BACTERIAL COMMUNITIES IN PEAT IN RELATION TO BOTANICAL COMPOSITION AS REVEALED BY PHOSPHOLIPID FATTY-ACID ANALYSIS

Analysis of phospholipids extracted from various moss and sedge peat types revealed significant differences in the patterns of the phospholipid fatty acids (PLFA) with respect to the major botanical constituents of the peats. Principal component analysis of the PLFA data showed that peats dominated by Carex residues had higher relative amounts of cyclopropane fatty acids and cis vaccenic fatty acid (18:1omega7c), but lower proportions of iso and anteiso methyl branched fatty acids compared to peat types dominated by Sphagnum residues. The data analysis also revealed a larger variation in the PLFA composition among the Sphagnum peats compared to the Carex types, which seems to relate to a larger variation in botanical composition among the Sphagnum than Carex peats. The differences in the fatty acid pattern indicate that the botanical composition influenced the bacterial community with Carex peats having a higher proportion of Gram-negative bacteria but lower proportion of Gram-positive bacteria compared to the Sphagnum peats. An exception was pure Sphagnum peats dominated by the subsection Acutifolia, where the bacterial community showed a closer similarity with the Carex peats. The ratios of trans to cis isomers of the unsaturated fatty acids 16:1omega7 and 18:1omega7 were positively correlated with the degree of decomposition of the peat types, and may be an indication of increased starvation in the bacterial community as the decomposition proceeds.