Lecture notes
gram positive spore forming rods
- Module
- Mechanisms of pathology
- Institution
- Aston University, Birmingham (Aston)
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Gram positive spore forming rodsClostridia part 1.
Clostridia belong to the kingdom of bacteria.
They belong to the family clostridiaceae.
They belong to the genus clostridium.
Clostridia are gram positive rods.
They are quite large at 20 microliters at length, the appear as cigar shapes under the
microscope.
The majority of clostridia are motile, and this is because they contain periticus
flagella, which is flagella that surrounds the entirety of the organism, it allows the
organism to move around particularly at nutrient sources.
If you were to extract the genetic material from clostridia, they have a low G/C
content, this is a unique feature of the organism.
Clostridia are ubiquitous in nature, and we can find them in the environment, such
as within soil and within decaying leaf matter.
We can also find clostridia in the gut flora of multiple mammals.
Clostridia can contaminate wounds. Clostridia exists within soil and it has the ability
to infect you within contaminating wounds, it is really important to wear
contaminating gloves.
Clostridia have an ability to form endospores, these hardy structures, allows the
organisms to withstand harsh environmental conditions, they can persist as spores
for many months, to many decades. This makes them problematic in hospital
settings because using common disinfectants does not work as they are resistant to
them. Therefore clostridia can form hospital acquired infections, referred to as
nosocomial infections. Patients can come into the hospital and then they can acquire
a type of clostridial infection that is found in hospitals.
Clostridia are strict anaerobes, they hate oxygen, they die in the presence of oxygen.
So, they undergo the process of anaerobic respiration and also fermentation
An introduction
There are 200 species of clostridia and there are 5 subspecies.
Out of the 200 species only a few are major pathogenic organisms.
An example is clostridium tetani and this is uncommon in the UK due to the
successful vaccine program that we have.
Clostridium tetani can give rise to the condition referred to as tetanus.
Clostridium perfringens is a common organism and it can cause infections of the
gastrointestinal tract through the reheating of food.
Clostridium botulinum, this is also uncommon in the UK and can also cause food
borne infections, that can also infect wounds. This type of organism produces a very
powerful toxin, botulinum toxin.
Clostridium difficile, this is very common within the UK, this can cause antibiotic
associated diahorrhea, the antibiotics can dessemate you’re commensal organisms,
allowing clostridium difficle to colonise and it can cause hospital acquired infections.
There are a number of different species of clostridia of which there are 4, which are
major human pathogens.
, Clostridia-anaerobic respiration
Clostridia are gram positive rods, and we can see that these are 20 micrometre rods
under the microscope, cigar shaped, and they are very large. If you stain them with a
gram stain, they appear purple.
These are anaerobic organisms.
How aerobic respiration works: glucose can be converted into pyruvate by the
process of glycolysis. This generates electrons and hydrogen ions, those electrons
will move across various cytochromes, that are part of the electron transport chain.
The n terminal electron acceptor in aerobic respiration is oxygen, and that is
exogenous to the organism because oxygen is outside of the organism.
Hydrogen ions will be pumped out of the cell, they will then be pumped back into
the cell to activate ATP synthase. This process is very economical producing lots of
ATP, which the organism can use.
In anaerobic respiration, which is the process clostridia undergo, it also involves the
electron transport chain, and the n terminal electron acceptor is also exogenous to
the organism, so outside the organism. The N terminal electron acceptor is sulphate.
Clostridia will reduce sulphate to sulphite. Anaerobic respiration is not as economical
compared to aerobic respiration; less ATP is produced compared to aerobic
respiration. Clostridia is slow growing due to the anaerobic respiration, in aerobic
organisms you can see colonies on a plate after 24 hours of incubation, whereas
organisms such as clostridia, which undergo anaerobic respiration they will grow
more slowly.
Clostridia have a distinctive unpleasant smell; this is because they use sulphate as
they’re N terminal electron acceptor and reduce that to sulphite.
Summary aerobic and anaerobic respiration:
Aerobic respiration (clostridia does not undergo this)
E- passes across cytochromes in the cell membrane (ETC)
Terminal exogenous electron acceptor is oxygen.
Organic energy source e.g. glucose (glucose to pyruvate)
H+ pumped outside of the cell- get a PMF.
H+ pumped back into the cell- activates ATP synthase.
Lots of ATP produced.
Anaerobic respiration (clostridia do undergo this)
Also involves ETC and the terminal electron acceptor is exogenous.
Terminal electron acceptor for clostridia is sulphate.
Sulphate is reduced to sulphite.
Less ATP is produced compared to aerobic respiration.
Organism grows more slowly.
Clostridia- fermentation.
Clostridia can also undergo the process of fermentation.
This is just another process for the organism to produce ATP.
But unlike anaerobic respiration the N terminal electron receptor is not exogenous
to the organism, it is not outside of the cell such as sulphate.
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