Bacterial respiration (long incubations)

[L. Antonio Cuevas]

Bacterial respiration (BR) is not a common measurement in microbial ecology compared to biomass and productivity. Most studies has measured <24h observing a lineal decrease in oxygen concentration and using the slope of the relationship between time and oxygen as a value of bacterial oxygen consumption (proxy for BR).

I'd love to have some feedback (comments, references) about long oxygen consumption experiments (>4 days) and especially experiments with mineral nutrients and carbon additions. The theory says that the exhaustion of primary substrates may be indicated by a plateau in the rate of oxygen consumption, that's the common response during ~24h incubation. I observed the same situation during the first 24h, but after ~72h a fast decrease in oxygen was observed (together with high bacterial biomass and productivity) only in amended bottles. So, my main question is the better approximation to calculate the oxygen consumption after ~6 days of incubation. There is at least 3 slopes for each experiment: one during the first 24 h, a 2nd one 'without oxygen changes' until 72h and a high slope after 72h.

Thanks in advance,
Antonio 

[shweta]

even I do have some queries in this regard
when we are doing BR how is it possible to control respiration by picoautotrophs?
and yes is it possible to include free living and particle associated bacteria while calculating BR
and yes as it has been mentioned about 24hrs incubation and the limitation, if we exceed the time of incubation and for that if we provide the nutrients wont our BR be influenced by the kind of nutrients that we provide and the kind of nutrients being actually present in situ?
 
if anyone can then plzzz..
 help me out
Shweta