美洲鲥鱼嗜水气单胞菌病原的分离与鉴定

2021年,山东省临沂市一养殖场养殖的美洲鲥鱼(Alosa sapidissima)突发疾病并出现严重死亡,日死亡率高峰期达到2.5%,累积死亡率约为90%。患病鱼主要症状为体表出血、溃疡,解剖可见腹腔腹水、肝脏暗红,并伴有肠炎。组织病理学检测发现,病鱼肝脏出现弥散性坏死,嗜碱性粒细胞增多和细胞肿胀空泡变性;脾脏出现出血性贫血性坏死灶、核破裂和核固缩;肾脏淋巴细胞坏死脱落,肾小体毛细血管球萎缩,近端小管和远端小管内的细胞出现不同程度的细胞结构消失。发病鱼肉眼和显微镜观察未见明显寄生虫,利用PCR方法检测鲤疱疹病毒2型(Cyprinid herpesvirus 2)、鲈鱼蛙病毒(largemouth bass ranavirus)等淡水鱼类常见病毒均为阴性。细菌分离培养结果显示,从发病鱼的肝脏、肾脏和脾脏中分离得到形态一致的优势菌,命名为AS-AH2101。经16S rRNA测序比对和生理生化鉴定,确定AS-AH2101为嗜水气单胞菌(Aeromonas hydrophila)。毒力基因检测结果显示,AS-AH2101携带气溶素(aerA)、溶血素(hlyA)、丝氨酸蛋白酶(ahpA)、...     

嫁接对西瓜根际微生物种群数量及群落结构的影响

分别采用微生物培养的方法、16S rDNA PCR-RFLP方法和phl D基因PCR-RFLP方法研究了嫁接对西瓜根际微生物种群数量、细菌群落结构及拮抗菌（2, 4-DAPG产生菌）群落结构的影响。结果表明：① 嫁接西瓜根际细菌和真菌数量有所提高,而放线菌数量则有所减少。② 嫁接西瓜与自根西瓜具有1个相同的主要根际细菌基因型;不同砧木嫁接的西瓜与自根西瓜也分别具有不同基因型的细菌。③ 嫁接西瓜具有与自根西瓜不同的主要根际拮抗菌基因型。     

Fractionation of the reference inoculum of epizootic rabbit enteropathy in discontinuous sucrose gradient identifies aetiological agents in high density fractions

Epizootic rabbit enteropathy (ERE) is a major cause of economic loss in intensive rabbit production. Since its first recognition in 1997, much work has been done to determine the pathogenic mechanisms of the disease and to identify the aetiological agent(s). Unfortunately, the quest for aetiology has only met with limited success despite the ability to reproduce the syndrome by inoculation of intestinal contents from field cases. These intestinal inocula contain a huge number of microorganisms which could all be involved in the aetiology of ERE. To decrease the number of putative agents, the French reference inoculum TEC3 was fractionated on a discontinuous sucrose gradient so that seven fractions (supernatant, 10%, 20%, 30%, 40%, 50% and pellet) were obtained. Specific-pathogen-free rabbits were inoculated with three out of these seven fractions (supernatant, 30%, and pellet). The objectives were: (1) to characterise the seven fractions by bacteriological examination; (2) to verify whether the aetiological agent was present in the fractions by inoculation of rabbits; (3) to assign the aetiological agent of ERE to a morphological group of pathogens; (4) to identify a fraction which could replace the reference inoculum TEC3 in applications such as cell cultures or egg inoculation. The results strongly suggest that ERE is a bacterial disease and does not have a viral or parasitic aetiology.     

冀北水稻田土壤细菌群落结构和多样性研究

为探讨冀北水稻田土壤细菌群落结构和多样性,以承德地区水稻主产区（河北隆化,河北滦平）稻田土壤为试验材料,采用高通量测序技术,对水稻大田土壤细菌群落结构和多样性进行研究。结果表明：不同地区水稻田土壤微生物多样性存在差异,其中样本ZYY.CKD9中微生物多样性最高且有益菌较多,主要有硫杆菌属（Thiobacillus）、拟衣藻属（Dechloromonas）和地杆菌属（Geobacter）;但也存在共有细菌菌群,如Kaistobacter、溶杆菌属（Lysobacter）、乳酸杆菌属（Lactobacillus）、Candidatus_Solibacter、硫杆菌属（Thiobacillus）、红长命菌属（Rubrivivax）、拟衣藻属（Dechloromonas）、Anaeromyxobacter、硝化螺旋菌属（Nitrospira）等;PCA分析结果显示,土壤细菌群落结构空间相关性不明显。这为冀北水稻田土壤修复、病害防治及功能菌肥开发,促进水稻高产栽培提供依据。     

Fungal biomass in pastures increases with age and reduced N input

Previous studies have shown that soil fungal biomass increases towards more natural, mature systems. Shifts to a fungal-based soil food web have previously been observed with abandonment of agricultural fields and extensification of agriculture. In a previous field experiment we found increased fungal biomass with reduced N fertilisation. Here, we explore relationships between fungi, bacteria, N input and grassland age on real dairy farms in the Netherlands. We hypothesised that also in pastures that are still in production there is a negative relationship between fungal biomass and fertilisation, and that fungal biomass increases with grassland age in pastures that are still in production. We expected the fungal/bacterial biomass ratio to show the same responses, as this ratio has often been used as an indicator for management changes. We sampled 48 pastures from eight organic dairy farms. Sites differed in age and fertilisation rate. We determined fungal and bacterial biomass, as well as ergosterol (a fungal biomarker). Fungal and bacterial biomass and ergosterol, showed a negative relationship with N application rate, and correlated positively with organic matter percentage. In old pastures, fungal biomass and ergosterol were higher than in younger pastures. Because bacterial biomass responded in the same way as fungal biomass, the F/B ratio remained constant, and can therefore—in our data set—not be used as an indicator for changing management. We conclude that the changes in fungal and bacterial biomass were driven by changes in organic matter quality and quantity. The negative relationship we found between N application rate and fungal biomass adds to earlier work and confirms the presence of this relationship in pastures with relatively small differences in management intensities. Earlier studies on shifts in fungal biomass focused on ex-agricultural fields or restoration projects. Here we show that fungal biomass is also higher in older agricultural pastures.     

Effects of substrate sterilization,fungicide treatment,and mycorrhization helper bacteria on ectomycorrhizal formation of pedunculate oak (Quercus robur) inoculated with Laccaria laccata in two peat bare-root nurseries

Summary Pedunculate oak seedlings (Quercus robur) inoculated with the ectomycorrhizal fungus Laccaria lacata were grown for 1 year on fertilized sphagnum peat in two nurseries. Three factors affecting microbial populations in the substrate were studied, fungicide treatment of the seeds, peat disinfection before sowing (methyl bromide or steam pasteurization), and inoculation with mycorrhization helper bacteria. Treatment of acorns with Iprodione had no depressive effect on mycorrhiza formation. Both disinfection techniques were equivalent, stimulating or depressing mycorrhiza formation depending on the initial microflora in the peat. The introduction of two previously selected mycorrhization helper bacteria (one Pseudomonas fluorescens and one unidentified fluorescent pseudomonad), isolated from L. laccata sporocarps associated with Douglas fir—L. laccata ectomycorrhizas in other nurseries, significantly increased the mycorrhizal rate from 30 to 53% of the short roots. The implications of these results for the controlled mycorrhization of planting stocks and the specificity of mycorrhization helper bacteria are discussed.     

不同温度对扬州盐水鹅品质的影响

[目的]为了保证扬州盐水鹅的卫生质量和品质。[方法]对扬州盐水鹅在不同保存温度下菌落总数、菌相和pH值的变化进行试验性观察。[结果]当菌落总数达到106 cfu/g、腿肌pH值为6.5以上时,均有异味产生;腐败过程中的优势菌种,37℃为肠球菌属和葡萄球菌属,20℃为变形杆菌属,4℃为假单胞菌属;对于当天制作并于中午出售的盐水鹅,其保存期限建议值为:37℃不超过7 h,20℃不超过24 h,4℃不超过6 d。[结论]该研究为建立健全可供盐水鹅新鲜度鉴定使用的卫生评价指标提供了依据。     

牛呼吸疾病综合征及其防治

牛呼吸疾病综合征是严重危害国内外肉牛养殖业的一种重要传染病,该病的致病因素复杂,包括支原体、病毒和细菌等特异性病原以及运输应激等多种因素。美国等发达国家对该病的攻关研究开始于上世纪80年代初,其研究和临床防控均已达到较高水平,但仍认为该病将是未来10～20年养牛业所面临的主要疾病。我国对该病的认识和研究尚处于起步阶段,借鉴世界上发达国家的先进经验将有助于提升我国对该病的防控水平。     

2,4-二乙酰基藤黄酚产生菌在番茄根部的定殖及对番茄青枯病的防治

2,4-二乙酰基藤黄酚(2,4-DAPG)产生菌是荧光菌对土传病害进行生物防治的主要类群之一。室内筛选结果表明：供试的12个2,4-DAPG产生菌菌株对番茄青枯病菌均有不同程度的抑制作用,其中CPF、10抑菌效果最佳,抑菌带宽为3．5mm;而2P24、5J10次之,抑菌带宽为3．0mm。CPF10和2P24培养原液对番茄胚根的生长均有明显的抑制作用。CPF10和2P24根部定殖结果表明,两菌株均可在番茄幼苗根部大量定殖,根表细菌数量随着时间延长呈下降趋势但仍维持较高数量;而根内细菌数量有明显上升的趋势。CPF10和2P24对番茄青枯病均有一定的防治效果,其中2P24的防治效果最好。而CPF10在所有的处理中变异系数(CV)最小,防治效果最稳定。     

新疆红雁池鱼场非洲鲫鱼传染病病原学研究初报

红雁池鱼场利用电场冷却电机回流水饲养非洲鲫鱼。１９８２～１９８３年分３批从北京小唐山温泉鱼场引进非洲鲫鱼，进场不久即大批死亡，死亡率由１８．３７％到几乎全群覆灭，造成很大的经济损失．经采样进行细菌分离与鉴定并对菌株作药敏试验，同时将病鱼组织磨碎，匀浆后进行差速离心和梯度离心沉淀，点样用磷钨酸和醋酸氧铀分别染色作电镜观察。其结果为；电镜检查未发现病毒，细菌学检查分离出８株细菌。分离出的细菌以气单胞菌属菌为主（８株菌中、气单胞属菌占６株），因此定名为气单胞菌感染复合症（ＡｅｒｏｍｏｎａｄＭｉｘｅｄＩｎｆｅｃｔｉｖｅ　Ｃｏｍｐｌｅｘ）。分离上述菌株对小白鼠有较强致病力，鉴于国外文献报道气单胞菌属偶能引起人传染性胃肠炎，故本病可能为人鱼共患病，特此报道．警惕注意。