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531.
Amino sugars are useful indicators for the accumulation of microbial residues. A 14-day incubation experiment with C4 and C3 sucrose additions was carried out to investigate the relationships between amino sugar-specific shifts in δ13C values and those of CO2 production, microbial biomass C, K2SO4 extractable C and soil organic C (SOC). High performance anion exchange chromatography (HPAEC-IRMS) was able to measure amino-sugar specific δ13C values for muramic acid (MurN), galactosamine (GalN), and glucosamine (GlcN) in the range of natural abundance. At day 7, the initial application of C4 sucrose significantly increased the δ13C value of MurN by 1.0‰ in comparison with the non-amended control treatment, whereas that of GalN and GlcN remained unchanged. This significant increase had disappeared by day 14. This means that the HPAEC-IRMS method is not useful for short-term incubation experiments in the natural abundance range, as the pool size, especially of GalN and GlcN, was too large for a significant response in δ13C values. The δ13C values significantly decreased in the order MurN (−23.2‰) > GalN (−25.7‰) > GlcN (−26.5‰) in the control treatment. Similar δ13C values were measured in GlcN, microbial biomass C, and SOC. MurN exhibited δ13C values similar to the K2SO4 extractable fraction. These results may be caused by differences in the access of bacteria and fungi to different SOC fractions or differences in metabolic fractionation in bacteria and fungi. C3 sucrose application without further nutrient supply seven days after C4 sucrose application together with N and P led to strong mineralization of freshly formed microbial residues. 相似文献
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Jouni Heikkinen Jouni Vielma Marja Tiirola Tapio Kiuru Atte von Wright 《Aquaculture (Amsterdam, Netherlands)》2006,261(1):259-268
Effects of soybean meal (SBM) based diet on growth performance, histology of the intestinal epithelium and on the gut microbiota of juvenile rainbow trout (Oncorhynchus mykiss) were investigated on two trials lasting for 8 weeks (Trial I) and 18 weeks (Trial II). The microbiological characterization was done both with conventional plating techniques, biochemical profiling and length heterogeneity analysis of PCR amplified 16S rDNA (LH-PCR).Typical histological changes were found after 18 weeks of SBM feeding (Trial II). Mean height of simple foldings were significantly higher within the group fed with fish meal (FM) based diet. These changes were not, however, reflected in the appearance, behavior and weight gain of the fish, although the feed conversion rate (FCR) was higher, compared to fish fed with the traditional FM feed.In both SBM and FM groups the counts of cultivable intestinal bacteria dropped within the first 4 weeks of feeding (Trial I). Subsequently, the bacterial numbers increased in the FM group, but not in the SBM group by the 8th week of the trial. The LH-PCR data suggested also that diet-related qualitative changes in the microbiota had occurred (Trial II). The main identified bacteria were mainly representatives of the genera Aeromonas, Sphingomonas and Chryseomonas, and among the lactic acid bacteria, Lactococcus and Lactobacillus.Future research will be directed to the identification and eventual elimination the SBM-associated factors involved in the inflammatory responses and unfavorable FCR, in particular by modifying the intestinal microbiota. 相似文献
534.
固定化光合细菌去除水中氨氮效果的初步研究 总被引:2,自引:0,他引:2
光合细菌固定化是一生物新技术,本文报导了利用这一技术去除水体中氨氮的效果,在运输鲤鱼鱼种中比添加游离光合细菌运输成活率提高10.9%;比对照组成活率提高13.9%。氨氮去除率敞口篓(96.44%),优于密封篓(71%)。本文并对固定化光合细菌在生产实际中的应用前景进行了讨论。 相似文献
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Lise?Torkildsen Christophe?Lambert Are?Nylund Thorolf?Magnesen ?ivind?BerghEmail author 《Aquaculture International》2005,13(6):575-592
A bacteriological study was carried out at a scallop (Pecten maximus) hatchery near Bergen, western Norway following a severe increase in mortality rates during the larval stages of the scallops.
No larvae survived to settling, except for those in groups treated prophylactically with chloramphenicol. In order to identify
pathogenic strains of bacteria, we performed a challenge test on 10- to 16-day-old larvae using isolated bacterial strains
from the hatchery. Infection with six of these strains produced mortalities that were not statistically different from that
resulting from infection with the known pathogen Vibrio pectenicida. However, about 5% of the strains tested in the challenge experiment produced higher motility rates than found in the unchallenged
control group, indicating a possible probiotic effect. On the basis of 16S rDNA analysis on these strains, the phylogenetic
tree indicated two groups of apparent pathogens: (1) one strain, LT13, grouped together with Alteromonas/Pseudoalteromonas; (2) a cluster of strains grouped together with Vibrio splendidus (LT06, LT21, LT73, PMV18 and PMV19). Strain LT13 was isolated from cultures of the microalga Chaetoceros calcitrans used for feed, while the other strains were isolated from larval cultures. Transmission electron microscopy showed intracellular
bacteria that resembled bacteria in the groups Chlamydiaceae and Rickettsiaceae. 相似文献
537.
广西沿海文蛤及其生境中细菌菌群的初步调查 总被引:15,自引:0,他引:15
对广西沿海文蛤及其养殖场的细菌菌群用VITEK微生物自动分析仪进行了初步检测,发现文蛤体内有腐败假单胞菌(Alteromonasputrefaciens)、河弧菌(Vibriofluvialis)、副溶血弧菌(V.parahaemolyticus)、溶藻弧菌(V.alginolyticus)、非发酵性革兰氏阴性芽胞菌(NonfermentingGram-negativeBacillus)、假单胞菌属(Pseudomonasspp.)以及一些未知菌。从海水中亦经常检测到腐败假单胞菌、溶藻弧菌、河弧菌、温和气单胞菌(Aeromonassobria)等细菌。分析表明,副溶血弧菌可能为文蛤的一种病原菌。药敏试验显示.上述所有细菌几乎都对环丙沙星、庆大霉素和氯霉素敏感。 相似文献
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540.
Microbial activities in Arctic and Antarctic soils are of particular interest due to uncertainty surrounding the fate of the enormous polar soil organic matter (SOM) pools and the potential to lose unique and vulnerable micro-organisms from these ecosystems. We quantified richness, evenness and taxonomic composition of both fungi and bacteria in 223 Arctic and Antarctic soil samples across 8 locations to test the global applicability of hypotheses concerning edaphic drivers of soil microbial communities that have been primarily developed from studies of bacteria in temperate and tropical systems. We externally validated our model's conclusions with an independent dataset comprising 33 Arctic heath samples. We also explored if our system was responding to large scale climatic or biogeographical processes that we had not measured by evaluating model stability for one location, Mitchell Pennisula, that had been extensively sampled. Soil Fertility (defined as organic matter, nitrogen and chloride content) was the most important edaphic property associated with measures of α-diversity such as microbial richness and evenness (especially for fungi), whereas pH was primarily associated with measures of β-diversity such as phylogenetic structure and diversity (especially for bacteria). Surprisingly, phosphorus emerged as consistently the second most important driver of all facets of microbial community structure for both fungi and bacteria. Despite the clear importance of edaphic factors in controlling microbial communities, our analyses also indicated that fungal/bacterial interactions play a major, but causally unclear, role in structuring the soil microbial communities of which they are a part. 相似文献