The bacterial population of a blanket peat

Abstract

The number of aerobic bacteria in a blanket peat decreased with depth from 26 times 106/g dry peat in the surface layers to 0.5 times 106/g dry peat at 30–40 cm down the profile, thereafter remaining roughly constant. Obligate psychrophiles comprised <2.5% of this population. Anaerobes were most numerous, 9 times 106/g dry peat at 6–10 cm depth, decreasing to 0.5 times 106/g at 20–30 cm. Calculations indicated that these counts, 103–104‐fold lower than the direct counts, substantially underestimated the active microbial population. Gram negative rods, the predominant aerobes in the surface layers, were replaced by unidentified Bacillus strains at 10–20 cm depth but became increasingly more numerous further down the profile. The Gram negative rods were the most numerous organisms/m2 but the Bacillus strains, one third of which were present as spores, made the largest contribution to the biomass/m2. Gram positive cocci, Arthrobacter and, infrequently, Nocardia were also isolated. Actinomyces‐like forms were the predominant obligate anaerobes and were approximately three times more numerous than clostridia and a curved Gram negative rod.