太湖地区水稻土优势反硝化细菌的数量、组成与酶活性

本研究结果表明太湖地区主要水稻土中反硝化细菌常在百万/克干土以上,占细菌总数的50—80%。同一类型土壤中,肥力高者含菌数多于肥力低者。各类土壤中反硝化细菌数与细菌总数呈显著正相关。其优势种中,以巨大芽孢杆菌、荧光假单胞菌和施氏假单胞菌等出现的机率最高,占反硝化细菌的10—50%;地衣芽孢杆菌及坚强芽孢杆菌等出现的机率较少。具有使NO₃^-还原为N₂O的菌株和使N₂O还原为N₂的菌株,分别占供试菌株的67%和56%;使¹⁵NO₃^-异化还原为¹⁵NH₄⁺的菌株占供试菌株的92%,其中以蜡质芽孢杆菌和地衣芽孢杆菌的这种能力特别强。

NUMBERS, COMPOSITIONS AND ENZYME ACTIVITIES OF DENITRIFIERS IN PADDY SOILS OF TAIHU LAKE DISTRICT

This article deals with numbers, compositions and enzyme activities of denitrifiers in paddy soil in Taihu Lake district. The results obtained are as follows. 1. The amount of denitrifiers teas rather numerous in paddy soil in this region, generally, more than million per gram of dry soil. Numbers of denitrifiers in soil with higher fertility were larger than that with lower fertility. In all the paddy soils, there was significant positive correlation between numbers of denitrifiers and bacteria. 2. The species in genus Bacillus and Pseudomonas were the predominant denitrifying bacteria in paddy soils in Taihu Lake district. The highest occurrence frequency of Bac. megotherium and Pseu. fluorecens has been found in these soils, they even constituted 10-50% of the total denitrifiers, while the frequencies of Bec. licheniformis and Bac. firmus were much lower than the former. 3. The enzyme activities of denitrifiers have been determined by means of GC-technique. The amount of the strains reducing NO₃^- to N₂O and those reducing N₂O to N₂ constituted 67% and 56% of the strains tested, respectively. The amount of denitrifiers being able to reduce ¹⁵NO₃^- to ¹⁵NH₄⁺ through dissimilatory reduction pathway constituted 92% of the strains tested. The dissimilatory reduction ability of Bac. cereus and Bac. licheniformis were vigorous.