不同乳酸菌组合对苜蓿青贮细菌群落结构的影响

为探讨不同乳酸菌互作对苜蓿(Medicago sativa)青贮细菌群落结构的影响,以2种植物乳杆菌、乳酸片球菌、戊糖片球菌及凝结芽孢杆菌形成的6种乳酸菌组合按1.5 mL·kg-1的添加量制作苜蓿青贮,以等量蒸馏水替代添加剂作为对照,45 d后运用高通量测序分析细菌群落结构.结果表明,各苜蓿青贮的优势乳酸菌群均为厚壁...     

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。     

Changes in soil microbial community composition in response to fertilization of paddy soils in subtropical China

Repeated fertilizer applications to cultivated soils may alter the composition and activities of microbial communities in terrestrial agro-ecosystems. In this study, we investigated the effects of different long term fertilization practices (control (CK), three levels of mineral fertilizer (N₁P₁K₁, N₂P₂K₂, and N₃P₃K₃), and organic manure (OM)) on soil environmental variables and microbial communities by using phospholipid fatty acid (PLFA) biomarkers analysis in subtropical China. Study showed that OM treatment led to increases in soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents, while the mineral fertilizer treatment led to increases in dissolved organic carbon (DOC) content. Changes in soil microbial communities (eg. bacteria, actinomycetes) were more noticeable in soils subjected to organic manure applications than in the control soils or those treated with mineral fertilizer applications. Fungal PLFA biomarkers responded differently from the other PLFA groups, the numerical values of fungal PLFA biomarkers were similar for all the OM and mineral fertilizer treatments. PCA analysis showed that the relative abundance of most PLFA biomarkers increased in response to OM treatment, and that increased application rates of the mineral fertilizer changed the composition of one small fungal PLFA biomarker group (namely 18:3ω6c and 16:1ω5c). Further, from the range of soil environmental factors that we examined, SOC, TN and TP were the key determinants affecting soil microbial community. Our results suggest that organic manure should be recommended to improve soil microbial activity in subtropical agricultural ecosystems, while increasing mineral fertilizer applications alone will not increase microbial growth in paddy soils.     

An investigation of the aetiological role of bovine herpesvirus 4 in bovine endometritis

Uteri from 31 infertile cattle were examined for the presence of bovine herpesvirus 4 (BoHV-4) by nested polymerase chain reaction (PCR). Samples were also tested for bacteria, including chlamydiae and Mycoplasma bovis. BoHV-4 was detected by PCR in 27/31 (87.1%) samples, but the presence and amount of viral DNA was not correlated with histological and bacteriological findings. Arcanobacterium pyogenes, Histophilus somni and Pasteurella multocida were isolated from five cows with endometritis. Chlamydiae were detected in four cases (12.9%), but only two of these had endometritis. The study does not support a role for BoHV-4 as primary agent in bovine endometritis.     

增香型菠萝果酒活性干酵母制备过程中内源海藻糖积累条件优化

以自行筛选的优良菠萝果酒酵母菌为出发菌株,添加一定比例的生香酵母后采用前期正常培养,后期胁迫培养的分段式培养方法,积累较高浓度的海藻糖以提高干酵母的活性.主要研究了后期胁迫培养过程中不同胁迫培养条件对菠萝果酒酵母菌菌体内源海藻糖含量及菌体生成量的影响.结果表明:培养液初始糖质量分数为14％,培养温度34.5℃,250 mL三角瓶装液量80 mL,添加1.3％的NaCl所得培养液菌体生成量最多,菌体内源海藻糖含量最高,活性最强.     

植物源抑菌物质的筛选及其应用

本试验主要研究了植物源抗菌物质特性,筛选可替代抗生素的原料。利用药敏试验（标准菌株大肠杆菌各型、金黄色葡萄球菌、沙门氏菌及霉菌）及临床攻毒试验对12种常见中草药进行研究分析。结果表明,12种单味中草药的粗提物中黄连、夏枯草、黄芩、连翘、石榴皮对大肠杆菌均有抑制作用,且效果明显强于其他提取液;临床试验结果表明黄芩、夏枯草、连翘和金银花对鸡的攻毒保护率高于感染对照组5%～10%。     

北虫草商品化栽培技术的研究

对4个北虫草菌株、5个培养基配方和3种栽培容器进行了北虫草栽培试验研究,并从经济效益方面对其进行了估算分析.结果表明:金地一号菌株优质、高产、商品性好、经济效益高,可作为今后北方地区室内栽培的当家优良菌株进行推广种植;小麦培养基栽培北虫草,不仅产量高、质量好,而且成本低,故采用小麦培养基更具有优势;塑料瓶栽培北虫草,具有重量轻、利于灭菌、可多次重复使用等特点,可作为今后商品化、规模化、工厂化栽培北虫草之首选容器.     

Evaluation of bacterial biological control agents for control of root-knot nematode disease on tomato

Among 19 bacterial strains isolated in Yunnan from rhizosphere soils and plant tissues, Bacillus methylotrophicus strain R2-2 and Lysobacter antibioticus strain 13-6 exhibited the highest antagonistic activity against the tomato root-knot nematode Meloidogyne incognita in plate and greenhouse pot experiments. The two strains, when applied as soil drenches or seed treatments in greenhouse experiments, reduced root-knot severity and incidence on tomato compared to no-bacteria controls. In tomato field trials conducted in separate years, soil drench treatment with either strain reduced root-knot disease levels and increased yields compared to the control. Levels of disease control and yield enhancement provided by the strains were higher than those using the chemicals abamectin and carbofuran. This is the first report of B. methylotrophicus being used as a biocontrol agent against a plant parasitic nematode and the first demonstration that B. methylotrophicus and L. antibioticus can suppress disease caused by root-knot nematodes in the field.     

Bacterial contamination of eggs and behaviour of poultry flocks in the free range environment

The free range production system is becoming more common in Australia and is expected to increase. Free range hens are exposed to more stressors in comparison to hens from barn and cage systems and it is suggested that stress can increase bacterial shedding on eggs. The aims of this study were to examine the level of total bacteria and Enterobacteriaceae populations, as well as the presence of Salmonella and Campylobacter, in eggs collected from two free range flocks on two different farms and to conduct longitudinal observations of the behaviour and welfare of hens in the free range production system. Hen age (weeks) was shown to have a significant effect (increase) on the level of total bacteria on the egg shell surface and in shell pores, as well as having an effect on feather condition score. As the hens aged, the frequency of external visual egg characteristics increased, as did feather condition score (where feather condition was poorer). These observations indicate areas which should be investigated further to improve the food safety of eggs and optimise the welfare of free range hens.