Jem,
We have tried to determine the half-saturation constants for various
substrates in flow cells and find that this is difficult because the
effective concentration caused by the sieving of substrates from solution
by exopolymers (and other mechanisms) makes it difficult to limit growth
rate by limiting substrate concentration.
Apparently organic contaminants in the air and lab environment are
sufficient to support growth at the maximum specific growth rate although
no carbon source is added to the irrigation solution. If this occurs in
your situation you may be able to verify it by turning off the flow to see
if growth then becomes substrate limited. Turning off flow reduces the
effectiveness of biofilm sieving mechanisms.
This means that it is possible to cultivate biolfilms on highly insoluble
compounds that are present in trace amount in the irrigation solution.
However, I no of know reports of a systematic/quantiative study regarding
the kinetics of this effect. If anyone else should be aware of a published
study of this kind I'd like to know more about it.
Regards - Doug
>Dear Biofilmers
>>I'm wondering if anyone could provide information on the minimum amount
>of carbon required to allow biofilm growth. I'm aware that Lawrence et
>al used 14 microgrammes of Diclofop, (equivalent to 7.8 microgrammes
>total carbon)when growing biofilms in flow cells running at approx 2mL
>per hour.
>>I am using the same flow cell system to view biofilms, but the compound
>of interest solubility (in water)is about 0.8 microgrammes per mL.
>>I'm aware that I could adjust the flow rate to increase the amount of
>carbon available over a given peroid of time; (information on the the
>upper limits of shear stresses on biofilms would also be appreciated),
>I'm interested to hear any comments on whether this amount of carbon is
>able to support growth; and how to adjust solubility whilst staying
>relevent to environmental models. Any comments would be extremely
>appreciated.
>>Thanks,
>>Jem Stach.
>
*********************************************************
Doug Caldwell
Microbial Colonization Laboratory
Department of Applied Microbiology and Food Science
51 Campus Drive, University of Saskatchewan
Saskatoon, Saskatchewan, S7N 5A8, Canada
Voice: (306) 966-5026 (office), -5042 (colonization lab), -7704 (laser
imaging facility), 934-0711 (home)
Fax: 306-966-8898
Email: caldwell at sask.usask.ca
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