Determination Of Microbial Biomass Research Articles

Method for rapid removal of ethanol from chloroform in soil microbial biomass determinations

Abstract A method is described for the removal of stabilising ethanol from reagent‐grade chloroform (CHCl3) which is quicker, safer, and as effective and reliable as the standard method described in Jenkinson and Powlson (1976). The proposed method foregoes the use of concentrated acid and distillation and involves shaking CHC13 with distilled water followed by drying the final chloroform phase over anhydrous calcium chloride (CaCl2). Both methods yielded CHC13 containing residual ethanol of less than 0.001% w/w.

Eliminating Nitrate Interference During Kjeldahl Digestion of Soil Extracts for Microbial Biomass Determination

AbstractNitrate interference in Kjeldahl digestion of soil and plant samples presents a significant problem in establishing N budgets in agricultural systems, where NO−3 is frequently abundant. During digestion, NO−3 can be reduced or it can cause volatilization of reduced N, resulting in either over‐ or under‐estimation of Kjeldahl N. A method has been developed to volatilize NO−3 from K2SO4 extracts of soil prior to Kjeldahl digestion for determination of microbial biomass N. Extracts were pretreated with H2O2 and H2SO4 at 97 °C for 48 h, and then were Kjeldahl digested using a procedure modified for microbial biomass extracts. This method volatilizes >99% of NO−3 in K2SO4 extracts, as determined by 15N recovery from spiked samples.

On line, non-destructive biomass determiantion of bacterial biofilms by fluorometry

The lack of on-line methodology for the determination of microbial biomass and activity of attached bacteria has severely limited the study of biofilm physiology. This study showed that the fluorescent emission of aromatic amino acids in microbial biofilms can be used to determine the biomass formed on 316 stainless steel coupons. Cells resuspended from the substratum were enumerated by viable and acridine orange showing correlation coefficients of 0.77 and 0.98, respectively, when compared to the tryptophane fluorescence. Substrata treated with a fluorescent epoxy coating (F-150) showed no fluorescence that could be attributed to the microorganisms. Bioluminescent emission of an actively growing bioluminescent bacterium, Vibrio harveyi, was correlated with acridine orange counts ( r 2 = 0.95) and fluorescence ( r 2 = 0.93). The results of these studies suggest that fluorescence measurements can be used to monitor microbial biomass associated with various substrata. Coupled with bioluminescence measurements, this method provides information on both biomass constituents and metabolic activity, and therefore possibly an indicator of sub-lethal toxicity.

Determination of microbial biomass and its community structure from the distribution of phospholipid ester-linked fatty acids in sediments of Hiroshima Bay and its adjacent bays

Phospholipid ester-linked fatty acid (PLFA) composition in sediment samples collected from 20 sampling stations of Hiroshima Bay and its adjacent bays are reported. Thirty-one individual fatty acids were identified in the sediments which comprised of saturated, monounsaturated, polyunsaturated and branched fatty acids. A majority of these fatty acids are characteristic of aerobic and anaerobic bacteria especially sulphate-reducing bacteria. PLFA profiles in the sediments varied among the stations indicating the differences in the contributing microbial communities. The calculated biomass also varied from 0·3 × 10 7 to 2·6 × 10 7 cells g −1 dry weight sediment. The shift in microbial community structure within the study area is understood from the seven clusters obtained by the similarity analysis of PLFA composition. The results of environmental parameters revealed the existence of both oxic and anoxic conditions in the study area and the PLFA composition in sediments is discussed in relation to these environmental parameters. Low concentrations of polyunsaturated fatty acids (PUFA) determined in sediments, characteristic of microeukaryotes, could be attributed to the existing environmental conditions and pollution in the study area. Small quantities of long chain fatty acids in sediments indicated that the terrestrial input is low.

Microbial biomass determinations in deciduous leaf litter

Microbial biomass determinations in deciduous leaf litter

Difficulties with ATP measurements in inshore waters1

When inshore waters are filtered for microbial biomass determinations, the amount of ATP recovered in the extracts is directly proportional to the volume filtered up to about 0.5 liter. With sample volumes of 1–3 liters, there is an apparent loss of ATP which can amount to 10–50% of that originally present. This loss is not due to cell lysis during filtration, but rather seems related to adsorption phenomena associated with the load of detrital or sedimentary material in suspension. When working in inshore waters it is therefore advisable to determine if such an inflection point occurs for ATP loss and to use smaller sample volumes if necessary to ensure against any loss of ATP. There is no such loss of ATP from open ocean samples.