Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: rubymelia on 29/12/2018 12:30:37
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I have recently used a synthesised Penicillin derivative to test its potency against a variety of bacterium.
I used a PDA agar plate with the fungi Saccharomyces and placed the Penicillin derivative on the plate. I did not see any inhibition against the fungi, is it to be assumed that this is because the Penicillin itself is a fungi?
Thanks
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Yes, penicillin is produced by a fungus in its ongoing war against bacteria (which are always trying to digest the same piece of detritus as the fungus).
- Penicillin is optimised to attack the weaknesses of (some kinds of) bacteria
- Unfortunately, due to this long-running war, strains of penicillin-resistant bacteria exist in nature
- Historically, it has only been a year or two after introduction of a new antibiotic before cases of resistant bacteria are detected in humans.
I am sure that bacteria also produce anti-fungal compounds - and even fungi produce compounds that are toxic to other fungi
- However, in some respects, fungi are more closely related to humans than are bacteria
- So many anti-fungal compounds are toxic to humans as well as the fungi
The main problem with finding new antibiotics is that it is almost impossible to grow most strains of microorganism in a laboratory monoculture - they naturally live as part of an ecosystem, depending on each other for nutrients
- Some success has been experienced by taking a soil sample, and inoculating separate very thin membrane "pages"
- This "book" is then buried back in its original location, in contact with the soil
- This allows nutrients and signaling molecules to pass between pages and exchanged with the surrounding soil
- But limits each colony of microorganism to grow on only a single page
- Any compounds produced can then be tested for effectiveness, and the microorganism's genome can be sequenced.
See: https://en.wikipedia.org/wiki/Antifungal
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Penicillin works by blocking the synthesis of chemicals needed in making the cell wall of (some) bacteria.
However the cell walls of fungi are typically made of something else (chitin) so penicillin doesn't affect them.
Looking on the bright side, the cell walls in humans are also different from those in bacteria which is why people can take penicillin to kill infections.
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Penicillin kills bacteria by interfering with the ability to synthesize cell wall. In this sequence, Escherichia coli were incubated in penicillin for 30 minutes. The bacteria lengthen, but cannot divide. Eventually the weak cell wall ruptures.
The inappropriate use of antibiotics (prophylactic treatment of herds in meat production and pointlessly treating viral infections with antibacterials) floods our environment with drugs that select for populations of antibiotic-resistant bacteria. Although penicillin was a wonder drug when discovered, some bacteria exposed to penicillin survived because they produced the enzyme β-lactamase that destroys penicillin’s structure. A solution was to devise other penicillin-like antibiotics (β-lactams) with structures that are not destroyed by β-lactamase. Methicillin is one of those drugs developed in the late 1950’s. Unfortunately, an increasing threat is now Methicillin-Resistant Staph aureus (MRSA) which avoids methicillin and other β-lactams by an alteration in MRSA's penicillin target-binding site. Bacteria are constantly evolving such new defenses, so treatment of bacterial infections requires a constant search for antibiotics with novel modes of action.
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I know that plants can develop an uncontrollable cell growing. But what about fungi or algae? Can they develop something as cancer?
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what about fungi or algae? Can they develop something as cancer?
I think you may have it backwards?
In single-celled organisms (algae, fungi, bacteria or archaea), it's "every cell for itself". Each near-identical cell tries to multiply as fast as it can within the ecosystem it finds itself in.
- At the other extreme, large plants and animals need a carefully orchestrated growth of many specialised cell types at the right time and place or the whole organism dies.
- In-between, you have the slightly-specialised organisms like mushrooms, slime moulds and algae that live together in communities with partial coordination and occasional specialisation.
Sometimes, due to multiple mutations, cells in complex plants and animals lose track of the complex signals that orchestrate growth and maintenance of the organism as a whole, and start growing uncontrollably. In effect, these relatively unspecialised cancer cells are acting "every cell for itself". Each cancer cell tries to multiply as fast as it can within the ecosystem it finds itself in (ie the body of the complex organism). At this point:
- The complex organism either controls the rampaging cancer cells (eg via the immune system, starving it of oxygen & nutrients, or limits growth by telomere shortening),
- Or, the out-of-control cells grow until they overwhelm the complex organism, and it dies.
So it's not as if single-celled organisms can get cancer - they always act like cancer
- Cancer is when the cells of a complex organism forget where they are, and start acting like single-celled organisms.
- Presumably, those intermediate-level organisms could have cells that go rogue, in which case it might disrupt some nearby coordination, but it would not have such a big impact as it does on more complex specialised creatures.
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Antibiotics where discovered as such, Arabian horsemen used the mould that grew upon there saddles to treat their and their horses cuts. It is quite possible that one fungus is either inhibited by or dependant upon another fungus though. Ergot is a type of fungus that makes witch trials happen, occouring sporadically upon grain, usually in the right conditions, I think i read it was the 13 fungus in a cycle to grow.
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Antibiotics where discovered as such, Arabian horsemen used the mould that grew upon there saddles to treat their and their horses cuts.
The trouble with that is that plenty of fungi produce serious toxins
Aflatoxin Amatoxin (alpha-amanitin, beta-amanitin, gamma-amanitin, epsilon-amanitin) beta-Nitropropionic acid Citrinin Cytochalasin Ergotamine Fumonisin (Fumonisin B1, Fumonisin B2) Gliotoxin Ibotenic acid Lolitrem B Muscimol Ochratoxin Patulin Phalloidin Sterigmatocystin Trichothecene Vomitoxin Zeranol Zearalenone
and relatively few produce anything helpful.