Soil microbial communities and extracellular enzyme activity in the New Jersey Pinelands

We have much to learn about the roles of various groups of soil microorganisms in the decomposition of soil organic matter. Any changes in the type or amount of organic matter entering the soil, due to increasing atmospheric nitrogen (N) deposition and elevated carbon dioxide, could directly affect soil microbial community structure or the decompositional functions performed by the various microbial groups. We experimentally altered soil microbial communities using a factorial combination of trenching and in-growth bags crossed with fertilization treatments consisting of two forms of inorganic N and three N-containing organic molecules of increasing molecular weight and complexity. We tested three hypotheses: (1) Different components of soil microbial communities change in different ways following the application of fertilization treatments; (2) soil fungi decrease with increased inorganic N but increase following the application of organic molecules; and (3) activity of the extracellular enzymes peroxidase and phenol oxidase, which are important in lignin degradation, decrease following the addition of inorganic N. We found that the abundance of soil microbes and their composition (measured by lipid analysis) was significantly altered following the addition of glutamic acid, but not with inorganic N or more complex N-containing organic molecules. Lipids indicative of ectomycorrhizal fungi experienced the greatest increase in abundance. Extracellular enzyme activity, in contrast, changed very little and did not parallel changes in the structure of the soil microbial community that resulted from the isolation treatments. We conclude that small additions of N-containing organic compounds can cause changes in the structure of the soil microbial community but that community changes do not necessarily have an impact on extracellular enzyme activity.     

酒酒球菌膜脂肪酸成分分析的样品处理方法比较

为筛选较适合的酒酒球菌膜脂肪酸提取和皂化方法,采用5种不同脂肪酸分析样品前处理方法,结合气相色谱质谱联用仪(GC/MS),分析酒酒球菌SD-2a膜脂肪酸成分,比较不同处理方法的效果。结果表明,先提取脂肪酸再采用NaOCH3甲酯化脂肪酸的方法能够较为准确和完整地检出酒酒球菌SD-2a的12种膜脂肪酸,相对标准误差(RSD)≤5%,特别对于环丙烷脂肪酸的检测效果较好,RSD=2%;独立的脂肪酸提取步骤对细菌膜脂肪酸分析是必要的,包含脂肪酸提取的样品处理方法比不包含脂肪酸提取的方法多检出3种脂肪酸,RSD均≤5%。     

Effects of culture density and live prey on growth and survival of juvenile cuttlefish, Sepia officinalis

The effects of culture density on growth and survival of juvenile cuttlefish were tested. Groups of 1, 3 and 5 hatchlings were placed in small containers with bottom surface of 80 cm², obtaining individual densities of 125, 375 and 625 cuttlefish m^–2, respectively. Additionally, groups of 5 hatchlings were placed in containers with 2 different bottom areas (80 and 240 cm²), providing culture densities of 625 and 42 cuttlefish m^–2, respectively. A total of 120 hatchlings were used and experiments lasted for 40 days. No differences were found in growth between any of the densities tested throughout the experiment until 35 days old. After this, cuttlefish placed in isolation grew significantly larger. A second experiment was conducted in a flow through system, using two rectangular tanks with bottom surface of 0.5 m². Two groups of 25 cuttlefish hatchlings were used in this experiment, which lasted for 40 days. Both groups were fed live juvenile shrimp (Crangon crangon) during the first 5 days. Afterwards, one group was fed live fish fry of different species, while the other continued to be fed shrimp. After day 10 and until the end of the experiment, hatchlings fed shrimp grew significantly larger than those fed fish fry. Survival of hatchlings fed shrimp or fish fry after 40 days was of 100% and 68%, respectively. Total protein content of both prey types was similar. Therefore, the higher polar lipid content, especially due to the higher phosphatidylcholine and phosphatidylethanolamine levels observed in the shrimp, compared to fish fry could possibly be one of the major factor to explain the significantly higher growth rates for S. officinalis juveniles fed shrimp. Also, the percentage of polar lipids in the shrimp (47.4%) was closer to the one of juvenile cuttlefish (38.1%) than the composition of polar lipids in fish fry (10.4%). This could also be an important factor to explain the poor growth and survival obtained when feeding fish fry to the cuttlefish.     

Influence of the gametogenic cycle on the biochemical composition of the ovary of the great scallop

The oogenic cycle and biochemical composition of the ovary of raft-cultured great scallop (Pecten maximus) were studied during the period April 1990–July 1991. The ovary condition index (FGI) and stereological studies showed the existence of two principal spawning periods, winter and late spring-early summer. No sexual resting period was found. Oocyte lysis was high throughout the year. Ovarian lipid levels displayed a clear seasonal pattern linked to the gametogenic cycle. Total lipid (TL, 16–21% dry weight), acylglycerol (AG, 20–65% TL) and free sterol (FS, 2.8–6.4% TL) levels were, generally, higher in the ripe ovary and a decrease coincided with spawning. Protein (59–63% dry weight), glycogen (<3% dry weight) and phospholipid (PL, 26–35% TL) levels showed no clear seasonal trend. The TL and AG were a good index of ovarian sexual maturity. The TL % of dry weight) correlated well with the female gonad condition index (r _s = 0.779, p < 0.001), and AG (% f TL) correlated well with the mean oocyte diameter (r _s = 0.630, p < 0.01) and the female gonad condition index (r _s = 0.443, p < 0.05).