PHOSPHOLIPID FATTY-ACID PROFILES AND CARBON UTILIZATION PATTERNS FOR ANALYSIS OF MICROBIAL COMMUNITY STRUCTURE UNDER FIELD AND GREENHOUSE CONDITIONS

The description of soil microbial community structure by phospholipid fatty acid (PLFA) profiles is based on the relationship between the ph ylogeny of microorganisms and their PLFA profiles. Based on this relat ionship, two community based microbiological measurements, namely, pot ential C source utilization patterns in Biolog microtiter plates and P LFA profiles were used to examine metabolic fingerprints of soil micro bial communities and changes in species composition between field and greenhouse soils. Field and greenhouse experiments were conducted usin g Palouse and Ritzville silt loams. Soil sampled under wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), pea (Pisum sativa L.), joi nted goatgrass (Aegilops cylindrica L.), downy brome (Bromus tectorum L.), and control soils (no plants) were used for these analyses. Princ ipal component analysis (PCA) of PLFA profiles and C source utilizatio n patterns were used to describe changes in microbial biomass and meta bolic fingerprints from the two soil types under field and greenhouse conditions. Biomass measurements from extractable PLFA profiles per g dry weight ranged from 28.8 nmol in wheat soil in the greenhouse to 71 .4 nmol in pea soil in the field. In general, biomass was higher in al l the field samples than in greenhouse samples. Principal component an alysis of the two soils with different plants in the field and greenho use showed clear separation. Principal component analysis of C utiliza tion patterns on the effects of environment on soil microbial communit y yielded similar results with PLFA measurements. However, higher vari ability observed among different plants with the Biolog data resulted in the low amount of variance for Biolog data explained by the first t wo dimensions of the PCA. This suggests that PLFA may be more sensitiv e for community analysis than the Biolog technique. (C) 1998 Published by Elsevier Science B.V. All rights reserved.