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Re: Aquatic Plants Digest V3 #1275

Dwight wrote:

> I confess I didn't know this. Karen; do you or any other list-lurker have
> more info about precisely what this gent found?  I'd like to know what is
> the breakdown of the nutrient active bacteria populations in our tanks.  I
> teach nitrogen cycling and use planted tanks in the classroom as "hands-on"
> examples. I can never confidently teach that lesson again w/o knowing what
> exactly is in the aquarium's bacteriological brew.
> <snip>

Well I have been lurking here for a few months so why not add two posts today?
During the initial phase of what is known affectionately as "The Cycle Wars" on
several of the popular boards, I had initially thought that these supplements
should aid a new tank to some degree.  After reading Dr. Hovanec's work on AFM I
had pretty much changed my mind but I still had some serious questions so I
emailed them to him.  To my surprise he actually phoned me to answer them.  I
have to say that if you ever want more information on this subject, Tim is
certainly willing to discuss it with anyone who is not trying to "flame" him.  In
our conversation he mentioned that of all the supplements they tested, Cycle was
the only one that contained a significant proportion of viable bacteria.  Using
RNA probes they were able to determine that the N oxidizing bacteria in Cycle
were Nitrobacter and Nitrosomonas.  In his 1998 paper they did actually find that
the nitrite levels decreased earlier in tanks that received Cycle.  However, they
were not able to find any Nitrobacter in these aquaria.  Instead they found
Nitrospira like bacteria in both the treated and untreated aquaria.  The presence
of the Nitrospira also coincided with nitrite oxidation.  He speculates that the
addition of Cycle may have added vitamins and other nutrients that may have
stimulated the growth of Nitrospira.

He also speculates that the reason these results seem to fly in the face or
'traditional' research is that previous research relied on culturing nitrifying
bacteria from various samples and then identifying them.  He goes on to cite
several studies which show that when some of the samples themselves (from a
variety of environments but not all) are tested very low (or below detection)
levels of Nitrosomonas or Nitrobacter are found.  However, when those same
samples are cultured they are predominantly composed of Nitrosomonas and
Nitrobacter.  Thus, it seems that the culture media itself may preferentially
enhance the growth of these bacteria, masking what the true bacterial assemblage
may have been.

The references for the two papers he sent me are as follows:

Hovanec, T.A., and E.F. DeLong.  1996.  Comparative analysis of nitrifying
bacteria associated with freshwater and marine aquaria.  Applied and
Environmental Microbiology. 62(8): 2888-2896.

Hovanec, T.A., L.T. Taylor, A. Blakis, and E.F. DeLong.  1998.  Nitrospira-like
bacteria associated with nitrite oxidation in freshwater aquaria.  Applied and
Environmental Microbiology.  64(1): 258-264.

If you have further questions I can send you copies of the papers (e-mail me) or
you can write to Tim Hovanec directly through AFM.  He was very approachable and
went out of his way to phone me long distance when an email would have sufficed.

Alec Dale
Dept. Biol. Sci.
Univ. Windsor,
Windsor, ON