The effect of C/N ratio on bacterial community and water quality in a mussel‐fish integrated system

A 30‐day experiment was conducted to evaluate the effect of C/N ratio on water quality and bacterial community in an integrated system comprising one molluscan species (pearl mussel Hyriopsis cumingii) and two fish species (gibel carp Carassius gibelio and silver carp Hypophthalmichthys molitrix) at five C/N ratios (6, 8, 10, 12 and 14). The mussel and fishes were reared in the experimental tanks (400 L), but gibel carp received formulated feed. Water quality in the experimental tanks was analysed on day 0, 10, 20 and 30, and bacterial community in the water column and sediment was analysed on day 30. Total nitrogen, total phosphorus and total organic carbon accumulated in the tanks over time. Ammonia and nitrite decreased with the increase in C/N ratio. Bacterial community in the water column and sediment changed at the phylum and genus levels with the increase in C/N ratio, and the critical C/N ratio causing a functional shift of bacterial community occurred at 10 in water column and 12 in sediment. The increase in C/N ratio benefited the growth of both potential probiotics and pathogenic bacteria. The high C/N ratio enhanced the bacterial functions of chemoheterotrophy and hydrocarbon degradation, but depressed the functions of nitrification and denitrification in the water column and sediment respectively. This study reveals that the C/N ratio can be used as a tool to manipulate the bacterial community and water quality in the mussel‐fish integrated system.     

Relationship between soak time and number of enmeshed animals in experimentally lost gill nets

In order to determine the effects of ghost fishing by lost gill nets, the relationship was examined between soak time and number of enmeshed animals in experimentally lost gill nets by using diving observations. Two experimental gill nets were set at 13 m depth in Tateyama Bay, Chiba Prefecture, Japan for approximately 200 days. One gill net was deployed in a small trough surrounded by artificial reefs, and the other was deployed on an adjacent open sandy bed. Twelve species of crustaceans, six species of gastropods, and five species of bony fish were enmeshed in the experimental gill nets. The number of enmeshed animals in the artificial reef gill net was substantially larger than that in the sandy bed gill net. The number of enmeshed animals in the experimental gill nets increased rapidly within one month after deployment, and then declined gradually showing fluctuations caused by the decrease in newly enmeshed animals, and the drop off from gill nets caused by the decomposition of dead animals. The decrease in the number of enmeshed animals was expressed by logarithmic equations, and based on these equations, the duration of capture function for the lost gill nets was calculated to be 284–561 days in the artificial reef gill net and 200 days in the sandy bed gill net. The duration of capture function for the lost gill nets for non-commercial by-catch species such as small crustaceans and gastropods was longer than for commercial species such as Japanese spiny lobster and bony fish.     

凡纳滨对虾不同养殖密度高位池水体细菌群落动态

通过对养殖水体环境基因组DNA中细菌16S rRNA基因V4–V5区的高通量测序和生物信息学分析,研究了两种养殖密度的凡纳滨对虾(Litopenaeus vannamei)高位池水体中细菌群落在养殖过程中的动态。结果显示,养殖过程中各菌群相对丰度变化明显,细菌多样性随时间逐渐提高,优势菌群为变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)、拟杆菌门(Bacteroidetes)、放线菌门(Actinobacteria)和浮霉菌门(Planctomycetes)。随着养殖时间增长,蓝藻丰度所占比例逐渐减少,而变形菌、拟杆菌和浮霉菌丰度逐渐增大,同时养殖前期高密度池浮霉菌丰度显著高于低密度池(P0.01),而其他菌群无显著差异。结果表明,养殖期前50 d不同养殖密度水体细菌群落差异较大,而后30 d内细菌群落的时间异质性大于空间异质性,这意味着高位池水体菌相被划分为两类,到养殖后期菌相快速转变,养殖密度所带来的影响被减弱。     

Tuna viscera protein hydrolysate: nutritive and disease resistance properties for Persian sturgeon (Acipenser persicus L.) larvae

The effect of fish protein hydrolysate (FPH) on the growth, feed utilization, digestive enzymes, gut microflora and resistance to bacterial challenge in Persian sturgeon (Acipenser persicus) larvae during a 45‐day feeding trial has been investigated. Artificial diets containing different levels of tuna visceral protein hydrolysate (PH0, PH10, PH25 and PH50) and live foods (Artemia: 5 days, Daphnia: 40 days) were fed to Persian sturgeon larvae. Larvae fed on the PH10 and PH25 had growth, feed utilization, protein content and trypsin activity significantly better than PH0 and PH50 groups (P < 0.05). Condition factors, survival rate and pepsin activity were not significantly different (P > 0.05). Brush border membrane enzymes to cytosolic enzyme ratio revealed that maturation had been occurred in 41 days post hatch (dph) at moderate FPH levels. In 54 dph larvae, this ratio was not affected by the level of FPH in the diet. No significant differences were observed in the total number of gut microflora or in the resistance to Aeromonas hydrophila (P > 0.05), whereas lactic acid bacteria was significantly higher in PH50 (P < 0.05). The results of this study show that application of moderate levels of FPH in Persian sturgeon diets could enhance larvae performance due to the early maturation in intestinal.     

鱼类细菌性败血症发病鱼池细菌数量及致病性气单胞菌的初步研究

本文对细菌性败血症发病鱼池细菌数量及气单胞菌的数量、溶血性及致病力进行了研究。结果表明:水温在28.5℃以下时,细菌数量与水温基本成正比,发病池与不发病池的细菌数量无显著性差异;水体中广泛存在气单胞菌,其占水体总菌量比例随水温的上升而升高;发病池及未发病池中均存在能产生hec毒素和不产生hec毒素的嗜水气单胞菌株,两者数量上无显著差异;水体中存在血清型为TPS—30及PBJS—76的嗜水气单胞菌,且大多数对鱼体有毒力,以5×10~7CFU/尾腹腔注射,可使试验鱼大部分或全部发病死亡。     

Diversity of Flavobacterium psychrophilum and the potential use of its phages for protection against bacterial cold water disease in salmonids

Flavobacterium psychrophilum causes rainbow trout fry syndrome (RTFS) and cold water disease (CWD) in salmonid aquaculture. We report characterization of F. psychrophilum strains and their bacteriophages isolated in Chilean salmonid aquaculture. Results suggest that under laboratory conditions phages can decrease mortality of salmonids from infection by their F. psychrophilum host strain. Twelve F. psychrophilum isolates were characterized, with DNA restriction patterns showing low diversity between strains despite their being obtained from different salmonid production sites and from different tissues. We isolated 15 bacteriophages able to infect some of the F. psychrophilum isolates and characterized six of them in detail. DNA genome sizes were close to 50 Kbp and corresponded to the Siphoviridae and Podoviridae families. One isolate, 6H, probably contains lipids as an essential virion component, based on its chloroform sensitivity and low buoyant density in CsCl. Each phage isolate rarely infected F. psychrophilum strains other than the strain used for its enrichment and isolation. Some bacteriophages could decrease mortality from intraperitoneal injection of its host strain when added together with the bacteria in a ratio of 10 plaque-forming units per colony-forming unit. While we recognize the artificial laboratory conditions used for these protection assays, this work is the first to demonstrate that phages might be able protect salmonids from RTFS or CWD.     

池塘养殖刺参腐皮综合征发病环境因素分析

通过对2014年7—8月山东省青岛市红岛邵哥庄(SGZ)和宿流(SL)两个社区的发生刺参腐皮综合征和未发病刺参养殖池的环境因子跟踪监测和对比,解析发病的原因。从发病前至发病后,分别监测了两地多个池塘水体中的4类可培养细菌(总异养菌、弧菌、硝化细菌和硫化细菌)和6项理化参数(温度、p H、盐度、溶解氧、无机氮、COD),以及沉积环境中6类可培养细菌(总异养菌、弧菌、硝化细菌、硝酸盐还原菌、硫化细菌、硫酸盐还原菌)和4项理化参数(pH、氧化还原电位、硫化物、有机碳)。结果表明,刺参发病时,邵哥庄发病池(SGZ-1~#)环境中细菌数量与未发病对照池(SGZ-2~#)无显著差异,但温度高达25.94℃,盐度低至24.47,均超过刺参耐受限度。水体NO_2-N含量为79.56μg/L,沉积物中硫化物含量为221.1 mg/g,均高于对照池;宿流发病池SL-南2弧菌数量(1.85×10~4 CFU/mL)在发病当日明显升高,高于对照池SL-北1和邵哥庄社区的发病池,而发病池的理化指标反而好于对照池。由此推断,邵哥庄社区的刺参发病与池塘理化指标突变有密切关系,而宿流的刺参发病与病原菌数量激增有密切关系。因此,应从理化指标和病害生物两方面对刺参病害进行预警及采取防治措施。     

中华绒螯蟹养殖期间细菌性疾病流行情况调查研究

1999~2004年对安徽省巢湖市6个乡镇的池塘、稻田养殖的中华绒螯蟹(Eriocheir sinensis)的细菌性疾病流行情况进行了调查研究。结果表明:中华绒螯蟹细菌性疾病发生与流行存在着季节性,其发病率年平均依次为47.3%、59.6%、51.9%、46.7%、60.0%、29.9%,逐月比较发病率最大峰值出现在每年的8月份;感染率年平均分别为66.6%、75.8%、57.8%、52.0%、86.0%、39.3%,死亡率年平均依次为38.3%、44.6%、36.3%、29.6%、43.5%、21.6%;中华绒螯蟹细菌性疾病发病率与出现的最高气温、最低气温以及气温、水温持续偏高呈正相关(r=0.7657、r=0.7385、r=0.7237,P<0.01)。     

Analysis of bacterial community and bacterial nutritional enzyme activity associated with the digestive tract of wild Chilean octopus (Octopus mimus Gould, 1852)

Information on the bacterial community associated with octopus is very scarce, unlike fish and other molluscs. This study revealed the bacterial community associated with digestive tract of wild Chilean octopus Octopus mimus using a culture‐dependent method and 16S rDNA clone library. Moreover, we analysed the bacterial nutritional enzyme activity of culturable bacteria. A culture‐dependent method showed that the composition of the culturable bacterial community was substantially different between female and male octopus. The predominant species in female octopus were Vibrionaceae and Streptococcaceae, whereas only Vibrionaceae was dominated in male octopus. Bacterial nutritional enzyme activities of culturable bacteria from male octopus were much higher than female octopus. The 16S rDNA clone library analysis showed that the bacterial community of male octopus exhibited a higher diversity than that of female octopus. The genus Mycoplasma was the predominant bacteria in the digestive tract of all octopus samples. The results obtained in this study raise the possibility that each octopus has different food consumption due to different bacterial community and nutritional enzyme activity, although Mycoplasma sp. is one of the predominant bacteria in the digestive tract. Moreover, our results are useful for the future of microbiological investigation associated with the octopus and for probiotics in the octopus aquaculture.     

不同健康程度和抗生素氟苯尼考干预下斑石鲷肠道菌群的结构差异

为了研究不同健康程度和抗生素氟苯尼考干预下斑石鲷肠道菌群结构的差异及其与养殖环境中菌群结构的相关性,采用Illumina Hi Seq PE250高通量测序的方法对健康、亚健康、典型黑身病和口服氟苯尼考条件下的斑石鲷肠道、养殖水体和颗粒饵料中的细菌多样性及群落结构进行了分析比较。结果显示,养殖水体中细菌多样性高于肠道和颗粒饵料。不同健康程度及氟苯尼考干预下斑石鲷肠道中细菌均以变形菌门、厚壁菌门和软壁菌门为主,且对应的操作分类单元(OTU)占样品全部OTU的比例均达到85%以上。黑身病的发生可影响斑石鲷肠道中丰度最高的前20种优势细菌种类的排名次序,其中变形菌门中的弧菌属的相对丰度显著增加,且随着弧菌属丰度的增加,斑石鲷的黑身病症状也逐渐加重。饵料中添加氟苯尼考投喂斑石鲷能使患病鱼肠道弧菌属的丰度从60.33%下降到1.29%,较大程度改变了肠道的菌群结构,并证实氟苯尼考有效防治黑身病。其次,养殖水体和颗粒饵料对斑石鲷肠道菌群也有一定影响,且养殖水体的影响高于颗粒饵料。本研究首次报道了斑石鲷肠道菌群结构,其研究结果为今后斑石鲷的健康养殖、疾病防控及其微生态学研究提供了参考依据和技术支撑。