2- + 2H+ –> H2O2 + O2
What enzyme breaks down superoxide radical to hydrogen peroxide and oxygen?
O2- + O2- + 2H+ –> H2O2 + O2
superoxide dismutase
obligate aerobes - defn
Use an oxygen-dependent system to generate ATP, with oxygen as the final electron acceptor in the electron transport chain
obligate aerobes - enzymes?
express catalase, peroxidase, and superoxide dismutase to prevent free radical damage
which type of bacteria express catalase, peroxidase, and superoxide dismutase?
obligate aerobes, to prevent free radical damage
Examples of obligate aerobes (4)
“Nagging Pests Must Breathe”
1) Nocardia
2) Pseudomonas aeroginosa
3) MycoBacterium tuberculosis
What kind of metabolism does Nocardia use?
obligate aerobe
What kind of metabolism does Pseudomonas aeroginosa use?
obligate aerobe
What kind of metabolism does Mycobacterium tuberculosis use?
obligate aerobe
Reactivation of what obligate aerobic microbe has a predilection for the apices of the lung?
M. tuberculosis (e.g. after immune compromise or TNFa inhibitor use), because apices of the lung have the highest PO2
What obligate aerobe is seen in burn wounds, complications of diabetes, nosocomial pneumonia, and pneumonia in cystic fibrosis patients?
Pseudomonas aeroginosa
Pseudomonas aeroginosa is seen in which cases? (4) (hint: P. aeroginosa is an obligate aerobe)
1) burn wounds
2) complications of diabetes
3) nosocomia pneumonia
4) pneumonias in cystic fibrosis patients
obligate anaerobe - defn
cannot survive in the presence of oxygen
obligate anaerobe - enzymes?
Lack catalase, peroxidase, and superoxide dismutase, and are thus susceptible to oxidative damage
3 characteristics of obligate anaerobes?
1) generally foul smelling (short-chain fatty acids)
2) difficult to culture
3) produce gas in tissue (CO2 and H2)
Examples of obligate anaerobes (3)
Anaerobes “Can’t Breathe Air”
1) Clostridium
2) Bacteriodes
3) Actinomyces
What kind of metabolism does Clostridium use?
obligate anaerobe
What kind of metabolism does Bacteriodes use?
obligate anaerobe
What kind of metabolism does Actinomyces use?
obligate anaerobe
Where are anaerobes found? (2)
1) normal flora in GI tract
2) pathogenic elsewhere
Are aminoglycosides effective against anaerobes? Why or why not?
AminOglycosides are ineffective against anaerobes because these antibiotics require O2 to enter into the bacterial cell.
Facultative anaerobes - defn
Use oxygen when present (have an electron transfer chain, catalase, superoxide dismutase), but can grow in the absence of oxygen by using fermentation in the absence of oxygen
Microaerophilic bacteria (aerotolerant anaerobes) - defn
use fermentation and have no electron transport chain, but they can tolerate low amounts of oxygen because they have superoxide dismutase but no catalase
Microaerophilic bacteria (aerotolerant anaerobes) - enzymes?
have superoixde dismutase, but lack catalase
obligate intracellular - defn
not capable of their own metabolic pathways for ATP synthesis, and thus must steal ATP from their host
obligate intracellular - examples (2)
“Stay inside (cells) when it is Really Cold”
1) Rickettsia
2) Chlamydia
facultative intracellular - examples (8)
“Some Nasty Bugs May Live FacultativeLY”
1) Salmonella
2) Neisseria
3) Brucella
4) Mycobacterium
5) Listeria
6) Francisella
7) Legionella
8) Yersinia pestis
facultative intracellular - examples (8)
“Listen Sally Yer Friend Bruce May Leave Now”
1) Listeria monocytogenes
2) Salmonella typhi
3) Yersinia pestis
4) Francisella tularensis
5) Brucella
6) Mycobacterium
7) Legionella
8) Neisseria
Which organisms are catalase positive?
“PLACESS” for your cats
1) Pseudomonas
2) Listeria
3) Aspergillus
4) Candida
5) E.coli
6) S. auereus
7) Serratia
Patients with what disease have recurrent infections with catalase positive organisms? Why?
chronic granulomatous disease
These patients lack NADPH oxidase (required for respiratory burst) in phagocytes, so they cannot kill bacteria. Catalase-positive bacteria can degrade H2O2 before it can by converted to microbicidal products by myeloperoxidase.
