Invasive potential of biofilm-forming Staphylococci bovine subclinical mastitis isolates

Staphylococcus (S.) aureus is a common infectious agent of bovine chronic mastitis, a disease that is difficult to eradicate. The abilities of Staphylococci to be internalized and form a biofilm can contribute to host immunological defence evasion that subsequently impairs antimicrobial therapy. The invasive capability of six S. aureus field isolates with different biofilm-forming profiles was compared in vitro using a bovine mammary epithelial cell line. This was further confirmed in primary cell cultures using fluorescent rRNA probes against S. aureus. The results suggest that S. aureus invasion levels are not related to biofilm formation.     

高产生物膜乳酸菌抗逆性及其抗氧化特性

为了揭示乳酸菌生物膜抵抗不良环境的作用机制,该研究以2株乳酸片球菌RJ2-1-4、TG1-1-10和2株植物乳杆菌RJ1-1-4、RM1-1-11(菌株均高产生物膜)为研究对象,探究浮游态、被膜态菌株对酸、碱、胆盐、模拟人工胃肠液的耐受能力以及抗氧化能力。结果表明:在极酸条件下,菌株生长受到抑制,但是p H值3.0时,被膜态RM1-1-11生长量显著高于浮游态(P0.05)。随着p H值递增,菌体密度增加,在p H值7.0-9.0时,碱性环境对除TG1-1-10外其他3株菌的生长有一定抑制作用;当胆盐浓度为0～0.03%时,菌株生长有小幅度上升,且被膜态菌株RJ2-1-4、TG1-1-10生长量显著低于浮游态(P0.05);但随着胆盐浓度继续增加,菌株生长受到抑制,除浮游态菌株TG1-1-10外,其余3株菌被膜态菌株生长量均显著高于浮游态;菌株在模拟人工胃肠液中处理3 h后发现,相比于浮游态菌株,被膜态各菌株在胃、肠液中的存活率均有所提高。4株菌对于不同种类自由基均有一定清除能力,清除率从高到低分别为HO·、DPPH·、脂质过氧化、超氧阴离子,其中RJ1-1-4浮游态菌悬液对DPPH·清除率为214.12μg/m L,RJ2-1-4被膜态无细胞提取物、TG1-1-10浮游态无细胞提取物对HO·清除率分别为713.81μg/m L和637.01μg/m L,RJ2-1-4浮游态无细胞提取物对超氧阴离子清除率为93.80μg/m L,RM1-1-11被膜态菌悬液对脂质过氧化物的清除率为122.82μg/m L。结果表明:生物被膜状态下的乳酸菌对于酸、碱、胆盐、模拟人工胃肠液均有一定的保护作用,但是菌株间存在特异性,即使是同一种属也不相同;被膜态菌株的抗氧化能力高于浮游态,但是对于不同种类自由基会有不同的结果。该结果为进一步研究乳酸菌在被膜态下抵抗环境胁迫的作用机制提供依据。     

The effects of periphyton substrate and fish stocking density on water quality, phytoplankton, periphyton and fish growth

The objectives of this study were to determine how periphyton and phytoplankton biomass vary with grazing pressure by tilapia Oreochromis niloticus, to evaluate the growth performance of fish when substrate is introduced and to calculate the efficiency of nitrogen utilization in substrate and non‐substrate systems. Ten circular 1000‐L plastic tanks were filled with 15 cm of loamy soil bottom and water. Five different treatments were applied: eight tilapias with substrate (treatment 8T/S), eight tilapias without substrate (treatment 8T), four tilapias with substrate (treatment 4T/S), four tilapias without substrate (treatment 4T) and no tilapia with substrate (treatment 0T/S). Each week, 2 g of NaNO₃ and 3.5 g of single superphosphate (SSP) were applied to each tank. Sixteen glass slides (1 m×4 cm×4 mm) were installed vertically in the tank bottom, one portion extending above the water surface and equally spaced within the water column in all substrate tanks. Periphyton and phytoplankton quantity and quality, water quality, fish growth and proximate fish composition were measured. Because of grazing, phytoplankton and periphyton biomass decreased after the introduction of fish to the tanks. The periphyton biomass was higher in non‐fish tanks (treatment 0T/S) throughout the experiment than that in tanks with fish (treatments 8T/S and 4T/S). The periphyton biomass was similar in the 4T/S and 8T/S treatments, suggesting that the grazing pressure on periphyton biomass reached threshold levels. Fish ate 25–36% of the total standing biomass every day. Tilapia growth was significantly higher in treatments with substrate. Nitrogen retention was double in substrate ponds compared with in control ponds. There were no significant effects of periphyton substrate or fish density on body composition of fish.     

茎瘤固氮根瘤菌ORS571受体TlpA1对琥珀酸的感应机理

趋化作用在根瘤菌与宿主建立共生关系的起始阶段起着至关重要的作用。TlpA1是茎瘤固氮根瘤菌ORS571重要的跨膜趋化受体，但其感应机理尚未清楚。考察茎瘤固氮根瘤菌ORS571跨膜趋化受体TlpA1对趋化物的感应机理及生物学功能。通过平末端连接的方法构建N端表达菌株进行原核表达蛋白及纯化，利用等温滴定量热法（isothermal titration calorimetry）检测蛋白与趋化物的相互作用，测定野生型与突变株的生物膜及絮凝等表型。结果显示，跨膜趋化受体TlpA1通过胞外部分第29～183位氨基酸与琥珀酸结合。固氮条件下，突变株ΔTlpA1生物膜形成量相较于野生型下降约38%。絮凝量与野生型无显著性差异。跨膜趋化受体TlpA1通过感应琥珀酸调控茎瘤固氮根瘤菌ORS571生物膜的形成，对细胞絮凝无调控作用。     

水处理生物膜载体研究进展

生物膜载体是生物膜工艺的核心部分,载体的选择适当与否直接影响到废水的处理效果。概述了废水处理用生物膜载体的现状与发展,重点介绍了有机合成高分子生物膜载体在亲水性、生物亲和性和磁性等方面的改性研究,壳聚糖、藻酸盐和纤维素等可降解材料作为生物膜载体在废水处理中的应用研究。针对当今生物膜载体应用带来的二次污染问题,提出了解决办法和发展方向,指出可降解生物膜载体的应用可有效避免废弃生物膜载体处理带来的二次污染,是生物膜载体研究的一个重要发展方向。参32     

废水处理系统生物膜中细菌的共凝集研究

从不同废水处理系统生物膜中分离得到22株细菌,测定它们的共凝集能力,并通过16SrRNA序列分析对未知细菌进行鉴定。共凝集结果显示,2h和20h时Bacillus cereus G5与其他21株细菌的共凝集率分别达到30%和45%以上,Bacillus megaterium T1与其他17株细菌的共凝集率分别达到34%和45%以上;同属于Shewanella菌属的H2和H3菌株与其它16株细菌配对的共凝集率在2h时达到30%～75%,20h时达到40%～82%;G5和T1与其他21株细菌共培养的生物膜形成能力进一步表明G5和T1的参与增加了单一细菌的生物膜形成量。研究结果表明,上述3种细菌具有将多种细菌固定于生物膜的功能。     

新疆南疆地区奶牛乳房炎性表皮葡萄球菌生物膜形成及其相关基因的检测

为了揭示新疆南疆地区奶牛乳房炎性表皮葡萄球菌生物膜形成状况,采用微孔板半定量法检测了分离自新疆南疆地区奶牛乳房炎乳样中表皮葡萄球菌的生物膜形成能力,并采用PCR技术扩增表皮葡萄球菌生物膜形成相关基因.结果表明,41％的表皮葡萄球菌能形成不同程度的生物膜,且生物膜形成相关基因较复杂,给本地区奶牛乳房炎的防制带来很大困难.     

Assessment of a biofilm‐based culture system within zero water exchange on water quality and on survival and growth of the freshwater shrimp Neocaridina heteropoda heteropoda

The contribution of biofilm to water quality and as a food source for the culture of the freshwater shrimp Neocaridina heteropoda heteropoda was assessed in indoor aquaria using a zero water exchange system. Two successive phases were conducted to evaluate biofilm development on different substrates (polyethylene net: PN, plastic bottles: PET, agrovelo: AV) and the effect of biofilm to shrimps culture. The biofilm grown on all substrates helped to keep a good water quality by the uptake of nitrogen compounds and the production of high levels of dissolved oxygen associated to the proliferation of autotrophic microorganisms. High survival, reproduction and hatching of shrimps were achieved in all groups mainly associated with good water quality. Final biomass of the shrimps was significant higher for PN and AV groups; while specific growth rate and the levels of lipids of the shrimps yielded similar values for all treatments indicating that the three substrates allowed the growth of a biofilm that resulted in a healthy food source with similar nutritional value for shrimps. The results show that the production of N. heteropoda heteropoda could be successfully conducted by a biofilm‐based culture system with no water exchange, and thus contributing to a better water use. All materials tested were suitable substrates for biofilm growth, though AV and PET could reduce significantly production costs when compared to the PN. Moreover, by the recycling and reuse of waste materials (such as plastic bottles) could contribute to the development of a responsible, sustainable and environmentally friendly culture method.     

Characterization of two bacteriophages for specific treatment of biofilm formed by a Vibrio sp. isolated from an abalone farm

Vibrio harveyi and related vibrios are potential pathogens causing luminous vibriosis in marine aquaculture systems. In this study, two lytic phages P4A and P4F isolated using Vibrio strains B4A and B4F as indicator bacteria, respectively, were isolated from seawater of an abalone farm. Vibrio strain B4F belongs to the Harveyi clade of the genus Vibrio and was found to cause mortality of abalones in laboratory microcosms. Both phages were able to lyse Vibrio strain B4F. Electron microscopy revealed that phage P4A had an icosahedral head while P4F possessed an elongated hexagonal head. Both phages belong to the family Siphoviridae with long non‐contractile tails. Restriction endonuclease analysis indicated that both phages were double‐stranded DNA viruses and the genome sizes of P4A and P4F were estimated to be about 49 and 44 kb respectively. One‐step growth curves revealed that these two phages exhibited distinct latent periods, exponential periods and burst sizes by infecting the same Vibrio strain B4F. Both phages were able to significantly reduce Vibrio population density in biofilm formed by Vibrio strain B4F on the surface of polyethylene film. It is suggested that these two phages may be promising candidates as biocontrol agents of infections caused by Vibrio strains belonging to the Haveyi clade in marine aquaculture systems.