Community electron transport of procaryotes in euryoxic estuarine sediment

Abstract

Rates of both tetrazolium and oxygen reduction were obtained seasonally from the top 8 cm of euryoxic estuarine sediment in southeastern New England, USA, over an in situ temperature range of 0 to 20 'C. Anoxic tetrazolium reduction was highest i n the 3 to 5 cm layers at 15 O C (up to 860 n m o l 2 e c m 3 h l ) . Changes in the chemistry of deeper pore-waters (20 to 60 cm) occurring over 90 d indicated that metabolic rates (ca 42 nmol 2 e c m 3 h ' ) were about an order of magnitude lower than those in the surface sediments. Parallel simultaneous estimates of 0; reduction (reduced sediment preincubated in Os-saturated ambient waters  10 mM NaN3) averaged 4 times greater than tetrazolium reduction. The postulated occurrence of a mixed metabolic community consisting of facultatively anaerobic heterotrophs and chemolithotrophs agrees with the field data. The community is spread out vertically through watery sediment of a quiescent, highly depositional cove. Soft-bodied infauna may help maintain the Eh potential at ca -200 mV from 1 to 60 cm; the sediment is not sufficiently cohesive to be strongly poised,

Application of a Tetrazolium Salt with a Water-Soluble Formazan as an Indicator of Viability in Respiring Bacteria

“…Careful comparison of XTT reduction with viability estimates obtained with other methods (e.g., plate counts) can also be potentially helpful in investigations of viable (i.e., metabolically active) but nonculturable bacteria (e.g., 11,16,23,26). In environmental studies, XTT can potentially substitute for some tetrazolium salts used previously to quantify overall ETS activity (e.g., 3,6,13,29). Further applications of the XTT assay in environmental and culture studies can thus alleviate some problems associated with the use of electron-coupling agents and tetrazolium salts with water-insoluble formazan products.…”

“…Attempts have also been made to establish colorimetric assays for the overall respiratory activity of microorganisms in environmental samples and cultures by dissolving and quantifying the amount of formazan produced (3,6,13,20,29). However, these assays are complicated by the insolu-* Corresponding author.…”

Dynamics of microbial growth in surface layers of a coastal marine sediment ecosystem

“…Our field data provide support for the hypothesis that cell growth and cell division are uncoupled, over the time scales investigated (hours to days). In this regard, our study site may be viewed as being analogous to the recently described Quiambog Cove ecosystem (Matson & Buck 1987) for which the authors conclude that sediment heterogeneity maintains a metabolic diversity throughout the year. For Kahana Bay sediments, w e cannot b e certain whether the growth of microorganisms is continuous or discontinuous, but it does appear to be unbalanced.…”