Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: kaylo_otee on 25/08/2011 15:09:14
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Greetings all, I am a student of the University of the East, Philippines undergoing his undergraduate thesis in BS Biology.
Screening of Pseudomonas spp. Isolated from Natural Environments for Biodegradation of Polyethylene and Polystyrene Products.
We intend to use Pseudomonas in our thesis. We have found a provider whom will supply us with frozen samples. They will be the ones to revive them for us too. Now, the Pseudomonas species and strains that we will choose are those isolated from natural outdoor environment, especially those isolated from soil of dump sites.
My question is: is there a specific method on acclimatizing the cultures to purely plastic medium?
What we were thinking was just use 50% nutrient broth and 50% plastic, inoculating the Pseudomonas . Then we inoculate them next to a tube with nothing but plastic suspended on the medium.
Is this viable? Is the first set up enough, to prove that the bacteria can survive on plastic rather than inoculating them again on a pure plastic medium? What about the growth phase of the bacteria? from which phase shall we attempt to take them from? lag, log, stationary phase?
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You can't grow bugs on just plastic, there's no nitrogen or phosphorus (or a few other things). You will need to provide them with most nutrient but a shortage of carbon to get them to eat the plastic.
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Kaylo - I realize you're not experienced in this field so, cutting to the chase, this approach is not viable and I doubt you have the experience and facilities to accomplish this work in a technically-defensible manner. You should start with what is known - look in the published literature - doubt you'll find pseudomonads as much as fungi effective to your purpose. Decide what "plastic" you want to study, some are more amenable to microbial breakdown than others, establish some measure by which you know it wll be degraded (is it to carbon dioxide and water? just to smaller pieces? loss of weight of filterable stuff?) and a reasonable time frame. You will probably be looking at limited weight changes (you'll have to discern this in context of biofilm deposition) and in co-culture with more useable substrates.
To bored chemist - you're wrong. Many of the pseudomonads including P. aeruginosa, Ralstonia and Burkholderia spp. (all current/former Pseudomonas sppecies) can grow to 10E5 and 10E6 in distilled water.
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Thank you Phil1907,
Much has already been confirmed about fungi that are capable of these. But not so much of Pseudomonads, there have been several pertaining to P. stutzeri and P. putida, which made us think if other microbes from the pseudomonas family are capable of achieving. We are doing an undergraduate study, I admit that we do not know advanced parameters on this topic, but in the most simplest way we want't to find out if other Pseudomonads could degrade PE and PS polymers.
And the roadblock we're experiencing now is the methodology. On how the set up should be. We have come across Minimal Salt Medium as the medium to use alongside the polymers. We've seen a study about acclimatization using a scale up technique which we're looking into. Indeed, our plan was to stick with weight changes. Although as we studied related literature, we found out that surface erosion does not equate to bio degradation. So we'll probably look into Gravimetry in measuring any changes.
I have no questions to ask, but if you have any suggestions or reprimand OoO then we'd welcome some input.
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Weight change is not going to be easy, as you saw. Surface change can't be relied upon to parallel weight change and such experiments can be confounded by microbial degradation of the much more degradable (and more soluble) plasticizers. Pseudomonads will form biofilms on plastics, esp. through the long time frames you'll need to use, that will screw up any weight measure. You could try EDTA to removal alginate-based biofilms and proteases but you'll still need to account for biofilm remnants.
What you might do is focus on the chemistry rather than on gross change of the solid material. Using small oligo's of the plastic in question exposed to culture supernatant from the gross culture experiments, IR might shw chnage in bond population.
I also refer you to recent work of Albertsson et al. and the most recent relevant article in ASM's "Microbe" describing the unique microbial flora found on marine plastics. It might be more productive to use isloates from plastics in marine environment than from landfills where plastics (and not much of anything) is effectively degraded and where water is limited (pseuds are most active in high water environments).
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Phil1907
DNA has phosphorus in it; water does not.
If you think you can grow any life form on just water you are mistaken. You may have been misled by the fact that the inoculum carries nutrients into the water as well as a the bugs. Also, a lot of water labelled as "distilled" is actually purified by reverse osmosis and de-ionisation. Both those processes fail to remove some organics (especially those of low molecular weight).
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Phil1907
DNA has phosphorus in it; water does not.
If you think you can grow any life form on just water you are wrong. You may have been misled by the fact that the inoculum carries nutrients into the water as well as a the bugs.
http://www.thenakedscientists.com/forum/index.php?topic=8535.msg99453#msg99453
"Keep it friendly
Do not use insulting, aggressive, or provocative language."
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Phil1907
DNA has phosphorus in it; water does not.
If you think you can grow any life form on just water you are wrong. You may have been misled by the fact that the inoculum carries nutrients into the water as well as a the bugs.
http://www.thenakedscientists.com/forum/index.php?topic=8535.msg99453#msg99453
"Keep it friendly
Do not use insulting, aggressive, or provocative language."
Why did you ignore Phil's near identical comment earlier in the thread?
"To bored chemist - you're wrong."
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Because, BC, you make a habit of being confrontational, and you've been here a lot longer.
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Reality is a lot more blunt than I am when it come to telling people that they are wrong. This is, after all, a science forum and so there's not a lot of room for things that are not true.
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Please read the context. As the poster offered - water and plastic - there could clearly be substantial growth tho' highly doubtful that plastic per se would be substrate. Report of microbes growing in distilled water and other purified waters indeed were in the context that could be seen as providing trace amounts of essential elements systems.