Re: Low pH nitrification

[WndrKdnomo@aol.com]

In a message dated 10/19/98 10:31:47 PM, mengerin@cs.utexas.edu writes:

<< The bacteria involved in the "typical" nitrogen cycle operate under the
>  same principle as our fish, the ammonium ion NH4+ does not pass the
>  cell membrane.  Thus it does not affect our fish, likewise, it is not

Do you have a reference which proves this is true for all bacteria, bar
none? >>

No, I do not, nor did I mean to imply that this was true.  In fact, I propose
that the opposite might be true.  The situation is like this; under acidic
conditions ammonia (NH3) converts to the ammonium ion (NH4+).  While the
uncharged ammonia molecule will pass freely across cell membranes, the charged
ammonium ion will not.  If a bacterium is to metabolize ammonium to nitrite,
it must first get it inside its cell membrane.  Since it will not do so on its
own, our putative bacterium would probably have to have a "gate" in the cell
membrane to pass ammonium ions selectively, and this would most likely involve
the expenditure of energy.  If, in fact, ammonia (ammonium) is being cycled to
nitrates in highly acidic environments, I would expect the bacterium involved
in the ammonium to nitrite stage to have such an "active transport" system,
where ammonium ions are selectively transported across the cell membrane at
the expense of cellular energy.  However, this is all strictly conjecture on
my part.  No offense to anyone intended, but I am still not convinced that
this actually takes place.  One thing to keep in mind, many test reagents will
give misleading results if the pH of the sample is outside a specific range.
Maybe some chemist one the list can tell us if nitrate tests commonly used
would be accurate at, say, a pH of 5.0.  Anyone?
Jeff
WndrKdnomo@aol.com


-------------------------------------------------------------------------
This is the apistogramma mailing list, apisto@majordomo.pobox.com.
For instructions on how to subscribe or unsubscribe or get help,
email apisto-request@majordomo.pobox.com.
Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!