Characterization of the bacterial community associated with early‐developmental stages of grass carp (Ctenopharyngodon idella)

Bacterial communities in eggs and larvae of grass carp were analysed. During the early‐developmental stages, grass carp harboured five bacterial phyla, i.e. Proteobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes and Firmicutes. However, the composition of bacterial communities varied among the different developmental stages. In eggs, the bacterial communities were dominated by Proteobacteria, while in larvae the dominant bacterial community was Bacterioidetes. With the exception of a large proportion (>50%) of uncultured bacteria, Sphingobacterium (14.75%) and Acinetobacter (13.11%) were the most abundant groups in eggs at the fertilization stage (FS). However, Aermonas was the most abundant group, ranging from 40.54% to 61.76% in eggs at the cleavage (CS), blastula (BS), organ differentiation (ODS) and hatching stages (HS). In larvae after first ingestion (OW), Chitinophagaceae (79.41%) formed the predominant bacterial community. Changes in the bacterial community were further confirmed by statistical analysis, which demonstrated significant differences in the bacterial communities of eggs at FS, eggs from CS to HS and OW. However, no significant difference was found in bacterial communities of eggs from CS to HS. Furthermore, the present study revealed that bacteria related to Chitinophagaceae persisted from CS to OW, suggesting that these bacteria form part of the autochthonous microbiota of the fish.     

Diversity and activity of cellulolytic bacteria,isolated from the gut contents of grass carp (Ctenopharyngodon idellus) (Valenciennes) fed on Sudan grass (Sorghum sudanense) or artificial feedstuffs

Herbivorous grass carp (Ctenopharyngodon idellus) has a powerful capability to digest cellulose from aquatic plants, depending on the cellulase complex produced by the cellulolytic bacterial community in the gastrointestinal (GI) tract. However, it remains uncertain which bacteria taxa may actively participate in the digestion of food fibre. In this study, a total of 499 cellulolytic bacteria from the gut content of grass carp fed on Sudan grass (242 strains) and artificial feedstuffs (257 strains) were randomly isolated and characterized using carboxymethyl‐cellulose, microcrystalline cellulose and cellobiose agar media. The results showed that more than half of the isolates were capable of degrading carboxymethyl‐cellulose and cellobiose, while the remaining isolates were restricted to microcrystalline cellulose decomposition, exclusively. The cellulolytic bacterial community was dominated by Aeromonas, followed by Enterobacter, Enterococcus, Citrobacter, Bacillus, Raoultella, Klebsiella, Hydrotalea, Pseudomonas, Brevibacillus and some unclassified bacteria, as revealed by 16S rDNA sequence analysis. Notably, grass carp fed on grass with high‐fibre content harboured a higher diversity of cellulolytic bacteria than the ones fed on low‐fibre feedstuffs. Our results provided evidence for a positive correlation between the content of food fibre and the diversity of cellulolytic bacteria in grass carp intestines. Thus, improving growth conditions and cellulase activities for GI cellulolytic microorganisms in grass carp intestines are critical for effective utilization of feedstuffs containing high fibre levels.     

德州市土壤肥力变化及分析

调查分析德州市土壤肥力变化规律,为黄淮海平原地区中低产土壤科学施肥提供依据.20年进行3次大规模土壤肥力分布状况调查,按照高中低和不同土壤类型分类布点,共采取土样63 546个,监测化验8万多项次.结果表明,全市土壤养分结构发生了变化,有机质有所增加但含量偏低,氮素不足,含磷量虽然增加幅度较大,但施用磷肥仍然具有显著的增产效果.速效钾含量由1982年以来的逐渐减少变为1998年以后的逐渐增加.部分土壤微量元素缺乏呈上升趋势.土壤肥力分布不均,范围较广,虽然经过耕作、施肥和灌溉,土壤肥力有所提高,但高产土壤分布面积较少,中低产土壤仍然占有相当大的比例,改良利用和培肥的潜力还很大.根据各种农作物的需肥规律及肥料特性,实行测土配方施肥技术,在增施有机肥料的基础上,本着稳氮、稳磷、补施钾及微肥和农作物缺什么补什么、缺多少补多少的原则,达到土壤供肥与农作物需肥的基本平衡.     

Adhesion and colonization properties of potentially probiotic Bacillus paralicheniformis strain FA6 isolated from grass carp intestine

Fisheries Science - As a prerequisite for probiotics to establish and settle in the host intestine, adhesion is an essential criterion for probiotic screening. However, adhesion of probiotics in...     

中国淡水鱼类寄生虫研究七十年

寄生虫是水产养殖中最主要的病原类群之一,对鱼类苗种直至成鱼各个阶段的危害都十分严重。我国的鱼病学即是从鱼类寄生虫的研究发端并逐步发展起来的。本文从病原生物学、生态学、药物学、免疫学四个方面回顾了我国淡水鱼类寄生虫自新中国建立初期至今70年间(1953年—2023年)的研究历程和已取得的成绩,并对未来的发展趋势和前沿热点进行了展望。本文为从事鱼类寄生虫学以及水产其他相关研究的读者提供了关于中国鱼类寄生虫研究的历史、现在发展水平和未来发展动向等较为全面的素材。     

Diversity of autochthonous bacterial communities in the intestinal mucosa of grass carp (Ctenopharyngodon idellus) (Valenciennes) determined by culture‐dependent and culture‐independent techniques

Traditional culture‐based technique and 16S rDNA sequencing method were used to investigate the mucosa‐associated autochthonous microbiota of grass carp (Ctenopharyngodon idellus). Twenty‐one phylotypes were detected from culturable microbiota, with Aeromonas, Shewanella, Lactococcus, Serratia, Brevibacillus, Delftia, Pseudomonas, Pantoea, Enterobacter, Buttiauxella and Yersinia as their closest relatives. Genomic DNA was directly extracted from the gut mucosa of C. idellus originating from six different geographical regions, and used to generate 609 random bacterial clones from six clone libraries and 99 archaeal clones from one library, which were grouped into 67 bacterial and four archaeal phylotypes. Sequence analysis revealed that the intestinal mucosa harboured a diversified bacterial microbiota, where Proteobacteria, Firmicutes and Bacteroidetes were dominant, followed by Actinobacteria, Verrucomicrobia and Deinococcus‐Thermus. The autochthonous bacterial communities in the gut mucosa of fish from different aquatic environments were not similar (C_s < 0.80), but γ‐Proteobacteria was a common bacterial class. In comparison to bacterial communities, the archaeal community obtained from one library consisted of Crenarchaeota and Euryarchaeota. These results demonstrate that molecular methods facilitate culture‐independent studies, and that fish gut mucosa harbours a larger bacterial diversity than previously recognized. The grass carp intestinal habitat selects for specific bacterial taxa despite pronounced differences in host environments.     

德州市土壤肥力变化及分析

摘 要： 【研究目的】调查分析德州市土壤肥力变化规律,为黄淮海平原地区中低产土壤科学施肥提供依据; 【方法】20年进行三次大规模土壤肥力分布状况调查,按照高中低和不同土壤类型分类布点,共采取土样63564个,监测化验8万多项次; 【结果】表明我市土壤养分结构发生了变化,有机质有所增加但含量偏低,氮素不足,含磷量虽然增加幅度较大,但施用磷肥仍然具有显著的增产效果。速效钾含量由1982年以来的逐渐减少变为1998年以后的逐渐增加。部分土壤微量元素缺乏呈上升趋势。土壤肥力分布不均,范围较广,虽然经过人们的耕作、施肥和灌溉,土壤肥力有所提高,但高产土壤分布面积较少,中低产土壤仍然占有相当大的比例,改良利用和培肥的潜力还很大; 【结论】根据各种农作物的需肥规律及肥料特性,实行测土配方施肥技术,在增施有机肥料的基础上,本着稳氮、稳磷、补施钾及微肥和农作物缺什么肥料补什么,缺多少肥料补多少的原则,达到土壤供肥与农作物需肥的基本平衡。     

Growth performance,immunity and intestinal microbiota of swamp eel (Monopterus albus) fed a diet supplemented with house fly larvae (Musca domestica)

Housefly larvae are widely used in livestock breeding industry as a functional feed additive with immunostimulant properties, but their effects as dietary additive are poorly understood in aquatic animals. We conducted an eight‐week rearing experiment to determine the effects of housefly larvae (complete) on growth performance, immunity and intestinal microbiota in swamp eel (Monopterus albus). Dietary treatments were as follows: BD (control group, fed a basal diet), FL7 (fly larvae supplemented once weekly, i.e., 6‐day basal diet, 1‐day larvae) and FL3 (larvae supplemented every third day, i.e., 2‐day basal diet, 1‐day larvae). The final body weight (FBW) and weight gain (WG) of the FL3 group significantly (p < .05) increased. Hepatosomatic index (HSI) and malondialdehyde (MDA) concentration significantly decreased in FL3 and FL7 groups. The expression of immune‐related genes was also influenced by the fly larvae. Aeromonas hydrophila challenge experiment produced higher survival rates in the FL3 (75%) and FL7 (37.5%) groups. Fly larvae also affected the composition of gut microbiota: the abundance of Bacteroides increased, and Pseudomonas decreased, in the treatment groups. Dietary supplementation of housefly larvae has positive effects on the growth and immunity of swamp eel, and we suggest supplementing housefly larvae every third day.