παραθετω ενα κομματι μιας ερευνας του
Timothy A. Hovanec, Ph.D πανω στο θεμα που εχει πολυ ενδιαφερον και που απανταει (εν μερει)στο θεμα της συζητησης.μπορειτε να βρειτε ολο το αρθρο και τη διαδικασια που ακολουθηθηκε
εδω.ενα χοντρο γενικο συμπερασμα ειναι οτι το προιον που προστεθηκε(
δεν λεει ποιο) λειτουργησε απλα ως βοηθεια.πραγμα που σημαινει πως αποτι φαινεται τα μπουκαλακια δεν περιεχουν βακτηρια οπως αυτα που βρισκονται σε στρωμενο φιλτρο η μπολι,η τουλαχιστον οχι σε αυτη τη μορφη τους.(τουλαχιστον σε αυτο που χρησιμοποιηθηκε)
απλα το βαζω μπας και βοηθηθει λιγο η συζητηση.δεν ξερω ποσο αξιοπιστη ειναι η ερευνα αλλα δεν εχω λογο προς το παρον να την αμφισβητησω.
Υ.Γ σορυ για το μεγαλο ποστ.
"The next thing I wanted to ascertain was whether I could tell when the Nitrospira-like bacteria appear in a newly set-up filter and then relate their appearance to the water chemistry. Meaning, could I see a correlation between the appearance of the Nitrospira-like bacteria and the oxidation of nitrite to nitrate.
For this, I used a process called the polymerase chain reaction (PCR) on aquarium samples. This procedure allows you to amplify (increase) the amount of target DNA in your sample when you mix it with special reagents and place it in a machine called a thermal cycler. I took this PCR product and ran it in a special electrophoresis machine called a denaturing gradient gel electrophoresis (DGGE). When you run DNA in the DGGE, the individual segments of DNA (each segment perhaps pertaining to a particular species of bacteria) are separated in the gel so you can see a band in the gel that corresponds to the bacteria you are interested in, as well as other bacteria in the sample. As an aside, the bands can also be cut out of the gel, purified and then sequenced just like in the clone library. This is one way for you to identify what species of bacteria the band may represent.
When you combine the data from the clone libraries with the DGGE data, you have strong evidence as to the makeup of the bacterial assemblage in your system. Using DGGE you can run many samples side by side, and by running controls (and from sequence knowledge) I would know which band in the gel lane would correspond to the Nitrospira-like bacteria.
So, I performed two experiments. In the first, I set up aquariums and ran them for nearly 140 days, taking bacterial samples every seven days. In the other, I ran the aquariums for 35 days, taking bacterial samples every day. I collected water samples (three times a week for the first test, daily for the second test) from each group and analyzed them for ammonia, nitrite and nitrate.
Using the DGGE technique, I ran the PCR-amplified samples to see what banding pattern was present. In the first test, the Nitrospira-like bacteria did not appear in the pattern with a strong signal until about day 22. After that they remained in the samples and were present in large numbers, as evidenced by the intensity of the band.
In the second test, the Nitrospira-like bacteria appeared starting on day 12, which was also the day an increase in nitrate was measurable in the samples. By day 18, the signal was quite strong and the water chemistry data showed that nitrate was increasing rapidly. In this manner I was able to show a correlation between the appearance of the Nitrospira-like bacteria in the samples (and thus on the filter) and the prevailing water chemistry in the aquarium.
For the final test, I looked at the effects of adding a bacterial additive to aquariums during the start-up phase. Duplicate aquariums were set up and dosed with ammonium chloride. A commercially available bacterial additive was added to one set on a weekly basis as per the manufacturer's instructions. The other set did not receive any additive. I measured water chemistry three times a week and took filter samples for bacterial analysis. I used the molecular probes for Nitrobacter and Nitrospira-like bacteria on these samples.
I did not detect Nitrobacter in either situation, but I did detect Nitrospira-like bacteria in both cases. Thus, even when adding Nitrobacter to the system, these bacteria fail to become established. The only possible benefit to adding the additive was that a greater percentage of the total bacteria DNA in the samples was from the Nitrospira-like bacteria in the tanks that received the additive.
While there are more tests to be performed, it seems that the additive did have a kind of "fertilization" effect. What I surmise is that there are nutrients in the additive that the Nitrospira-like bacteria can use to increase their numbers faster than in tanks without the additive. Whether this is a significant increase or not I cannot answer at this time. In addition, the nitrite concentration in the additive tanks still rose to toxic levels, indicating that the additive did nothing to "shorten" the break in period for the tank."