海洋鱼类和甲壳类抗菌肽的研究进展与应用前景

抗菌肽的发现与研究已有几十年的历史,抗菌肽是一类生物体中普遍存在并具有广谱抗微生物活性的小分子多肽,被科学家誉为"天然抗生素"。海洋动物抗菌肽是鱼、虾、蟹、贝等海洋动物的非特异性免疫防御系统的重要组成部分,在海洋环境中对于防御外源病原菌的入侵起到重要作用。海洋抗菌肽的研发与应用,不仅具有重要的医学开发价值,也是减少抗生素污染、实现海水健康养殖的重要保障。本文主要以鱼类抗菌肽和甲壳类抗菌肽为例,从抗菌肽的来源与分类、结构特点以及生物学活性等方面,简要概述近年来海洋鱼类和甲壳类抗菌肽的一些研究进展及其开发利用前景。     

抗菌肽在生猪防治上的应用

抗菌肽指由动物体产生的一类具有抗菌活性的碱性多肽物质,很多细菌的代谢产物中也含有抗菌肽。它的主要作用是广谱抗菌,不产生耐药性,调节和修复动物机体的免疫系统,提高动物的免疫力和抵抗力。抗茵肽作为抗生素替代品被应用在养殖业,特别是养猪业上,抗菌肽可以提高保育仔猪的抗病力,调节仔猪肠道微生态平衡、促进营养物质消化吸收、提高饲料利用率等作用。     

水产动物抗菌肽研究进展

抗菌肽是一类广泛存在于自然界生物体内的小分子多肽物质,为机体固有免疫系统的重要组成部分,对革兰氏阴性菌、革兰氏阳性菌、真菌、病毒和寄生虫等均具有较好的抑制或杀伤作用。抗菌肽具有无污染、无残留、广谱抗菌及不易产生耐药性等特点,有望代替抗生素用于水产动物病原性疾病的防控。近年来,抗菌肽已在水生甲壳动物、水产软体动物、鱼类和两栖类等水产动物中得到报道,但其分类和作用机制有待深入研究。本文对不同水产动物中的抗菌肽进行了分类,对各类抗菌肽的结构特征和功能进行了分析,并从直接杀伤作用、非膜靶向作用和免疫调节作用等三个方面对抗菌肽的免疫作用机制进行了分析,期望能够为今后在水产动物中开展抗菌肽的相关研究和应用提供一定的理论支持。     

抗菌肽及其在水生动物中的研究现状

面对滥用抗生素所带来的诸多负面影响,抗菌肽以其独特的抗菌机制、广谱、高效的抗菌活性以及靶菌株难以产生抗性等优点而有望成为抗生素的替代品。水产动物抗菌肽是其自身先天免疫的重要组成部分,对抗菌肽的深入研究有望通过充分调动开发动物自身的防御潜力达到抗病的目的,是实现养殖业可持续发展的重要方向。综述了水生动物抗菌肽的类型、结构及抗菌机制,分析了抗菌肽研究中存在问题,并展望其应用前景。     

传统抗生素替代物抗菌肽在水产养殖中的应用前景

抗菌肽(antibacterial peptides)是具有抗菌活性基因编码的一类短肽,目前发现抗菌肽或类似抗菌肽的小分子肽类广泛存在于昆虫、两栖类、水产动物及哺乳动物中,这种内源性抗菌肽经诱导而合成,在机体抵抗病原的入侵方面起着重要的作用,更被认为是缺乏特异性免疫功能生物的重要防御成分.该文系统介绍了抗菌肽的定义、结构、作用机理、与传统抗生素的差异以及在水产养殖中的应用前景,以期为抗菌肽进一步深入研究提供参考.     

动物抗菌肽饲料添加剂的应用与展望

动物抗菌肽是动物机体内一种小分子肽,具有较好的广谱抗菌作用,并兼具抗病毒、抗肿瘤等生物活性,同时作为一种高效安全的绿色添加剂,对畜禽的生长性能有促进作用,有望成为抗生素的替代品。     

抗菌肽与鱼类肠道健康研究进展

我国是水产养殖大国,随着高密度、集约化养殖模式的发展,养殖中各种病害频繁发生,大量甚至提前使用抗生素进行病害预防相当普遍,抗生素的残留及耐药性对我国水产养殖业造成了严重影响。在纷纷寻求抗生素替代物的背景下,抗菌肽具有广谱抗菌性,较抗生素而言具有独特的抗菌机理,养殖过程中使用抗菌肽不易产生耐药性菌株,又具有提高鱼类等水生动物的生产性能及非特异性免疫功能等作用,正逐渐成为替代抗生素的新型抗菌药物而用于水产养殖中。目前有关抗菌肽在水产养殖上的应用研究主要集中在鱼类等水生动物自身产生的抗菌肽以及作为饲料添加剂的外源性抗菌肽。外源抗菌肽经摄食途径进入肠道,改善鱼类肠道的肠绒毛、肠皱襞高度及肌层厚层等组织形态结构,促进消化吸收功能;调节肠道菌群结构,在杀灭肠道有害微生物的同时增加益生菌含量,改善肠道微环境;在提高肠道消化酶活性和抗氧化能力等方面保障鱼类的肠道健康,同时提高鱼类生产性能、改善其品质、增强鱼体抗氧化和免疫功能[1-3]。笔者着重从水产养殖中抗菌肽饲料添加剂的来源及其与肠道菌群、肠道组织结构、肠道消化功能等相关研究进行总结分析,探讨存在的问题和对策,为抗菌肽在水产养殖中的应用,特别是保护鱼类肠道健康提供参考。     

再谈抗菌肽及其在水产养殖上的应用(上)

正随着我国水产养殖业快速发展,各种疾病频频发生,抗生素大量使用甚至滥用的情况也日趋严重,寻找抗生素的替代物已迫在眉睫。而抗菌肽作为一种新型的高效抗菌药物,由于其具有分子量小、水溶性好、抗菌谱广且作用机制特别、不易产生耐药性等优点,成为新型抗生素开发的良好候选资源。鱼类抗菌肽的研究不仅加深了人     

张超峰:我们都在宣传健康养殖的理念

抗菌肽作为替代抗生素的“新秀”．近年来在动物养殖、饲料加工、疾病防控等领域成了高频词。深圳市圣西马生物技术有限公司是国内专业生产抗菌肽的高新技术企业．也是全球最早将抗菌肽技术应用于畜牧养殖业的企业．近期也在致力于从事水产动物专用抗菌肽方面的研究及产品开发。近日。圣西马高级工程师、市场部经理张超峰先生在接受本刊专访时。诠释了圣西马健康养殖的理念。     

鱼源抗菌肽研究进展

<正>抗菌肽是生物体内的小分子多肽,是构成生物体先天免疫系统的重要成分。抗菌肽具有广谱抗菌及抗病毒等特性,细菌对抗菌肽比传统抗生素更难产生抗性,是传统抗生素的理想替代品。目前已从各种生物中分离出了逾2000种抗菌肽[1-3]。鱼类种类繁多,生境复杂,是抗菌肽的重要来源,目前已报道了150余种鱼源抗菌肽[4]。鱼源抗菌肽不仅具有抗菌肽的共有特征,如广谱抗菌性能、免疫调控性能,还有一些种类特异性,以利于鱼类应对复     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).